Marking of carbonaceous fluids

Abstract

A method is provided for marking a petroleum fuel or other carbonaceous fluid with a marker or tracer. The method includes introducing the marker into the fluid. The marker is a substance that is extractable from a plant (including synthetically manufactured versions of such substances). The plant may be a Cannabis plant and the marker may comprise a cannabinoid, e.g. tetrahydrocannabinol (THC). A detection method is further provided for detecting the presence of the marker in the fuel or other carbonaceous fluid. The detection method may comprise extracting the marker from the fluid into an aqueous layer and analysing the aqueous layer for the presence of the marker. A marked carbonaceous product is also provided, comprising a carbonaceous fluid and a marker as above.

Description

FIELD OF THE INVENTION 5 This invention relates to a method for marking carbonaceous fluids with markers or tracers, and to carbonaceous fluids marked using the method. Without limitation thereto, the carbonaceous fluid may comprise a fuel such as a liquid or gaseous petroleum fuel. BACKGROUND 10 Petroleum fuels and other carbonaceous fluids can be marked for easy identification. For example, a marker or tracer may be added to a petroleum fuel to identify the origin of the fuel or the batch and manufacturer of the fuel, which has several useful applications. Marking may facilitate the detection of a fuel that has been adulterated with a different fuel that is not taxed. 15 Criminal enterprises may, for example, mix paraffin and diesel and sell it as diesel only, thereby paying less for tax. As a result of this, customers may be supplied with diesel of lower quality, which can cause negative effects in engines. Criminal enterprises have also been known to install valves on fuel pipelines used to transport 20 crude oil over long distances. They may then divert the crude oil from the pipeline and distil and sell it. Several types of fuel markers, tracers or taggants have been developed over the years for identification of fuel to detect fuel fraud and theft. The markers are generally easy to detect, 25 even in low concentrations, and miscible with the fuel. A limitation of these markers is that criminals aware of the technology have found ways to wash or launder the marker out of the fuel, making the fuel undetectable. This allows the criminals to evade prosecution for possession of stolen fuel, or to carry on supplying low 30 quality fuel and avoid taxes. The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common 35 general knowledge in the art as at the priority date of the application. 20 09 24 SUMMARY OF THE INVENTION In accordance with an aspect of the invention there is provided a method for marking a 5 carbonaceous fluid with a marker, the method comprising introducing the marker into said carbonaceous fluid, wherein said marker comprises a cannabinoid or a derivative thereof. The cannabinoid may comprise a phytocannabinoid. 10 The marker may comprise a cannabinoid selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV) and cannabichromene (CBC), and mixtures thereof. 15 The cannabinoid may be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC) and cannabinol (CBN). The cannabinoid may be preselected with reference to its normal boiling point, such that this parameter of the cannabinoid falls within a boiling point range of the carbonaceous fluid to be 20 marked. The cannabinoid may have a normal boiling point in a range from 140°C to 220°C inclusive. The cannabinoid may have a normal boiling point in a range from about 150°C to about 220°C. The cannabinoid may have a boiling point selected from the group consisting of about 157°C, about 160°C to about 180°C, about 185°C, and about 220°C. 25 The step of introducing the marker into the carbonaceous fluid may include dissolving the marker in the carbonaceous fluid. Instead, or in addition, the step may include creating a suspension of the marker in the carbonaceous fluid. Instead, or in addition, the step may include mixing the marker with the carbonaceous fluid. 30 The carbonaceous fluid may be selected from the group consisting of gasoline (petrol), diesel fuel, bio-diesel, methanol, ethanol, bio-ethanol, benzene, liquid paraffin, aviation kerosene, heating oil, fuel oil, bunker fuel, crude oil, liquefied petroleum gas, hydraulic fluid, lubricating oil, natural gas, methane, propane, butane, and any mixture thereof. 35 The carbonaceous fluid may comprise a fuel. The fuel may comprise a petroleum fuel. The 20 09 24 fuel may be liquid. The fuel may be gaseous. The concentration of the cannabinoid in the fuel may be less than about 0.25 ppm w / v (250 ng / ml). It will be appreciated, however, that any detectable concentration of the marker will 5 also fall within the scope of the invention. For example, in embodiments where a cannabinoid marker is provided in the form of a cannabis oil extract, the oil may be spiked into the marked fluid at a higher concentration of about 5000 ppm, i.e., 5 mg / ml, or even higher. The marking of the carbonaceous fluid may be carried out for purposes of identification of the 10 carbonaceous fluid. The marking may be carried out for purposes of tracing the carbonaceous fluid. The method for marking a carbonaceous fluid may include a step of detecting the presence of the marker in the carbonaceous fluid, thereby to identify the carbonaceous fluid as a marked 15 fluid. This step may comprise analysing the carbonaceous fuel for the presence therein of a marker, the marker being as hereinbefore described. The step may include performing a detection method as disclosed in the following paragraphs. In accordance with a further aspect of the invention there is provided a detection method for 20 detecting the presence of a marker in a carbonaceous fluid, said method comprising: (I) extracting said marker from said carbonaceous fluid into an aqueous layer; and (II) analysing said aqueous layer for the presence of said marker; wherein said marker comprises a cannabinoid or a derivative thereof. 