CN104267123A - Analysis method of free sterol components in edible oil sample and swill-cooked dirty oil identification method - Google Patents
Analysis method of free sterol components in edible oil sample and swill-cooked dirty oil identification method Download PDFInfo
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Abstract
The invention relates to an analysis method of free sterol components in an edible oil sample and a swill-cooked dirty oil identification method. The analysis method comprises the following steps: carrying out solid phase extraction on the edible oil sample to be tested to separate out the free sterol in the sample, carrying out silylation derivatization on the free sterol, injecting a comprehensive two-dimensional gas chromatography-time-of-flight mass spectrum into the free sterol for detection, and realizing qualitative and quantitative analysis on the free sterol components in the edible oil sample. Compared with a traditional sterol compound analysis method, the analysis method has the characteristics of high sensitiveness, rapidness and high efficiency, an adulterated edible oil identification and swill-cooked dirty oil identification method is established through analyzing a proportional relation between phytosterol in cholesterol in different edible oil as well as a proportional relation between the cholesterol and other specific phytosterol, and the authenticity identification of the edible oil and the identification of the swill-cooked dirty oil can be realized.
Description
Technical field
The present invention relates to free sterol proximate analysis method and waste oil discrimination method in a kind of edible oil sample, can be used for carrying out qualitative and quantitative analysis to the free plant sterol in edible oil and cholesterol, and can differentiate waste oil according to Assessing parameters.
Background technology
The quality of edible oil and safety have become a hot issue of public attention.The grease that " waste oil " of broad sense comprises waste oil, hogwash fat (swill oil), frying oil and refined by tankage etc.Some by refining " waste oils " in the physical and chemical indexs such as color and luster, smell, peroxide value, acid value, iodine value and normal edible oil and fat significantly do not distinguish, bring very large difficulty to the quality supervision of edible oil and safety management.Due to the temptation of interests, " waste oil " of refining is used as edible oil or is added in normal edible oil according to certain ratio and sell by some illegal retailers.Research shows: " waste oil " is owing to there occurs oxidation and becoming sour, generate a large amount of micromolecular aldehyde, ketone, acid and hydrocarbon compound, and the thermal polymerization at high temperature to occur due to grease and heat of oxidation polymerization, also form certain cyclic hydrocarbon, epoxy hydrocarbon, polyester and benzo ratio etc., add some environmental contaminants, as heavy metal ion, aflatoxin etc., this just causes it to there is very large potential safety hazard, and long-term eating has pathogenic and carcinogenic risk.Current China not yet sets up the unified standard of detection " waste oil ".
Sterol is a kind of important bioactivator be extensively present in biosome, and every vegetable oil has oneself specific sterol compositional model, and they are also the important component parts of grease unsaponifiables.Plant sterol common in vegetable oil has campesterol, rape sterol, stigmasterol, cupreol, △
5-oat steroid enol, △
5,23-beans steroid dienol, △
5,24-beans steroid dienol, △
7-stigmastenol etc., in animal oil, sterol is then based on cholesterol." waste oil " is due to through Reusability, higher with the contact probability of animal fat, often containing higher cholesterol.In addition, " waste oil ", usually through high temperature frying and refining treatment repeatedly, its sterol compositional model also can change, and therefore can be determined by the proportionate relationship determining between the kind of sterol in edible oil and specific sterol " waste oil " that may exist.
In current edible oil, the detection method of phytosterin compound mainly contains gas chromatography-flame ion and detects (GC-FID) and gas chromatography-mass spectrum (GC-MS) method.These class methods are before sample introduction, and sample all needs the pre-treatment through complexity, as the saponification of grease, the extraction, alumina column chromatography, thin-layer chromatography etc. of unsaponifiables; process time and effort consuming; and need to consume more organic solvent, daily environmental protection can not be met, require (ISO 12228:1999, Food Chemistry 2013 fast; 136; 251-258, Food Research International, 2011; 44,103-108).In addition, GC-FID often scarce capacity when analyzing the sterol that content is lower in edible oil sample, and be especially easily subject to the interference of sample mesostroma, the quantitative error for micro-sterol is larger; One-dimensional gas chromatograph is compared with comprehensive two dimensional gas chromatography simultaneously, and its chromatogram separating capacity is not enough, and some isomerss for sterol often can not reach satisfied separating effect, bring interference to single sterol accurate quantification.Therefore, the separation and detection method of inventing free sterol in a kind of edible oil of quick, easy, environmental protection has important actual application value.
Summary of the invention
The technical problem to be solved in the present invention is to provide free sterol proximate analysis method and waste oil discrimination method in a kind of edible oil sample, specifically be exactly through Solid-Phase Extraction process by edible oil sample, isolate free sterol wherein, last again by after free sterol compound Silylation, detect with comprehensive two dimensional gas chromatography-flight time mass spectrum, and qualitative and quantitative analysis is carried out to the free plant sterol in edible oil and cholesterol.The discriminating of waste oil is can be used for further based on the method analysis result.The method, compared with traditional sterol compound analytical approach, has sensitive, feature fast and efficiently.
