Rice meal standard substance containing organophosphorus flame retardant and preparation method thereof

Abstract

The invention discloses a rice meal standard substance containing an organophosphorus flame retardant and a preparation method thereof, and the preparation method comprises the following steps: providing a standard solution containing a plurality of organophosphorus flame retardant standard substances; mixing the standard solution with a diluent to obtain a to-be-immersed solution; mixing rice with the to-be-soaked liquid, performing soaking treatment, and after the to-be-soaked liquid is completely sucked in the soaking process, obtaining soaked rice; performing freeze drying treatment on the soaked rice so as to obtain dried rice; performing grinding treatment on the dried rice so as to obtain rice powder; and sieving and mixing the rice powder so as to obtain the rice meal standard substance containing the organic phosphorus flame retardant. The rice flour standard substance prepared by the method is good in uniformity and high in assignment accuracy, and can be used for evaluation of an analysis method in trace residue detection of the organophosphorus flame retardant in rice, quality control in an analysis process and laboratory ability assessment.

Description

Technical Field

[0001] The invention relates to the field of analytical chemistry, in particular to a rice flour standard substance containing an organophosphorus flame retardant and a preparation method thereof. Background Art

[0002] Organophosphorus flame retardants (OPFRs), commonly known as organophosphorus flame retardants, are additives used in polymer materials to act as flame retardants and plasticizers. They are widely used in plastics, coatings, textiles and electronic products. At present, the types and quantities of OPFRs are increasing, and their production and use are also expanding worldwide. China has the highest market share of OPFRs in the global market and is the country that produces and uses the most OPFRs. As organophosphorus flame retardants are found in human blood and breast milk, the toxicity and hazards of OPFRs have received widespread attention. The World Health Organization has found that some alkane OPFRs are neurotoxic and have long-term effects on human immunity. Some halogenated OPFRs are carcinogenic and are persistently distributed in human internal organs such as the liver, kidneys and brain. The European Union and the United States have included some OPFRs in the list of risk pollutants and banned the use of several OPFRs.

[0003] Reference material (RM) is a substance or material that has been determined to have one or more sufficiently uniform characteristic values. As a "measuring tool" in the analytical measurement industry, it plays an indispensable role in calibrating measuring instruments and devices, evaluating measurement and analysis methods, measuring the characteristic values ​​of substances or materials, and assessing the operational technical level of analysts, as well as in the quality control of products during the production process.

[0004] At present, most matrix standard substances contain only one target substance. However, with the continuous increase in the number of new pollutants, multi-type and high-throughput analysis of compounds has become a new detection trend. In order to ensure the accuracy, traceability and comparability of the detection results of organophosphorus flame retardant residues in my country, it is necessary to develop matrix standard substances for multiple types of organophosphorus flame retardants in rice on the basis of fully studying the measurement methods of organophosphorus flame retardants in rice.

[0005] The successful development of this standard substance ensures the accuracy, comparability and traceability of the measurement results of organophosphorus flame retardant residues, and has extremely significant social and economic benefits for food safety testing. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one purpose of the present invention is to propose a method for preparing a rice flour standard substance containing an organophosphorus flame retardant. The rice flour standard substance prepared by the method has good uniformity, which is conducive to improving the matrix matching degree between the standard substance and the sample in the detection of trace residues of various types of organophosphorus flame retardants in rice, thereby improving the accuracy and reliability of the detection results; and the standard substance can simultaneously meet the accurate analysis of various organophosphorus flame retardants, meet the detection needs of multiple targets, and improve the analysis efficiency of the experimental process.

[0007] According to one aspect of the present invention, the present invention provides a method for preparing a rice powder standard substance containing an organophosphorus flame retardant. According to an embodiment of the present invention, the method comprises: providing a standard solution containing several organophosphorus flame retardant standards; mixing the standard solution with a diluent to obtain a solution to be immersed; mixing rice with the solution to be immersed and soaking the rice, and after the solution to be immersed is dried, the soaked rice is obtained; freeze-drying the soaked rice to obtain dry rice, the dry rice having a moisture content of 10-20%; grinding the dry rice to obtain rice powder; and sieving and mixing the rice powder to obtain the rice powder standard substance containing the organophosphorus flame retardant.