25 The cannabinoid may comprise a phytocannabinoid. The cannabinoid may be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV) and cannabichromene (CBC), 30 and mixtures thereof. The cannabinoid may be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC) and cannabinol (CBN). The carbonaceous fluid may be selected from the group consisting of gasoline (petrol), diesel fuel, bio-diesel, methanol, ethanol, bio-ethanol, benzene, liquid paraffin, aviation kerosene, 35 heating oil, fuel oil, bunker fuel, crude oil, liquefied petroleum gas, hydraulic fluid, lubricating 20 09 24 oil, natural gas, methane, propane, butane, and any mixture thereof. The step of extracting the marker into the aqueous layer may be performed using an extraction buffer comprising HRB, i.e., a composition comprising 0.5M Tris, pH 10, 0.02% Magnesium 5 Chloride, 0.02% Calcium Chloride, 0.5% Casein, and 0.1% Sodium Azide. The analysis of the aqueous layer may be performed using a lateral flow assay. Instead, or in addition, any other suitable analytical or molecular assay methodology capable of detecting the presence of the marker may be employed for the analysis. 10 The carbonaceous fluid may comprise a fuel. The fuel may comprise a petroleum fuel. The fuel may be liquid. The fuel may be gaseous. In accordance with a further aspect of the invention there is provided a marked carbonaceous 15 product comprising a carbonaceous fuel and a marker comprising a cannabinoid or derivative thereof. The cannabinoid may comprise a phytocannabinoid. 20 The cannabinoid may be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV) and cannabichromene (CBC), and mixtures thereof. 25 The concentration of the cannabinoid in the carbonaceous fluid may be less than about 0.25 ppm w / v (250 ng / ml). It will be appreciated, however, that any detectable concentration of the cannabinoid will also fall within the scope of the invention. For example, in embodiments where a cannabinoid marker is provided in the form of a cannabis oil extract, the oil may be spiked into the marked fluid at a concentration of about 5000 ppm, i.e., 5 mg / ml, or even higher. 30 The cannabinoid may be preselected with reference to its normal boiling point, such that this parameter of the cannabinoid falls within a boiling point range of the carbonaceous fluid to be marked. The cannabinoid may have a normal boiling point falling within temperature ranges as described above for the subsets of modes of performing the method of the invention in a 35 range as described above. The cannabinoid may have a normal boiling point in a range from 20 09 24 140°C to 220°C inclusive. The carbonaceous fluid may comprise a fuel. The fuel may comprise a petroleum fuel. The fuel may be liquid. The fuel may be gaseous. 5 The carbonaceous fuel may be selected from the group consisting of gasoline (petrol), diesel fuel, bio-diesel, methanol, ethanol, bio-ethanol, benzene, liquid paraffin, aviation kerosene, heating oil, fuel oil, bunker fuel, crude oil, liquefied petroleum gas, natural gas, methane, propane, butane, and any mixture thereof. 10 In accordance with a further aspect of the invention there is provided a use of a cannabinoid or derivative thereof as a marker in a carbonaceous fluid. The cannabinoid may comprise at least one phytocannabinoid. 15 The cannabinoid may be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV), cannabichromene (CBC), and any mixture thereof. 20 A concentration of the cannabinoid or derivative thereof in the carbonaceous fluid may be less than about 0.25 ppm w / v. The carbonaceous fluid may comprise a fuel. The fuel may comprise a petroleum fuel. The 25 fuel may be liquid. The fuel may be gaseous. Modes for performing the disclosed method and embodiments of the derived products will now be described, by way of example only, with reference to the accompanying drawings. 30 BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: Figure 1 shows, schematically, a set of THC lateral flow assay strips, each of which 20 09 24 illustrates a different result from a series of tests conducted using the strips. DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS 5 In the following description, modes for performing a method of marking a carbonaceous fluid with a marker are explained in greater detail. The method comprises introducing the marker into the carbonaceous fluid, e.g., by dissolution, mixing or suspension. The marker comprises a cannabinoid or a derivative thereof. 10 In this specification, a reference to a substance or compound being “extractable from a plant” shall include reference both to naturally occurring and synthetically manufactured versions of that substance or compound, i.e., the source or origin of a particular sample of such substance or compound is immaterial provided the substance or compound in question satisfies the limitation that exemplars of that substance may be found in at least one plant and are capable 15 of being extracted from said plant. Synthetically manufactured versions of such compounds may be produced by recombinant techniques or otherwise. The disclosed method may extend to the use, as markers, of compounds which are manufactured synthetically to have properties approximating those of naturally occurring plant 20 constituents, i.e., of the substances extractable from plants. The cannabinoid may comprise at least one compound extractable from a Cannabis plant. The Cannabis plant may be Cannabis sativa, Cannabis indica or Cannabis ruderalis. The cannabinoid may comprise a phytocannabinoid. 