A method for analyzing thioether compounds in garlic

Abstract

The invention discloses an analysis method for sulfide compounds in garlic, and relates to the technical field of sulfide compound detection. Gas chromatography-tandem mass spectrometry is used to detect sulfide compounds in garlic bulbs, and the target sulfide compounds are efficiently extracted, highly selectively separated and accurately detected by optimizing the extraction process of garlic bulbs and the instrument parameters of gas chromatography-tandem mass spectrometry. The analysis method is a qualitative and quantitative method that can simultaneously analyze eight sulfide compounds in garlic, has the characteristics of high sensitivity, high selectivity and high accuracy, and is suitable for qualitative and quantitative detection of sulfide compounds in garlic samples.

Description

Technical Field

[0001] The invention relates to the technical field of thioether compound detection, and in particular to an analysis method for thioether compounds in garlic. Background Art

[0002] Garlic (Allium sativum L.) is an underground bulb of the Liliaceae and Allium genus. Fresh garlic is rich in a variety of quality components and bioactive substances, such as organic sulfur compounds, saponins, phenolic compounds, etc. Sulfur-containing compounds such as alliin, allicin, allicene, allyl sulfide, S-allyl-L-cysteine, and S-allylthio-L-cysteine ​​are important bioactive substances in garlic. Among them, the smell of garlic mainly comes from volatile sulfur-containing compounds, including allicin and sulfide compounds such as diallyl tetrasulfide (DATTS), diallyl disulfide (DADS), methyl allyl disulfide (AMDS), diallyl trisulfide (DATS), methyl allyl sulfide (AMS), diallyl sulfide (DAS), dimethyl trisulfide (DMTS), and methyl propyl disulfide (MPDS).

[0003] At present, the pretreatment methods for sulfide compounds in garlic are mainly headspace solid phase microextraction and distillation. However, headspace solid phase microextraction cannot achieve accurate quantification of highly volatile or high-content compounds, and the distillation method has low extraction efficiency and lacks selectivity. The detection methods of sulfide compounds in garlic include gas chromatography-mass spectrometry, gas chromatography-olfactory detection, electronic nose, gas chromatography-ion flow detection, etc. The most commonly used method is gas chromatography-mass spectrometry, which has the characteristics of high resolution and high sensitivity. However, the existing gas chromatography-mass spectrometry methods are all for preliminary qualitative determination of sulfide compounds, and can only quantify DADS and DATS by internal standard method, or quantify AMS, DAS and DATS by external standard method, and cannot achieve qualitative and quantitative determination of multiple sulfide compounds. Therefore, it is urgent to seek a method with simple and easy sample processing, good repeatability of test results, high accuracy, and can be widely used for qualitative and quantitative determination of sulfide compounds in garlic samples.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a method for analyzing thioether compounds in garlic to solve the above-mentioned technical problems.

[0006] The present invention is achieved in that:

[0007] In a first aspect, an embodiment of the present invention provides a method for analyzing sulfide compounds in garlic, comprising the following steps:

[0008] Gas chromatography-tandem mass spectrometry was used to detect sulfide compounds in garlic bulbs;

[0009] When performing gas chromatography, the chromatographic column used is a bonded and cross-linked 5% diphenyl / 95% dimethylpolysiloxane gas chromatography column, and the heating program is: maintain 40-80°C for 1-5 minutes, heat to 90-130°C at a heating rate of 8-12°C / min, then heat to 150-200°C at a heating rate of 13-17°C / min, and finally heat to 240-280°C at a heating rate of 28-32°C / min; high-pressure injection, the pressure is 220-260kPa.

[0010] In a second aspect, an embodiment of the present invention provides a method for extracting sulfide compounds as in the aforementioned analysis method, comprising: adding an extraction solvent to the garlic homogenate prepared by pretreatment to extract sulfide compounds, the extraction temperature is 25-55°C, the extraction time is 5min-4h, and a mixed solution is obtained; the mixed solution is centrifuged to obtain an extract; and the extract is made into the sample to be tested for standby use.

[0011] The present invention has the following beneficial effects:

[0012] The analysis method of sulfide compounds in garlic provided by the embodiment of the present invention adopts gas chromatography-tandem mass spectrometry to detect sulfide compounds in garlic bulbs, and optimizes the extraction process of garlic bulbs and the instrument parameters of gas chromatography-tandem mass spectrometry, so that the target sulfide compounds can be efficiently extracted, highly selectively separated and accurately detected. The analysis method is a qualitative and quantitative method that can simultaneously analyze eight sulfide compounds in garlic, has the characteristics of high sensitivity, high selectivity and high accuracy, and is suitable for qualitative and quantitative detection of sulfide compounds in garlic samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0014] Figure 1-Figure 6 The GCMS-TQ8040 total ion current chromatogram of the analytical method of Examples 1-6 applied to a mixed standard solution of eight sulfide compounds with a concentration of 1000 μg / L;

[0015] Figure 7 The results of the analysis of eight sulfide compounds in garlic preserved in different ways;

[0016] Figure 8The results of the analysis of eight sulfide compounds in garlic extracted with a single extraction solvent;

[0017] Fig. 9 The results of the analysis of eight sulfide compounds in garlic extracted by mixed extraction solvents;

[0018] Fig.10 The results are the analysis of eight sulfide compounds in garlic with different solid-liquid ratios of garlic and extraction solvent;

[0019] Fig.11 The results of the analysis of eight sulfide compounds in garlic extracted at different extraction temperatures are shown below;

[0020] Fig.12 These are the analysis results of the contents of eight sulfide compounds in garlic extracted at different extraction times. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0022] In a first aspect, an embodiment of the present invention provides a method for analyzing sulfide compounds in garlic, comprising the following steps:

[0023] Gas chromatography-tandem mass spectrometry was used to detect sulfide compounds in garlic bulbs;

[0024] When performing gas chromatography, the chromatographic column used is a bonded and cross-linked 5% diphenyl / 95% dimethylpolysiloxane gas chromatography column, and the heating program is: maintain 40-80°C for 1-5 minutes, heat to 90-130°C at a heating rate of 8-12°C / min, then heat to 150-200°C at a heating rate of 13-17°C / min, and finally heat to 240-280°C at a heating rate of 28-32°C / min; high-pressure injection, the pressure is 220-260kPa.

