SOLUTION COMPRISING NICOTINE IN DEPROTONED AND PROTONED FORM

Abstract

A nicotine solution comprising: (i) a vehicle; (iii) nicotine in non-protonated and protonated form; and (iv) one or more acids, including at least benzoic acid, levulinic acid, or a mixture thereof, and wherein the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis.

Description

SOLUTION COMPRISING NICOTINE IN DEPROTONED AND PROTONED FORM FIELD OF INVENTION The present invention relates to a nicotine solution, to containers containing the nicotine solution, and to electronic vapor delivery systems such as electronic nicotine delivery systems (e.g., electronic cigarettes) incorporating said solution. BACKGROUND TO THE INVENTION Electronic vapor delivery systems, such as e-cigarettes, typically contain a reservoir of liquid to be vaporized, which usually contains nicotine. When a user inhales through the device, a heater is activated to vaporize a small amount of liquid, which is then inhaled by the user. In the United Kingdom, the use of electronic cigarettes has grown rapidly, and it has been estimated that there are now more than one million people who use them. One challenge faced when providing such systems is to supply, from the vapor-providing device, a vapor to be inhaled that provides consumers with an acceptable experience. Some consumers may prefer an electronic cigarette that generates an aerosol that 'mimicks' the inhaled smoke from a tobacco product such as a cigarette, closely resembling it. The aerosols from electronic cigarettes and the smoke from tobacco products such as cigarettes provide the user with a complex chain of flavor in the mouth, absorption of > κ C * Nicotine is absorbed into the mouth and throat, followed by nicotine absorption in the lungs. These various aspects are described by users in terms of flavor, intensity / quality, impact, irritation / smoothness, and nicotine reward. Nicotine contributes to several of these factors and is strongly associated with factors such as impact, irritation, and smoothness; these are easily perceived by consumers, and e-cigarettes may offer too much or too little of these parameters, depending on individual preferences.Nicotine reward is particularly complex because it results from both the amount of nicotine absorbed through the oral mucosa and the rate at which this occurs—typically as nicotine in the vapor phase—and the amount and rate of nicotine absorbed in the lungs—typically as nicotine in the particulate phase of the inhaled aerosol. Each of these factors, and their balance, can significantly contribute to a consumer's acceptability of an e-cigarette. Therefore, it is desirable for e-cigarette manufacturers to provide ways to optimize the overall vaping experience. SUMMARY OF THE INVENTION In one aspect, a nicotine solution is provided comprising (i) a vehicle; (i) nicotine in non-protonated and protonated form; and (iii) one or more acids, including at least benzoic acid, levulinic acid, or a mixture thereof, and > κ C * C ko » where the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. In one aspect, a nicotine solution is provided in a container comprising (a) a container; and (b) a nicotine solution, comprising (i) a vehicle; (i) nicotine in non-protonated and protonated form; and (iii) one or more acids, including at least benzoic acid, levulinic acid or a mixture thereof, and wherein the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. In one aspect, an electronic system is provided that supplies steam, comprising: a vaporizer for vaporizing liquid to be inhaled by a user of the electronic system that provides vapor, a power supply comprising a cell or battery for supplying power to the vaporizer, a nicotine solution, comprising (i) a vehicle; (i) nicotine in non-protonated and protonated form; and (ii) one or more acids, among which there is at least benzoic acid, levulinic acid, or a mixture thereof, and wherein the total acid content present in the > κ C * C κ ο -X solution is not greater than 0.6 molar equivalents based on nicotine. In one aspect, a process is provided for improving the organoleptic properties of the nicotine solution for vaporization, wherein the process comprises the following steps: (a) providing a nicotine solution comprising (i) a vehicle; (i) nicotine in non-protonated and protonated form; and (iii) one or more acids, among which there is at least benzoic acid, levulinic acid or a mixture thereof, and wherein the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis; (b) vaporize the nicotine solution. In one aspect, the use of one or more acids is provided to improve the organoleptic properties of the nicotine solution for vaporization, where the nicotine solution comprises (i) a vehicle; (i) nicotine in non-protonated and protonated form; and (iii) one or more acids, including at least benzoic acid, levulinic acid or a mixture thereof, and wherein the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. > κ C * C κ ο DETAILED DESCRIPTION As set forth herein, the present invention provides a nicotine solution comprising: (i) a vehicle; (ii) nicotine in non-protonated and protonated form; and (iii) one or more acids, among which there is at least benzoic acid, levulinic acid or a mixture thereof, and wherein the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. The inventors have discovered that by protonating some, and only some, of the nicotine present in a solution, such that the solution contains both non-protonated and protonated nicotine, vaporizing and inhaling the solution provides desirable properties of flavor, impact, irritation, smoothness, and / or nicotine reward to the user. In particular, the inventors have discovered that the levels of acid addition required by the present invention—that is, where the total acid content present in the solution is no greater than 0.6 molar equivalents based on nicotine—can be used across a wide range of nicotine contents in the solutions.At the levels of acid addition required by the present invention, solutions can be provided with desirable properties of flavor, impact, irritation, smoothness and / or nicotine reward for the user both when the nicotine content is relatively low, for example 1.8% by weight of nicotine or less, and when the nicotine content is relatively high, for example greater than 1.8% by weight of nicotine. As someone with experience in the art will understand, nicotine can exist in non-protonated, monoprotonated, or diprotonated form. The structures of each of these forms are given below. In the product description, references to protonated forms refer to both monoprotonated and diprotonated nicotine. References in the product description to quantities in the protonated form refer to the combined amount of monoprotonated and diprotonated nicotine. Furthermore, when a fully protonated formulation is referred to, it is understood that very small amounts of unprotonated nicotine may be present at any given time, for example, less than 1% unprotonated nicotine. For ease of reference, these and other aspects of the present invention are now set forth under appropriate section headings. However, the descriptions under each section are not necessarily limited to that particular section. The vehicle for the nicotine solution may be any suitable solvent, such that the nicotine solution can be vaporized for use. In one aspect, the solvent is selected from glycerol, propylene glycol, and mixtures thereof. In one aspect, the solvent is at least glycerol. In one aspect, the solvent consists essentially of glycerol. In one aspect, the solvent consists of glycerol. In one aspect, the solvent is at least > κ C * Propylene glycol. In one aspect, the solvent consists essentially of propylene glycol. In one aspect, the solvent consists of propylene glycol. In one aspect, the solvent is at least a mixture of propylene glycol and glycerol. In one aspect, the solvent consists essentially of a mixture of propylene glycol and glycerol. In one aspect, the solvent consists of a mixture of propylene glycol and glycerol. The vehicle of the nicotine solution may be present in any appropriate amount. In one aspect, the vehicle is present in an amount of between 1 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 5 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 10 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 20 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 30 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 40 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 50 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 60 and 98% by weight based on the solution.In one aspect, the vehicle is present in an amount between 70 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount between 80 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount between 90 and 98% by weight based on the solution. In one aspect, the vehicle is present in an amount between 1 and 90% by weight based on the solution. In one aspect, the vehicle is present in an amount between 5 and 90% by weight based on the solution. In one aspect, the vehicle is >. κ C8τ C ko -X present in an amount of between 10 and 90% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 20 and 90% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 