[0008] According to the method for preparing a rice flour standard substance containing an organophosphorus flame retardant according to an embodiment of the present invention, rice grains are directly mixed with an organophosphorus flame retardant mixed standard solution and a diluent in an appropriate proportion to ensure that the rice grains are in uniform contact with the organophosphorus flame retardant and the preparation concentration is easy to control. As a result, the prepared rice flour standard substance has good uniformity and high value assignment accuracy, and can be widely used in the detection and accurate determination of organophosphorus flame retardants in rice samples, providing technical support for the evaluation of analytical methods in the detection of trace residues of organophosphorus flame retardants in rice, the quality control of the analytical process, and the laboratory capacity assessment; and, as a standard substance, it can also be used to calibrate measuring instruments and evaluate measuring methods, and is simple to operate and easy to promote.

[0009] In addition, the method for preparing a rice flour standard substance containing an organophosphorus flame retardant according to the above embodiment of the present invention may also have the following additional technical features:

[0010] According to an embodiment of the present invention, the solvent of the standard solution is methanol.

[0011] According to an embodiment of the present invention, the diluent is water.

[0012] According to an embodiment of the present invention, the ratio of the diluent to the standard solution is 5-7:1, preferably 6:1.

[0013] According to an embodiment of the present invention, the ratio of the rice to the liquid to be soaked is 1 kg: 200-300 mL, preferably, 1 kg: 240-260 mL.

[0014] According to an embodiment of the present invention, the freeze-drying treatment conditions are as follows: pre-freezing the sample: placing the soaked rice in a pre-freezing tray, setting the pre-freezing temperature to -20 to -30°C; the pre-freezing rate is 10-20°C / min; rapid pre-freezing for 2-4 hours to obtain the pre-frozen rice; first-stage sublimation drying: placing the pre-frozen rice in a freeze drying oven, the oven pressure is 0.070mbar, and the shelf temperature is reduced at a rate of 5°C / time until -45 to -55°C, and drying is continued for 5 hours; second-stage sublimation drying: setting the shelf temperature to below -50°C; automatically adjusting the air permeation, the pressure is 0.070mbar, and the time is more than 2 hours; after the sample temperature drops below -50°C, the vacuum degree in the oven is restored and the temperature is kept constant for 5 hours.

[0015] According to an embodiment of the present invention, the grinding process is performed at a rate of 15000 rpm and for a time of 2 min.

[0016] According to an embodiment of the present invention, a 35-mesh sieve is used for the screening.

[0017] According to an embodiment of the present invention, the mixing time is 8-12 hours.

[0018] According to an embodiment of the present invention, the several organophosphorus flame retardants are no less than 5 organophosphorus flame retardants.

[0019] According to an embodiment of the present invention, the organophosphorus flame retardant is at least five selected from dibutylphenyl phosphate (DBPHP), triethyl phosphate (TEP), tripropyl phosphate (TnPP), tributyl phosphate (TnBP), tri(2-chloroethyl) phosphate (TCEP), triphenyl phosphate (TPHP) and tricresyl phosphate (TMPP).

[0020] Furthermore, according to another aspect of the present invention, the present invention provides a rice flour standard substance containing an organophosphorus flame retardant. According to an embodiment of the present invention, the rice flour standard substance is prepared by the aforementioned method. Therefore, the rice flour standard substance of the embodiment of the present invention has good uniformity and high value assignment accuracy, and can be used for the evaluation of analytical methods in the detection of trace residues of organophosphorus flame retardants in rice, the quality control of the analytical process, and the assessment of laboratory capabilities; and, as a standard substance, it can also be used for calibrating measuring instruments and evaluating measuring methods, and is simple to operate and easy to promote.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0023] Figure 1 The molecular structures of seven organophosphorus flame retardants are shown;