[0025] It should be noted that the sulfide compounds in garlic detected by the present invention belong to volatile sulfur-containing compounds in garlic, including diallyl tetrasulfide (DATTS), diallyl disulfide (DADS), methyl allyl disulfide (AMDS), diallyl trisulfide (DATS), methyl allyl sulfide (AMS), diallyl sulfide (DAS), dimethyl trisulfide (DMTS), methyl propyl disulfide (MPDS), 3-vinyl-4H-1,2-dithiene, 2-vinyl-4H-l,3-dithiene, etc.

[0026] Furthermore, the analysis method provided in the embodiment of the present invention can detect eight sulfide compounds in garlic, which are diallyl sulfide (DAS), methyl allyl disulfide (AMDS), methyl propyl disulfide (MPDS), dimethyl trisulfide (DMTS), diallyl disulfide (DADS), diallyl tetrasulfide (DATTS), methyl allyl sulfide (AMS) and diallyl trisulfide (DATS).

[0027] Before testing, the instrument conditions need to be optimized. The present invention first creates a full scan method, determines the standard of sulfide compounds, clarifies the precursor ion, then determines the daughter ion and optimizes the collision energy, and finally completes the MRM method establishment. The retention time of eight sulfide compounds in garlic and the MRM qualitative and quantitative ion pairs and collision energy information are shown in Table 1.

[0028] Table 1 Chromatographic and mass spectrometric information of eight sulfide compounds in garlic

[0029]

[0030] In order to obtain a suitable separation effect for the target compound, the gas chromatography parameters were further optimized. The setting of the gas chromatography temperature program is mainly based on the separation requirements of complex composite compounds. The low-boiling point components are separated by first setting a lower column temperature, and then the high-boiling point components are separated by gradually increasing the column temperature. The chromatographic column temperature program is set according to the boiling range of the component, and the column temperature is continuously increased linearly or nonlinearly over time, so that the column temperature corresponds to the boiling point of the component, so that both the low-boiling point component and the high-boiling point component have appropriate retention in the chromatographic column, improving the separation efficiency and resolution. In addition, the reasonable setting of the program temperature increase has the characteristics of effectively improving separation, narrowing the component peak, reducing the detection limit and saving time. This process involves multiple key steps and parameter settings, including starting temperature, holding time of starting temperature, heating rate, first-order arrival temperature, holding time of first-order arrival temperature, second-order heating rate, second-order arrival temperature, holding time of second-order arrival temperature, etc. Multi-stage program temperature increase can be set according to the analysis requirements. It should be noted that the temperature raising program of the present invention is related to the boiling point of the sulfide compounds in the detected garlic, and can be reasonably adjusted according to the actual detected substances.

[0031] In a preferred embodiment of the present invention, in order to establish a general analysis method for sulfide compounds in garlic, eight characteristic sulfide compounds in garlic samples are selected for analysis. In order to detect the target compound, the gas chromatograph used in the present invention is a chromatographic column of Shimadzu Corporation, specifically SH-Rxi-5Sil MS, whose stationary phase has excellent inertness to active compounds. The embodiment of the present invention specifically uses a weakly polar stationary phase bonded cross-linked TMPolyarylene, 1,4-di(dimethyl)phenylmethylpolysiloxane. In other embodiments of the present invention, reasonable adjustments can be made according to actual needs.

[0032] In an optional embodiment of the present invention, when performing gas chromatography, the column length of the chromatographic column used is 25-100m, the inner diameter is 0.25-0.53mm, and the film thickness is 0.10-0.36μm; the injection port temperature is set to 100-300℃; the carrier gas flow rate is 1-2mL / min; high pressure injection, the injection time is 1-2min; the injection volume is 1-2μL.

[0033] Furthermore, the column length of the chromatographic column is 30m, the inner diameter is 0.25mm, and the film thickness is 0.25μm; the injection port temperature is set to 280°C; the carrier gas flow rate is 1.59mL / min, and the carrier gas pressure is 94.1kPa; during high-pressure injection, the pressure is 250kPa, the injection time is 1min; and the injection volume is 1μL.

[0034] It should be noted that when high-pressure injection is not performed, the injection pressure of the sample to be tested is maintained at the carrier gas pressure.

[0035] For the selection of carrier gas, according to the needs of actual analysis, the carrier gas should not easily participate in any reaction, be less corrosive to instrument components, and its diffusion coefficient and molecular weight should be moderate, with better separation effect. And high-purity carrier gas can provide better analysis results, especially for the analysis of compounds with lower content, high-purity carrier gas can avoid interference with background signals. Therefore, the embodiment of the present invention selects high-purity helium. In the embodiment of the present invention, the type of carrier gas can be reasonably adjusted according to actual needs.

[0036] It should be noted that the column length of the chromatographic column will affect the column efficiency, retention time and carrier gas pressure; the inner diameter and film thickness directly affect the effect of sample separation and the sensitivity of analysis; the injection port temperature will affect the volatility of the sample and the stability of injection, thereby affecting the analysis results. Reasonable control of the carrier gas flow rate and carrier gas pressure can increase the residence time of the compound on the stationary phase, with good peak morphology, sharp peak shape and high separation, thereby improving the separation effect and column efficiency. A higher carrier gas flow rate can accelerate the transfer speed of the compound in the chromatographic column, shorten the retention time between the components, and thus improve the separation effect. However, if the carrier gas flow rate is too high or too low, the residence time of the compound in the chromatographic column will change, resulting in peak broadening and even incomplete separation. The regulation of the carrier gas flow rate and carrier gas pressure in the present invention needs to be comprehensively evaluated according to the properties of the sulfide compounds in garlic, so that the peak morphology is good, the peak shape is sharp, and the separation degree of each substance in the component can be finally obtained.

[0037] In an optional embodiment of the present invention, when performing mass spectrometry detection, the mass spectrometry detection conditions are as follows: the ion source type is an electron impact (EI) source; the scanning mode is a multiple reaction monitoring (MRM) mode; the injection port temperature is set to 250-300°C, and the ion source temperature is set to 200-250°C.

[0038] Furthermore, the injection port temperature was set to 280°C, and the ion source temperature was set to 230°C.