30 and 90% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 40 and 90% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 50 and 90% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 60 and 90% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 70 and 90% by weight based on the solution. In one aspect, the vehicle is present in an amount of between 80 and 90% by weight based on the solution. The nicotine solution may also include flavoring components. In this case, the preferred carrier may be propylene glycol. As used herein, the terms “flavor” and “flavoring” refer to materials that, where permitted by local regulations, may be used to create a desired flavor or aroma in a product for adult consumers.These may include extracts (for example, licorice, hydrangea, white Japanese magnolia bark and leaves, chamomile, fenugreek, clover, menthol, Japanese mint, anise, cinnamon, herbs, wintergreen, cherry, forest fruits, peach, apple, Drambuie®, bourbon, scotch, whiskey, spearmint (Mentha spicata), mint, lavender, cardamom, celery, cascarilla, nutmeg, sandalwood, bergamot, geranium, honey essence, rose oil, vanilla, lemon oil, orange oil, Chinese cinnamon, caraway, cognac, jasmine, ylang-ylang, sage, fennel, pepper, ginger, anise, coriander, coffee, or a mint oil of any species of the genus Mentha), flavor enhancers, blockers >. κ C * C-X of bitter taste receptor sites, activators or stimulators of sensory receptor sites, sugars and / or sugar substitutes (e.g., sucralose, acesulfame potassium, aspartame, saccharin, cyclamates, lactose, sucrose, glucose, fructose, sorbitol, or mannitol), and other additives such as charcoal, chlorophyll, minerals, botanical agents, or breath fresheners. These may be imitation, synthetic, or natural ingredients or mixtures thereof. They may be in any appropriate form, e.g., as oils, liquids, or powders. In one aspect, the nicotine solution also comprises water. The water may be present in any appropriate amount. In one aspect, water is present in an amount of between 1 and 50% by weight based on the solution. In one aspect, water is present in an amount of between 5 and 50% by weight based on the solution. In one aspect, water is present in an amount of between 10 and 50% by weight based on the solution. In one aspect, water is present in an amount of between 20 and 50% by weight based on the solution. In one aspect, water is present in an amount of between 1 and 40% by weight based on the solution. In one aspect, water is present in an amount of between 5 and 40% by weight based on the solution. In one aspect, water is present in an amount of between 10 and 40% by weight based on the solution. In one aspect, water is present in an amount of between 20 and 40% by weight based on the solution.In one aspect, water is present in an amount of between 1 and 30% by weight based on the solution. In one aspect, water is present in an amount of between 5 and 30% by weight based on the solution. In one aspect, water is present in an amount of between 10 and 30% by weight based on the solution. In one aspect, water is present in an amount of between 20 and 30% by weight. κ C10τ C κ ο > based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 1 and 98% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 5 and 98% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 10 and 98% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 20 and 98% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 30 and 98% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 40 and 98% by weight based on the solution. In one respect, the combined amount of vehicle and water in the nicotine solution is between 50 and 98% by weight based on the solution.In one aspect, the combined amount of vehicle and water in the nicotine solution is between 60 and 98% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 70 and 98% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 80 and 98% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 90 and 98% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 1 and 90% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 5 and 90% by weight based on the solution. In one respect, the combined amount of vehicle and water in the nicotine solution is between 10 and 90% by weight based on the >. κ C11τ C ko » solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 20 and 90% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 30 and 90% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 40 and 90% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 50 and 90% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 60 and 90% by weight based on the solution. In one aspect, the combined amount of vehicle and water in the nicotine solution is between 70 and 90% by weight based on the solution. In one respect, the combined amount of vehicle and water in the nicotine solution is between 80 and 90% by weight based on the solution.In one respect, the combined amount of vehicle and water in the nicotine solution is between 90 and 90% by weight based on the solution. In one respect, nicotine solution may contain solvents that allow for advantageous formulation preparation. In another respect, nicotine solution contains ethanol, which improves the solubility of benzoic acid when incorporated into the formulation. The system components may be present in the following quantities. Water may represent up to 30% weight by weight of the total solution. The vehicle may represent up to 98% weight by weight of the total solution. Nicotine may represent between 0% and 6% weight by weight of the total solution. In the context of the present invention, references to a nicotine solution comprising nicotine in both protonated and non-protonated forms > κ C * C κ υ ~χ generally means that the amount of nicotine in its non-protonated form is not minimal. For example, the amount of non-protonated nicotine is typically greater than 1% weight by weight. The nicotine solution comprises nicotine in its non-protonated form and nicotine in its protonated form. In one aspect, the nicotine solution comprises nicotine in its non-protonated form and nicotine in its monoprotonated form. Although the solution is typically expected to comprise nicotine in its non-protonated form and nicotine in its monoprotonated form, small amounts of diprotonated nicotine may be present. In one aspect, the nicotine solution comprises nicotine in its non-protonated form, nicotine in its monoprotonated form, and nicotine in its diprotonated form. As explained herein, the inventors have discovered that by protonating a portion of the nicotine, and only a portion of the nicotine, the desired characteristics are observed. In one aspect, between 1 and 80% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 2 and 80% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 3 and 80% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 4 and 80% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 5 and 80% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 10 and 80% by weight of the nicotine present in the solution is in protonated form. In one respect, between 15 and 80% by weight of the nicotine present in the solution is in protonated form.In one respect, between 20 and 80% by weight of the nicotine present in the solution is in protonated form. In another respect, between 25 and 80% by weight of the >. κ C13τ The nicotine present in the solution is in its protonated form. In one aspect, between 30 and 80% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 35 and 80% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 40 and 80% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 45 and 80% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 50 and 80% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 55 and 80% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 5 and 80% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 5 and 75% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 5 and 70% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 5 and 65% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 5 and 60% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 5 and 55% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 5 and 50% by weight of the nicotine present in the solution is in its protonated form. In one aspect, between 5 and 45% by weight of the nicotine present in the solution is in protonated form. In another aspect, between 5 and 40% by weight of the nicotine present in the solution is in protonated form.In one aspect, between 5 and 35% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 5 and 30% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 5 and 25% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 5 and 20% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 5 and 15% by weight of the nicotine present in the solution is in protonated form. In one aspect, between 5 and 10% by weight of the nicotine present in the solution is in protonated form. The relevant amounts of nicotine present in protonated form in the solution are specified here. Someone experienced in this field can easily calculate these amounts. Nicotine, 3-(1-methylpyrrolidine-2-yl)pyridine, is a diprotic base with a pKa of 3.12 for the pyridine ring and 8.02 for the pyrrolidine ring. Depending on the pH, it can exist in protonated (mono- and di-) and non-protonated (free base) forms, which have different bioavailabilities. 