Method for determining the moisture content in a sample using sulfonic acid

Abstract

A first method for determining moisture content in a sample includes the steps of providing a reagent comprising sulfur dioxide or a derivative thereof; a base; optionally a hydrogen halide or a hydrogen halide donor; a solvent; and a sulfonic acid; and titrating the sample with the reagent. A second method for determining moisture content in a sample includes the steps of providing the reagent described above, mixing the sample with the reagent; and adding an iodine source to the sample and / or the reagent. The reagent can alternatively consist essentially of sulfur dioxide or a derivative thereof; imidazole and / or a derivative thereof; optionally a hydrogen halide or a hydrogen halide donor; acetonitrile; methanesulfonic acid; and methanol and / or ethanol.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 107,233, filed on October 29, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to a method for determining the moisture content in a sample using sulfonic acid. The present disclosure more specifically relates to the use of sulfur dioxide or a derivative thereof, a base, a solvent, and one or more types of sulfonic acid. Background Art

[0004] The determination of water according to the Karl Fischer method (i.e., by Karl Fischer titration) utilizes the following reaction, in which the stoichiometry between iodine and water is 1:1:

[0005] In alcoholic or protic solutions:

[0006]

[0007]

[0008] In non-alcoholic or aprotic solutions:

[0009]

[0010] Unwanted side reactions (e.g., Bunsen reaction (4) and SO3 hydrolysis reaction (5)) lead to deviations from the desired 1:1 stoichiometry, which results in too low a water content being found in cases where the overall stoichiometry between iodine and water is 1:n, where n = 1-2.

[0011] (4) 2H2O+SO2+I2→H2SO4+2HI

[0012]

[0013] Where B is a base and ROH is an alcohol. This titration is performed in two basic forms: volumetric and coulometric.

[0014] In a typical Karl Fischer titration, the reagent contains an alkyl sulfite, which is oxidized in the presence of water to form an alkyl sulfate. Karl Fischer titrations are typically performed in an alcoholic solution, such as methanol. The use of a large amount of alcohol helps stabilize the stoichiometry of the Karl Fischer reaction by shifting the equilibrium toward reactions (1) and (2). However, unwanted side reactions (4) and (5) may still occur.

[0015] It has been described in the literature to stabilize stoichiometry using reagents that include excess pyridine. However, in such systems, the water equivalent that can be determined depends greatly on the experimental conditions. For example, in such systems, a pyridine-SO3 adduct is formed that participates in a water-consuming side reaction (5) that can falsely alter the titration results.

[0016] Furthermore, one difficulty with using non-alcoholic (aprotic) Karl Fischer reagents is the variation in stoichiometry. Depending on the aprotic solvent and base used, the ratio of iodine to water in the Karl Fischer reaction is typically 1 : 1-2 (rather than 1 : 1). If the hydrolysis of the base-SO3 adduct could be suppressed, then the stoichiometry of I2:H2O would still be 1 : 1.

[0017] Therefore, there remains an opportunity to develop a Karl Fischer reagent with a stoichiometry that is stabilized to 1 : 1 that allows for highly accurate titrations in both alcoholic and non-alcoholic solvents. SUMMARY

[0018] The present disclosure describes embodiments that utilize sulfonic acids to stabilize the Karl Fischer reaction stoichiometry (I2:H2O, 1 : 1) in both protic and aprotic solvents. In other words, by adding a sulfonic acid to the Karl Fischer reagent, the aforementioned unwanted side reactions (such as (4) and (5)) can be better suppressed.

[0019] The present disclosure provides a first method for determining the moisture content in a sample, the first method comprising the steps of: providing a reagent comprising: sulfur dioxide or a derivative thereof; a base; optionally a hydrogen halide or a hydrogen halide donor; a solvent; and a sulfonic acid; and titrating the sample with the reagent.

[0020] The present disclosure also provides a second method for determining the moisture content in a sample. The method comprises the steps of: providing the above-mentioned reagent, mixing the sample with the reagent; and adding an iodine source to the sample and / or the reagent.

[0021] The present disclosure also provides a reagent that can alternatively consist essentially of: sulfur dioxide or a derivative thereof; imidazole and / or a derivative thereof; optionally a hydrogen halide or a hydrogen halide donor; methanesulfonic acid; acetonitrile and / or methanol and / or ethanol and / or 1 -methoxy-2-propanol and / or propylene glycol. DETAILED DESCRIPTION

[0022] The following detailed description is merely exemplary in nature and is not intended to limit the method or reagent. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

[0023] Embodiments of the present disclosure generally relate to titration methods and solutions thereof. For the sake of brevity, the traditional technology can not be described in detail herein. Furthermore, the various tasks and process steps described herein can be incorporated in more comprehensive processes or programs having additional steps or functions, as would be understood by those of ordinary skill. In particular, the various steps of the titration method are well known, and thus for brevity, many conventional steps will not be described in detail herein, without providing well-known process details. Various desired features and characteristics of the present disclosure will become apparent from the detailed description of the present disclosure and the appended claims, taken in conjunction with the accompanying drawings and the background of the present disclosure.

[0024] The present disclosure provides a method for determining the moisture content in a sample. Generally, the method can be described as a version or variation of Karl Fischer titration for determining the content of moisture or humidity in a sample. Generally, there are two methods for performing Karl Fischer titration. The first method is known as volumetric Karl Fischer titration. In this titration, the determination of the moisture content in the sample is based on the amount or volume of reagent used for the conversion of moisture. In this titration, the sample is dissolved in a solvent before the titration begins. The reagent is added until the moisture is removed.

[0025] The second method is known as coulometric Karl Fischer titration. In this titration, the reagent is mixed with the solvent in a titration cell. When the sample is introduced into the titration cell and dissolved, iodine is released by an induced current. The amount of current needed for the conversion of moisture is determinative of the moisture content in the sample. One advantage of coulometric Karl Fischer titration is the ability to accurately measure small amounts of moisture content (e.g., as low as 0.1 microgram (pg) of moisture). The various titrations are described in more detail below.