[0039] It should be noted that the mass spectrometer used in the present invention is a triple quadrupole mass spectrometer, and the solvent delay is set to 1.05 min according to the peak situation. The data can be qualitatively and quantitatively analyzed using the post-operation analysis function of the Shimadzu gas chromatograph. Microsoft Excel is used for linear regression and statistical analysis. In other embodiments of the present invention, data analysis can be performed in other forms according to actual needs and convenience.

[0040] In order to evaluate the feasibility of the analytical method of garlic thioether compounds in the present invention, the present invention is evaluated by detection limit (LOD), quantification limit (LOQ), linear curve, accuracy, matrix effect and precision. LOD and LOQ are compound concentrations of 3 times and 10 times the signal-to-noise ratio (S / N) respectively; at least 7 series of concentrations are set for drawing the standard curve; the accuracy is evaluated by spiked recovery rate. In the evaluation process of recovery rate, three spiked recovery levels of L (low), M (medium) and H (high) are designed, and the calculation formula is: recovery rate = (detection amount - original amount) / added amount × 100%. The matrix effect is evaluated by the slope method, and the calculation formula is: matrix effect = matrix standard curve slope / solvent standard curve slope. When the matrix effect is 0.8-1.2, it means that the matrix effect has little effect on the method, and solvent standardization can be used for quantification; when the matrix effect is lower than 0.8 or higher than 1.2, it means that the matrix effect has an inhibitory or enhanced effect on the method, and the matrix standard needs to be used for quantification. The precision of the method was evaluated based on repeatability (intra-day precision) and reproducibility (inter-day precision). The intra-day precision was evaluated by performing six replicates of the sulfide compound mixture at different time points on the same day, and the inter-day precision was evaluated by performing six replicates on three consecutive days. The results were expressed as relative standard deviation (RSD).

[0041] In an optional embodiment of the present invention, the sample to be analyzed in the analysis method is obtained by the following method:

[0042] The garlic bulb is pretreated to obtain a garlic homogenate; an extraction solvent is added to the garlic homogenate to extract sulfide compounds at an extraction temperature of 25-55° C. for 5 min-4 h to obtain a mixed solution; the mixed solution is centrifuged to obtain an extract; and the extract is prepared into a sample to be tested.

[0043] In an optional embodiment of the present invention, the garlic bulb is pretreated before extraction; the pretreatment includes peeling the garlic bulb, directly storing the garlic bulb or storing the garlic bulb after drying; wherein the condition for directly storing the garlic bulb is selected from any one of -20°C to room temperature or liquid nitrogen; the condition for drying the garlic bulb is selected from any one of liquid nitrogen freeze drying, freeze drying and oven drying.

[0044] Specifically, for samples directly stored in the form of garlic bulbs, take no less than 20 garlic bulbs, remove the dust on the surface, peel off a layer of the bulb skin, and wrap it in tin foil for storage. When analysis is required, take out the sample, peel off the bulb skin and the bulb bud inner skin, and then use a grinder to homogenize it to make garlic slurry for later use.

[0045] Further, the storage conditions of the garlic bulbs are selected from any one of -20°C to room temperature or liquid nitrogen; specifically, the storage conditions of the garlic bulbs can be selected from any one of liquid nitrogen, -20°C, 0°C, 4°C, 10°C, room temperature and other temperatures between -20°C and room temperature.

[0046] The drying condition of the garlic bulb is selected from any one of liquid nitrogen freeze drying, freeze drying and oven drying. Considering that the garlic bulb is a block structure and is not easy to dry, the present invention slices the garlic bulb and then dries it to prepare a powder form for standby use.

[0047] Specifically, liquid nitrogen freeze drying is to first treat the garlic bulb with liquid nitrogen, then slice and freeze dry it to make powder for later use; freeze drying is to directly slice the garlic bulb and freeze dry it to make powder for later use; oven drying is to directly slice the garlic bulb and oven dry it to make powder for later use. In other embodiments of the present invention, the drying conditions or specific operation methods of the garlic bulb can be reasonably adjusted according to actual needs.

[0048] It should be noted that the eight sulfide compounds in the garlic processed in the present invention are the following components, diallyl sulfide (DAS), methyl allyl disulfide (AMDS), methyl propyl disulfide (MPDS), dimethyl trisulfide (DMTS), diallyl disulfide (DADS), diallyl tetrasulfide (DATTS), methyl allyl sulfide (AMS) and diallyl trisulfide (DATS), which are all volatile natural sulfur-containing compounds. The different storage conditions of garlic will have a greater impact on the content of sulfide compounds. In order to ensure that the content of sulfide compounds in garlic is not lost due to human factors, the present invention takes undamaged fresh garlic bulbs, wraps them with tin foil and performs storage treatment for standby use. In other embodiments of the present invention, different types of sulfide compounds can be selected for detection and analysis according to actual needs.

[0049] In a preferred embodiment of the present invention, the garlic bulbs are directly stored in the form of garlic bulbs at a storage condition of -20°C.

[0050] In a second aspect, an embodiment of the present invention provides a method for extracting sulfide compounds as in the aforementioned analysis method, comprising: adding an extraction solvent to the garlic homogenate prepared by pretreatment to extract sulfide compounds, the extraction temperature is 25-55°C, the extraction time is 5min-4h, and a mixed solution is obtained; the mixed solution is centrifuged to obtain an extract; and the extract is made into the sample to be tested for standby use.

[0051] Specifically, the extraction temperature is selected from any one of 25°C, 35°C, 45°C, 55°C and other temperatures between 25-55°C; the extraction time is selected from any one of 5min, 10min, 20min, 30min, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h and other times between 5min-4h.

[0052] In an optional embodiment of the present invention, the extraction solvent is selected from at least one of n-hexane, ethyl acetate, petroleum ether and dichloromethane.

[0053] It should be noted that, considering the complexity of the garlic sample matrix and the physicochemical properties of thioether compounds, the present invention optimizes the extraction solvent. Garlic bulbs stored at -20°C were taken as the analysis object, prepared into garlic homogenate, and the thioether compounds therein were extracted. The present invention selected 4 different extraction solvents, namely n-hexane, ethyl acetate, petroleum ether and dichloromethane, to compare the effects of different extraction solvents on the extraction efficiency of thioether compounds. The extraction effect of a single solvent on thioether compounds is not very ideal, so the inventors use a mixed extraction solvent for extraction. Petroleum ether can be miscible with dichloromethane in any proportion. This experiment selected different ratios of dichloromethane and petroleum ether for subsequent experiments.