[0024] Figure 2 The extracted ion chromatograms of seven OPFRs compounds according to one embodiment of the present invention are shown. DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0026] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0027] According to one aspect of the present invention, the present invention provides a method for preparing a rice flour standard substance containing an organophosphorus flame retardant. According to the method for preparing a rice flour standard substance containing an organophosphorus flame retardant according to an embodiment of the present invention, rice grains are directly mixed with an organophosphorus flame retardant mixed standard solution and a diluent in an appropriate proportion to ensure that the rice grains are in uniform contact with the organophosphorus flame retardant, and the preparation concentration is easily controlled, and freeze-dried rice is obtained by a freeze-drying method, and then subjected to the steps of grinding, sieving, and mixing. Thus, the prepared rice flour standard substance has good uniformity and high value assignment accuracy, and can be widely used in the detection and accurate determination of organophosphorus flame retardants in rice samples, and provides technical support for the evaluation of analytical methods in the detection of trace residues of organophosphorus flame retardants in rice, the quality control of the analytical process, and the laboratory capacity assessment; and, as a standard substance, it can also be used to calibrate measuring instruments and evaluate measuring methods, and is simple to operate and easy to promote.

[0028] In order to facilitate understanding of the method for preparing the rice flour standard substance containing the organophosphorus flame retardant, the method is explained here. According to an embodiment of the present invention, the method comprises:

[0029] S100 standard solution provided

[0030] According to an embodiment of the present invention, a standard solution containing several organophosphorus flame retardant standard products is provided, wherein the several organophosphorus flame retardant standard products constitute the organophosphorus flame retardant components in the subsequent rice flour standard material.

[0031] According to an embodiment of the present invention, the solvent of the standard solution is methanol. Therefore, the organic phosphorus flame retardant has high solubility in the methanol solvent, and the polarity of methanol is closer to that of water, which is beneficial to the subsequent preparation of the soaking solution.

[0032] According to an embodiment of the present invention, the several organophosphorus flame retardants are no less than 5 organophosphorus flame retardants. Therefore, as the number of new pollutants continues to increase, rice standards containing multiple organophosphorus flame retardants meet the needs of multi-type, high-throughput analysis and detection.

[0033] According to an embodiment of the present invention, the organophosphorus flame retardant is selected from at least five of dibutylphenyl phosphate (DBPHP), triethyl phosphate (TEP), tripropyl phosphate (TnPP), tributyl phosphate (TnBP), tri(2-chloroethyl) phosphate (TCEP), triphenyl phosphate (TPHP) and tricresyl phosphate (TMPP). The structures of the seven organophosphorus flame retardants are shown in FIG. Figure 1 The extracted ion chromatograms of seven organophosphorus flame retardants are shown in Figure 2 shown.

[0034] S200 with immersion liquid

[0035] According to an embodiment of the present invention, the standard solution is mixed with the diluent to obtain the soaking liquid, thereby forming the soaking liquid that is easy to combine with rice.

[0036] According to an embodiment of the present invention, the diluent is water. The main components of rice include starch, protein and fat, of which starch accounts for about 85%. The efficiency of starch in absorbing organic solvents is much lower than that of water. The hydrogen bonds between starch molecules are tightly bound, but when soaked in water, water molecules can bind to -OH between starch molecules, causing rice to absorb water. Therefore, water is selected as the diluent to configure the soaking liquid.

[0037] The inventors experimentally investigated the absorption efficiency and theoretical preparation concentration of the organophosphorus mixed standard solution and water at different ratios of 1:4, 1:5, 1:6 and 1:7, and found that with the increase of the water ratio, the absorption efficiency gradually increased. According to an embodiment of the present invention, the ratio of the diluent to the standard solution is 5-7:1, the concentration of the organophosphorus flame retardant is appropriate, and the absorption efficiency is high. The inventors found that the absorption efficiency at the ratio of 1:6 and 1:7 is similar and reaches a peak value, but a lower ratio of the mixed standard solution will cause the theoretical preparation concentration to decrease. Furthermore, according to a preferred embodiment of the present invention, the ratio of the diluent to the standard solution is 6:1. As a result, the rice has a high absorption efficiency for the soaking liquid and a high content of the standard substance.