[0026] Referring now to the sample itself, the sample can be any kind of sample that contains moisture. The moisture content in the sample is not particularly limited and can be selected by one of skill in the art. For example, in coulometric titration, the moisture content in the sample is about 0.1 pg to about 10,000 pg of moisture, about 0.1 pg to about 3,000 pg of moisture, about 20 pg to about 3,000 pg of moisture, or about 1 pg to about 10,000 pg of moisture. In volumetric titration, the moisture content can be much greater than 10,000 pg. In other embodiments, the maximum moisture content is determined by the size of the vessel due to the amount of reagent required. The sample can be a liquid, gas, or solid, provided that the sample contains an amount of moisture. The sample is typically a liquid that contains an amount of moisture. In various embodiments, the reagents of the present disclosure are used with traditionally problematic samples that have side reactions with traditional reagents (e.g., solutions of ketones and / or aldehydes and unsaturated compounds (e.g., vinylene carbonate)).

[0027] The method includes a step of providing a reagent. Optionally, the reagent can be described as a "Karl Fischer reagent." The reagent is used to titrate a sample containing an amount of moisture therein. For example, the reagent can be used in the Karl Fischer method described above (e.g., volumetric titration or coulometric titration). For example, when used in a coulometric titration, the reagent can be described as a titration solution. In a volumetric titration, the reagent of the present disclosure can be used as a solvent, for example, in one or both of the component reagents. In addition, a mixture of iodine and the reagent can be used as a single component reagent.

[0028] The reagent can be free of alcohol or can include alcohol. Generally, the term "free of" describes embodiments containing less than 30 wt.%, 20 wt.%, 10 wt.%, 9 wt.%, 8 wt.%, 7 wt.%, 6 wt.%, 5 wt.%, 4 wt.%, 3 wt.%, 2 wt.%, 1 wt.%, 0.5 wt.%, 0.1 wt.%, 0.05 wt.%, or 0.01 wt.% of alcohol, based on the total weight of the reagent. In one embodiment, the reagent is completely free of alcohol (i.e., contains 0 wt.% of alcohol or an amount of alcohol below typical detection limits). Optionally, the reagent can include any alcohol, including but not limited to: methanol, ethanol, propanol, mono- and di- glycol monoalkyl ethers, and combinations thereof. In one embodiment, the reagent includes a solvent that includes or is an alcohol selected from the group consisting of methanol, ethanol, propanol, 1-methoxypropan-2-ol, mono- and di-glycol monoalkyl ethers, and combinations thereof.

[0029] The reagent includes: sulfur dioxide or a derivative thereof; a base; optionally a hydrogen halide donor or a hydrogen halide; a solvent; and a sulfonic acid; and a step of titrating a sample with the reagent. The reagent can be, consist essentially of, or consist of the compounds described above. The term "consist essentially of can describe embodiments that are free of compounds that are not a hydrogen halide donor or a hydrogen halide. Alternatively, the term "consist essentially of can describe embodiments that include or are free of one or more soluble halides that are not a hydrogen halide donor described above or a second imidazole derivative described below. For example, the reagent can include or be free of one or more of sodium halide, or a halide of an organic cation (e.g., tetrabutylammonium iodide, imidazole hydrogen iodide, or trimethylamine hydrogen iodide), and / or a dissociated organic salt (e.g., one or more of tetrabutylammonium chloride, diethanolamine hydrogen bromide, guanidinium salts (e.g., guanidinium benzoate), and / or combinations thereof. The reagent can include or be free of imidazole itself. The reagent can also include or be free of nitrogen bases, such as: salts or carboxylic acids, such as tetramethylammonium acetate, trimethylammonium acetate, tetrabutylammonium benzoate, lithium propanoate acetate, propanoic acid, butyric acid, benzoic acid, buffering substances (e.g., diethanolammonium benzoate or imidazolium acetate), or combinations thereof.

[0030] Throughout the specification, it is contemplated that whenever the term "halide" is used, any halide can be used, i.e., fluorine, chlorine, bromine, iodine, or combinations thereof, in various non-limiting embodiments. Further, whenever the term "iodide" is used, it can be used in place of fluoride, chloride, or bromide, in other non-limiting embodiments.

[0031] Sulfur dioxide or a derivative thereof:

[0032] With the foregoing in mind, the reagent comprises sulfur dioxide (S02) or a derivative thereof. As understood by one of skill in the art, the term "derivative thereof" describes a compound that acts the same or substantially similar to sulfur dioxide in Karl Fischer titration. For example, derivatives that can be used include, but are not limited to, reducing agents, i.e., sulfites (e.g., dimethyl sulfite, diethyl sulfite, and combinations thereof).

[0033] In another embodiment, the sulfur dioxide or derivative thereof is present in an amount of about 0.05 moles per liter of reagent to about 5 moles per liter of reagent. In other embodiments, the sulfur dioxide or derivative thereof is present in an amount of about 0.05 moles per liter of reagent to about 1 moles per liter of reagent, about 0.1 moles per liter of reagent to about 1 moles per liter of reagent, or about 0.1 moles per liter of reagent to about 0.5 moles per liter of reagent. In various non-limiting embodiments, all values and ranges of values between and including the above-noted values (including integers and decimals) are expressly contemplated for use herein.

[0034] Base :

[0035] Referring now to the base, the base can be any base known in the art that is suitable for use in Karl Fischer titration. For example, the base can be a nitrogen-containing base, or can be a non-nitrogen-containing base. For example, the base can be a primary amine, a secondary amine, or a tertiary amine. In alternative embodiments, the base can be pyridine or a derivative thereof. In another embodiment, the base can be a primary amine. Alternatively, the base can be imidazole, a derivative of imidazole, or combinations thereof. The base and reagent can comprise less than 10 wt.%, 9 wt.%, 8 wt.%, 7 wt.%, 6 wt.%, 5 wt.%, 4 wt.%, 3 wt.%, 2 wt.%, 1 wt.%, 0.5 wt.%, or 0.1 wt.% pyridine, or can be completely free of pyridine.