For solving the problems of the technologies described above, the technical solution used in the present invention is as follows:
A kind of free sterol proximate analysis method in edible oil sample is provided: by edible oil sample to be measured through Solid-Phase Extraction process, isolate free sterol wherein, inject comprehensive two dimensional gas chromatography-flight time mass spectrum after again free sterol being carried out Silylation to detect, then qualitative and quantitative analysis is carried out to the phytosterin compound in edible oil sample.
By such scheme, described comprehensive two dimensional gas chromatography-flying time mass spectrum analysis optimum condition used is: injector temperature 300 ~ 320 DEG C, and take helium as carrier gas, flow velocity is 0.7 ~ 1mL/min, split ratio is 15 ~ 20:1, and modulator temperature compensation is 35 ~ 40 DEG C; Modulation period is 3s, and wherein the hot blow time is 1.15s, and the cold blowing time is 0.35s; Transmission line temperature is located at 310 ~ 315 DEG C; Scanning of the mass spectrum scope: from 50m/z to 700m/z, solvent delay is 500 ~ 700s, and detector voltage is 1650 ~ 1750V, and ion source temperature is located at 230 ~ 250 DEG C.
By such scheme, in described comprehensive two dimensional gas chromatography-flying time mass spectrum analysis, one dimension post is DB-5ms (30m × 0.25mm I.D. × 0.25 μm) or HP-5ms (30m × 0.25mm I.D. × 0.25 μm), provides by U.S. Agilent Technologies; Two-dimensional columns is Rxi-17Sil MS (2.0m × 0.15mm I.D. × 0.15 μm), is provided by Restek company of the U.S., or DB-17ht (1.5m × 0.10mm I.D. × 0.15 μm), is provided by U.S. Agilent Technologies.The heating schedule of One Dimensional Furnace incubator is: initial temperature 180 ~ 190 DEG C, keeps 1min, is then raised to 250 DEG C with the speed of 10 ~ 15 DEG C/min, keep 1min, then be raised to 280 DEG C with the speed of 2 ~ 3 DEG C/min, keep 2min, finally be raised to 300 DEG C with the speed of 9 ~ 11 DEG C/min, keep 20min; The temperature of two dimension furnace temperature case is higher than One Dimensional Furnace incubator 15 DEG C, heating schedule: initial temperature 195 ~ 205 DEG C, keep 1min, then 265 DEG C are raised to the speed of 10 ~ 15 DEG C/min, keep 1min, then be raised to 295 DEG C with the speed of 2 ~ 3 DEG C/min, keep 2min, finally be raised to 315 DEG C with the speed of 9 ~ 11 DEG C/min, keep 20min; Mass spectrometric data frequency acquisition is 100 spectrograms/s (spectra/s); Sample size is 1 ~ 2 μ L.
By such scheme, described method for qualitative analysis is: according to the two-dimensional chromatogram of the edible oil sample to be measured obtained, the retention time and the mass spectrogram that one peacekeeping two dimension retention time of each phytosterin compound and the mass spectrogram of correspondence sterol standard items corresponding to it thereof are detected after Silylation acquisition carry out corresponding comparison, and the standard mass spectrogram of sterol Silylation thing corresponding to NIST storehouse is compared simultaneously, carry out qualitative analysis, obtain the qualitative results of phytosterin compound in edible oil, wherein, for sterol compound (the 24-methylene cholesterol being difficult to obtain standard items, rape stanols, △
7-rape steroid enol, △
5,23-beans steroid dienol, sitostamol, △
5-oat steroid enol, △
5,24-beans steroid dienol, △
7-stigmastenol, △
7-oat steroid enol), the relative retention time reported in its relative retention time and ISO 12228:1999 standard is compared, its mass spectrogram is compared to the standard mass spectrogram that NIST composes corresponding sterol Silylation thing in storehouse simultaneously, obtain qualitative results, described relative retention time is the ratio of each sterol compound one dimension retention time/cholesterol trimethylsilyl ethers one dimension retention time.
By such scheme, described quantitative analysis method is: set up mark curve in each phytosterin compound reference material, be specially: accurately take each phytosterin compound reference material of different quality in different reaction bulbs, and add in cholestanol in each reaction bulb and mark, add silylating reagent again, obtain each sterol reference material system of a series of variable concentrations, then after Silylation reaction, room temperature is cooled to respectively, sample introduction is analyzed to comprehensive two dimensional gas chromatography-flight time mass spectrum, with the concentration of each reference material for horizontal ordinate, the ratio of the peak area that each reference material is corresponding when variable concentrations and internal standard compound peak area is ordinate, obtain marking curve in each reference material through regression fit, cholesterol in edible oil sample, campesterol, rape sterol, the content of stigmasterol and cupreol adopts the interior mark curve of respective corresponding standard items to calculate, use in stigmasterol for there is no the quantitative test of other sterol of corresponding standard items in edible oil sample and mark curve replacement,
According to GC × GC-TOF/MS total ion current figure of free sterol in the edible oil sample of above-mentioned acquisition, the peak area of each sterol compound and the ratio of interior mark peak area in calculation sample, utilize corresponding interior mark curve, obtain the content of each sterol compound in edible oil.