[0054] In an optional embodiment of the present invention, the extraction solvent is a mixture of dichloromethane and petroleum ether in a volume ratio of (5-9):(5-1); further, the volume ratio of dichloromethane and petroleum ether is 5:5.

[0055] In an optional embodiment of the present invention, the solid-liquid ratio of garlic bulb to extraction solvent is 1:(1-100) (g / mL); further, the solid-liquid ratio is 1:(10-20) (g / mL).

[0056] It should be noted that because the ratio of garlic sample to extraction solvent affects the extraction efficiency of the compound, and out of consideration of experimental cost and ease of operation during the experiment, the present invention optimizes the solid-liquid ratio. A reasonable amount of solid-liquid ratio can significantly improve the extraction efficiency of sulfide compounds in garlic bulbs. If the extraction solvent is too much or too little, the extraction efficiency is not ideal, and too much extraction solvent will increase the experimental cost and have an adverse effect on the environment.

[0057] The optimal solid-liquid ratio selected by the present invention is 1:10 (g / mL); in other embodiments of the present invention, it can be reasonably adjusted according to the type of compound actually treated and the extraction solvent.

[0058] In an optional embodiment of the present invention, the extraction temperature is 25-45°C; further 25°C.

[0059] It should be noted that the setting of the extraction temperature needs to improve the extraction efficiency of sulfide compounds in garlic bulbs on the one hand, and on the other hand, the solvent volatilization caused by the increase in temperature needs to be considered. Taking into account the experimental efficiency and time cost, the extraction temperature was selected as 25°C.

[0060] In an optional embodiment of the present invention, the extraction time is 2-4 hours; further 2.5 hours.

[0061] It should be noted that the extraction process of sulfide compounds in garlic bulbs is carried out in a constant temperature oscillator, which mainly utilizes the mass transfer principle to fully mix the garlic homogenate and the extraction solvent to improve the extraction efficiency of sulfide compounds in garlic bulbs. Reasonable control of the extraction time can improve the extraction efficiency.

[0062] In an optional embodiment of the present invention, after the garlic homogenate is extracted, a mixed solution is obtained; the mixed solution needs to be centrifuged to prepare a sample to be tested for later use.

[0063] It should be noted that the centrifugal treatment of the mixed solution includes a first centrifugal treatment and a second centrifugal treatment; the supernatant of the first centrifugal treatment is dried and then subjected to a second centrifugal treatment to obtain an extract; and the extract is prepared into a sample to be tested.

[0064] Specifically, the centrifugal treatment is mainly to effectively separate the solid matter and the extract after the extraction treatment. In the embodiment of the present invention, the temperature of the centrifugal treatment is 4°C and the speed is 4000rpm. The drying treatment is mainly to remove a small amount of water in the garlic homogenate prepared from the garlic bulb to avoid it causing trouble for subsequent detection. The centrifugation again after drying is mainly to separate the desiccant solid particles from the extract and improve the purity of the extract.

[0065] Furthermore, the desiccant used in the drying process is a neutral desiccant, which is selected from any one of anhydrous magnesium sulfate or anhydrous sodium sulfate. Furthermore, the desiccant is anhydrous magnesium sulfate. It should be noted that the type of desiccant can be reasonably adjusted according to actual needs.

[0066] The extract obtained by the second centrifugation treatment was filtered through a 0.20 μm PTFE filter membrane and placed in a sample injection vial to prepare a sample to be tested for later use.

[0067] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0068] Example 1

[0069] The analysis method of sulfide compounds in garlic provided in this embodiment comprises:

[0070] (1) Preparation of standard solution

[0071] First, accurately weigh 10 mg (accurate to 0.01 mg) of the sulfide compound standard on an electronic balance, dissolve it in n-hexane solution, transfer it to a 10 mL brown volumetric flask and make up to a 1000 mg / L standard stock solution, and store it in a -20 ° C refrigerator. Use the standard stock solution to prepare a mixed standard intermediate solution with a concentration of 100 mg / L, and store it in a -20 ° C refrigerator for standby use. Dilute the above mixed standard intermediate solution step by step with n-hexane solution to prepare standard working solutions with mass concentrations of 1 μg / L, 2 μg / L, 5 μg / L, 10 μg / L, 20 μg / L, 50 μg / L, 100 μg / L, 200 μg / L, 500 μg / L, 1000 μg / L, 2000 μg / L, and 5000 μg / L, respectively. The standard working solutions are all prepared and used immediately. Setting multiple concentration gradient standard working solutions is mainly to find representative concentration points as the concentration range for drawing standard curves.

[0072] (2) Garlic bulb pretreatment

[0073] Take no less than 20 garlic bulbs, remove the dust on the surface, peel off a layer of the bulb skin, wrap it with tin foil, and store it in a -20℃ refrigerator for later use. Before testing, peel off the bulb skin and bulb bud inner skin, use a grinder to homogenize, and make garlic slurry for later use.

[0074] (3) Garlic homogenate extraction

[0075] Accurately weigh 1.000 g (± 0.001 g) of garlic homogenate in a 50 mL centrifuge tube, add 10 mL of extraction solvent (dichloromethane: petroleum ether = 5:5), vortex with a parallel vortex instrument for 1 min, shake on a shaker (300 rpm) at 25 ° C for 2.5 h, centrifuge the mixed solution at 4 ° C, 4000 rpm for 10 min, take 5 mL of the supernatant, add 1.5 g of anhydrous magnesium sulfate for drying, centrifuge the mixed solution at 4 ° C, 4000 rpm for 10 min, filter through a 0.20 μm PTFE membrane into a sampling vial to prepare a sample to be tested for later use.