[0036] In various embodiments, the reagent comprises a molar ratio of base to sulfur dioxide or derivative thereof that is greater than or less than 1 : 1. In various embodiments, the molar ratio of base to sulfur dioxide or derivative thereof is about 1.5: 1, about 2: 1, about 2.5: 1, about 3: 1, about 3.5: 1, about 4: 1, about 4.5: 1, about 5: 1, about 5.5: 1, about 6: 1, about 6.5: 1, about 7: 1, about 7.5: 1, about 8: 1, about 8.5: 1, about 9: 1, about 9.5: 1, about 10: 1, about 10.5: 1, about 11: 1, about 11.5: 1, about 12: 1, about 12.5: 1, about 13: 1, about 13.5: 1, about 14: 1, about 14.5: 1, about 15: 1, about 15.5: 1, about 16: 1, about 16.5: 1, about 17: 1, about 17.5: 1, about 18: 1, about 18.5: 1, about 19: 1, about 19.5: 1, or about 20: 1. It is also contemplated that each of these molar ratios can be reversed, thereby indicating a molar ratio of base to sulfur dioxide or derivative thereof that is less than 1: 1. In various embodiments, if a liquid base is used, the molar ratio can be much higher than 20: 1, for example, 30: 1, 40: 1, or 50: 1, or even higher. In one embodiment, the molar ratio of base to sulfur dioxide or derivative thereof is greater than 2: 1. In another embodiment, the molar ratio of base to sulfur dioxide or derivative thereof is greater than 5: 1. In yet another embodiment, the molar ratio of base to sulfur dioxide or derivative thereof is about 14: 1. Further, it is contemplated that the reagent can comprise an amount that is “greater than” any of the above ratios, for example, “greater than” about 2: 1, greater than about 2.5: 1, etc. In other embodiments, the base is present in an amount of about 0.5 moles per liter of reagent to about 5.5 moles per liter of reagent, or about 0.5 moles per liter of reagent to about 5 moles per liter of reagent, or about 0.5 moles per liter of reagent to about 2.5 moles per liter of reagent. In various non-limiting embodiments, it is also contemplated that all values and ranges of values between and including the above values (including integers and fractions) are expressly contemplated for use herein.

[0037] Reference is now made to the imidazole derivative, which can be described as the “first derivative of imidazole,” especially when a “second” derivative is used, as described below. It is understood that “imidazole derivative” and “first derivative of imidazole” are used interchangeably throughout.

[0038] The first derivative of imidazole can have the following structure:

[0039]

[0040] wherein R, R 1 and R 2each of R, R and R is independently a hydrogen atom, a phenyl group, a substituted phenyl group, a first hydrocarbyl group having 1 to 6 carbon atoms, or a second hydrocarbyl group having 1 to 6 carbon atoms interrupted at at least one position by a heteroatom. In this structure, R, R 1 and R 2 cannot both be hydrogen atoms, as that would be the imidazole itself. In various embodiments, the first hydrocarbyl group has 1, 2, 3, 4, 5, or 6 carbon atoms. The second hydrocarbyl group can also independently comprise 1, 2, 3, 4, 5, or 6 carbon atoms, wherein at one or more points in the chain of the group, the heteroatom includes, but is not limited to, nitrogen, oxygen, phosphorus, chlorine, bromine, or iodine. Further, each of R, R 1 and R 2 may be located at any point on the ring. In another embodiment, each of R, R 1 and R 2 is independently a hydrogen atom or a methyl, ethyl, propyl, or butyl group, with the proviso that R, R 1 and R 2 are not all hydrogen atoms.

[0041] In various embodiments, the first imidazole derivative is present in the reagent in the amounts described above with respect to the base and sulfur dioxide or its derivatives. In other embodiments, the first imidazole derivative is present in an amount of about 0.5 moles per liter of reagent to about 5.5 moles per liter of reagent, or about 0.5 moles per liter to about 5 moles per liter of reagent, or about 0.5 moles per liter to about 2.5 moles per liter of reagent. In other embodiments, the first imidazole derivative is present in an amount that reflects one or more of the above-described greater than 1:1 molar ratios of the first imidazole derivative to sulfur dioxide or its derivatives. For example, regardless of the number of moles of sulfur dioxide or its derivatives in the reagent, the first imidazole derivative can be present in a greater than 1:1 molar amount, for example, in any of the above-described ratios or, for example, as used in excess as a solvent. In various non-limiting embodiments, all values and ranges of values between and including the above-described values are expressly contemplated for use herein, including integers and decimals.

[0042] Hydrogen halide donor :

[0043] Referring now to the hydrogen halide donor, the donor can be a hydrogen halide of an amine. The amine can be any amine known in the art (including imidazoles), such that the donor can be a hydrohalide of the imidazole itself, for example: a hydroiodide, a hydrochloride, or a hydrobromide. Further, the amine can be any amine described herein. In various embodiments, the amine is an optionally substituted aliphatic amine, a cyclic amine, a heterocyclic amine, or an aromatic amine (e.g., pyridine and derivatives thereof), a trialkylamine (e.g., trimethylamine, triethylamine, tri-n-butylamine), N,N-dimethylethylamine, N,N-diethylmethylamine, imidazole, N-ethylmorpholine, N-methylmorpholine, 2-morpholinoethanol, 1-methylpiperidine, 1-ethylpiperidine, 1-methylpyrrolidine, 2-(dimethylamino)-2-methyl-1-propanol, diethanolamine, pyridine and derivatives thereof, and combinations thereof. Thus, the hydrogen halide donor can be a hydrogen iodide / hydrogen bromide / hydrogen chloride of any of the amines described above. The reagent can not contain any of the hydrogen halide donors described above, but rather utilizes a hydrogen halide donor described immediately below.

[0044] In one embodiment, the hydrogen halide donor is a hydrohalide of a second imidazole derivative (e.g., a hydroiodide of a second imidazole derivative). In one embodiment, the hydrogen halide donor is a hydrobromide of a second imidazole derivative. In another embodiment, the hydrogen halide donor is a hydrochloride of a second imidazole derivative.

[0045] In one embodiment, the hydrogen halide donor is a hydroiodide, a hydrobromide, a hydrochloride, or a combination thereof of a second imidazole derivative, wherein the second imidazole derivative can have the structure:

[0046]

[0047] wherein R, R 1 and R 2 each independently is a hydrogen atom, a phenyl group, a substituted phenyl group, a first hydrocarbyl group having 1 to 6 carbon atoms, or a second hydrocarbyl group having 1 to 6 carbon atoms interrupted at at least one point by a heteroatom. In one structure, R, R 1 and R 2 cannot both be hydrogen atoms. In another embodiment, each of R, R 1 and R 2 is a hydrogen atom. In various embodiments, the first hydrocarbyl group has 1, 2, 3, 4, 5, or 6 carbon atoms. The second hydrocarbyl group can also independently comprise 1, 2, 3, 4, 5, or 6 carbon atoms, wherein at one or more points in the chain of the group, the heteroatom includes, but is not limited to, nitrogen, oxygen, phosphorus, chlorine, bromine, or iodine. Further, each of R, R 1 and R 2 may be located at any point on the ring. R, R 1 and R2 each of R, R 1 and R 2 may be different than the above R, R 1 and R 2 of the first imidazole derivative. 3 4 5 In another embodiment, each of R, R 1 and R 2 is independently a hydrogen atom or a methyl, ethyl, propyl or butyl group, with the proviso that R, R 1 and R 2 are not all hydrogen atoms.