By such scheme, described used when quantitative test carried out to cholesterol, campesterol, rape sterol, stigmasterol and cupreol in edible oil sample in mark in curve: in cholesterol, the concentration gradient of mark curve is: 0.1,0.2,0.4,0.8,1.5,3.0 μ g/100 μ L; In campesterol, rape sterol, stigmasterol, the concentration gradient of mark curve is all located at 1,5,10,20,30,40 μ g/100 μ L; In cupreol, mark curve concentration gradient is 5,10,20,40,80,120 μ g/100 μ L; The described concentration gradient to marking stigmasterol in curve in stigmasterol used when not having other sterol compounds of standard substance to carry out quantitative test in edible oil sample is 0.1,0.5,1,2,4,8 μ g/100 μ L.
By such scheme, the quota ion calculating each phytosterin compound peak area during described quantitative test is combined as: cholesterol trimethylsilyl ethers: 247+353+329+368+458; Cholestanol trimethylsilyl ethers: 215+306+355+445+460; Campesterol trimethylsilyl ethers: 255+341+365+380+470; 24-methylene cholesterol trimethylsilyl ethers: 253+296+371+386+470; Rape sterol trimethylsilyl ethers: 255+343+367+382+472; Rape stanols trimethylsilyl ethers: 215+305+343+382+474; Stigmasterol trimethylsilyl ethers: 255+355+379+394+484; △
7-rape steroid trimethylsilyl enol ether: 255+367+382+457+472; △
5,23-beans steroid dienol trimethylsilyl ethers: 255+355+379+394+484; Cupreol trimethylsilyl ethers: 255+357+381+396+486; Sitostamol trimethylsilyl ethers: 215+305+383+473+488; △
5-oat steroid trimethylsilyl enol ether: 257+281+296+386+484; △
5,24-beans steroid dienol trimethylsilyl ethers: 253+281+343+386+484; △
7-stigmastenol trimethylsilyl ethers: 255+357+381+471+486; △
7-oat steroid trimethylsilyl enol ether: 255+343+386+469+484.
By such scheme, described edible oil sample is soybean oil, rapeseed oil, peanut oil, sunflower oil, corn oil and waste oil.
By such scheme, described phytosterin compound is cholesterol, campesterol, 24-methylene cholesterol, rape sterol, rape stanols, stigmasterol, △
7-rape steroid enol, △
5,23-beans steroid dienol, cupreol, sitostamol, △
5-oat steroid enol, △
5,24-beans steroid dienol, △
7-stigmastenol and △
7-oat steroid enol.
By such scheme, described Solid-Phase Extraction disposal route is:
(1) preparation of Solid-Phase Extraction sample solution: add in cholestanol in edible oil sample and mark, then use n-hexane dissolution, vortex concussion is evenly, for subsequent use;
(2) loading: the uniform sample liquid of concussion in step (1) is injected in the solid-phase extraction column after activation (SPE), discards efflux;
(3) drip washing: be that the hexane solution (v/v) of the ether of 5 ~ 6% carries out drip washing with concentration of volume percent, discard efflux;
(4) wash-out: hexane solution (v/v) the wash-out free sterol with concentration of volume percent being the ether of 15 ~ 25%.
By such scheme, described Solid-Phase Extraction disposal route concrete steps are:
(1) preparation of Solid-Phase Extraction sample solution: accurately take 0.04 ~ 0.06g edible oil sample, and add mark in 20 μ g cholestanols, then use 5 ~ 8mL n-hexane dissolution, vortex concussion is evenly, for subsequent use;
(2) loading: the uniform sample liquid of concussion in step (1) be injected in the solid-phase extraction column after activation (SPE), coutroi velocity is 1.2 ~ 1.6mL/min, discards efflux; Described solid-phase extraction column is silicagel column; The activation of described solid-phase extraction column is: take the top that 1.0 ~ 1.5g anhydrous sodium sulfate is added to solid-phase extraction column (SPE), and then with the activation of 10 ~ 15mL hexane solution, flow velocity is 1.0 ~ 2.0mL/min, discards efflux;
(3) drip washing: carry out drip washing with diethyl ether hexane solution (v/v) solution that concentration of volume percent is 5 ~ 6%, flow control, at 1.2 ~ 1.6mL/min, discards efflux;
(4) wash-out: be diethyl ether hexane (v/v) the eluant solution free sterol of 15 ~ 25% with concentration of volume percent, flow control is at 1.2 ~ 1.6mL/min.
By such scheme, described Silylation be by Solid-Phase Extraction process after sample desolvation, then add silylating reagent be cooled to after Silylation room temperature for analyze.
By such scheme, described desolvation is at 35 ~ 40 DEG C, removes most of solvent with vacuum rotary evaporator, then transfers in reaction bulb, and continuation nitrogen slowly dries up solvent.
By such scheme, described silylating reagent forms for counting 93 ~ 95:7 ~ 5 by volume by N methyl N trimethylsilyl heptafluorobutyramide and 1-methylimidazole, described silylating reagent consumption is every mg edible oil sample 1.5 ~ 2.5 μ L, and Silanization reaction condition is: 102 ~ 108 DEG C of reaction 15 ~ 20min.
Waste oil discrimination method, is characterized in that: adopted by sample to be identified free sterol proximate analysis method in above-mentioned edible oil sample to carry out detection and analyze, obtain the content of each sterol compound in sample to be identified, then calculate (△ in sample thus
5-oat steroid enol+△
5,24-beans steroid dienol+△
7-oat steroid enol) ratio of/cholesterol and Assessing parameters, as Assessing parameters > 5, be judged to normal edible oil, Assessing parameters≤5 item are judged to waste oil.