[0038] S300 immersion treatment

[0039] According to an embodiment of the present invention, the rice is mixed with the soaking liquid for soaking, and the soaked rice is obtained after the soaking liquid is dried. Thus, the organophosphorus flame retardant standard product is uniformly mixed with the rice sample through the soaking process.

[0040] According to an embodiment of the present invention, the ratio of the rice to the liquid to be soaked is 1kg: 200-300mL, preferably 1kg: 240-260mL. When the liquid to be soaked is too little, the sample preparation concentration will be reduced. When the liquid to be soaked is too much, the rice cannot completely absorb the liquid to be soaked, which is not conducive to uniform preparation of the sample. The above ratio of rice and liquid to be soaked is conducive to preparing a high-concentration and uniform rice sample.

[0041] S400 Freeze Drying

[0042] According to an embodiment of the present invention, the soaked rice is freeze-dried to obtain dried rice, and the moisture content of the dried rice is 10-20%.

[0043] According to an embodiment of the present invention, the moisture content of the dried rice is 13-17%.

[0044] The inventors used a small batch of rice flour to investigate low-temperature drying and freeze-drying, calculated the preparation recovery rates of the two drying methods, and selected the process with the least preparation loss rate.

[0045]

[0046] (1) Low-temperature drying method: The rice sample was placed on a drying tray and placed in a 50°C oven for low-temperature drying for 12 hours. After the rice sample was completely dried, it was taken out and ground. After the sample was mixed, it was tested on a machine. The recovery rates of the seven organophosphorus flame retardants in the rice sample prepared by the drying method were between 12% and 55%.

[0047] (2) Freeze drying method: The rice sample was placed in a freezing tray, pre-frozen at -25°C for 3 hours, then subjected to the first stage of sublimation drying for 5 hours, gradually cooled to -50°C, and then subjected to the second stage of sublimation drying. After the sample temperature gradually dropped to -50°C, it was kept dry for 5 hours. After the rice sample was completely dried, it was taken out for grinding. After the sample was mixed, it was tested on a machine. The preparation recovery rates of the 7 organophosphorus flame retardants in the rice sample prepared by freeze drying were between 21% and 62%. Obviously, the recovery rate of freeze drying was higher, and freeze drying was selected to dry the soaked rice.

[0048] According to an embodiment of the present invention, the freeze-drying process is performed under the following conditions:

[0049] Prefreezing samples: placing the soaked rice in a prefreezing tray, setting the prefreezing temperature to -20 to -30°C; the prefreezing rate to 10-20°C / min; and rapid prefreezing for 2-4 hours to obtain the prefrozen rice;

[0050] The first stage of sublimation drying: the pre-frozen rice is placed in a freeze drying oven with a pressure of 0.070 mbar, and the shelf temperature is reduced at a rate of 5°C / time until it reaches -45 to -55°C to prevent the sample from being overcooled, provide energy for sublimation, and accelerate the sublimation speed. When the interface between the sample dry layer and the freeze-dried layer reaches the bottom of the dish and disappears, the sample temperature rises to a temperature close to the shelf temperature or the vacuum degree of the drying oven and the vacuum degree of the cold trap are close to and remain constant, continue drying for 5 hours to completely eliminate the residual ice crystals in the sample and the unevenness of the sample drying, and the first stage of sublimation ends;

[0051] The second stage of sublimation drying: set the shelf temperature to below -50°C; to avoid the influence of too low pressure in the drying box on heat transfer, automatically adjust the gas permeation pressure to 0.070mbar and the time to more than 2 hours, so that the sample temperature can reach the lowest temperature as soon as possible and increase the sublimation rate; after the sample temperature drops below -50°C, restore the vacuum degree in the drying box and keep the temperature constant for 5 hours, and the second stage of sublimation drying is completed.

[0052] S500 grinding process

[0053] According to an embodiment of the present invention, the dried rice is ground to obtain rice powder.