[0076] (4) GC-QQQ-MS analysis

[0077] The samples to be tested were detected and analyzed using Shimadzu's gas chromatography-triple quadrupole mass spectrometer; the chromatographic conditions included: chromatographic column: SH-Rxi-5Sil MS (Shimadzu, Japan), column length 30m, inner diameter 0.25mm, film thickness 0.25μm; injection port temperature 280℃; heating program: first 50℃ for 1min, then heated to 100℃ at a heating rate of 10℃ / min, then heated to 200℃ at a heating rate of 15℃ / min, and finally heated to 280℃ at a heating rate of 30℃ / min; carrier gas was helium, carrier gas flow rate was 1.59mL / min, carrier gas pressure was 94.1kpa; no splitting, high pressure injection, pressure was 250kPa; injection time was 1min; injection volume was 1μL. The total running time for the simultaneous determination of eight sulfide compounds by this method was 15.33 minutes.

[0078] The triple quadrupole mass spectrometry conditions included: ion source type: electron impact (EI) source; scanning mode: multiple reaction monitoring (MRM) mode; the injection port temperature was 280°C, the ion source temperature was set to 230°C, and the solvent delay was set to 1.05 min according to the peak conditions.

[0079] The data were analyzed qualitatively and quantitatively using the post-run analysis function of the Shimadzu gas chromatograph. Linear regression and statistical analysis were performed using Microsoft Excel.

[0080] Example 2

[0081] The analysis method of sulfide compounds in garlic provided in this embodiment is different from that in Example 1 only in that:

[0082] GC-QQQ-MS analysis

[0083] The temperature program of the chromatographic column was as follows: first, maintained at 40°C for 5 min, then heated to 200°C at a heating rate of 10°C / min, and finally heated to 240°C at a heating rate of 30°C / min; the carrier gas was helium, and the carrier gas flow rate was 1.59 mL / min; no split; injection time was 1 min; injection volume was 1 μL, and the total running time was 22.33 min.

[0084] Example 3

[0085] The analysis method of sulfide compounds in garlic provided in this embodiment is different from that in Example 1 only in that:

[0086] GC-QQQ-MS analysis

[0087] Temperature program: maintain at 40℃ for 5min, increase the temperature to 100℃ at a heating rate of 10℃ / min, then increase the temperature to 150℃ at a heating rate of 15℃ / min, increase the temperature to 200℃ at a heating rate of 20℃ / min, and finally increase the temperature to 250℃ at a heating rate of 30℃ / min; the carrier gas is helium, the carrier gas flow rate is 1.59mL / min; no split; injection time is 1min; the injection volume is 1μL, and the total running time is 20.50 minutes.

[0088] Example 4

[0089] The analysis method of sulfide compounds in garlic provided in this embodiment is different from that in Example 1 only in that:

[0090] GC-QQQ-MS analysis

[0091] Temperature program: maintain at 80℃ for 1 min, increase the temperature to 200℃ at a heating rate of 10℃ / min, and finally increase the temperature to 280℃ at a heating rate of 30℃ / min; the carrier gas is helium, and the carrier gas flow rate is 1.59mL / min; no split; injection time is 1min; injection volume is 1μL, and the total running time is 15.67 minutes.

[0092] Example 5

[0093] The analysis method of sulfide compounds in garlic provided in this embodiment is different from that in Example 1 only in that:

[0094] GC-QQQ-MS analysis

[0095] Temperature program: maintain at 80℃ for 2min, increase the temperature to 100℃ at a heating rate of 10℃ / min, then increase the temperature to 200℃ at a heating rate of 15℃ / min, and finally increase the temperature to 280℃ at a heating rate of 30℃ / min; the carrier gas is helium, the carrier gas flow rate is 1.59mL / min; no split; injection time is 1min; the injection volume is 1μL, and the total running time is 13.33 minutes.

[0096] Example 6

[0097] The analysis method of sulfide compounds in garlic provided in this embodiment is different from that in Example 1 only in that:

[0098] GC-QQQ-MS analysis

[0099] Temperature program: maintain at 80℃ for 2min, increase the temperature to 100℃ at a heating rate of 10℃ / min, then increase the temperature to 200℃ at a heating rate of 15℃ / min, and finally increase the temperature to 280℃ at a heating rate of 30℃ / min; the carrier gas is helium, and the carrier gas flow rate is 1.59mL / min; no split; high-pressure injection, the pressure is 250kPa; the injection time is 1min; the injection volume is 1μL, and the total running time is 13.33 minutes.

[0100] Embodiment 7-13

[0101] The method for extracting sulfide compounds from garlic provided in Examples 7-13 is different from that in Example 1 only in that:

[0102] The storage conditions of samples in garlic bulb pretreatment are different:

[0103] Example 7: The garlic bulb samples wrapped in tin foil were placed in liquid nitrogen for preservation and set aside.

[0104] Example 8 The garlic bulb samples wrapped in tin foil were stored at 4° C. for later use.

[0105] Example 9 The garlic bulb samples wrapped in tin foil were placed at room temperature for storage and set aside.

[0106] Example 10 The garlic bulb sample is first treated with liquid nitrogen, then sliced ​​and freeze-dried to prepare powder for later use.

[0107] Example 11: The garlic bulb is directly sliced ​​and freeze-dried to prepare powder for later use.

[0108] Example 12: The garlic bulb is directly sliced ​​and dried to prepare powder for later use.

[0109] Example 13: The garlic bulbs are directly ground to prepare garlic homogenate, which is then stored in liquid nitrogen for later use.

[0110] Examples 14-21

[0111] The method for extracting sulfide compounds from garlic provided in Examples 14-21 is different from that in Example 1 only in that:

[0112] Garlic homogenate extraction

[0113] The extraction solvent used in Examples 14-17 is a single solvent:

[0114] The extraction solvents of Examples 14-17 were n-hexane, ethyl acetate, petroleum ether, and dichloromethane, respectively;

[0115] Examples 18-21 used a mixed solvent:

[0116] The extraction solvents of Examples 18-21 are dichloromethane:petroleum ether in ratios of 6:4, 7:3, 8:2, and 9:1, respectively.

[0117] Examples 22-29

[0118] The method for extracting sulfide compounds from garlic provided in Examples 22-29 differs from that in Example 1 only in that:

[0119] Garlic homogenate extraction

[0120] The solid-to-liquid ratio of garlic homogenate and extraction solvent is different:

[0121] The solid-to-liquid ratio of garlic homogenate to extraction solvent in Examples 22-29 is 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, and 1:90 g / mL.