15) fjsϊ Pyrrolidine ring HJA pKa 8.02 Pyridine ring pKa 3.16 The distribution of protonated and non-protonated nicotine will vary with different pH increases. H ...............'WW' kr '' 'ΜΗ* 'ky-' ' NH* HJ -------- i J v ..................... ' J >4' The unprotonated nicotine fraction will predominate at high pH levels, while a decrease in pH will result in an increase in the protonated nicotine fraction (mono- or di-protonated depending on the pH). If the relative fraction of protonated nicotine and the total amount of nicotine in the sample are known, the absolute amount of protonated nicotine can be calculated. The relative fraction of protonated nicotine in solution can be calculated using the Henderson-Hasselbalch equation, which describes pH as a derivation of the acid dissociation constant equation and is widely used in chemical and biological systems. Consider the following equilibrium: The Henderson-Hasselbalch equation for this equilibrium is: Where [B] is the amount of unprotonated nicotine (i.e., free base), [BH+] is the amount of protonated nicotine (i.e., the conjugate acid), and pKa is the reference pKa value for the nitrogen of the pyrrolidine ring of nicotine (pKa=8.02). The relative fraction of protonated nicotine can be obtained from the alpha value of unprotonated nicotine calculated from the Henderson-Hasselbalch equation as: M for faith. prdtomda = i oó — f __* s mi ' L , _ WI ......Jr ' wvp The determination of pKa values ​​in nicotine solutions was carried out using the basic approach described in “Spectroscopic investigations into > κ C16τ C κ ο -X the acid-base properties of nicotine at different temperatures”, Peter M. Clayton, Cari A. Vas, Tam TT Bui, Alex F. Drake and Kevin McAdam. Anal. Methods, 2013, 5, 81-88. As set forth herein, the nicotine solution comprises nicotine in its non-protonated form and nicotine in its protonated form. As anyone experienced in the art will understand, the protonated form of nicotine is prepared by reacting non-protonated nicotine with an acid. The acids are one or more suitable acids, among which at least benzoic acid, levulinic acid, or a mixture thereof are present, and where the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. As is clear, at least benzoic acid, levulinic acid, or a mixture thereof must be present. However, one or more other acids besides benzoic acid and / or levulinic acid may also be present. The presence of acids other than benzoic acid and levulinic acid is neither excluded nor required.Therefore, in an additional aspect, the present invention provides a nicotine solution comprising (i) a vehicle; (i) nicotine in non-protonated and protonated form; and (iii) a first acid, wherein the first acid is selected from benzoic acid, levulinic acid and mixtures thereof; and (iv) an optional second acid, wherein, if present, the optional second acid is selected from acids other than benzoic acid, levulinic acid, and mixtures thereof; and wherein the total content of the first acid and the second acid present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. > κ C * C κ ο The protonation of nicotine can be provided in such a way as to obtain the desired degree of protonation. In one respect, the second optional acid is an organic acid. In one respect, the second optional acid is a carboxylic acid. The carboxylic acid can be any suitable carboxylic acid. In one respect, the second optional acid is a monocarboxylic acid. In one respect, the second optional acid is selected from the group consisting of: acetic acid, lactic acid, formic acid, citric acid, pyruvic acid, succinic acid, tartaric acid, oleic acid, sorbic acid, propionic acid, phenylacetic acid, and mixtures thereof. In one aspect of the present invention, at least benzoic acid is present in the solution. In one aspect of the present invention, at least levulinic acid is present in the solution. In one aspect of the present invention, both benzoic acid and levulinic acid are present in the solution. As set forth herein, the presence of acids other than benzoic acid and levulinic acid is not required. In one aspect, the presence of acids other than benzoic acid and levulinic acid is excluded. Therefore, in one aspect, the nicotine solution contains acids selected from the group consisting of benzoic acid, levulinic acid, and mixtures thereof. Therefore, in one aspect, the present invention provides a nicotine solution comprising: (i) a solvent; (ii) nicotine in non-protonated and protonated forms; and (iii) an acid selected from the group consisting of benzoic acid, levulinic acid, and mixtures thereof; and wherein the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. > κ C18τ C κ ο -X In one respect, benzoic acid is the only acid present. In another respect, the nicotine solution contains the acid selected from the group consisting solely of benzoic acid. In one respect, levulinic acid is the only acid present. In another respect, the nicotine solution contains an acid that is selected from the group consisting only of levulinic acid. In one respect, benzoic acid and levulinic acid are the only acids present. In another respect, the nicotine solution contains acids selected from the group consisting of mixtures of benzoic acid and levulinic acid. In one aspect, the amount of levulinic acid present in the solution is less than 0.1 molar equivalents based on nicotine. In one aspect, the amount of levulinic acid present in the solution is not greater than 0.05 molar equivalents based on nicotine. In one aspect, the amount of levulinic acid present in the solution is not greater than 0.02 molar equivalents based on nicotine. In one aspect, the amount of levulinic acid present in the solution is not greater than 0.01 molar equivalents based on nicotine. In one aspect, the amount of levulinic acid present in the solution is not greater than 0.005 molar equivalents based on nicotine. In one aspect, the amount of levulinic acid present in the solution is not greater than 0.001 molar equivalents based on nicotine. In one aspect, the solution does not contain levulinic acid. Benzoic and levulinic acids are advantageous because the inventors have discovered that by heating solutions containing benzoic acid and / or levulinic acid in an electronic system that provides steam, the level of transfer > κ C19τ The transfer rate of the acid to the aerosol is higher, with lower production of degradation products compared to many other acids. Therefore, the inventors have found that aerosol transfer for such acids is more efficient. The inventors have also discovered that benzoic acid provides a particularly desirable flavor when the vaporized solution is inhaled. Therefore, unlike acids such as lactic acid, acetic acid, and succinic acid, benzoic acid provides both good flavor and / or improved transfer efficiency to the aerosol. Therefore, as disclosed herein in one aspect of the present invention, at least benzoic acid is present in the solution. Incidentally, when benzoic acid is present, it is not necessary to observe the overall limit on acid content described herein. Therefore, in a further broad aspect, the present invention provides a nicotine solution comprising (i) a vehicle; (i) nicotine in protonated and non-protonated form; and (ii) benzoic acid. In one aspect, when benzoic acid is present, the nicotine solution contains no more than 0.1 molar equivalents (based on nicotine) of each of: lactic acid, acetic acid, and succinic acid. In another aspect, the nicotine solution contains no more than 0.01 molar equivalents (based on nicotine) of each of: lactic acid, acetic acid, and succinic acid. Each of the preferred aspects of the present invention is equally valid for this broader aspect of the invention. The total acid content present in the solution is no greater than 0.6 molar equivalents based on nicotine. In one respect, the content > κ C20τ The total acid content present in the solution is not greater than 0.55 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not greater than 0.5 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not greater than 0.45 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not greater than 0.4 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not greater than 0.35 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not greater than 0.3 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not greater than 0.6 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not greater than 0.55 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not greater than 0.5 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not greater than 0.45 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not greater than 0.4 molar equivalents based on nicotine.In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not greater than 0.35 molar equivalents on a nicotine basis. In one aspect, the combined amount of benzoic acid and acid >. κ C * The levulinic acid present in the solution is not greater than 0.3 molar equivalents based on nicotine. The amount of benzoic acid present in