[0054] The inventors grind the freeze-dried samples in a grinder, and experimentally investigated the effects of different grinding rates and times on the sample preparation recovery rate. Both the grinding rate and grinding time affect the temperature in the cavity. Too high a cavity temperature will cause the sample to volatilize or decompose quickly. The investigation scheme 1 is a rotation speed of 15000rpm and grinding for 2min; scheme 2 is a rotation speed of 30000rpm and grinding for 1min. The ground rice flour samples are sieved respectively, mixed and sampled for analysis. In the experiment, the recovery rates of 7 kinds of organophosphorus flame retardants prepared at 15000rpm and grinding for 2min are between 21 and 62%, and the recovery rates of 7 kinds of organophosphorus flame retardants prepared at 30000rpm and grinding for 1min are between 17 and 61%. According to an embodiment of the present invention, the grinding process rate is 15000rpm and the time is 2min. As a result, the recovery rate of organophosphorus flame retardants is high.

[0055] S600 sieving and mixing

[0056] According to an embodiment of the present invention, the rice powder is sieved and mixed to obtain the rice powder standard substance containing the organophosphorus flame retardant.

[0057] According to an embodiment of the present invention, a 35-mesh sieve is used for the sieving. Thus, the rice sample is evenly distributed at a small particle size, and the uneven phenomenon caused by larger particles is optimized.

[0058] According to an embodiment of the present invention, the mixing time is 8-12 hours, preferably 10 hours. Further, the sample is placed in a mixing barrel, and the sample does not exceed 1 / 2 of the barrel volume for mixing. Thus, the mixing is more uniform.

[0059] Furthermore, according to another aspect of the present invention, the present invention provides a rice flour standard substance containing an organophosphorus flame retardant. According to an embodiment of the present invention, the rice flour standard substance is prepared by the aforementioned method. Therefore, the rice flour standard substance of the embodiment of the present invention has good uniformity and high value assignment accuracy, and can be used for the evaluation of analytical methods in the detection of trace residues of organophosphorus flame retardants in rice, the quality control of the analytical process, and the assessment of laboratory capabilities; and, as a standard substance, it can also be used for calibrating measuring instruments and evaluating measuring methods, and is simple to operate and easy to promote.

[0060] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and should not be construed as limiting the present invention.

[0061] Below in conjunction with embodiment, the scheme of the present invention will be explained.It will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.Unrepresented specific techniques or conditions in the embodiment, according to the technology or conditions described in the document in this area or according to the product specification sheet.Reagents used or instruments that do not indicate manufacturers are conventional products that can be obtained commercially, for example, can be purchased from Sigma company.

[0062] Example 1

[0063] In this embodiment, the rice flour standard substance is prepared by the method for preparing a rice flour standard substance containing an organophosphorus flame retardant according to an embodiment of the present invention, as follows:

[0064] 1. Rice sample pretreatment:

[0065] (1) Source of rice samples: commercially available Wuchang rice.

[0066] (2) Preparation of organophosphorus mixed standard solution: Accurately weigh seven standards (accurate to 0.1 mg), dissolve them in methanol respectively, transfer them to a 10-mL volumetric flask, dilute to the mark with methanol, mix well, and store at 4°C in the dark to prepare a standard stock solution (1000 μg / g, methanol). Accurately transfer seven standard stock solutions to a 250-mL volumetric flask, dilute to the mark with methanol, and prepare a mixed standard solution (10 μg / g, methanol).

[0067] (3) Rice soaking method: 1 kg of rice sample was mixed with 250 ml of organophosphorus mixed standard solution and allowed to soak until the solution was completely absorbed by the rice grains to obtain the soaked rice sample.

[0068] (4) The rice sample is placed in a freezing tray and waits for subsequent freeze drying.

[0069] 2. Preparation of freeze-dried rice powder:

[0070] (1) Prefreeze samples: set the prefreezing temperature to -25°C; the prefreezing rate to 15°C / min; and prefreeze for 3 hours;

[0071] (2) The first stage of sublimation drying:

[0072] After the pre-freezing is completed, the first stage of sublimation begins. When the pressure of the dry box remains constant for a long time, the shelf temperature is gradually reduced at a rate of 5°C / time until it reaches -50°C to prevent the sample from being overcooled, provide energy for sublimation, and accelerate the sublimation speed.