[0122] Examples 30-32

[0123] The method for extracting sulfide compounds from garlic provided in Examples 30-32 is different from that in Example 1 only in that:

[0124] Garlic homogenate extraction

[0125] The extraction temperature of garlic homogenate and extraction solvent is different:

[0126] The extraction temperatures of the garlic homogenate and the extraction solvent in Examples 30-32 are 35° C., 45° C., and 55° C., respectively.

[0127] Examples 33-43

[0128] The method for extracting sulfide compounds from garlic provided in Examples 33-43 is different from that in Example 1 only in that:

[0129] Garlic homogenate extraction

[0130] The extraction time of garlic homogenate and extraction solvent is different:

[0131] The extraction temperatures of the garlic homogenate and the extraction solvent in Examples 33-43 are 5 min, 10 min, 20 min, 30 min, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, and 4 h, respectively.

[0132] Comparative Example 1

[0133] The method for extracting sulfide compounds from garlic provided in this comparative example is different from that in Example 1 only in that:

[0134] In the pretreatment of garlic bulbs, the samples were not preserved or dried, and fresh garlic bulbs were used. When testing, about 1 kg of each garlic sample was selected, peeled, and homogenized using a grinder to prepare garlic slurry for later use.

[0135] Test Example 1

[0136] Using the analytical method of Examples 1-6, a mixed standard solution of eight sulfide compounds in garlic (mass concentration of 1000 μg / L) was analyzed using GCMS-TQ8040. The total ion current chromatogram is shown in FIG. Figure 1-Figure 6 .

[0137] The eight sulfide compounds in the garlic treated in this test example are diallyl sulfide (DAS), methyl allyl disulfide (AMDS), methyl propyl disulfide (MPDS), dimethyl trisulfide (DMTS), diallyl disulfide (DADS), diallyl tetrasulfide (DATTS), methyl allyl sulfide (AMS), and diallyl trisulfide (DATS).

[0138] In order to effectively separate the target compounds, the present invention optimizes the chromatographic parameters, the temperature optimization range of the heating program is between 40°C and 280°C, and the heating rate optimization range is between 10°C / min and 30°C / min. Finally, 50°C was selected to maintain for 1 min, the temperature was increased to 100°C at a heating rate of 10°C / min, then the temperature was increased to 200°C at a heating rate of 15°C / min, and finally the temperature was increased to 280°C at a heating rate of 30°C / min; the carrier gas was helium, the carrier gas flow rate was 1.59mL / min, and the carrier gas pressure was 94.1kpa; no splitting, high pressure injection, pressure of 250kPa; time was 1min; injection volume was 1μL. The above is the chromatographic parameters in Example 1 of the present invention.

[0139] from Figure 1It can be concluded that the total running time for the simultaneous determination of eight sulfide compounds by this analytical method is 15.33 minutes, and the peak elution order is diallyl sulfide (DAS), methyl allyl disulfide (AMDS), methyl propyl disulfide (MPDS), dimethyl trisulfide (DMTS), diallyl disulfide (DADS), diallyl tetrasulfide (DATTS), methyl allyl sulfide (AMS), and diallyl trisulfide (DATS). No co-elution peaks were observed within the retention time of each compound, indicating that the analytical method has excellent selectivity. Figure 1 In comparison, Figure 2-Figure 6 There are significant defects in the peaking effect. Figure 2 There are obvious miscellaneous peaks in the 2-3min and 6.5-8min peaking periods. Figure 3 There are obvious miscellaneous peaks in the 2-3min peak period, and Figure 2 and Figure 3 The peak elution effect of allyl methyl sulfide (AMS, peak 7) is poor. Figure 4 In the results, diallyl sulfide (DAS, peak 1) and methyl allyl disulfide (AMDS, peak 2) have serious peak tailing, methyl propyl disulfide (MPDS, peak 3) shows a bifurcated peak, and dimethyl trisulfide (DMTS, peak 4) and diallyl disulfide (DADS, peak 5) also have the problem of peak tailing. Figure 5 In the results, diallyl sulfide (peak 1) was not completely eluted, and methyl allyl disulfide (peak 2), methyl propyl disulfide (peak 3), dimethyl trisulfide (peak 4) and methyl allyl sulfide (peak 7) showed peak bifurcation and peak tailing. Figure 6 In the above, methyl allyl disulfide (peak 2), methyl propyl disulfide (peak 3) and dimethyl trisulfide (peak 4) have peak tailing, and methyl allyl sulfide (peak 7) shows peak bifurcation. In summary, the parameter setting of Example 1 enables the eight sulfide compounds to elute in sequence within the programmed temperature rise time without co-elution, peak tailing, peak bifurcation and miscellaneous peaks.

[0140] Test Example 2

[0141] This test example analyzes the contents of eight sulfide compounds in garlic bulbs stored under different conditions in Example 1, Examples 7-13 and Comparative Example 1. Among them, the sample of Comparative Example 1 that was not stored was named fresh garlic, and the pretreated garlics were named: -20℃ garlic, liquid nitrogen garlic, liquid nitrogen freeze-dried garlic, freeze-dried garlic, 4℃ garlic, room temperature garlic, and liquid nitrogen ground garlic. The specific analysis results are shown in Figure 7 .

[0142] from Figure 7It can be seen that compared with fresh garlic, the content of sulfide compounds in garlic at -20°C is closest to that of fresh garlic, while storage methods such as liquid nitrogen storage, room temperature storage, and 4°C storage will significantly reduce the content of sulfide compounds. Considering the ease of operation of each method and the influence of the operation process on the content of sulfide compounds in garlic, the present invention selects the -20°C storage method. Take undamaged fresh garlic bulbs, wrap them in tin foil, and store them at -20°C.

[0143] Test Example 3

[0144] This test example analyzes the extraction effects of different extraction solvents in Example 1 and Examples 14-21 on sulfide compounds. The specific analysis results of the single solvent in Examples 14-17 are shown in Figure 8 The specific analysis results of the mixed solvents of Example 1 and Examples 18-21 are shown in Fig. 9 .