the solution is not greater than 0.6 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not greater than 0.55 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not greater than 0.5 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not greater than 0.45 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not greater than 0.4 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not greater than 0.35 molar equivalents based on nicotine. In one respect, the amount of benzoic acid present in the solution is no more than 0.3 molar equivalents on a nicotine basis.In each of these aspects, preferably the only acid present is benzoic acid and the nicotine solution contains the acid that is selected from the group consisting only of benzoic acid. In one aspect, the total acid content present in the solution is not less than 0.01 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not less than 0.05 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not less than 0.1 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not less than 0.15 molar equivalents based on nicotine. > κ C * C κ ο -X In one aspect, the total acid content present in the solution is not less than 0.2 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not less than 0.25 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not less than 0.3 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not less than 0.35 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is not less than 0.4 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not less than 0.01 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not less than 0.05 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not less than 0.1 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not less than 0.15 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not less than 0.2 molar equivalents based on nicotine.In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not less than 0.25 molar equivalents on a nicotine basis. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not less than 0.3 molar equivalents on a nicotine basis. In one aspect, the combined amount of acid >. κ C * The amount of benzoic acid and levulinic acid present in the solution is not less than 0.35 molar equivalents on a nicotine basis. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is not less than 0.4 molar equivalents on a nicotine basis. In one aspect, the amount of benzoic acid present in the solution is not less than 0.01 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not less than 0.05 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not less than 0.1 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not less than 0.15 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not less than 0.2 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is not less than 0.25 molar equivalents based on nicotine. In one respect, the amount of benzoic acid present in the solution is not less than 0.3 molar equivalents on a nicotine basis.In one aspect, the amount of benzoic acid present in the solution is not less than 0.35 molar equivalents based on nicotine. In another aspect, the amount of benzoic acid present in the solution is not less than 0.4 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is between 0.1 and 0.6 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is between 0.1 and 0.5 molar equivalents based on nicotine. In one aspect, the total content of > κ C * The acid content of C ko -X present in the solution is between 0.2 and 0.6 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is between 0.1 and 0.4 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is between 0.3 and 0.6 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is between 0.2 and 0.5 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is between 0.3 and 0.5 molar equivalents based on nicotine. In one aspect, the total acid content present in the solution is between 0.2 and 0.4 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is between 0.1 and 0.6 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is between 0.1 and 0.5 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is between 0.2 and 0.6 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is between 0.1 and 0.4 molar equivalents based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is between 0.3 and 0.6 molar equivalents based on nicotine.In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is between 0.2 and 0.5 molar equivalents based on nicotine. In another aspect, the combined amount of benzoic acid and levulinic acid present in the solution is between 0.3 and 0.5 equivalents. κ C * C ko » molars based on nicotine. In one aspect, the combined amount of benzoic acid and levulinic acid present in the solution is between 0.2 and 0.4 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is between 0.1 and 0.6 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is between 0.1 and 0.5 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is between 0.2 and 0.6 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is between 0.1 and 0.4 molar equivalents based on nicotine. In one aspect, the amount of benzoic acid present in the solution is between 0.3 and 0.6 molar equivalents based on nicotine. In one respect, the amount of benzoic acid present in the solution is between 0.2 and 0.5 molar equivalents based on nicotine.In one aspect, the amount of benzoic acid present in the solution is between 0.3 and 0.5 molar equivalents based on nicotine. In another aspect, the amount of benzoic acid present in the solution is between 0.2 and 0.4 molar equivalents based on nicotine. In each of these aspects, preferably the only acid present is benzoic acid, and the nicotine solution contains the acid selected from the group consisting solely of benzoic acid. As set forth herein, the inventors have discovered that the levels of acid addition required by the present invention, i.e., where the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis, can be achieved through a > κ C * Nicotine solutions offer a wide range of nicotine content. Nicotine can provide solutions with desirable properties such as flavor, impact, irritation, smoothness, and / or nicotine reward for the user, whether the nicotine content is relatively low (e.g., 1.9% or 1.8% by weight) or lower, or relatively high (e.g., greater than 1.9% or 1.8% by weight). Therefore, in one respect, the nicotine solution comprises nicotine in an amount not greater than 1.9% or 1.8% by weight based on the total weight of the solution. Nicotine can be provided in any appropriate amount, depending on the desired dosage when inhaled by the user. In one aspect, nicotine is present in an amount not exceeding 6% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount between 0.4% and 6% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount between 0.8% and 6% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount between 1% and 6% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount between 1.8% and 6% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount between 0.4% and 5% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.8 and 5% by weight based on the total weight of the solution.In one aspect, nicotine is present in an amount of between 1 and 5% by weight based on the total weight of the >. κ C * C ko -X solution. In one aspect, nicotine is present in an amount of between 1.8 and % by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount not greater than 4% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.4 and 4% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.8 and 4% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 1 and 4% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 1.8 and 4% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount not greater than 3% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.4 and 3% by weight based on the total weight of the solution.In one aspect, nicotine is present in an amount of between 0.8 and 3% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 1 and 3% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 1.8 and 3% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount not greater than 1.9% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount not greater than 1.8% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.4 and 1.9% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.4 and 1.8% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.5 and 1.9% by weight based on the total weight of the solution.In one aspect, nicotine is present >. κ C28τ C κ ο > in an amount of between 0.5 and 1.8% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.8 and 1.9% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 1 and 1.9% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 1 and 1.8% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of less than 1.9% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of less than 1.8% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.4% and less than 1.9% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.4% and less than 1.8% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.5% and less than 1.9% by weight based on the total weight of the solution.In one aspect, nicotine is present in an amount of between 