[0048] The hydrohalide can be a hydriodide, a hydrochloride or a hydrobromide of any of the above amines or combinations thereof. In other words, the hydrohalide can be a hydriodide / bromide / chloride acid with any of the above amines or any of the above embodiments of the second imidazole derivative, as understood by one of skill in the art. Except that the second imidazole derivative is a hydrohalide, the second imidazole derivative and the first imidazole derivative can have the same general structure. In other words, the only difference between the first imidazole derivative and the second derivative can be that the first imidazole derivative is not a hydrohalide, while the second derivative is a hydrohalide, even though the five-membered ring structure and the substituents can be the same or substantially the same.

[0049] The halogenated hydrogen donor can be only any of the above compounds, can be only a hydrohalide of the second imidazole derivative or can comprise combinations thereof. The halogenated hydrogen can be a hydriodide, a hydrochloride or a hydrobromide or combinations thereof without an amine donor.

[0050] The halogenated hydrogen donor or the halogenated hydrogen can be present in any amount selected by one of skill in the art, such as in an amount of about 0.01 mole per liter of reagent to about 5 moles per liter of reagent, about 0.1 mole per liter of reagent to about 2 moles per liter of reagent, about 0.2 mole per liter of reagent to about 1.5 moles per liter of reagent or about 0.2 mole per liter of reagent to about 1 mole per liter of reagent. In various non-limiting embodiments, all values and ranges of values between and including the above values are expressly contemplated for use herein, including integers and decimals.

[0051] The reagent can also comprise a halogenated hydrogen acceptor. The acceptor can have a pK A ​​The receptor can be any receptor known in the art, including but not limited to: an optionally substituted aliphatic amine, a cyclic amine, a heterocyclic amine, or an aromatic amine (e.g., pyridine and derivatives thereof), a trialkylamine (e.g., trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine), N,N-dimethylethylamine, N,N-diethylmethylamine, N,N-dimethyl-n-butylamine, N,N,N',N'-tetramethylethylenediamine, imidazole, 1-methylpiperidine, 1-ethylpiperidine, 1,2-dimethylpyrrolidine, 2-(dimethylamino)-2-methyl-1-propanol, 1-methylpyrrolidine, N-ethylmorpholine, N-methylmorpholine, 2-morpholinoethanol, and combinations thereof. In various embodiments, the hydrogen halide receptor is selected from 2-morpholinoethanol, 2-(dimethylamino)-2-methyl-1-propanol, diethanolamine, and combinations thereof. In various embodiments, the receptor is used in an amount of 0.005 moles per liter of reagent to 5 moles per liter of reagent. In various non-limiting embodiments, all values and ranges of values (including integers and fractions) between and including these values are expressly contemplated as being expressly contemplated for use herein.

[0052] Solvent :

[0053] Referring now to the solvent, the solvent can be any solvent known in the art. The solvent can be, include, consist essentially of, or consist of a protic solvent, an aprotic solvent, or a combination thereof. In one embodiment, the solvent can be, include, consist essentially of, or consist of a protic solvent. In another embodiment, the solvent can be, include, consist essentially of, or consist of an aprotic solvent. In another embodiment, the solvent can be, include, consist essentially of, or consist of an alcohol, a nitrile solvent, or a combination thereof. In one embodiment, the solvent can be, include, consist essentially of, or consist of an alcohol. In another embodiment, the solvent can be, include, consist essentially of, or consist of a nitrile solvent. It is contemplated that the reagent can be free of one or more of an aprotic solvent, a protic solvent, an alcohol, or a nitrile solvent, or include less than 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, or 0.1 wt% of one or more of an aprotic solvent, a protic solvent, an alcohol, or a nitrile solvent, based on the total weight of the reagent. The term “consist essentially of’ can describe one or more embodiments that can be free of one or more of an aprotic solvent, a protic solvent, an alcohol, or a nitrile solvent, or any other solvent in the art, or include less than 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, or 0.1 wt% of one or more of an aprotic solvent, a protic solvent, an alcohol, or a nitrile solvent, or any other solvent in the art, based on the total weight of the reagent. In various non-limiting embodiments, all values and ranges of values between and including the above-enumerated values are also expressly contemplated for use herein.

[0054] In one embodiment, the solvent can be, include, consist essentially of, or consist of a solvent selected from the group consisting of acetonitrile, propionitrile, and combinations thereof. In another embodiment, the solvent can be, include, consist essentially of, or consist of acetonitrile. In another embodiment, the solvent can be, include, consist essentially of, or consist of an alcohol selected from the group consisting of methanol, ethanol, propanol, 1-methoxypropan-2-ol, mono- and di-ethylene glycol monoalkyl ethers, and combinations thereof.

[0055] If a non-protic solvent is utilized, the non-protic solvent can be any solvent known in the art, including but not limited to: ethers (e.g., diisopropyl ether, dibutyl ether, dioxane, tetrahydrofuran, diglyme, diethylene glycol dimethyl ether, diethylene glycol diethyl ether); nitriles (e.g., acetonitrile), esters (e.g., ethyl acetate, ethyl propionate, isobutyl acetate, n-butyl acetate, vinyl carbonate, propylene carbonate, butyrolactone), halogenated hydrocarbons (e.g., chloroform, dichloromethane, carbon tetrachloride, bromoform, dibromomethane, 1,2-dichloropropane), amides (e.g., dimethylformamide, N-methylformamide, formamide, dimethylacetamide), 2-pyrrolidinone, N-methylpyrrolidinone, ketones (e.g., acetone, methyl ethyl ketone, diethyl ketone, cyclohexanone, methylcyclohexanone), ethylene carbonate, acetylacetone, and other non-protic solvents (e.g., dimethyl acetal). In one embodiment, the non-protic solvent is selected from acetonitrile, propylene carbonate, ethyl acetate, tetrahydrofuran, dioxane, dimethylformamide, or dichloromethane, and combinations thereof. In another embodiment, the non-protic solvent is selected from cyclic and acyclic carbonates, ethers, esters, halogenated hydrocarbons, amides, nitriles, ketones, glycol ethers, and combinations thereof. In another embodiment, the non-protic solvent is selected from acetonitrile, ethylene carbonate, propylene carbonate, and combinations thereof. In another embodiment, the non-protic solvent is selected from acetonitrile, propylene carbonate, and combinations thereof. In one embodiment, the non-protic solvent is acetonitrile. In another embodiment, the non-protic solvent is propylene carbonate. In another embodiment, the non-protic solvent is dimethylformamide. In another embodiment, the non-protic solvent is selected from dimethylformamide, acetonitrile, and combinations thereof. In other embodiments, the non-protic solvent can be a pure (liquid) derivative of imidazole, such as any derivative described herein. It is contemplated that the reagent can be free of one or more of the above non-protic solvents, or can include less than 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, or 0.1 wt% of one or more of the above non-protic solvents, based on the total weight of the reagent. The non-protic solvent can be present in any amount selected by one of skill in the art, and for example, can be present in an amount that "balances" the above compounds, such that the titration composition has a total of 100 parts. In various non-limiting embodiments, all values and ranges of values between and including the above values are expressly contemplated as being expressly contemplated for use herein, including integers and fractions.