[0073] When the interface between the sample dry layer and the freeze-dried layer reaches the bottom of the dish and disappears, the sample temperature rises to close to the shelf temperature or the vacuum degree of the drying box and the vacuum degree of the cold trap are close to and remain constant, continue drying for 5 hours to completely eliminate the residual ice crystals in the sample and the unevenness of the sample drying, and the first stage of sublimation is completed.

[0074] (3) Second stage sublimation drying

[0075] Adjust the shelf temperature to the maximum temperature allowed by the sample below -50℃. To avoid the low pressure in the dry box affecting heat transfer, automatically adjust the air permeation to make the sample temperature reach the minimum temperature as soon as possible and increase the sublimation rate. The time is more than 2 hours.

[0076] After the sample reaches the maximum allowable temperature, the vacuum degree in the drying oven is restored and the temperature is kept constant for 5 hours, and the second stage of sublimation drying is completed.

[0077] (4) Turn off the machine and take out the freeze-dried sample.

[0078] 3. Grinding and powdering: The freeze-dried sample was ground in a grinder at a grinding rate of 3000 rpm for 2 min.

[0079] 4. Screening: Use 35 mesh screen and ultrasonic pulse to screen the sample.

[0080] 5. Mixing: Place the sample in a 10L mixing bucket (not exceeding 1 / 2 of the bucket volume) and mix continuously for 10 hours.

[0081] 6. Packaging: The samples are packaged in 15mL transparent sample bottles, each bottle contains about 2.5g.

[0082] Example 2

[0083] In this example, the freeze-dried rice powder standard product containing trace amounts of organophosphorus flame retardant prepared in Example 1 was tested for uniformity.

[0084] Homogeneity is a basic property of reference materials and is used to describe the spatial distribution characteristics of reference material properties. Homogeneity evaluation must be performed during the development (production) of reference materials to prove that they have good homogeneity. The following is an analysis of the homogeneity of seven organophosphorus flame retardants.

[0085] 1. Uniformity detection method:

[0086] (1) QuEChERS sample pretreatment:

[0087] Weigh about 1.0 g of the sample (accurately weighed to 0.01 g) into a glass centrifuge tube, add 10 mL of acetonitrile solution containing 0.5% formic acid into the glass centrifuge tube, vortex for 1 min, and ultrasonicate in a water bath for 5 min; add an extraction salt bag containing 1 g of sodium chloride, 4 g of anhydrous magnesium sulfate, 1 g of sodium citrate, and 0.5 g of disodium hydrogen citrate into the glass centrifuge tube, vortex for 1 min, centrifuge at 3000 rpm for 5 min, and extract the supernatant into a new glass centrifuge tube; add 150 mg of MgSO 4 , 50 mg PSA and 50 mg C18, vortex for 1 min, centrifuge at 3000 rpm for 5 min, extract the supernatant. The supernatant was filtered with a 0.22 μm PTFE filter, the filtrate was dried under mild nitrogen conditions, enriched and re-dissolved with 1 mL of methanol solvent, centrifuged at 3000 rpm for 5 min, and 0.8 mL of supernatant was taken for sample loading.

[0088] (2) Instrumental method:

[0089] Chromatographic column: Thermo Hypersil GOLD C18 column (100mm×2.1mm, 1.9μm); mobile phase: A is water (5mM / L ammonium formate + 0.01% formic acid), B is methanol (5mM / L ammonium formate + 0.01% formic acid. Gradient elution program: 0-1min, 1% B; 1-3min, 1% B-39% B; 3-14min, 39% B-99% B; 14-17min, 99% B; 17.1-21min, 1% B. Flow rate: 0.25mL / min; column temperature: 30℃; injection volume: 2μL;

[0090] Mass spectrometry conditions: Q Exactive Plus was equipped with a heated electrosprayionization (HESI) source, the scan mode was positive ion scan, the experiment used a full-scan primary mass spectrometer and parallel reaction detection mode (Full MS / PRM), the mass scan range of the parent ion was m / z 100-1500; the primary mass spectrometer resolution was 70000, the secondary mass spectrometer resolution was 35000; the collision energy (CE) was set to 10, 40 and 80 eV. The spray voltage was set to 2 kV, the capillary temperature was 400 ° C, the auxiliary gas temperature was 250 ° C, the automatic gain control of the number of ions entering the orbital trap (AGC target) was 1E+06, and the maximum injection time was 100 ms.