0.5 and less than 1.8% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.8 and less than 1.9% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 0.8 and less than 1.8% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 1 and less than 1.9% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount of between 1 and less than 1.8% by weight based on the total weight of the solution. In one respect, when levulinic acid is present, nicotine is > κ C * C ko » present in an amount not greater than 1.9% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 0.4 and 1.9% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 0.5 and 1.9% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 0.8 and 1.9% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 1 and 1.9% by weight based on the total weight of the solution. In one respect, when levulinic acid is present, nicotine is present in an amount less than 1.9% by weight based on the total weight of the solution.In one aspect, when levulinic acid is present, nicotine is present in an amount of between 0.4 and less than 1.9% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 0.5 and less than 1.9% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 0.8 and less than 1.9% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 1 and less than 1.9% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount not greater than 1.8% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount between 0.4 and 1.8% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine > κ C30τ C ko -X is present in an amount of between 0.5 and 1.8% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 0.8 and 1.8% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 1 and 1.8% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of less than 1.8% by weight based on the total weight of the solution. In one aspect, when levulinic acid is present, nicotine is present in an amount of between 0.4 and less than 1.8% by weight based on the total weight of the solution. In one respect, when levulinic acid is present, nicotine is present in an amount of between 0.5 and less than 1.8% by weight based on the total weight of the solution.In one aspect, when levulinic acid is present, nicotine is present in an amount of between 0.8 and less than 1.8% by weight based on the total weight of the solution. In another aspect, when levulinic acid is present, nicotine is present in an amount of between 1 and less than 1.8% by weight based on the total weight of the solution. In one aspect, nicotine is present in an amount less than 1.8% by weight, and the acids present are only benzoic acid, levulinic acid, or mixtures thereof. Therefore, in one aspect, the present invention provides a nicotine solution comprising: (i) a vehicle; (ii) nicotine in non-protonated and protonated forms, wherein the nicotine is present in an amount less than 1.8% by weight based on the total weight of the solution; and (iii) an acid selected from the group consisting of benzoic acid, levulinic acid, and mixtures thereof; and wherein the total acid content present in the solution is not greater than 0.6 molar equivalents based on the nicotine.In this respect, the combined amount of benzoic acid and levulinic acid present in the solution can be between 0.1 and 0.6 molar equivalents based on nicotine, for example between 0.1 and 0.5 molar equivalents based on nicotine, for example between 0.2 and 0.6 molar equivalents based on nicotine, for example between 0.1 and 0.4 molar equivalents based on nicotine, for example between 0.3 and 0.6 molar equivalents based on nicotine, for example between 0.2 and 0.5 molar equivalents based on nicotine, for example between 0.3 and 0.5 molar equivalents based on nicotine, for example between 0.2 and 0.4 molar equivalents based on nicotine. In one aspect, nicotine is present in an amount less than 1.9% by weight, and the acids present are only benzoic acid. Therefore, in one aspect, the present invention provides a nicotine solution comprising: (i) a vehicle; (ii) nicotine in non-protonated and protonated forms, wherein the nicotine is present in an amount less than 1.9% by weight based on the total weight of the solution; and (iii) an acid selected from the group consisting of benzoic acid, wherein the total acid content present in the solution is not greater than 0.6 molar equivalents based on the nicotine.In this respect, the amount of benzoic acid present in the solution can be between 0.1 and 0.6 molar equivalents based on nicotine, for example between 0.1 and 0.5 molar equivalents based on nicotine, for example between 0.2 and 0.6 molar equivalents based on nicotine, for example between 0.1 and 0.4 molar equivalents based on nicotine, for example between. 0.3 0.6 molar equivalents based on nicotine, for example between 0.2 0.5 molar equivalents based on nicotine, for example between 0.3 0.5 molar equivalents based on nicotine, for example between 0.2 0.4 molar equivalents based on nicotine. In one aspect, nicotine is present in an amount less than 1.8% by weight, and the acids present are only benzoic acid. Therefore, in one aspect, the present invention provides a nicotine solution comprising: (i) a vehicle; (ii) nicotine in non-protonated and protonated forms, wherein the nicotine is present in an amount less than 1.8% by weight based on the total weight of the solution; and (iii) an acid selected from the group consisting of benzoic acid, wherein the total acid content present in the solution is not greater than 0.6 molar equivalents based on the nicotine.In this respect, the amount of benzoic acid present in the solution can be between 0.1 and 0.6 molar equivalents based on nicotine, for example between 0.1 and 0.5 molar equivalents based on nicotine, for example between 0.2 and 0.6 molar equivalents based on nicotine, for example between 0.1 and 0.4 molar equivalents based on nicotine, for example between. 0.3 0.6 molar equivalents based on nicotine, for example between 0.2 0.5 molar equivalents based on nicotine, for example between 0.3 0.5 molar equivalents based on nicotine, for example between 0.2 0.4 molar equivalents based on nicotine. As someone experienced in the art will understand, the present invention requires that the nicotine be partially protonated before vaporization. This protonation can occur at any time before vaporization. In one aspect, the nicotine is partially protonated very shortly before vaporization. For example, the nicotine can be partially protonated as part of the process to provide vaporization. Therefore, it is foreseen that an 'in-line' process can be provided in which the nicotine in non-protonated form is partially protonated. κ C33τ The protonated C κ υ ~χ is brought into contact with the desired acid, and the resulting partially protonated nicotine solution is then vaporized. It is also envisaged that the necessary acid can be supplied to the end user and combined with the purchased non-protonated nicotine. The partially protonated nicotine solution can then be used in an electronic system that delivers vapor instead of the non-protonated nicotine.Therefore, in a further aspect, a set of elements for a nicotine solution of the invention is provided, wherein the set of elements comprises: (a) a nicotine solution comprising a vehicle and nicotine in its non-protonated form; and (b) one or more acids, including at least benzoic acid, levulinic acid, or a mixture thereof, in separate packages or containers; with instructions for mixing and / or bringing them into contact and / or using them to provide a partially protonated nicotine solution wherein the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. In a further aspect, a process for improving the organoleptic properties of the vaporizable nicotine solution is also provided, wherein the process comprises the following steps: (a) providing a nicotine solution comprising (i) a vehicle; (i) nicotine in non-protonated form; and (b) providing an acid solution comprising one or more acids, including at least benzoic acid, levulinic acid, or a mixture thereof; and (c) vaporizing the nicotine solution and the acid solution; and (d) combining the vaporized nicotine solution and the acid solution. κ C34τ C κ ο -X vaporized, in such a way that the acid is present in an amount that is not greater than 0.6 molar equivalents on a nicotine basis. The solution may be contained or delivered by any means. In one aspect, the present invention provides a nicotine solution in a container comprising (a) a container; and (b) a nicotine solution comprising: (i) a vehicle; (ii) nicotine in non-protonated and protonated forms; and (iii) one or more acids, including at least benzoic acid, levulinic acid, or a mixture thereof, and wherein the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. The container may be any suitable container, for example, for storage or delivery of the solution. In one aspect, the container is configured to be coupled to an electronic vapor delivery system.The container can be configured to establish fluid communication with an electronic vapor delivery system, such that the solution can be supplied to the electronic vapor delivery system. As described above, the present invention relates to a container that can be used in an electronic