Beneficial effect of the present invention:
The present invention adopts Solid-Phase Extraction that the free sterol in edible oil is carried out to enrichment and is separated, and consumption of organic solvent is few, has fast, the feature of economy and environmental protection, can meet the quick pretreatment demand of a large amount of sample.
The comprehensive two dimensional gas chromatography that the present invention adopts compares chromatogram separating capacity with common one-dimensional gas chromatograph strong, has larger advantage when analyzing the sample of matrix complexity.Flight time mass spectrum (TOF/MS) data acquiring frequency is high simultaneously, in the parsing of follow-up peak, peak match, there is stronger advantage, thus when object quantitative, multiple quota ion better, more conveniently can be selected rapidly to combine integration is carried out to object, both improve the signal intensity that selectivity in turn enhances trace object, it is quantitatively more accurate to make.The method, compared with traditional sterol compound analytical approach, has sensitive, feature fast and efficiently.
Due to through Reusability and pyroprocessing, usually more animal sources sterol is contained in waste oil and other recovered oils, also can there is oxidation and degradation in other plant source sterol simultaneously, therefore, the method is by the cholesterol in differentiation edible oil and plant sterol, and analyze the proportionate relationship of cholesterol and other specified plant sterols, for the poor oil measuring and distinguish waste oil and other recyclings that may exist further lays the foundation.
Accompanying drawing explanation
GC × GC-TOF/MS the chromatogram of Fig. 1 sterol standard substance after Silylation;
GC × GC-TOF/MS the chromatogram of free sterol after Silylation in Fig. 2 soybean oil;
GC × GC-TOF/MS the chromatogram of free sterol after Silylation in Fig. 3 rapeseed oil;
GC × GC-TOF/MS the chromatogram of free sterol after Silylation in Fig. 4 peanut oil;
GC × GC-TOF/MS the chromatogram of free sterol after Silylation in Fig. 5 sunflower oil;
GC × GC-TOF/MS the chromatogram of free sterol after Silylation in Fig. 6 corn oil;
GC × GC-TOF/MS the chromatogram of free sterol after Silylation in Fig. 7 waste oil 1;
The sterol that in accompanying drawing, each peak is corresponding is as follows, and 1: cholesterol, 2: cholestanol, 3: campesterol, 4:24-methylene cholesterol, 5: rape sterol, 6: rape stanols, 7: stigmasterol, 8: △
7-rape steroid enol, 9: △
5,23-beans steroid dienol, 10: cupreol, 11: sitostamol, 12: △
5-oat steroid enol, 13: △
5,24-beans steroid dienol, 14: △
7-stigmastenol, 15: △
7-oat steroid enol.
Embodiment
Following embodiment will contribute to understanding the present invention, but not limit content of the present invention.
Embodiment 1: the qualitative and quantitative analysis of free sterol in edible oil sample
(1) preparation of sample solution: accurately take 0.05g (after being accurate to radix point 4) and eat oil sample (soybean oil, rapeseed oil, peanut oil, sunflower oil, corn oil and waste oil), and add mark in 20 μ g cholestanols, then 5mL n-hexane dissolution is used, vortex concussion is evenly, for subsequent use.
(2) loading: be injected in the SPE post after activation by the uniform sample liquid of concussion in (1), coutroi velocity is 1.2 ~ 1.6mL/min, discards efflux; Described SPE post is 0.5mg/6mL silicagel column, and described activation is added to the top of SPE post for taking 1.0g anhydrous sodium sulfate, and then with the activation of 10 ~ 15mL hexane solution, flow velocity is 1.0 ~ 2.0mL/min, discards efflux;
(3) drip washing: carry out drip washing with diethyl ether hexane solution (v/v) solution of 10mL concentration of volume percent 5 ~ 6%, flow control, at 1.2 ~ 1.6mL/min, discards efflux;
(4) wash-out: with diethyl ether hexane (v/v) the eluant solution phytosterin compound of 10 ~ 15mL concentration of volume percent 15 ~ 25%, flow control is at 1.2 ~ 1.6mL/min.
(5) by the eluent that obtains in step (4) at 35 ~ 40 DEG C of rotary evaporation in vacuo to about 1mL, then transfer in reaction bulb, slowly solvent is dried up with nitrogen, add 100 μ L silylating reagents (N methyl N trimethylsilyl heptafluorobutyramide: 1-methylimidazole=95:5 again, v/v), screwing reaction bottle cap, be put in the constant temperature oven of 105 DEG C and react 15min, being then cooled to room temperature for analyzing.
(6) each sample in step (5) is injected into comprehensive two dimensional gas chromatography-flight time mass spectrum with the sample size of 1 μ L to analyze.GC × GC-TOF/MS the chromatogram of sterol standard substance after Silylation as shown in Figure 1; In soybean oil, rapeseed oil, peanut oil, sunflower oil, corn oil and waste oil 1, the GC × GC-TOF/MS chromatogram of free sterol after Silylation is as shown in Fig. 2,3,4,5,6,7.