25 In this specification the term “phytocannabinoid” shall have its widest meaning and shall include any plant-derived natural product capable of either directly interacting with cannabinoid receptors or sharing chemical similarity with cannabinoids or both. 30 The marker may comprise a crude phytocannabinoid extract in the form of an oil (“cannabis oil”). The cannabis oil may contain a mixture of substances extracted from the Cannabis plant or may comprise a purified or isolated cannabinoid extracted from the Cannabis plant. The cannabinoid may be selected from the group consisting of naturally occurring and 35 synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol 20 09 24 (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV) and cannabichromene (CBC), and mixtures thereof. The cannabinoid may be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC) and cannabinol (CBN). In one embodiment, the marker may comprise naturally occurring or synthetic tetrahydrocannabinol 5 (THC). The carbonaceous fluid may comprise a hydrocarbon fluid. The carbonaceous fluid may be selected from the group consisting of carbonaceous fuels, including liquid carbonaceous fuels and gaseous carbonaceous fuels. Without limitation thereto, the carbonaceous fluid may 10 comprise a liquid carbonaceous fuel selected from the group consisting of gasoline (petrol), diesel fuel, bio-diesel, methanol, ethanol, bio-ethanol, benzene, liquid paraffin, aviation kerosene, heating oil, fuel oil, bunker fuel, crude oil, liquefied petroleum gas, and mixtures thereof. Without limitation thereto, the carbonaceous fluid may comprise a gaseous carbonaceous fuel selected from the group consisting of natural gas, methane, propane, and 15 butane. Whenever reference is made to “fuel” it will be understood to mean a fluid carbonaceous fuel. It will be appreciated that the carbonaceous fluid need not be limited to fluids intended to be 20 used as fuels. Instead, or in addition, the carbonaceous fluid may comprise a fluid such as hydraulic fluid, lubricating oil, or the like. When introducing the marker into the carbonaceous fluid, the marker may become incorporated into the carbonaceous fluid to form a solution, mixture or suspension of the 25 marker in the fluid. The process of adding a marker, tracer or taggant to a fuel or other carbonaceous fluid may be referred to as “spiking” the fluid with the tracer so that it forms a suspension in the fluid or becomes dissolved in it or mixed with it. As suggested above, the cannabinoid may, in some embodiments, comprise an oil, i.e., a 30 nonpolar substance that is a viscous liquid at ambient temperatures and is both hydrophobic and lipophilic. Accordingly, in some modes of performing the disclosed method the marker may be provided as cannabis oil. In such cases the fuel may, for example, be spiked at a working concentration of about 5000 ppm, i.e., 5 mg / ml, although it will be appreciated that concentrations at both higher and lower thresholds are also feasible provided the marker is 35 detectable in the marked fuel or other carbonaceous fluid. In testing with cannabis oil, false 20 09 24 negatives were found to start occurring as concentrations of the cannabis oil were lowered to around 500 ppm (500 pg / ml) and beyond. Where, instead, the marker is a compound instead of a crude plant extract, i.e., where the 5 marker employed is a substantially pure, isolated, or synthetically manufactured cannabinoid like THC or CBN, the concentration of the marker when spiked into the fuel may, for example, be in a range from about 0.05 ppm to about 0.25 ppm w / v (50 - 250 ng / ml) inclusive. The working concentration of the marker may thus be less than about 0.25 ppm w / v (250 ng / ml). Again, however, it will be appreciated that the marker may still be used at concentrations in 10 excess of 0.25 ppm w / v (250 ng / ml) for other applications. The cannabinoid may have at least one property similar to a corresponding property of the carbonaceous fuel in which it is intended to be dissolved or suspended. It may, for example, have properties similar to those of petroleum fuels. The property in question may, for example, 15 be that of normal boiling point, in other words, the boiling point of the cannabinoid (or other disclosed marker) may correspond approximately to the boiling point of the fuel in which it is to be dissolved or suspended. The cannabinoid may be preselected with reference to its normal boiling point, such that this 20 parameter of the cannabinoid falls within a boiling point range of the fuel or other carbonaceous fluid to be marked. Although carbonaceous fluids may have a widely varying range of boiling points, in some modes of the disclosed marking method the cannabinoid may have a normal boiling point in a range from about 140°C to about 220°C inclusive. Without limitation thereto, the cannabinoid may have a normal boiling point in a range from about 25   150°C to about 220°C, this being the range in which many cannabinoids have their normal boiling points. The cannabinoid may, for example, have a boiling point selected from the group consisting of about 157°C, about 160°C to about 180°C, 185°C, and 220°C. An advantage of arranging for the boiling points of the two components to be similar in this 30 way, may be that fractional distillation methods for removing the marker from the fuel can be rendered more difficult for criminals to carry out. Other suitable properties of the marker may include its propensity to be washed out of a fuel solution by an acid or base buffer, or its propensity to be absorbed by solid absorbents such 35 as activated charcoal or bentonite clay. Thus, the marker may be selected such that these 20 09 24 propensities match to a statistically significant level the corresponding properties of the particular carbonaceous fuel to be marked. As indicated, tetrahydrocannabinol (THC), a cannabinoid found in the Cannabis plant, may be 5 a useable marker in fuel. THC may have potential advantages when used as a marker. Due to