vapor delivery system, for example, an electronic cigarette. Throughout the following description, the term “electronic cigarette” is used; however, this term can be used synonymously with “electronic vapor delivery system.” As set forth herein, the container of the present invention is typically provided for administering a nicotine solution to or within an electronic cigarette. The nicotine solution may be contained within an electronic cigarette or may be marketed as a container. κ C35τ C κ ο » separated for subsequent use with or in an electronic cigarette. As someone familiar with the craft will understand, electronic cigarettes may contain a unit known as a detachable cartomizer, which typically comprises a nicotine solution reservoir, wicking material, and a heating element for vaporizing the nicotine. In some electronic cigarettes, the cartomizer is part of a single-piece device and is not detachable. In one sense, the container is a cartomizer or part of a cartomizer. In another sense, the container is not a cartomizer, or a part of it is not a cartomizer, but rather a receptacle, such as a tank, that can be used to deliver the nicotine solution to or into an electronic cigarette. In one aspect, the container is part of an electronic cigarette. Therefore, in a further aspect, the present invention provides an electronic vapor-providing system comprising: a vaporizer for vaporizing liquid to be inhaled by a user of the electronic system that provides vapor, a power supply comprising a cell or battery for supplying power to the vaporizer, a nicotine solution, comprising (i) a vehicle; (i) nicotine in non-protonated and protonated form; and (ii) one or more acids, among which at least benzoic acid, levulinic acid, or a mixture thereof are present, and wherein the total acid content present in the > κ C36τ C κ ο -X solution is not greater than 0.6 molar equivalents based on nicotine. In addition to the solution of the present invention and systems such as containers and electronic vapor delivery systems containing it, the present invention provides a process for improving the organoleptic properties of the nicotine solution for vaporization. The process comprises the steps of: (a) providing a nicotine solution comprising (i) a vehicle; (ii) nicotine in non-protonated and protonated forms; and (iii) one or more acids, including at least benzoic acid, levulinic acid, or a mixture thereof, wherein the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis; (b) vaporizing the nicotine solution. References to an improvement in the organoleptic properties of the nicotine solution for vaporization may include an improvement in the smoothness of the vaporized nicotine solution as perceived by a user. The process of the present invention may comprise additional steps either before the steps mentioned, after the steps mentioned, or between one or more of the steps mentioned. In addition to the solution of the present invention and systems such as containers and electronic vapor delivery systems containing it, the present invention provides for the use of one or more acids to improve the organoleptic properties of the nicotine solution for vaporization. The use of the nicotine solution comprises: (i) a vehicle; (ii) nicotine in non-protonated and protonated forms; and (iii) one or more acids, among which at least benzoic acid, levulinic acid, or a mixture of these are present. κ C * C κ ο -X same, and where the total acid content present in the solution is not greater than 0.6 molar equivalents on a nicotine basis. BRIEF DESCRIPTION OF THE FIGURES The present invention will now be described in more detail by means of examples, with reference only to the accompanying figure, where: Figure 1 shows a graph illustrating the variation of psKa2 with nicotine concentration The invention will now be described by reference to the following non-limiting example. Examples Determination of pKa values The determination of the pKa values ​​of nicotine in glycerol / water systems was carried out using the basic approach described in “Spectroscopic investigations into the acid-base properties of nicotine at different temperatures”, Peter M. Clayton, Cari A. Vas, Tam TT Bui, Alex F. Drake, and Kevin McAdam. Anal. Methods, 2013, 5, 81-88, and summarized below. Since the system is predominantly non-aqueous, the parameter psKa2 was measured, where the subscript s refers to the solvent composition in this mainly non-aqueous system, and the subscript 2 refers to the pKa value of the pyrrolidone nitrogen. Further information on the determination of nicotine pKa values ​​can be found in “Use of chiroptical spectroscopy to determine the ionisation status of (S)-nicotine in e-cigarette formulations and snus”, Clayton et al, ST 49, CORESTACongress, Québec City, Canada, October 12-16. κ C38τ C κ ο -X 2014 (available at http: / / www.batscience.com / groupms / s¡tes / BAT_9GVJXS.nsf / vwPagesWebL¡ve / DO9PVC3G / $ FILE / CORESTA_PC_2014.pdf) A range of glycerol / water / nicotine solutions was prepared, with the water concentration set at 9%, the nicotine concentration ranging between 30pg / ml and 3mg / ml; and where the glycerol content is the remainder of the solutions. Simultaneous UV and CD spectra of glycerol / nicotine / water solutions were measured on a Chirascan Plus spectrometer from Applied Photophysics Ltd (Leatherhead, UK). UV and CD absorbance spectra were measured in the 300–200 nm region, with various optical path lengths depending on the nicotine concentration of the solution—10 mm, 5 mm, 2 mm, 1 mm, 0.5 mm, 0.1 mm, and 0.01 mm. The instrument was continuously rinsed with pure evaporated nitrogen during all measurements. Spectra were recorded with a 0.5 nm step size, a 1 s measurement time per point, and a spectral bandwidth of 2 nm. Where possible, all CD spectra were smoothed with a window factor of 4 using the Savitzky-Golay method for improved visualization. S-nicotine solutions in glycerol / water were pH titrated at 23°C. The pH of these solutions was raised to alkaline values ​​by adding small aliquots of NaOH (~pH 10) and then lowered to pH 2 by adding small aliquots of HCl. A series of HCl and NaOH solutions (0.1 M, 0.5 M, 1 M, 5 M, and 10 M) were used during the pH titration. pH values ​​were measured at 23°C using a Corning pH 105 pH meter with a pH RMS electrode. The psKa2 values ​​changed systematically with the nicotine concentration (Figure 1), and therefore psKa2 values ​​were calculated for each nicotine concentration level (Table 1). Due to the viscosity of the solutions, and the optical density in the CD spectra of the solutions with high nicotine concentration, for nicotine concentrations greater than 3mg / ml, very short optical path cells were required.At these concentrations, satisfactory sample preparations and spectroscopies could not be obtained with the small cells required, and therefore the psKa2 at higher concentrations were calculated by regression fitting of Figure 1. Table 1: psKa2 values ​​measured at various nicotine concentrations in a 9% water, nicotine / glycerol system. PsKa2 conc (g / L) conc (mM) logia [cone] 7.49 Π 0.185 -0.732 7.34 CO oooo -C 431 / ,·3θ 0.3 1.85 268 7.27 0.6 3.70 0.569 7.25 18.53 1 .,268 The curve fitting, using the equation y = 0.0233e('(log10[Nicotinal) / 0.325) + 7.26), yielded a psKa2 value of 7.26 with a nicotine concentration of 30 mg / ml. Using this psKa2 value with the Henderson-Hasselbalch equation allows the calculation of the degree of nicotine protonation at any pH value. Example 1 > κ “ C κ ο > A series of tests were carried out using electronic cigarettes Vype E-pen. The “non-protonated nicotine control” devices were loaded with a solution containing 1.86% (w / w) nicotine, 25% propylene glycol containing tobacco flavor “A”, 25% water, and 48.1% glycerol. A pH of 8.7 was measured in this solution, indicating 4% protonation of the nicotine. A similar set of devices was prepared in which 0.55% w / w (0.4 meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content reduced proportionally to 47.6% w / w. A pH of 7.4 was measured in this solution, indicating 43% protonation of the nicotine. A third set of devices was prepared in which 0.25% w / w (0.2 Meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content adjusted proportionally to 47.9% w / w. A pH of 7.8 was measured in this solution, indicating a 24% protonation of the nicotine. Each of these e-cigarettes was presented to 15 panelists comprising e-cigarette users, and the panelists were asked to vape the e-cigarettes using a monodic approach in sequence for 10 puffs with each device. They were then asked to identify their preferred e-cigarette from the three offered. Of the panelists, 7 preferred the control electronic cigarette with non-protonated nicotine, and 8 people preferred the acidified samples - 4 preferred the device with 0.2Meq and 4 preferred the device with 0.4Meq. Example 2 > κ C * C κ ο A series of tests were conducted using Vype E-pen electronic cigarettes. The “non-protonated nicotine control” devices were loaded with a solution containing 1.86% (w / w) nicotine, 35.3% mint-flavored propylene glycol, 25% water, and 37.9% glycerol. This solution had a pH of 9.7, indicating <1% nicotine protonation. A similar set