[0145] from Figure 8 It can be seen that dichloromethane has the best extraction effect on diallyl sulfide (DAS), methyl allyl disulfide (AMDS), methyl propyl disulfide (MPDS), dimethyl trisulfide (DMTS), diallyl disulfide (DADS) and diallyl tetrasulfide (DATTS), and the extraction effect on methyl allyl sulfide (AMS) and diallyl trisulfide (DATS) is slightly lower than that of n-hexane and petroleum ether. Therefore, a mixed solvent of dichloromethane and petroleum ether was selected for further extraction.

[0146] from Fig. 9 It can be seen that when the ratio of dichloromethane to petroleum ether is 5:5, the extraction effect of methyl propyl disulfide (MPDS), diallyl disulfide (DADS), diallyl tetrasulfide (DATTS), methyl allyl sulfide (AMS) and diallyl trisulfide (DATS) is the best, and the extraction effect of diallyl sulfide (DAS), methyl allyl disulfide (AMDS) and dimethyl trisulfide (DMTS) is slightly lower than 7:3, but better than the other three different ratios. Therefore, dichloromethane: petroleum ether 5:5 was finally selected as the extraction reagent for this experiment.

[0147] Test Example 4

[0148] This test example analyzes the effect of the solid-liquid ratio of garlic homogenate to the extraction solvent on the extraction of sulfide compounds in Example 1 and Examples 22-29. The specific analysis results are shown in Fig.10 .

[0149] from Fig.10It can be seen that as the solid-liquid ratio increases from 1:10 g / mL to 1:90 g / mL, the contents of diallyl sulfide (DAS), dimethyl trisulfide (DMTS), methyl propyl disulfide (MPDS) and diallyl trisulfide (DATS) show a downward trend; the contents of methyl allyl disulfide (AMDS) and diallyl tetrasulfide (DATTS) remain stable between 1:10 g / mL and 1:20 g / mL, and increase between 1:20 g / mL and 1:60 g / mL. The content of diallyl disulfide (DADS) shows a downward trend between 1:10g / mL and 1:20g / mL, remains stable between 1:20g / mL and 1:30g / mL, and shows a downward trend between 1:30g / mL and 1:70g / mL; the content of methyl allyl sulfide (AMS) shows a downward trend between 1:10g / mL and 1:60g / mL, and remains stable between 1:60g / mL and 1:90g / mL. Therefore, considering the comprehensive extraction effect, cost and environmental factors, the optimal solid-liquid ratio selected by the present invention is 1:10g / mL.

[0150] Test Example 5

[0151] This test example analyzes the effect of garlic homogenate and extraction temperature of extraction solvent on the extraction of sulfide compounds in Example 1 and Examples 30-32. The specific analysis results are shown in Fig.11 .

[0152] Preliminary experiments have shown that when the extraction temperature reaches 65°C or above, the extraction solvent evaporates strongly. At an extraction temperature of 55°C, a slight evaporation of the extraction solvent was observed. Therefore, the extraction effects at 25°C, 35°C, 45°C, and 55°C were optimized respectively. Fig.11 It can be seen that the contents of diallyl sulfide (DAS), methyl allyl disulfide (AMDS), methyl propyl disulfide (MPDS), and dimethyl trisulfide (DMTS) are basically stable from 25°C to 55°C; the extraction effects of diallyl disulfide (DADS), diallyl tetrasulfide (DATTS), methyl allyl sulfide (AMS), and diallyl trisulfide (DATS) are basically stable from 25°C to 55°C, and the extraction effect at 55°C is the best. Therefore, considering the extraction effect, solvent volatilization, and time cost, the optimal extraction temperature selected by the present invention is 25°C.

[0153] Test Example 6

[0154] This test example analyzes the effect of garlic homogenate and extraction solvent extraction time on the extraction effect of sulfide compounds in Example 1 and Examples 33-43. The specific analysis results are shown in Fig.12 .

[0155] from Fig.12It can be seen that with the increase of extraction time, the contents of methyl allyl disulfide (AMDS), diallyl disulfide (DADS), and diallyl tetrasulfide (DATTS) showed an upward trend, the contents of diallyl sulfide (DAS) and methyl propyl disulfide (MPDS) remained stable, the contents of dimethyl trisulfide (DMTS) and methyl allyl sulfide (AMS) showed an upward trend between 5min and 2.5h, and remained stable between 2.5h and 4h, and the content of diallyl trisulfide (DATS) showed an upward trend between 5min and 3h, and a downward trend between 3h and 4h. Therefore, considering the comprehensive extraction time and saving efficiency, the final extraction time was selected as 2.5h.

[0156] Test Example 7

[0157] The present invention evaluates the matrix effect by the slope method, and the calculation formula of the slope method is: slope = matrix standard curve slope / solvent standard curve slope * 100%. When the slope is 80%-120%, it means that the matrix effect of the method is not significant, and the solvent standard curve can be used for quantification; when the slope is lower than 80% or higher than 120%, it means that the sample matrix has an inhibitory or enhancing effect on the method, and the matrix standard curve needs to be used for quantification. The results of the evaluation of the matrix effect of eight thioether compounds in garlic by the slope method are shown in Table 2.

[0158] Table 2 Matrix effects of the methods

[0159] Compound Name Matrix effect (%) DAS 99.6 AMDS 98.7 MPDS 87.0 DMTS 97.4 DADS 89.8 DATTS 120.0 AMS 117.1 DATS 90.1

[0160] As can be seen from Table 1, the matrix effects of all sulfide compounds are between 87.0% and 120.0%, indicating that the matrix effect of this method is not significant and meets the conditions for quantitative analysis using a solvent standard curve. Therefore, this method is suitable for the qualitative and quantitative detection of eight sulfide compounds in garlic.

[0161] Test Example 8

[0162] In order to evaluate the feasibility of the analytical method of the present invention, the sensitivity, linearity, accuracy and precision of the method were evaluated. The compound concentrations at signal-to-noise ratios (S / N) of 3 and 10 were determined, and the LODs and LOQs of eight thioether compounds were determined. The peak areas at concentrations of 1 μg / L, 5 μg / L, 50 μg / L, 100 μg / L, 500 μg / L, 1000 μg / L and 2000 μg / L were plotted as standard curves to obtain the corresponding linear equations. The accuracy was evaluated by spike recovery, and three spike recovery levels of L (low), M (medium) and H (high) were designed. The content of the added thioether compounds was approximately 50%, 100% and 200% of the original content of the thioether compounds in garlic. The intra-day precision was evaluated by performing six replicates of the thioether compound mixed standard at different time points on the same day, and the inter-day precision was evaluated by performing six replicates for three consecutive days. The results were expressed as relative standard deviations (RSD). The results of the methodological investigation are shown in Table 3.