Described comprehensive two dimensional gas chromatography-flying time mass spectrum analysis condition used is: comprise 2 capillary posts in comprehensive two dimensional gas chromatography analysis, wherein one dimension post is DB-5ms (30m × 0.25mm I.D. × 0.25 μm), is provided by U.S. Agilent Technologies; Two-dimensional columns is Rxi-17Sil MS (2.0m × 0.15mm I.D. × 0.15 μm), is provided by Restek company of the U.S..Injector temperature is located at 320 DEG C, take helium as carrier gas, and flow velocity is 0.7mL/min.Sample size is 1 μ L, and split ratio is 20:1.The heating schedule of One Dimensional Furnace incubator is: initial temperature 180 DEG C, keeps 1min, is then raised to 250 DEG C with the speed of 10 DEG C/min, keep 1min, then be raised to 280 DEG C with the speed of 2 DEG C/min, keep 2min, finally be raised to 300 DEG C with the speed of 10 DEG C/min, keep 20min; The temperature of two dimension furnace temperature case is higher than One Dimensional Furnace incubator 15 DEG C, heating schedule: initial temperature 195 DEG C, keep 1min, then 265 DEG C are raised to the speed of 10 DEG C/min, keep 1min, then be raised to 295 DEG C with the speed of 2 DEG C/min, keep 2min, finally be raised to 315 DEG C with the speed of 10 DEG C/min, keep 20min.Modulator temperature compensation is 40 DEG C; Modulation period is 3s, and wherein the hot blow time is 1.15s, and the cold blowing time is 0.35s; Transmission line temperature is located at 315 DEG C.Mass spectrometric data frequency acquisition is 100spectra/s, and quality of scanning number is from 50m/z to 700m/z, and solvent delay is 700s.Detector voltage is 1750V, and ion source temperature is located at 250 DEG C.
(7) spectrum analysis, carries out qualitative and quantitative analysis to free sterol in edible oil.
Described qualitative analysis is: according to the two-dimensional chromatogram of the edible oil sample to be measured obtained, the retention time and the mass spectrogram that one peacekeeping two dimension retention time of each phytosterin compound and the mass spectrogram of correspondence sterol standard items corresponding to it thereof are detected after Silylation acquisition carry out corresponding comparison, and the standard mass spectrogram of sterol Silylation thing corresponding to NIST storehouse is compared simultaneously, carry out qualitative analysis, obtain the qualitative results of phytosterin compound in edible oil.Wherein, for the sterol compound (24-methylene cholesterol, rape stanols, the △ that are difficult to obtain standard items
7-rape steroid enol, △
5,23-beans steroid dienol, sitostamol, △
5-oat steroid enol, △
5,24-beans steroid dienol, △
7-stigmastenol, △
7-oat steroid enol), the ratio of retention time/cholesterol trimethylsilyl ethers one dimension retention time and relative retention time and mass spectrogram can be tieed up according to one to judge, specific practice is: the relative retention time reported in its relative retention time and ISO 12228:1999 standard compared, its mass spectrogram is compared to the standard mass spectrogram that NIST composes corresponding sterol Silylation thing in storehouse simultaneously, obtain qualitative results.
Described quantitative test is: first set up mark curve in each sterol compound, be specially: accurately take different quality and (first standard substance is made into certain density hexane solution, then pipette the solution of different volumes respectively) each phytosterin compound reference material in different reaction bulbs, and respectively add in cholestanol in each reaction bulb and mark 20 μ g, then slowly normal hexane is dried up with nitrogen, add 100 μ L silylating reagents (N methyl N trimethylsilyl heptafluorobutyramide: 1-methylimidazole=95:5 again, v/v), screw reaction bottle cap, obtain the system of each sterol reference material of variable concentrations, subsequently reaction bulb is put in the constant temperature oven of 102 ~ 108 DEG C and adds thermal response 15 ~ 20min, then be cooled to room temperature to analyze according to step (6), and with the concentration of reference material for horizontal ordinate, the ratio of the peak area that each reference material is corresponding when variable concentrations and internal standard compound peak area is ordinate, obtain marking curve and computing formula in each standard substance through regression fit.In oil sample, the calculating of cholesterol, campesterol, rape sterol, stigmasterol and sitosterol adopts mark curve separately respectively, and wherein in cholesterol, the concentration gradient of mark curve is: 0.1,0.2,0.4,0.8,1.5,3.0 μ g/100 μ L; In campesterol, rape sterol, stigmasterol, the concentration gradient of mark curve is all located at 1,5,10,20,30,40 μ g/100 μ L; In cupreol, mark curve concentration gradient is 5,10,20,40,80,120 μ g/100 μ L.In addition, for other sterols (24-methylene cholesterol, rape stanols, the △ that there is no standard substance in oil sample
7-rape steroid enol, △
5,23-beans steroid dienol, sitostamol, △
5-oat steroid enol, △
5,24-beans steroid dienol, △
7-stigmastenol, △
7-oat steroid enol), it calculates unified use in stigmasterol and marks curve, and in interior mark curve, the concentration gradient of stigmasterol is 0.1,0.5,1,2,4,8 μ g/100 μ L;
According to GC × GC-TOF/MS total ion current figure of free sterol in the edible oil sample of above-mentioned acquisition, the peak area of each sterol compound and the ratio of interior mark peak area in calculation sample, utilize corresponding interior mark curve, obtain the content of each sterol compound in edible oil.