the molecule having similar properties to that of petroleum fuel, it may be less prone to being washed out of the fuel. Further, it may be expected that THC will remain generally intact and present in fuel after distillation, that it will react only sparingly with the fuel or not at all, and that it may be stable in fuel over extended periods of time. 10 Experiments were conducted to test the efficacy of the proposed markers and the method of detection thereof in fuel. The experimental information and results are discussed in more detail below. While the experiments described below focus on cannabis oil and THC as markers, it should be appreciated that other suitable cannabinoids may be used. 15 In the experiments, cannabis oil (with THC) was added to diesel and petrol to mark the fuel. The fuel was then mixed with an extraction buffer, shaken vigorously for approximately one minute, and the aqueous solution allowed to settle to the bottom of the mixture. The aim of the tests was to assess whether the aqueous solution would then contain THC at a concentration 20 high enough to be detected if it was present in the fuel to begin with. The aqueous solution was removed and placed into a new, clean tube and a THC lateral flow assay strip was dipped into the aqueous solution until the test ran. The test strips used included THC-Bovine Serum Albumin (THC-BSA) immobilized at a test line region. If THC was 25 present in the solution, it would bind to the antibodies on the conjugate, therefore blocking off any binding sites on the antibody epitope. The conjugate would therefore flow past the THC-BSA immobilized at the test line region and not bind, presenting no test line and only a control line and therefore a positive result. If THC was not present, the epitope on the antibodies on the conjugate would be free and would therefore bind to the THC-BSA immobilized on the test 30 line region of the test, bringing about two lines, indicating a negative result. For the tests that were conducted, the lateral flow strips used were those which are commonly used for testing urine. These are selective for the THC metabolite (THC-COOH). It will, however, be appreciated that lateral flow strips or analytical methods sensitive to other 35 cannabinoids or markers may be used as appropriate. For example, test strips sensitive to the 20 09 24 parent THC compound (Delta-9-THC) may be used; or strips or other analytical methods for detecting CBN or other suitable cannabinoids may be employed. Detection Method 5 The following steps indicate an exemplary method for testing for the presence of the marker: 1) One ml of fuel was placed into an Eppendorf tube. 2) 200 pl of extraction buffer was added to the fuel. 10   3) The mixture was shaken vigorously for 1 minute. 4) The solution was left upright until a clear visible separation between the fuel and extraction buffer was observed. This usually took about 5 minutes. 5) 200 pl of the lower aqueous solution was removed and placed into a fresh Eppendorf tube. 15   6) A lateral flow assay strip was then placed into the extraction buffer until the liquid was seen flowing across the membrane. 7) The strip was removed and placed onto a flat surface and allowed to run for 5-15 minutes. 8) The results were interpreted by the presence or absence of a test line at the test line region of the strip. 20 Figure 1 shows an exemplary set of results obtained after conducting the steps set out above. Two lines appearing on a strip indicate a negative test result. In other words, those strips in the drawings which show both the test and control lines indicate that the marker was not present in the fuel tested using that strip. 25 For detection of the marker, it was necessary to employ an extraction buffer because lateral flow test strips are not typically able to detect THC directly in fuel; the antibodies used on such tests are not soluble in fuel or oil. However, whilst a relatively high concentration of extraction buffer (200 pl / ml) is required to carry out detection, only a small proportion (e.g., about 5%) of 30 the THC in the fuel is removed from the fuel and passes into the aqueous phase where it can be detected. This stands in contrast to washing operations performed on fuels marked with other types of markers, e.g., the Marker A discussed further below. Since Marker A is water soluble, it can 35 typically be substantially entirely removed from the fuel phase during washing or laundering. 20 09 24 THC, on the other hand, is only sparingly soluble in water, and so goes into the aqueous phase at a much lower concentration compared to Marker A. Thus, whilst it would theoretically be feasible for criminal enterprises to wash THC (or other 5 cannabinoids) from fuel marked with such compounds, it would not typically be economically viable to do so since the cost of the washing would exceed any additional profit which might be derivable from carrying out the unauthorized washing. It may be expected that the cost of the amount of extraction buffer required would be prohibitively high for this purpose. 10 Buffer Identification Five buffers commonly used as either running buffers or extraction buffers were used to determine a suitable buffer to be used as an extraction buffer. The buffers tested were Diesel Extraction Buffer, Phosphate Buffer Saline (PBS), COVID Saliva Buffer, Dengue Buffer, HIV 15 Running Buffer (HRB) and Malaria Running Buffer (MRB). The compositions of these buffers were as follows: • PBS: 0.8% Sodium Chloride, 0.02% Potassium Chloride, 0.115% Di-Sodium Hydrogen Phosphate, 0.02% Potassium Di-Hydrogen Phosphate 20      • COVID Saliva Buffer: 5mM Borate, 150mM NaCI, 20%PBS, 5% Tween20, 2% Triton- X-100, 1% Sodium Dodecyl Sulphate • Dengue Buffer: 300mM Tris pH 8, 2% Brij, 150mM NaCI • HRB: 0.5M Tris, pH10, 0.02% Magnesium Chloride, 0.02% Calcium Chloride, 0.5% Casein, 0.1% Sodium Azide 25      • MRB: 1.2% Hepes, 1% Triton X, 0.87% Sodium chloride,0.5% EDTA, 0.5% BSA, 0.5% PEG 3350, 1% Tween 20, 0.1% Sodium Azide Each buffer was substituted in Step 2 of the Detection Method as indicated above and the rest of the protocol was followed. 