[0163] Table 3 Methodological investigation results

[0164]

[0165]

[0166] As shown in Table 3, the detection limits of the eight sulfide compounds are between 0.2-50 μg / L, and the quantification limits are between 0.5-100 μg / L, which can meet the detection requirements. The linearity of this analytical method is good, with a correlation coefficient of R 2 >0.9993. The low-level recovery rate was between 85.2% and 106.7%, the intermediate-level recovery rate was between 81.4% and 112.7%, and the high-level recovery rate was between 80.3% and 107.2%. The intra-day and inter-day reproducibility RSDs were less than 20%, indicating that this analytical method met the requirements of methodological evaluation. Therefore, this method is suitable for high-sensitivity and high-accuracy analysis of sulfide compounds in garlic samples.

[0167] In summary, the analysis method of sulfide compounds in garlic provided by the present invention adopts gas chromatography-tandem mass spectrometry to analyze sulfide compounds in garlic bulbs, and optimizes the extraction process of garlic bulbs and the instrument parameters of gas chromatography-tandem mass spectrometry, so that the target sulfide compounds can be efficiently extracted, highly selectively separated and accurately detected. The analysis method is a qualitative and quantitative method that can simultaneously analyze eight sulfide compounds in garlic, has the characteristics of high sensitivity, high selectivity and high accuracy, and is suitable for qualitative and quantitative detection of sulfide compounds in garlic samples.

[0168] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for analyzing sulfide compounds in garlic, characterized in that: The analytical method comprises the following steps: Gas chromatography-tandem mass spectrometry was used to detect sulfide compounds in garlic bulbs; When performing gas chromatography, the chromatographic column used is a bonded cross-linked 5% diphenyl / 95% dimethylpolysiloxane gas chromatography column, and the temperature program is: 40-80°C for 1-5 min, then heated to 90-130°C at a heating rate of 8-12°C / min, then heated to 150-200°C at a heating rate of 13-17°C / min, and finally heated to 240-280°C at a heating rate of 28-32°C / min; high pressure injection, the pressure is 220-260 kPa; When performing mass spectrometry detection, the mass spectrometry detection conditions are as follows: the ion source type is an electron bombardment source; the scanning mode is a multiple reaction monitoring mode; the interface temperature is set to 250-300°C, and the ion source temperature is set to 200-250°C; The sample to be tested in the analytical method is obtained by the following method: pre-treating the garlic bulb to obtain garlic homogenate; adding an extraction solvent to the garlic homogenate to extract sulfide compounds to obtain a mixed solution; centrifuging the mixed solution to obtain an extract; and preparing the sample to be tested from the extract; The extraction solvent is selected from at least one of n-hexane, ethyl acetate, petroleum ether and dichloromethane; The sulfide compound is selected from at least one of diallyl sulfide, methyl allyl disulfide, methyl propyl disulfide, dimethyl trisulfide, diallyl disulfide, diallyl tetrasulfide, methyl allyl sulfide and diallyl trisulfide.

2. The analysis method according to claim 1, characterized in that The chromatographic column is SH-Rxi-5Sil MS.

3. The analysis method according to claim 1, characterized in that When performing gas chromatography, the injection port temperature of the chromatographic column used is 100-300°C; the carrier gas flow rate is 1-2 mL / min; the injection time is 1-2 min; and the injection volume is 1-2 μL.

4. The analysis method according to claim 3, characterized in that The injection port temperature of the chromatographic column is 280°C; the carrier gas flow rate is 1.59 mL / min; the injection time is 1 min; and the injection volume is 1 μL.

5. The analysis method according to claim 1, characterized in that The interface temperature was set to 280 °C and the ion source temperature was set to 230 °C.

6. The analysis method according to claim 1, characterized in that The pretreatment comprises peeling the garlic bulbs, directly storing the garlic bulbs or storing the garlic bulbs after drying; The garlic bulbs are directly stored under a condition selected from any one of -20°C to room temperature or liquid nitrogen; The garlic bulb drying condition is selected from any one of liquid nitrogen freeze drying, freeze drying and oven drying.

7. The analysis method according to claim 6, characterized in that The garlic bulbs are directly stored at -20°C.

8. A method for extracting sulfide compounds in the analytical method according to any one of claims 1 to 7, characterized in that: It includes: The extraction solvent is added to the pre-treated garlic homogenate to extract the sulfide compounds, the extraction temperature is 25-55°C, the extraction time is 5 min-4 h, and a mixed solution is obtained; the mixed solution is centrifuged to obtain an extract; the extract is prepared into a sample to be tested and set aside.

9. The extraction method according to claim 8, characterized in that The extraction solvent is a mixture of dichloromethane and petroleum ether in a volume ratio of (5-9):(5-1).

10. The extraction method according to claim 9, characterized in that The volume ratio of the dichloromethane to the petroleum ether is 5:

5.

11. The extraction method according to claim 8, characterized in that The solid-liquid ratio of the garlic bulb to the extraction solvent is 1: (1-100) g / mL.

12. The extraction method according to claim 11, characterized in that The solid-to-liquid ratio is 1:(10-20) g / mL.

13. The extraction method according to claim 8, characterized in that The extraction temperature is 25-45°C; the extraction time is 2-4 h; The centrifugal treatment of the mixed solution includes a first centrifugal treatment and a second centrifugal treatment; Drying the supernatant of the first centrifugation treatment, and then performing the second centrifugation treatment to obtain the extract; preparing the extract into the sample to be tested; The desiccant used in the drying process is a neutral desiccant.

14. The extraction method according to claim 13, characterized in that The extraction temperature is 25°C.

15. The extraction method according to claim 13, characterized in that The extraction time is 2.5 h.

16. The extraction method according to claim 13, characterized in that The desiccant is selected from any one of anhydrous magnesium sulfate or anhydrous sodium sulfate.

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