The one dimension retention time that in described edible oil sample, 14 kinds of free sterols obtain through comprehensive two dimensional gas chromatography-flying time mass spectrum analysis and two-dimentional retention time as shown in table 1; Described qualitative analysis is as shown in table 2 with the quota ion calculating each sterol compound peak area when qualitative fragmention and quantitative test.
The one dimension retention time that in table 1. edible oil sample, 14 kinds of free sterols obtain through comprehensive two dimensional gas chromatography-flying time mass spectrum analysis and two-dimentional retention time
14 kinds of qualitative fragment ions of free sterol and quota ion combination in table 2. edible oil sample
In each edible oil sample that above-mentioned analysis obtains, free sterol content is as shown in table 3.
In table 3. edible oil sample, different free sterol is quantitative
aanalysis result
ain edible oil, the content of free sterol represents with mg/kg; Same sample carries out 3 independent determination tests, and in sample, the content of each sterol compound represents with mean value ± standard deviation;
bjudge the factor: with (△
5-oat steroid enol+△
5,24-beans steroid dienol+△
7-oat steroid enol) ratio of/cholesterol represents.
Embodiment 2: free sterol proximate analysis and waste oil qualification in waste oil sample
Accurately take 0.06g (be accurate to radix point after 4) waste oil and each 2 of rapeseed oil sample, and add mark in 20 μ g cholestanols, then use 6mL n-hexane dissolution, vortex concussion is evenly, obtain sample solution, then carry out comprehensive two dimensional gas chromatography-flying time mass spectrum analysis.Obtain qualitative and quantitative result.Its analytical procedure is substantially the same manner as Example 1, and just selected comprehensive two dimensional gas chromatography-flying time mass spectrum analysis condition is slightly different, and being specially: injector temperature is located at 310 DEG C, take helium as carrier gas, and flow velocity is 0.9mL/min.Sample size is 2 μ L, and split ratio is 15:1.The heating schedule of One Dimensional Furnace incubator is: initial temperature 190 DEG C, keeps 1min, is then raised to 250 DEG C with the speed of 10 DEG C/min, keep 1min, then be raised to 280 DEG C with the speed of 2 DEG C/min, keep 2min, finally be raised to 300 DEG C with the speed of 10 DEG C/min, keep 20min; The temperature of two dimension furnace temperature case is higher than One Dimensional Furnace incubator 15 DEG C, heating schedule: initial temperature 205 DEG C, keep 1min, then 265 DEG C are raised to the speed of 10 DEG C/min, keep 1min, then be raised to 295 DEG C with the speed of 2 DEG C/min, keep 2min, finally be raised to 315 DEG C with the speed of 10 DEG C/min, keep 20min.Modulator temperature compensation is 40 DEG C; Modulation period is 3s, and wherein the hot blow time is 1.15s, and the cold blowing time is 0.35s; Transmission line temperature is located at 310 DEG C.Mass spectrometric data frequency acquisition is 100spectra/s, and quality of scanning number is from 50m/z to 700m/z, and solvent delay is 500s.Detector voltage is 1650V, and ion source temperature is located at 230 DEG C.
Utilize qualitative and quantitative analysis method in case 1, free sterol content (see table 4) in 2 rapeseed oils obtained and 2 waste oil samples, utilizes formula [to judge the factor=(△
5-oat steroid enol+△
5,24-beans steroid dienol+△
7-oat steroid enol)/cholesterol] calculate the judgement factor, as can be seen from Table 4, the judgement factor of waste oil 1 and waste oil 2 is respectively 0.04 and 2.13, according to the threshold value of this patent setting, is judged to be waste oil; Rapeseed oil 1 and rapeseed oil 2 judge that the factor is as 15.07 and 8.70, equally according to the threshold value of this patent setting, be judged as normal edible oil.Therefore, the judgement factor utilizing the present invention to propose can expand the difference between waste oil and normal edible oil.
In table 4. edible oil sample, different free sterol is quantitative
aanalysis result
ain edible oil, the content of free sterol represents with mg/kg; Same sample carries out 3 independent determination tests, and in sample, the content of each sterol compound represents with mean value ± standard deviation;
bjudge the factor: with (△
5-oat steroid enol+△
5,24-beans steroid dienol+△
7-oat steroid enol) ratio of/cholesterol represents.
Claims (11)
1. free sterol proximate analysis method in an edible oil sample, it is characterized in that: by edible oil sample to be measured through Solid-Phase Extraction process, isolate free sterol wherein, inject comprehensive two dimensional gas chromatography-flight time mass spectrum after again free sterol being carried out Silylation to detect, then qualitative and quantitative analysis is carried out to the phytosterin compound in edible oil sample.
2. free sterol proximate analysis method in edible oil sample according to claim 1, it is characterized in that: described comprehensive two dimensional gas chromatography-flying time mass spectrum analysis analysis condition used is: injector temperature 300 ~ 320 ° of C, take helium as carrier gas, flow velocity is 0.7 ~ 1mL/min, split ratio is 15 ~ 20:1, and modulator temperature compensation is 35 ~ 40 ° of C; Modulation period is 3s, and wherein the hot blow time is 1.15s, and the cold blowing time is 0.35s; Transmission line temperature is located at 310 ~ 315 ° of C; Scanning of the mass spectrum scope: from 50
m/
zto 700
m/
z,solvent delay is 500 ~ 700s, and detector voltage is 1650 ~ 1750V, and ion source temperature is located at 230 ~ 250 ° of C.