[0056] If a protic solvent is used, the protic solvent can be any protic solvent known in the art. For example, the protic solvent can be an alcohol, such as: methanol, ethanol, propanol, monoalkyl ethers of glycols having 1, 2, 3, 4, 5, 6, 7, or 8 carbon atoms, and / or di-alkyl ethers of glycols, or combinations thereof. The protic solvent can be used in any amount relative to the aprotic solvent as described above. In various non-limiting embodiments, all values and ranges of values (including integers and decimals) between and including the above-mentioned values are also expressly contemplated as being expressly contemplated as being within the scope of the present disclosure.

[0057] The solvent can be used in any amount as determined by one of skill in the art. For example, it can be used in an amount that “balances” all other components of the reagent, such that the total amount of all components of the reagent is 100 parts or 100% by weight. Alternatively, the solvent can be used in an amount of about 1% to about 99% by weight, about 5% to about 95% by weight, about 10% to about 90% by weight, about 15% to about 85% by weight, about 20% to about 80% by weight, about 25% to about 75% by weight, about 30% to about 70% by weight, about 35% to about 65% by weight, about 40% to about 60% by weight, about 45% to about 55% by weight, about 50% to about 55% by weight, about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% by weight, or about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% by weight, based on the total weight of the reagent. In various non-limiting embodiments, all values and ranges of values (including integers and decimals) between and including the above-mentioned values are also expressly contemplated as being expressly contemplated as being within the scope of the present disclosure.

[0058] Sulfonic acid :

[0059] The reagent also includes a sulfonic acid. The sulfonic acid can be any sulfonic acid known in the art. Generally, the sulfonic acid is an alkyl sulfonic acid, an aryl sulfonic acid, or a combination thereof. For example, the alkyl sulfonic acid can include an alkyl group having 1 to 8 carbon atoms, such as 1, 2, 3, 4, 5, 6, 7, or 8 carbon atoms. In various embodiments, the alkyl sulfonic acid is selected from the group consisting of methanesulfonic acid, ethanesulfonic acid, and combinations thereof. In other embodiments, the aryl sulfonic acid is selected from the group consisting of toluenesulfonic acid, alkylbenzenesulfonic acid (including, but not limited to, linear alkylbenzenesulfonic acid), and combinations thereof. In other embodiments, the sulfonic acid is selected from the group consisting of methanesulfonic acid, ethanesulfonic acid, toluenesulfonic acid, alkylbenzenesulfonic acid, and combinations thereof. In one embodiment, the sulfonic acid is methanesulfonic acid. In various non-limiting embodiments, all values and ranges of values (including integers and decimals) between and including the above-mentioned values are also expressly contemplated as being expressly contemplated as being within the scope of the present disclosure.

[0060] In various embodiments, the sulfonic acid is present in an amount of about 0.1 wt% to about 80 wt%, about 0.1 wt% to about 1 wt%, about 0.2 wt% to about 0.9 wt%, about 0.3 wt% to about 0.8 wt%, about 0.4 wt% to about 0.7 wt%, about 0.5 wt% to about 0.6 wt%, about 5 wt% to about 75 wt%, about 10 wt% to about 70 wt%, about 15 wt% to about 65 wt%, about 20 wt% to about 60 wt%, about 25 wt% to about 55 wt%, about 30 wt% to about 50 wt%, about 35 wt% to about 45 wt%, about 40 wt% to about 45 wt%, about 8 wt% to about 15 wt%, or about 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%, based on the total weight of the reagent. In other embodiments, the sulfonic acid is present in an amount of about 0.01 mole / liter of reagent to about 20 mole / liter of reagent, about 0.01 mole / liter of reagent to about 0.1 mole / liter of reagent, about 0.02 mole / liter of reagent to about 0.09 mole / liter of reagent, about 0.03 mole / liter of reagent to about 0.08 mole / liter of reagent, about 0.04 mole / liter of reagent to about 0.07 mole / liter of reagent, about 0.05 mole / liter of reagent to about 0.06 mole / liter of reagent, about 1 mole / liter of reagent to about 20 mole / liter of reagent, about 2 mole / liter of reagent to about 19 mole / liter of reagent, about 3 mole / liter of reagent to about 18 mole / liter of reagent, about 4 mole / liter of reagent to about 17 mole / liter of reagent, about 5 mole / liter of reagent to about 16 mole / liter of reagent, about 6 mole / liter of reagent to about 15 mole / liter of reagent, about 7 mole / liter of reagent to about 14 mole / liter of reagent, about 8 mole / liter of reagent to about 13 mole / liter of reagent, about 9 mole / liter of reagent to about 12 mole / liter of reagent, about 10 mole / liter of reagent to about 11 mole / liter of reagent, about 0.5 mole / liter of reagent to about 1.5 mole / liter of reagent, or about 0.5 mole / liter of reagent, 0.6 mole / liter of reagent, 0.7 mole / liter of reagent, 0.8 mole / liter of reagent, 0.9 mole / liter of reagent, 1 mole / liter of reagent, 1.1 mole / liter of reagent, 1.2 mole / liter of reagent, 1.3 mole / liter of reagent, 1.4 mole / liter of reagent, or 1.5 mole / liter of reagent. In various non-limiting embodiments, all values and ranges of values (including integers and fractions) between and including the above-mentioned values are expressly contemplated as being expressly contemplated for use herein.