of devices was prepared in which 0.55% w / w (0.4 meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content reduced proportionally to 37.3% w / w. This solution had a pH of 7.4, indicating 43% protonation of the nicotine. A third set of devices was prepared in which 0.25% w / w (0.2 Meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content adjusted proportionally to 37.6% w / w. This solution had a pH of 7.8, indicating 22% protonation of the nicotine. Each of these e-cigarettes was presented to 15 panelists comprising e-cigarette users, and the panelists were asked to vape the e-cigarettes using a monodic approach in sequence for 10 puffs with each device. They were then asked to identify their preferred e-cigarette from the three offered. Of the panelists, 4 preferred the control electronic cigarette with non-protonated nicotine, and 11 people preferred the acidified samples - 2 preferred the device with 0.2Meq and 9 preferred the device with 0.4Meq. Example 3 A series of tests were carried out using electronic cigarettes > κ C * C κ ο -X Vype E-pen. The “non-protonated nicotine control” devices were loaded with a solution containing 1.86% (w / w) nicotine, 25% cherry-flavored propylene glycol, 25% water, and 48.1% glycerol. This solution had a pH of 8.4, indicating a nicotine protonation level of 7%. A similar set of devices was prepared in which 0.55% w / w (0.4 meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content reduced proportionally to 47.6% w / w. This solution had a pH of 7.4, indicating a nicotine protonation level of 43%. A third set of devices was prepared in which 0.25% w / w (0.2 meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content adjusted proportionally to 47.9% w / w. This solution had a pH of 7.8, indicating a nicotine protonation level of 24%. Each of these e-cigarettes was presented to 15 panelists comprising e-cigarette users, and the panelists were asked to vape the e-cigarettes using a monodic approach in sequence for 10 puffs with each device. They were then asked to identify their preferred e-cigarette from the three offered. Panelists preferred the control electronic cigarette with non-protonated nicotine, and 12 people preferred the acidified samples - 8 preferred the device with 0.2Meq and 4 preferred the device with 0.4Meq. Example 4 A series of tests were carried out using electronic cigarettes > κ C43τ C κ υ ~χ Vype E-pen. The “non-protonated nicotine control” devices were loaded with a solution containing 1.86% (w / w) nicotine, 25% propylene glycol containing tobacco flavor “A”, 25% water, and 48.1% glycerol. This solution had a pH of 8.6, indicating a nicotine protonation level of 4%. A similar set of devices was prepared in which 0.41% w / w (0.3 meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content reduced proportionally to 47.7% w / w. This solution had a pH of 7.7, indicating a nicotine protonation level of 26%. A third set of devices was prepared in which 0.39% w / w (0.3 meq on a nicotine basis) of levulinic acid was added to the formulation, with the glycerol content adjusted proportionally to 47.8% w / w. This solution had a pH of 7.26, indicating a 50% protonation level of nicotine. Each of these e-cigarettes was presented to 14 panelists comprising e-cigarette users, and the panelists were asked to vape the e-cigarettes using a monodic approach in sequence for 10 puffs with each device. They were then asked to identify their preferred e-cigarette from the three offered. Panelists preferred the control electronic cigarette with non-protonated nicotine, and 11 people preferred the acidified samples - 7 preferred the device with 0.3Meq of benzoic acid and 4 preferred the device with 0.3Meq of levulinic acid. Example 5 > κ C * C κ ο -X A series of tests were carried out using electronic cigarettes Vype E-pen. The “non-protonated nicotine control” devices were loaded with a solution containing 1.8% (w / w) nicotine, 25% propylene glycol containing tobacco flavor “B”, 25% water, and 48.1% glycerol. This solution had a pH of 9.3, indicating a nicotine protonation level of 1%. A similar set of devices was prepared in which 0.41% w / w (0.3 meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content reduced proportionally to 47.7% w / w. This solution had a pH of 7.7, indicating a nicotine protonation level of 28%. A third set of devices was prepared in which 0.39% w / w (0.3 meq on a nicotine basis) of levulinic acid was added to the formulation, with the glycerol content adjusted proportionally to 47.8% w / w. This solution had a pH of 7.4, indicating a nicotine protonation level of 41%. Each of these e-cigarettes was presented to 11 panelists comprising e-cigarette users, and the panelists were asked to vape the e-cigarettes using a monodic approach in sequence for 10 puffs with each device. They were then asked to identify their preferred e-cigarette from the three offered. Of the panelists, 4 preferred the control electronic cigarette with non-protonated nicotine, and 7 people preferred the acidified samples - 4 preferred the device with 0.3Meq of benzoic acid and 3 preferred the device with 0.3Meq of levulinic acid. > κ C45τ C ko » Example 6 A series of tests were conducted using Vype E-stick electronic cigarettes. The “non-protonated nicotine control” devices were loaded with a solution containing 4% (w / w) nicotine, 25% cherry-flavored propylene glycol, 9% water, and 62% glycerol. This solution had a pH of 8.3, indicating a nicotine protonation level of 7%. A similar set of devices was prepared in which 1.2% wt% (0.4 meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content reduced proportionally to 60.8% wt%. This solution had a pH of 7.4, indicating a nicotine protonation level of 41%. A third set of devices was prepared in which 1.15% w / w (0.4 meq on a nicotine basis) of levulinic acid was added to the formulation, with the glycerol content adjusted proportionally to 60.9% w / w. This solution had a pH of 6.9, indicating a nicotine protonation level of 68%. Each of these e-cigarettes was presented to 11 panelists comprising e-cigarette users, and the panelists were asked to vape the e-cigarettes using a monodic approach in sequence for 10 puffs with each device. They were then asked to identify their preferred e-cigarette from the three offered. Of the panelists, one preferred the control e-cigarette with non-protonated nicotine, and 10 people preferred the acidified samples - 6 preferred the device with 0.4 Meq of benzoic acid and 4 preferred the > κ C * C κ ο -X device with 0.4Meq of levulinic acid. Example 7 A series of tests were conducted using Vype E-stick electronic cigarettes. The “non-protonated nicotine control” devices were loaded with a solution containing 4% (w / w) nicotine, 36.5% mint-flavored propylene glycol, 9% water, and 50.5% glycerol. This solution had a pH of 9.6, indicating a nicotine protonation level of <1%. A similar set of devices was prepared in which 1.2% wt% (0.4 meq on a nicotine basis) of benzoic acid was added to the formulation, with the glycerol content reduced proportionally to 49.3% wt%. This solution had a pH of 7.3, indicating a nicotine protonation level of 51%. A third set of devices was prepared in which 1.15% w / w (0.4 Meq on a nicotine basis) of levulinic acid was added to the formulation, with the glycerol content adjusted proportionally to 49.35% w / w. This solution had a pH of 6.8, indicating a nicotine protonation level of 73%. Each of these e-cigarettes was presented to 11 panelists comprising e-cigarette users, and the panelists were asked to vape the e-cigarettes using a monodic approach in sequence for 10 puffs with each device. They were then asked to identify their preferred e-cigarette from the three offered. Of the panelists, 2 preferred the control e-cigarette with non-protonated nicotine, and 9 people preferred the acidified samples - 5 > κ C * C ko » preferred the device with 0.4Meq of benzoic acid and 4 preferred the device with 0.4Meq of levulinic acid. Example 8 A series of tests were conducted using Vype E-pen electronic cigarettes. The devices were loaded with the following solutions A - 1.86% wt% nicotine, 0.42% wt% benzoic acid (~0.3 Meq based on nicotine), 47.72% wt% glycerol, 25% wt% water, 19.5% wt% propylene glycol and 5.5% wt% flavoring B - 1.86% wt% nicotine, 0.42% wt% benzoic acid (~0.3 Meq based on nicotine), 47.72% wt% glycerol, 25% wt% water, 13% wt% propylene glycol and 12% wt% flavoring C - 1.86% wt% nicotine, 0.42% wt% benzoic acid (~0.3 Meq based on nicotine), 37.22% wt% glycerol, 25% wt% water, 30% wt% propylene glycol and 5.5% wt% flavoring There will be various modifications and variations of the present invention that will be obvious to those skilled in the art without departing from the scope or spirit of the invention. Although the invention has been described with regard to specific preferred embodiments, it should be understood that the invention, as claimed, should not be unduly restricted to such specific embodiments. Indeed, it is the intention that the various modifications to the described embodiments for carrying out the invention that are obvious to those skilled in the fields of chemistry or related fields be within the scope of the following claims.