3. free sterol proximate analysis method in edible oil sample according to claim 1 and 2, it is characterized in that: in described comprehensive two dimensional gas chromatography-flying time mass spectrum analysis, one dimension post is DB-5ms(30m × 0.25mm I.D. × 0.25 μm) or HP-5ms(30m × 0.25mm I.D. × 0.25 μm), provide by U.S. Agilent Technologies; Two-dimensional columns is Rxi-17Sil MS(2.0m × 0.15mm I.D. × 0.15 μm), thered is provided by Restek company of the U.S., or DB-17ht(1.5m × 0.10mm I.D. × 0.15 μm), thered is provided by U.S. Agilent Technologies, the heating schedule of One Dimensional Furnace incubator is: initial temperature 180 ~ 190 ° of C, keep 1min, then 250 ° of C are raised to the speed of 10 ~ 15 ° of C/min, keep 1min, 280 ° of C are raised to again with the speed of 2 ~ 3 ° of C/min, keep 2min, be finally raised to 300 ° of C with the speed of 9 ~ 11 ° of C/min, keep 20min; The temperature 15 ° Cs higher than One Dimensional Furnace incubator of two dimension furnace temperature case, heating schedule: initial temperature 195 ~ 205 ° of C, keep 1min, then 265 ° of C are raised to the speed of 10 ~ 15 ° of C/min, keep 1min, then be raised to 295 ° of C with the speed of 2 ~ 3 ° of C/min, keep 2min, finally be raised to 315 ° of C with the speed of 9 ~ 11 ° of C/min, keep 20min; Mass spectrometric data frequency acquisition is 100 spectrograms/s(spectra/s); Sample size is 1 ~ 2 μ L.
4. free sterol proximate analysis method in edible oil sample according to claim 1 and 2, it is characterized in that: described method for qualitative analysis is: according to the two-dimensional chromatogram of the edible oil sample to be measured obtained, the retention time and the mass spectrogram that one peacekeeping two dimension retention time of each phytosterin compound and the mass spectrogram of correspondence sterol standard items corresponding to it thereof are detected after Silylation acquisition carry out corresponding comparison, and the standard mass spectrogram of sterol Silylation thing corresponding to NIST storehouse is compared simultaneously, carry out qualitative analysis, obtain the qualitative results of phytosterin compound in edible oil, wherein, for sterol compound (the 24-methylene cholesterol being difficult to obtain standard items, rape stanols, △
7-rape steroid enol, △
5,23-beans steroid dienol, sitostamol, △
5-oat steroid enol, △
5,24-beans steroid dienol, △
7-stigmastenol, △
7-oat steroid enol), the relative retention time reported in its relative retention time and ISO 12228:1999 standard is compared, its mass spectrogram is compared to the standard mass spectrogram that NIST composes corresponding sterol Silylation thing in storehouse simultaneously, obtain qualitative results, described relative retention time is the ratio of each sterol compound one dimension retention time/cholesterol trimethylsilyl ethers one dimension retention time,
Described quantitative analysis method is: set up mark curve in each phytosterin compound reference material, be specially: accurately take each phytosterin compound reference material of different quality in different reaction bulbs, and add in cholestanol in each reaction bulb and mark, add silylating reagent again, obtain each sterol reference material system of a series of variable concentrations, then after Silylation reaction, room temperature is cooled to respectively, sample introduction is analyzed to comprehensive two dimensional gas chromatography-flight time mass spectrum, with the concentration of each reference material for horizontal ordinate, the ratio of the peak area that each reference material is corresponding when variable concentrations and internal standard compound peak area is ordinate, obtain marking curve in each reference material through regression fit, cholesterol in edible oil sample, campesterol, rape sterol, the content of stigmasterol and cupreol adopts the interior mark curve of respective corresponding standard items to calculate, use in stigmasterol for there is no the quantitative test of other sterol of corresponding standard items in edible oil sample and mark curve replacement,
According to GC × GC-TOF/MS total ion current figure of free sterol in the edible oil sample of above-mentioned acquisition, the peak area of each sterol compound and the ratio of interior mark peak area in calculation sample, utilize corresponding interior mark curve, obtain the content of each sterol compound in edible oil.
5. free sterol proximate analysis method in edible oil sample according to claim 4, is characterized in that: described used when quantitative test carried out to cholesterol, campesterol, rape sterol, stigmasterol and cupreol in edible oil sample in mark in curve: in cholesterol, the concentration gradient of mark curve is: 0.1,0.2,0.4,0.8,1.5,3.0 μ g/100 μ L; In campesterol, rape sterol, stigmasterol, the concentration gradient of mark curve is all located at 1,5,10,20,30,40 μ g/100 μ L; In cupreol, mark curve concentration gradient is 5,10,20,40,80,120 μ g/100 μ L; The described concentration gradient to marking stigmasterol in curve in stigmasterol used when not having other sterol compounds of standard substance to carry out quantitative test in edible oil sample is 0.1,0.5,1,2,4,8 μ g/100 μ L.