[0061] In another embodiment, sulfur dioxide or a derivative thereof is present in an amount of about 0.05 moles per liter of reagents to about 1 mole per liter of reagents, a base is present in an amount of about 0.5 moles per liter of reagents to about 2.5 moles per liter of reagents or about 0.5 moles per liter of reagents to about 5 moles per liter of reagents, a hydrohalide donor or hydrogen halide is present in an amount of about 0.01 moles per liter of reagents to about 2 moles per liter of reagents, and a sulfonic acid is present in an amount of about 0.5 moles per liter of reagents to about 1.5 moles per liter of reagents. A solvent can make up the balance of the reagents.

[0062] In another embodiment, sulfur dioxide or a derivative thereof is present in an amount of about 0.10 moles per liter of reagents to about 0.30 moles per liter of reagents, a base is present in an amount of about 0.5 moles per liter of reagents to about 1 mole per liter of reagents, a hydrohalide donor or hydrogen halide is present in an amount of about 0.1 moles per liter of reagents to about 1.5 moles per liter of reagents, and a sulfonic acid is present in an amount of about 0.5 moles per liter of reagents to about 1.5 moles per liter of reagents. A solvent can make up the balance of the reagents.

[0063] In yet another embodiment, sulfur dioxide or a derivative thereof is present in an amount of about 0.2 moles per liter of reagents, a first imidazole derivative is present in an amount of about 1.4 moles per liter of reagents, wherein each of R, R 1 and R 2 is independently a hydrogen atom or a methyl, ethyl, propyl, or butyl group, provided that R, R 1 and R 2 are not all hydrogen atoms, a hydrohalide of a second imidazole derivative is present in an amount of about 0.2 moles per liter of reagents, wherein each of R, R 1 and R 2 is independently a hydrogen atom or a methyl, ethyl, propyl, or butyl group, provided that R, R 1 and R 2 are not all hydrogen atoms; and a sulfonic acid is present in an amount of about 0.5 moles per liter of reagents to about 1.5 moles per liter of reagents. A solvent can make up the balance of the reagents. In various non-limiting embodiments, all values and ranges of values between and including these values are expressly contemplated for use herein.

[0064] In another embodiment (e.g., an embodiment related to the use of an alcohol coulometric reagent), sulfur dioxide or a derivative thereof is present in an amount of about 0.05 moles per liter of reagents to about 1 mole per liter of reagents, a base is present in an amount of about 0.5 moles per liter of reagents to about 2.5 moles per liter of reagents or about 0.5 moles per liter of reagents to about 5 moles per liter of reagents, a hydrohalide donor or hydrogen halide is present in an amount of about 0.01 moles per liter of reagents to about 2 moles per liter of reagents, and a sulfonic acid is present in an amount of about 0.5 moles per liter of reagents to about 1.5 moles per liter of reagents. A solvent can make up the balance of the reagents.

[0065] In another embodiment, sulfur dioxide or a derivative thereof is present in an amount of about 0.2 moles per liter of reagent to about 1.0 moles per liter of reagent, a base is present in an amount of about 1.0 moles per liter of reagent to about 1.7 moles per liter of reagent, a hydrohalide donor or hydrogen halide is present in an amount of about 0.1 moles per liter of reagent to about 1.1 moles per liter of reagent, and a sulfonic acid is present in an amount of about 0.5 moles per liter of reagent to about 1.5 moles per liter of reagent. Solvent can make up the remainder of the reagent.

[0066] In yet another embodiment, sulfur dioxide or a derivative thereof is present in an amount of about 0.9 moles per liter of reagent, a first imidazole derivative is present in an amount of about 1.2 moles per liter of reagent, wherein each of R, R 1 and R 2 is independently a hydrogen atom or a methyl, ethyl, propyl, or butyl group, provided that R, R 1 and R 2 are not all hydrogen atoms, a hydrohalide of a second imidazole derivative is present in an amount of about 0.9 moles per liter of reagent, wherein each of R, R 1 and R 2 is independently a hydrogen atom or a methyl, ethyl, propyl, or butyl group, provided that R, R 1 and R 2 are not all hydrogen atoms; and a sulfonic acid is present in an amount of about 0.5 moles per liter of reagent to about 1.5 moles per liter of reagent. Solvent can make up the remainder of the reagent. In various non-limiting embodiments, all values and ranges of values between and including the above-mentioned values are expressly intended to be anticipated by this document.

[0067] In another embodiment (e.g., an embodiment related to the use of alcohol volumetric titration of a single component reagent), sulfur dioxide or a derivative thereof is present in an amount of about 0.01 moles per liter of reagent to about 1 moles per liter of reagent, a base is present in an amount of about 0.5 moles per liter of reagent to about 2.5 moles per liter of reagent or about 0.5 moles per liter of reagent to about 5 moles per liter of reagent, a hydrohalide of a second imidazole derivative is present in an amount of about 0.01 moles per liter to about 2 moles per liter, wherein each of R, R 1 and R 2 is independently a hydrogen atom or a methyl, ethyl, propyl, or butyl group, provided that R, R 1 and R 2 are not all hydrogen atoms or a hydrohalide of a second imidazole derivative is present in an amount of about 0.3 moles per liter of reagent to about 1.0 moles per liter of reagent, wherein each of R, R 1 and R 2 is independently a hydrogen atom or a methyl, ethyl, propyl, or butyl group, provided that R, R 1 and R 2not all hydrogen atoms; iodine is present in an amount of about 0.5 mole per liter of reagent to about 5 moles per liter of reagent, and sulfonic acid is present in an amount of about 0.5 mole per liter of reagent to about 1.5 moles per liter of reagent. The solvent can make up the balance of the reagent. In various non-limiting embodiments, all values and ranges of values between and including these values are expressly contemplated for use herein.

[0068] With particular reference to the step of providing the reagent, any order of addition can be used to form / provide the reagent. For example, any total or partial amount of any one of the above-described components can be mixed with any total or partial amount of any other component.

[0069] In one embodiment, for example, about 130 g of base is mixed and dissolved in a solvent with about 130 g of a hydrohalide donor or hydrogen halide. Subsequently, about 8 g of sulfur dioxide or a derivative thereof is introduced into the solution.

[0070] In yet another embodiment, the reagents can be used in the anodic and / or cathodic regions of a coulometric dual cell, or as a general electrolyte in a single cell. The reagents of the present disclosure can also be used as a solvent component of a single component reagent or a two component reagent. For example, if a reagent of the present disclosure is used as a solvent, a single component reagent or a two component reagent can be added thereto to titrate the moisture content of a sample. If iodine is added to a reagent of the present disclosure, the corresponding reagent can be used as a single component reagent.