30 Diesel was used as the fuel of choice during these tests. The diesel was marked with cannabis oil to a final concentration of 5 mg / ml and aliquoted to five tubes. Each tube was extracted with a different buffer selected from the above list. The negatives for all the buffers came up as they normally would (two distinct lines) and only the Diesel Extraction Buffer brought about 35 a false negative (faint line on positive). 20 09 24 When marking diesel with cannabis oil to a lower concentration (500 pg / ml), false negatives appeared when using PBS and COVID Saliva Buffer as extraction buffer. When diluting the cannabis oil to 100 pg / ml, false negative results appeared on MRB. When diluting the 5 cannabis oil to 10 pg / ml, false negatives appeared on all; however, a false negative was the least prominent on the HRB buffer. Concentration of Cannabis Oil in Fuel 10   200 mg of cannabis oil was measured out into an Eppendorf tube and was re-suspended into 1 ml of ethanol. Undissolved plant debris was evident; therefore, the solution was spun down at full speed for 5 minutes to precipitate the cellular debris. The cellular debris was air dried to determine the mass of undissolved plant material. The undissolved quantity was subtracted from the initial mass added to the tube to determine the concentration of the working solution. 15 A serial dilution of the working solution was made and added to diesel. The Detection Method, as described above, was then followed. An extraction was done on all concentrations and the extraction was run on strips to determine the cut-off for the lowest detectable concentration of cannabis oil in the fuel. The cut-off was 20 determined by observing the lines on the strip. When a faint line was observed at the test line region this dilution was considered to be slightly above the cut-off and the dilution before (next highest dilution) was determined to be the cut-off. Diesel was marked with cannabis oil to 200 pg / ml and extracted using Dengue Buffer, HRB 25 and MRB. The positives produced slight shadows on each. Using this information, the limit of detection was determined to be >200 and <500 pg / ml. The preferred concentration of cannabis oil to be used when marking the diesel was determined to be 500 pg / ml. 30 Methods to Wash Markers out of Fuel Experiments were conducted to compare the washing or laundering of different types of markers from fuel using a variety of aqueous acids and bases, to assess the relatively difficulty 35 of washing the different markers from the fuel. The aim was to compare the washing of fuels 20 09 24 containing markers as herein disclosed (e.g., cannabis oil containing THC), against washing of fuels containing a commonly used conventional fuel marker (“Marker A”). A) Aqueous Acids and Bases 5 Four buffer solutions, namely, 1M HCI, 5M HCI, 1M NaOH and 5M NaOH were prepared to serve as aqueous washing solutions. Each washing solution was added to diesel containing cannabis oil (with THC) and the initial steps of the Detection Method were followed; however, instead of testing the lower aqueous solution after separation, the fuel portion in each case was separated from the washing solution and placed in a fresh 10 Eppendorf tube. Thereafter the extraction and testing methods as described for the Detection Method were performed again on all the fuel portions removed from the aqueous solution. Thus, for each buffer or washing solution the Detection Method was run on the separated fuel portion to determine if that buffer had been able to remove or denature the THC in the fuel. 15 The same procedure was followed for fuel containing the commonly used conventional marker (“Marker A”), to compare Marker A washing to THC washing. For the washing step, the concentration of buffer solution to the marked fuel sample was 20 approximately 5% v / v, whereas for the subsequent extraction step the usual concentration of about 20% v / v extraction buffer to fuel portion was used, as described in Step 2 of the Detection Method. After washing the diesel with the buffers, i.e., the four aqueous acids and bases, it was 25 found that the four buffers had little to no effect in washing the THC out of the diesel i.e., the tests remained positive. On the other hand, it was found that the aqueous acids and bases were able to wash out or denature some or all the Marker A from the fuel for 1M HCI, 5M HCI and 1M NaOH. 30 Based on the finding that the 1M NaOH produced a negative result (faint negative), it may have been expected that 5M NaOH might wash the marker out completely and bring about a more definitive negative result. However, 5M NaOH brought about a positive result, indicating that the high concentration of NaOH may have inactivated the antibodies on the Marker A test. 20 09 24 B) Solid Absorbents Activated charcoal, bentonite clay and silica gel were used during this test. Fifty milligrams (50 mg) of each were weighed out into fresh Eppendorf tubes, corresponding approximately to 5% of the fuel volume in each case. One millilitre (1 ml) of THC marked 5 fuel was added to each of the tubes. The tubes were shaken vigorously for one minute and thereafter the solid absorbents were allowed to settle for ten minutes. The fuel was removed from the solid absorbents and placed into fresh Eppendorf tubes. From this point on, the Detection Method as described above was followed on all the fuels to determine if the solid absorbents were able to remove or denature the THC in the fuel. The same 10 procedure was followed for Marker A to compare Marker A washing to THC washing. None of the absorbents were able to wash and remove the THC from the fuel. The lateral flow strip remained positive, indicating a sufficient quantity of THC remained in the fuel to present a positive result. 