Claims

CLAIMS 1. A nicotine solution characterized in that it comprises (i) a vehicle; (ii) nicotine in non-protonated form and in protonated form; and (iii) benzoic acid.

2. A nicotine solution according to claim 1 further comprising water.

3. A nicotine solution according to claim 1 or 2 wherein the nicotine solution contains no more than 0.1 molar equivalents, based on nicotine, of each of lactic acid, acetic acid, and succinic acid.

4. A nicotine solution according to claim 1 to 3 wherein the nicotine solution contains no more than 0.01 molar equivalents, based on nicotine, of each of lactic acid, acetic acid, and succinic acid.

5. A nicotine solution according to any of claims 1 to 4 comprising nicotine in an amount not greater than 2% by weight based on the total weight of the solution.

6. A nicotine solution according to any of claims 1 to 4 comprising nicotine in an amount not greater than 1.8% by weight based on the total weight of the solution.

7. A nicotine solution according to any of claims 1 to 6 wherein the vehicle is a solvent.

8. A nicotine solution according to claim 7 wherein the solvent is selected from: glycerol, propylene glycol and mixtures thereof.

9. A nicotine solution in a container characterized in that N C ι\ comprises (a) a container; and (b) a nicotine solution, comprising (i) a vehicle; (ii) nicotine in non-protonated form and in protonated form; and (iii) benzoic acid.

10. A nicotine solution in a container according to claim 9, wherein the nicotine solution further comprises water.

11. A nicotine solution in a container according to claim 10 wherein the container is configured to be coupled to an electronic vapor-providing system.

12. A nicotine solution in a container according to claim 10 or 11 wherein the nicotine solution is as defined in any of claims 2 to 8.

13. An electronic vapor-providing system characterized in that it comprises: a vaporizer for vaporizing liquid to be inhaled by a user of the electronic vapor-providing system, a power supply comprising a cell or battery for supplying power to the vaporizer, and a nicotine solution comprising (i) a carrier; (ii) nicotine in non-protonated and protonated form; and (iii) benzoic acid.

14. An electronic system providing vapor according to claim 13 wherein the nicotine solution is as defined in any of claims 2 to 8.

15. A process for improving the organoleptic properties of a nicotine solution for vaporization, the process being characterized in that it comprises the steps of: (a) providing a nicotine solution comprising (i) a vehicle; (ii) nicotine in non-protonated and protonated forms; and (iii) benzoic acid; (b) vaporizing the nicotine solution 16. A process according to claim 15 wherein the nicotine solution is as defined in any of claims 2 to 8.

17. The use of one or more acids to improve the organoleptic properties of the nicotine solution for vaporization, wherein the nicotine solution is characterized in that it comprises (i) a vehicle; (ii) nicotine in non-protonated and protonated form; and (iii) benzoic acid.