[0071] In other embodiments, a solution of the reagents described herein can be used as an anodic electrolyte in a coulometric cell having only one chamber, or additionally as a cathodic electrolyte in a coulometric cell having two separate chambers. Further, the solution can also be filled into a volumetric titration cell as a solvent component. An aqueous sample can be added to the titration cell and titrated using a commercially available iodine reagent (e.g., a single component or two component reagent).

[0072] In one embodiment, the method includes a step of titrating the sample with the reagent. This is generally described as a volumetric method. In another embodiment, the method includes a step of mixing the sample with the reagent so that the sample can be titrated. In this embodiment, the method generally includes a step of providing a source of iodine (I2). The iodine source can be any iodine source known in the art, such as solid I2 dissolved in any suitable solvent and / or any of the above-described reagents. In various embodiments, the solution to which the iodine is added can have from about 1 wt% to about 10 wt% iodine after the iodine is added. In coulometric methods, the iodine can be generated by anodic oxidation of iodide, so that no additional or external source of iodine can be required / used. By employing one of the above-described Karl Fischer methods, the sample can be titrated to determine the moisture content in the sample. In various non-limiting embodiments, all values and ranges of values between and including these values (including integers and fractions) are expressly contemplated as being expressly intended for use herein.

[0073] For example, any necessary iodine can be added via an iodine solution as described above, or can be generated by anodic oxidation of added iodide. In the method, the added or anodically generated iodine is generally reduced to iodide by reaction with sulfur dioxide or a derivative thereof and water. When no more moisture is present, free iodine remains. Excess iodine can be used to indicate the endpoint, such as for visual or photometric indication. The endpoint can also be indicated electrochemically, such as by a bipotentiometric or biampere method.

[0074] Volumetric determination can be performed by introducing the reagent into the titration vessel as a solvent component. The sample can then be added to the titration vessel so that the moisture is titrated by introduction of the iodine-containing single component reagent or the two component reagent. Generally, titration with a single component reagent, which traditionally is a solution of iodine, base, and SO2, includes providing a solvent in the vessel, adding the sample to the vessel containing the solvent, and then adding the single component reagent to the combination of sample and solvent in the vessel. The reagent of the present disclosure can be used as the solvent in this titration method. Titration with a two component reagent generally includes providing a solvent, such as a reagent of the present disclosure, containing a base and SO2 in the vessel. The sample is then generally added to the vessel. Finally, the two component reagent is then generally added to the vessel so that the titration reaction can begin.

[0075] The reagent of the present disclosure can also be used as a single component titration reagent in a volumetric titration method. When used, 1 wt% to 10 wt% iodine must be added to the reagent.

[0076] For example, a coulometric determination can be performed by introducing the components of the reagent into a coulometric cell, such as a divided cell, and then adding the sample and electrolyzing by applying an electrolysis current until the moisture present in the sample is converted, depending on the configuration of the cell.

[0077] Prior to determining the moisture content in a sample, the water contained in the aprotic solvent can be removed in a blank titration (e.g., by pre-electrolysis in the case of coulometric determination). Typically, in coulometric titration methods, the first imidazole derivative described above is mixed with a hydrohalide of a second imidazole derivative. In various embodiments, for example, if the coulometric cell requires a reagent having a conductivity of about 5 mS / cm to about 20 mS / cm, it can be necessary to add additional supporting electrolyte. These supporting electrolytes can be soluble inorganic salts such as: tetrabutylammonium chloride, imidazole hydrogen bromide, and the like.

[0078] To indicate the endpoint in both volumetric analysis and coulometric titration, it is contemplated to utilize dual potential indication or dual amperometric indication. For example, one or more known compounds having a known reproducible endpoint can be incorporated into the reagent and / or sample. These compounds can be selected by one of skill in the art. In addition, one or more buffers can be utilized. In other embodiments, the method can or can not include one or more compounds, method steps, and the like as described in U.S. Patent No. 5,401,662, which is expressly incorporated by reference herein in its entirety in various non-limiting embodiments.

[0079] In various embodiments, the methods of the present disclosure produce a starting drift of less than about 15 pg / min, 14 pg / min, 13 pg / min, 12 pg / min, 11 pg / min, 10 pg / min, 9 pg / min, 8 pg / min, 7 pg / min, 6 pg / min, 5 pg / min, 4 pg / min, 3 pg / min, 2 pg / min, or 1 pg / min, as determined by one of skill in the art using any of the titration methods described above. In various non-limiting embodiments, all values and ranges of values (including integers and decimals) between and including the values described above are expressly contemplated for use herein.

[0080] In other embodiments of the present disclosure, it is contemplated that the reagent is free of a hydrohalide donor. In other embodiments, it is contemplated that the reagent is one in which all numbers are approximate molar / liter amounts of the reagent.

[0081]

[0082] In various non-limiting embodiments, all values and ranges of values (including integers and decimals) between and including the values described above are expressly contemplated for use herein.

[0083] In other embodiments, the reagent includes sulfur dioxide, an iodide (hydroiodide of imidazole or one of the above-mentioned derivatives thereof), one of the above-mentioned imidazole derivatives, or a mixture thereof with one or more amines such as those mentioned above. In related embodiments, the solvent is an anhydrous aprotic solvent such as propylene carbonate (PC) or acetonitrile (or a mixture of different aprotic solvents such as ethers, esters, halogenated hydrocarbons, amides, and combinations thereof).

[0084] In various embodiments, it has been found that using a mixture of a sulfonic acid and acetonitrile as a solvent allows for the possible preparation of Karl Fischer reagent that reacts in the same or similar manner as the alcohol-containing reagent. For example, some reagents of the present disclosure show stoichiometric reactions identical to those in many alcohol solutions, i.e., 1 : 1 H2O : I2. In addition, some reagents show a series of additional advantages. For example, methanesulfonic acid significantly increases the conductivity of Karl Fischer reagent prepared from protic and aprotic solvents (see Example 3). High conductivity values are extremely important, especially in coulometric Karl Fischer methods. Thus, methanesulfonic acid-based Karl Fischer reagent is well suited for coulometric determination of water. Since sulfonic acids are good proton donors, reagents with sulfonic acids can be used as general anolyte reagents in titration cells without a membrane and as catholyte in titration cells with a membrane. In various embodiments, the reagent is prepared by dissolving a base (e.g., imidazole, 1-ethylimidazole, 2-ethylimidazole) in acetonitrile. Other solvents such as propylene carbonate or amides such as 2-pyrrolidone can also be added. Imidazole hydroiodide or hydroiodide of a substituted imidazole derivative or another source of hydrogen iodide can be added with the sulfonic acid. Finally, sulfur dioxide can be bubbled into the solution.