15 The same was attempted for Marker A. The activated charcoal and bentonite clay were able to wash Marker A out of the fuel completely, while silica gel had no effect in washing out Marker A. 20 Testing Stability of THC in Fuel Cannabis oil and THC-BSA (a compound used on the test line of a typical urine-based THC test) were spiked into diesel at approximately the lowest detectable concentrations. Two tubes of each were placed in a 40°C oven and at room temperature for seven days. After incubating 25 for seven days, the Detection Method as described above was performed on all the fuels to determine if the THC remained stable in the fuel. After the incubation period, both the THC in the cannabis oil and the THC-BSA remained stable. 30 Determining if THC Co-Distils with Fuel Two distillation methods were used and are described below: 35 A) Home-made Distillation Apparatus 20 09 24 A home-made distillation apparatus was made from copper pipes and fittings. THC marked and unmarked fuel was processed through the apparatus by heating the loading pipe with a butane torch. Distilled fuel was collected in a glass for processing. From this point on, the Detection Method as described above was performed on all the fuels in order to 5 determine if the THC co-distilled with the fuel and remained intact. After distilling the fuel containing the cannabis oil on the home-made distillation apparatus and extracting the THC and running it on lateral flow assay strips, the results remained positive. This implies that the THC co-distilled with the fuel and was detectable on the 10 lateral flow strips after distillation. After the THC marked diesel was run through the distiller, a negative sample (i.e., diesel containing no added THC) was distilled three times and tested. After the first negative distillation, a faint negative line was evident. It was surmised that this occurred on account of a residue of THC remaining in the system and causing some contamination. After the second distillation, the test line increased in visibility and 15 further increased in strength after the third distillation. B) Independent Distillation An independent service provider was engaged to distil fuel at their facility using an ISL AD86 5G distillation machine. Once the fuel was distilled, the fuel was tested on the THC 20 strips as per the Detection Method against negative and positive distillations. The negative distillation produced a negative result while the fuel containing the cannabis oil produced a positive result. This confirms that the THC co-distils with the fuel, remains intact after distillation, and produces a positive result on the test. 25 Furthermore, two fractions of the distillation were collected, one between 20°C and 110°C and one between 110°C and 198°C. The fraction from the 20°C to 110°C range produced a faint negative result, showing that the THC had not distilled at this temperature. However, THC is known to sublimate long before its boiling point of 157°C, which may explain the 30 weak negative. On the other hand, this implies that some THC may have been co-distilled in the 20°C to 110°C bracket. The 110°C to 198°C fraction was entirely positive for THC, therefore showing that THC co-distilled in this temperature range. The above-mentioned tests and experiments all demonstrate how cannabis oil containing THC 35 may be used as a marker to identify fuel. The tests indicate that even after the washing 20 09 24 process, the THC remained present and detectable in the fuel while Marker A was washed out. Also, the THC co-distilled with the fuel and remained intact and detectable. The distillation 5 range for petrol is from 25°C to 210°C whereas diesel’s distillation range is from 150°C to 371 °C. THC has a boiling point of approximately 157°C. Thus, it may be expected that when crude oil that has been spiked, tagged or marked with THC is distilled, the THC will be likely to end up in both the petrol and diesel fractions. Several advantages may be derived from this. For example, in the context of the theft of fuel from oil pipelines, THC (or a similar compound 10 or naturally occurring substance or synthetic equivalent), which co-distils with the fuel, can be added to the fuel before it is pumped, allowing fuel stolen from the pipeline to be tracked or identified even after it has been distilled. The exemplary tests described above focused on the detection of THC in the samples, and 15 hence employed lateral flow assays designed to detect THC. However, it will be appreciated that where other markers are targeted, other suitable assays or analytical methods adapted to detect such other markers would be substituted for the TCH assays. For example, where CBN is used as the marker, a lateral flow assay designed to be sensitive to CBN may be appropriate to use. 20 It is important to note that cannabis oil contains a large number (>100) of compounds, not just THC. A concentration of 200-500pg / ml may be too high to be used in the field, but because cannabis oil is a mixture of many different compounds, it is probably that purified, isolated or synthesized THC (or other cannabinoid) may be suitable for use at a more workable 25 concentration range, e.g., approximately 50-250 ng / ml. Currently known THC lateral flow tests strips can detect THC down to a limit of detection of about 50 ng / ml. The cannabis oil constituents may improve or promote the performance of the fuel due to their combustion potential. Compared to current biomarker additives, cannabis plant constituents 30 may be more combustible as they may form a natural oil when extracted. THC is a molecule that shares many of the same properties as that of petroleum fuels but it is highly unlikely to occur naturally in