6. free sterol proximate analysis method in the edible oil sample according to claim 1 or 4, is characterized in that: the quota ion calculating each phytosterin compound peak area during described quantitative test is combined as: cholesterol trimethylsilyl ethers: 247+353+329+368+458; Cholestanol trimethylsilyl ethers: 215+306+355+445+460; Campesterol trimethylsilyl ethers: 255+341+365+380+470; 24-methylene cholesterol trimethylsilyl ethers: 253+296+371+386+470; Rape sterol trimethylsilyl ethers: 255+343+367+382+472; Rape stanols trimethylsilyl ethers: 215+305+343+382+474; Stigmasterol trimethylsilyl ethers: 255+355+379+394+484; △
7-rape steroid trimethylsilyl enol ether: 255+367+382+457+472; △
5,23-beans steroid dienol trimethylsilyl ethers: 255+355+379+394+484; Cupreol trimethylsilyl ethers: 255+357+381+396+486; Sitostamol trimethylsilyl ethers: 215+305+383+473+488; △
5-oat steroid trimethylsilyl enol ether: 257+281+296+386+484; △
5,24-beans steroid dienol trimethylsilyl ethers: 253+281+343+386+484; △
7-stigmastenol trimethylsilyl ethers: 255+357+381+471+486; △
7-oat steroid trimethylsilyl enol ether: 255+343+386+469+484.
7. free sterol proximate analysis method in edible oil sample according to claim 1 and 2, is characterized in that: described edible oil sample is soybean oil, rapeseed oil, peanut oil, sunflower oil, corn oil and waste oil; Described phytosterin compound is cholesterol, campesterol, 24-methylene cholesterol, rape sterol, rape stanols, stigmasterol, △
7-rape steroid enol, △
5,23-beans steroid dienol, cupreol, sitostamol, △
5-oat steroid enol, △
5,24-beans steroid dienol, △
7-stigmastenol and △
7-oat steroid enol.
8. free sterol proximate analysis method in edible oil sample according to claim 1 and 2, is characterized in that: described Solid-Phase Extraction disposal route is:
(1) preparation of Solid-Phase Extraction sample solution: add in cholestanol in edible oil sample and mark, then use n-hexane dissolution, vortex concussion is evenly, for subsequent use;
(2) loading: the uniform sample liquid of concussion in step (1) is injected in the solid-phase extraction column after activation, discards efflux;
(3) drip washing: be that the hexane solution of the ether of 5 ~ 6% carries out drip washing with concentration of volume percent, discard efflux;
(4) wash-out: the hexane free sterol with concentration of volume percent being the ether of 15 ~ 25%.
9. free sterol proximate analysis method in edible oil sample according to claim 1 and 2, is characterized in that: described Solid-Phase Extraction disposal route concrete steps are:
(1) preparation of Solid-Phase Extraction sample solution: accurately take 0.04 ~ 0.06g edible oil sample, and add mark in 20 μ g cholestanols, then use 5 ~ 8mL n-hexane dissolution, vortex concussion is evenly, for subsequent use;
(2) loading: be injected in the solid-phase extraction column after activation by the uniform sample liquid of concussion in step (1), coutroi velocity is 1.2 ~ 1.6mL/min, discards efflux; Described solid-phase extraction column is silicagel column; The activation of described solid-phase extraction column is: take the top that 1.0 ~ 1.5g anhydrous sodium sulfate is added to solid-phase extraction column, and then with the activation of 10 ~ 15mL hexane solution, flow velocity is 1.0 ~ 2.0mL/min, discards efflux;
(3) drip washing: carry out drip washing with the diethyl ether hexane Solutions Solution that concentration of volume percent is 5 ~ 6%, flow control, at 1.2 ~ 1.6mL/min, discards efflux;
(4) wash-out: be the diethyl ether hexane eluant solution free sterol of 15 ~ 25% with concentration of volume percent, flow control is at 1.2 ~ 1.6mL/min.
10. free sterol proximate analysis method in edible oil sample according to claim 1 and 2, it is characterized in that: described Silylation be by Solid-Phase Extraction process after sample desolvation, then add silylating reagent be cooled to after Silylation room temperature for analyze;
Described silylating reagent is served as reasons
n-methyl-
n-TMS seven Flutamide and 1-methylimidazole are counted 93 ~ 95:7 ~ 5 by volume and are formed, and described silylating reagent consumption is every mg edible oil sample 1.5 ~ 2.5 μ L, and Silanization reaction condition is: 102 ~ 108 ° of C react 15 ~ 20min.
11. waste oil discrimination methods, it is characterized in that: adopted by sample to be identified free sterol constituent analytical approach in edible oil sample described in claim 1 or 2 to carry out detection and analyze, obtain the content of each sterol compound in sample to be identified, then calculate (△ in sample thus
5-oat steroid enol+△
5,24-beans steroid dienol+△
7-oat steroid enol) ratio of/cholesterol and Assessing parameters, as Assessing parameters > 5, be judged to normal edible oil, Assessing parameters≤5 item are judged to waste oil.
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| CN111879862A (en) * | 2020-05-09 | 2020-11-03 | 江南大学 | Method for simultaneously determining free sterols and sterol glycosides in oil material by GC-MS-SSDMC method |
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| CN114577925A (en) * | 2021-12-29 | 2022-06-03 | 西南大学 | Method for rapidly detecting fecal sterol substances in water sample |
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