[0085] In one embodiment, a single-component volumetric titration reagent is prepared. For example, the reagent can be prepared by dissolving a base (e.g., imidazole, 1-ethylimidazole) in acetonitrile. Other solvents such as propylene carbonate or amides such as 2-pyrrolidone can also be added. Imidazole hydroiodide or hydroiodide of a substituted imidazole derivative or another source of hydrogen iodide can be added with the sulfonic acid. Sulfur dioxide can be bubbled into the solution. Finally, iodine is added to the solution.

[0086] In another embodiment, a two-component volumetric titration reagent is prepared. For example, the titrant can be prepared by dissolving iodine in acetonitrile. Other solvents such as propylene carbonate or amides such as 2-pyrrolidone can also be added. In addition, the solvent can be prepared by dissolving a base (e.g., imidazole, 1-ethylimidazole) in acetonitrile. Other solvents such as propylene carbonate or amides such as 2-pyrrolidone can also be added. Imidazole hydroiodide or hydroiodide of a substituted imidazole derivative or another source of hydrogen iodide can also be added with the sulfonic acid. Finally, sulfur dioxide is bubbled into the solution.

[0087] It is also contemplated that acetonitrile can also be used in combination with other solvents such as amides, chloroform, xylenes, alcohols, or alcohol reagents, such that the solvent combination of acetonitrile with alcohols and / or other solvents can be matched to the requirements of the sample.

[0088] Example

[0089] A series of titrations were performed in accordance with the present disclosure and as comparative examples.

[0090] Example 1:

[0091] The first example involves the titration of a water standard using a Metrohm 852 Titrando device as shown below. This example focuses on the KF stoichiometry of a protic KF reagent and shows that without methanesulfonic acid, the error is unacceptably high (about 86%). However, once methanesulfonic acid is used, the error drops to approximately 0.

[0092]

[0093]

[0094] Example 2:

[0095] The second example involves the titration of a water standard using a Metrohm 852 Titrando device as shown below. This example focuses on the KF stoichiometry of an aprotic KF reagent and shows that without methanesulfonic acid, the error is about 7%. However, once methanesulfonic acid is used, the error drops to approximately 0.

[0096]

[0097] Example 3:

[0098] The third example involves the measurement of the conductivity of protic solvents (e.g., methanol) and aprotic solvents (e.g., acetonitrile) with and without methanesulfonic acid. The conductivity can be significantly improved by 2500-8000 times when methanesulfonic acid is added.

[0099]

[0100] In various non-limiting embodiments, it is contemplated that any term of an alcohol solvent, solution, and / or reagent can be replaced by an aprotic solvent, solution, and / or reagent. Similarly, in various non-limiting embodiments, it is contemplated that any term of an aprotic solvent, solution, and / or reagent can be replaced by a protic solvent, solution, and / or reagent.

[0101] While at least one exemplary embodiment has been presented in the foregoing detailed description of the application, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability or configuration in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment. It should be understood that various changes can be made in the function and arrangement of elements described in the exemplary embodiment without departing from the scope as set forth in the appended claims.

Claims

1. A method for determining moisture content in a sample, the method comprising the steps of: A. providing a reagent, the reagent comprising: (1) sulfur dioxide or a derivative thereof; (2) a base; (3) optionally a hydrogen halide or a hydrogen halide donor; (4) a solvent; and (5) a sulfonic acid; and B. titrating the sample with the reagent.

2. The method of claim 1, wherein the sulfonic acid is an alkyl or aryl sulfonic acid or a combination thereof.

3. The method of claim 1, wherein the sulfonic acid is selected from the group consisting of methanesulfonic acid, ethanesulfonic acid, toluenesulfonic acid, alkylbenzenesulfonic acid, and combinations thereof.

4. The method of claim 1, wherein the sulfonic acid is methanesulfonic acid.

5. The method of any one of claims 1 to 4, wherein the solvent comprises an alcohol, a nitrile solvent, or a combination thereof.

6. The method of any one of claims 1 to 4, wherein the solvent is selected from the group consisting of acetonitrile, propionitrile, and combinations thereof.

7. The method of any one of claims 1 to 4, wherein the solvent comprises an alcohol selected from the group consisting of methanol, ethanol, propanol, 1-methoxy-2-propanol, mono- and di-ethylene glycol monoalkyl ethers, and combinations thereof.

8. The method of any one of claims 1 to 4, wherein the base is imidazole and / or a derivative thereof, and wherein the imidazole derivative has the structure: wherein each of R, R 1 and R 2 is independently a hydrogen atom, a phenyl group, a substituted phenyl group, a first hydrocarbyl group having 1 to 6 carbon atoms, or a second hydrocarbyl group having 1 to 6 carbon atoms interrupted at least once by a heteroatom, provided that R, R 1 and R 2 are not all hydrogen atoms.

9. The method of any one of claims 1 to 4, wherein the hydrogen halide donor is a hydrohalide of imidazole or a second imidazole derivative, wherein the second imidazole derivative has the structure: wherein each of R, R 1 and R 2 is independently a hydrogen atom, a phenyl group, a substituted phenyl group, a first hydrocarbyl group having 1 to 6 carbon atoms, or a second hydrocarbyl group having 1 to 6 carbon atoms interrupted at least once by a heteroatom, and wherein the sulfur dioxide or derivative thereof is present in an amount of 0.01 mole per liter of reagent to 5 moles per liter of reagent, the base is present in an amount of 0.1 mole per liter of reagent to 10 moles per liter of reagent, and the sulfonic acid is present in an amount of 0.5 mole per liter of reagent to 1.5 moles per liter of reagent.

10. A reagent for Karl Fischer titration, the reagent consisting of: (1) sulfur dioxide or a derivative thereof; (2) imidazole and / or a derivative thereof; (3) optionally a hydrogen halide or a hydrogen halide donor; (4) acetonitrile; (5) methanesulfonic acid; and (6) methanol and / or ethanol and / or 1-methoxy-2-propanol and / or propylene glycol.

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