petroleum fuels. THC, like crude oil, is an oil by nature at ambient temperature. It is very stable at high temperatures, does not react with fuel and is 35 stable for extended periods of time in the presence of petroleum. THC can also be used in 20 09 24 other fractions post distillation, whether heavier or lighter than petrol or diesel. Besides THC, the above research shows that many different cannabinoids found in the Cannabis plant may be candidate molecules for use as markers, tracers or taggants. For 5 example, THC may decompose after extended heat exposure to form the more stable CBN. CBN antibodies are also available for detection purposes. The boiling point of CBN is 185°C which also falls well within the distillation range for both petrol and diesel. The experimental results described above suggest that THC and other cannabinoid markers 10 may resist attempts at unauthorised washing or laundering of fuels that have been marked with such markers, irrespective of whether such attempts are based on distillation, treatment with aqueous acids and bases, absorption or adsorption methods, or size exclusion methods. Whilst laundering methods appeared to remove most of the conventional Marker A from fuels that were tested (or the high concentrations of acids and bases denatured the Marker A), by 15 comparison only about 5% of the THC marker appears to have been removed from tested fuel during the extraction process. For the solid absorbents, the test results suggest that the solid absorbents absorbed a high proportion of the Marker A but not the THC marker. As previously discussed, a detection method is also disclosed for detecting the presence of a 20 marker in a carbonaceous fluid. The method comprises a step of extracting the marker from the fuel into an aqueous layer. The method further includes analysing the aqueous layer for the presence of said marker. The marker that is detectable using the detection method comprises a cannabinoid. It may comprise a phytocannabinoid. 25 The marker may be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV) and cannabichromene (CBC), and mixtures thereof. In certain embodiments, the marker may be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC) and cannabinol 30 (CBN). The concentration of the cannabinoid in the fuel may be less than about 0.25 ppm w / v (250 ng / ml) although it will be appreciated that a wide range of other suitable concentrations are feasible, provided that the cannabinoid remains detectable. 20 09 24 The step of extracting the marker into the aqueous layer may be performed using an extraction buffer. The extraction buffer may be selected from the group consisting of PBS, COVID Saliva Buffer, Dengue Buffer, HRB and MRB. 5 HRB may advantageously be used as the extraction buffer. It gave the lowest detection limit in testing. The analysis of the aqueous layer may be performed using a lateral flow assay. In the case of THC being used as marker, a THC lateral flow strip may be used to perform the lateral flow 10 assay. In accordance with another aspect of the invention there is provided a marked carbonaceous product which includes a carbonaceous fluid and a marker comprising acannabinoid. 15 The cannabinoid in the product may comprise at least one substance or compound extractable from a Cannabis plant, the definition of such substance or compound extending to synthetically manufactured versions of such substance or compound. The Cannabis plant may be Cannabis sativa, Cannabis indica or Cannabis ruderalis. The marker may be cannabis oil (containing a mixture of substances extracted from the Cannabis plant) or may be an isolated or purified 20 cannabinoid extracted from the Cannabis plant (or a synthetically manufactured version thereof). The marker may comprise a phytocannabinoid. The marker may be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), 25 tetrahydrocannabivarin (THCV), cannabidivarin (CBDV) and cannabichromene (CBC), and mixtures thereof. In certain embodiments, the marker may advantageously be selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC) and cannabinol 30 (CBN). Naturally occurring or synthetic tetrahydrocannabinol (THC) has been found to be suitable in experimental testing. In certain embodiments, the concentration of the marker in the fuel may be less than about 0.25 ppm w / v (250 ng / ml). However, as mentioned above, it will be appreciated that a wide 35 range of other concentrations may also be feasible. 20 09 24 The cannabinoidmay have a normal boiling point in a range from about 140°C to about 220°C inclusive. The cannabinoidmay have a boiling point selected from the group consisting of about 157°C, about 160°C to about 180°C, 185°C, and 220°C. In one embodiment, the 5 cannabinoidmay have a normal boiling point of about 157°C. As discussed, in accordance with a further aspect of the invention there is provided a use of a cannabinoid or derivative thereof as a marker in a carbonaceous fluid. The carbonaceous fluid may comprise a fuel, in which case the marker may comprise a fuel marker. 10 The cannabinoid may be dissolvable in the fuel. It may be capable of going into suspension in the fuel. The cannabinoid may have characteristics and properties as described elsewhere in this 15 specification. It may be selected from the various groups of compounds listed in this specification. The foregoing description has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise modes or forms disclosed. Persons 20 skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure. The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the 25 inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims. 30 Finally, throughout the specification and accompanying claims, unless the context requires otherwise, the word ‘comprise’ or variations such as ‘comprises’ or ‘comprising’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

1. A method for marking a carbonaceous fluid with a marker, the method comprising introducing the marker into said carbonaceous fluid, wherein said marker comprises a cannabinoid or a derivative thereof.

2. The method as claimed in claim 1, wherein the marker comprises a cannabinoid selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV), cannabichromene (CBC), and any mixture thereof.

3. The method as claimed in claim 2, wherein the cannabinoid is selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC) and cannabinol (CBN).

4. The method as claimed in any one of the preceding claims, wherein the cannabinoid or derivative thereof has a normal boiling point in a range from 140°C to 220°C inclusive.

5. The method as claimed in any one of the preceding claims, wherein the carbonaceous fluid is a liquid petroleum fuel.

6. The method as claimed in any one of claims 1 to 4, wherein the carbonaceous fluid is selected from the group consisting of gasoline (petrol), diesel fuel, bio-diesel, methanol, ethanol, bioethanol, benzene, liquid paraffin, aviation kerosene, heating oil, fuel oil, bunker fuel, crude oil, liquefied petroleum gas, hydraulic fluid, lubricating oil, natural gas, methane, propane, butane, and any mixture thereof.

7. The method as claimed in any one of the preceding claims, wherein the concentration of the cannabinoid or derivative thereof in the carbonaceous fluid is less than about 0.25 ppm w / v.

8. The method as claimed in any one of the preceding claims, which further includes a step of analysing the carbonaceous fluid for the presence therein of the marker, thereby to detect the presence of the marker in the carbonaceous fluid.

9. A detection method for detecting the presence of a marker in a carbonaceous fluid, said method comprising:(I) extracting said marker from said carbonaceous fluid into an aqueous layer; and17 06 24(II) analysing said aqueous layer for the presence of said marker; wherein said marker comprises a cannabinoid or a derivative thereof.

10. The detection method as claimed in claim 9, wherein the cannabinoid is selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV), cannabichromene (CBC), and any mixture thereof.

11. The detection method as claimed in claim 10, wherein the cannabinoid is selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC) and cannabinol (CBN).

12. The detection method as claimed in any one of claims 9 to 11, wherein the carbonaceous fluid is selected from the group consisting of gasoline (petrol), diesel fuel, bio-diesel, methanol, ethanol, bio-ethanol, benzene, liquid paraffin, aviation kerosene, heating oil, fuel oil, bunker fuel, crude oil, liquefied petroleum gas, hydraulic fluid, lubricating oil, natural gas, methane, propane, butane, and any mixture thereof.

13. The detection method as claimed in any one of claims 9 to 12, wherein the step of extracting the marker into the aqueous layer is performed using an extraction buffer comprising HRB.

14. The detection method as claimed in any one of claims 9 to 13, wherein the analysis of the aqueous layer is performed using a lateral flow assay.

15. A marked carbonaceous product comprising a carbonaceous fuel and a marker comprising a cannabinoid or derivative thereof.

16. The marked carbonaceous product as claimed in claim 15, wherein the cannabinoid is selected from the group consisting of tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV) and cannabichromene (CBC), and any mixture thereof.

17. The marked carbonaceous product as claimed in claim 15 or 16, wherein the concentration of the cannabinoid in the fuel is less than about 0.25 ppm w / v.

18. The marked carbonaceous product as claimed in any one of claims 15 to 17, wherein the cannabinoid has a normal boiling point in a range from 140°C to 220°C inclusive.17 06 2419. The marked carbonaceous product as claimed in any one of claims 15 to 18, wherein the carbonaceous fuel is a liquid petroleum fuel.

20. The marked carbonaceous product as claimed in any one of claims 15 to 18, wherein the carbonaceous fuel is selected from the group consisting of gasoline (petrol), diesel fuel, biodiesel, methanol, ethanol, bio-ethanol, benzene, liquid paraffin, aviation kerosene, heating oil, fuel oil, bunker fuel, crude oil, liquefied petroleum gas, natural gas, methane, propane, butane, and any mixture thereof.

21. Use of a cannabinoid or derivative thereof as a marker in a carbonaceous fluid.

22. The use as claimed in claim 21, wherein the cannabinoid is selected from the group consisting of naturally occurring and synthetic tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV), cannabichromene (CBC), and any mixture thereof.

23. The use as claimed in either one of claims 21 and 22, wherein a concentration of the cannabinoid or derivative thereof in the carbonaceous fluid is less than about 0.25 ppm w / v.

24. The use as claimed in any one of claims 21 to 23, wherein the carbonaceous fluid is a liquid petroleum fuel.

25. The use as claimed in any one of claims 21 to 23, wherein the carbonaceous fluid is selected from the group consisting of gasoline (petrol), diesel fuel, bio-diesel, methanol, ethanol, bio-ethanol, benzene, liquid paraffin, aviation kerosene, heating oil, fuel oil, bunker fuel, crude oil, liquefied petroleum gas, hydraulic fluid, lubricating oil, natural gas, methane, propane, butane, and any mixture thereof.

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