[0091] Four packages were randomly selected from the developed standard material, and three subsamples were taken from each package for inter-bottle and intra-bottle homogeneity testing. The minimum sampling amount was 1 g, and the test was performed according to the liquid chromatography tandem mass spectrometry method described below. The homogeneity variance analysis results were s bbReproducibility of the method used r Or the expected target of the uncertainty of the characteristic value. If it is not significant, the standard material is considered to be uniform. The uncertainty component u introduced by the inhomogeneity of the characteristic value to be measured should be calculated. bb , and include it in the total uncertainty of the standard material. The standard material was tested for uniformity according to the above method, and the results of the uniformity test are shown in Tables 1 to 7.

[0092] This statistic is the number of degrees of freedom (v 1 , v 2 ) of the F-distributed variable.

[0093] According to the degrees of freedom (v 1 , v 2 ) and a given significance level α, the critical F α If F<F α , it is considered that there is no significant difference between the groups and the samples are uniform; if F ≥ F α , then it is suspected that there are systematic differences between the groups, that is, there are differences between the samples.

[0094] like In this case, bb Equivalent to the uncertainty component u caused by unevenness between bottles bb .

[0095] Then we have:

[0096]

[0097] When the measurement method for uniformity assessment has poor repeatability, When , the formula becomes:

[0098]

[0099] Table 1 Uniformity test results of dibutylphenyl phosphate (DBPHP)

[0100]

[0101] According to the data in Table 1, the data of dibutylphenyl phosphate were statistically analyzed and it was found that s1 2 >s2 2 , calculated according to formula (2), the uniformity uncertainty is: 0.087.

[0102] Table 2 Uniformity test results of triethyl phosphate (TEP)

[0103]

[0104] According to the data in Table 2, the data of triethyl phosphate were statistically analyzed and it was found that s1 2 >s2 2 , calculated according to formula (2), the uniformity uncertainty is: 0.072.

[0105] Table 3 Uniformity test results of tripropyl phosphate (TnPP)

[0106]

[0107]

[0108] According to the data in Table 3, the data of tripropyl phosphate were statistically analyzed and it was found that s1 2 >s2 2 , calculated according to formula (2), the uniformity uncertainty is: 0.237.

[0109] Table 4 Uniformity test results of tributyl phosphate (TnBP)

[0110]

[0111] According to the data in Table 4, the data of tributyl phosphate were statistically analyzed and it was found that s1 2 >s2 2 , calculated according to formula (2), the uniformity uncertainty is: 0.009.

[0112] Table 5 Uniformity test results of tris(2-chloroethyl) phosphate (TCEP)

[0113]

[0114]

[0115] According to the data in Table 5, the data of tri(2-chloroethyl) phosphate was statistically analyzed and it was found that s1 2 >s2 2 , calculated according to formula (2), the uniformity uncertainty is: 0.064.

[0116] Table 6 Uniformity test results of triphenyl phosphate (TPHP)

[0117]

[0118] According to the data in Table 6, the data of triphenyl phosphate were statistically analyzed and it was found that s1 2 >s2 2 , calculated according to formula (2), the uniformity uncertainty is: 0.055.

[0119] Table 7 Uniformity test results of tricresyl phosphate (TMPP)

[0120]

[0121] According to the data in Table 7, the data of tricresyl phosphate were statistically analyzed and it was found that s1 2 >s2 2 , calculated according to formula (2), the uniformity uncertainty is: 0.049.

[0122] In summary, the freeze-dried rice powder standard containing multiple types of organophosphorus flame retardants prepared by this method has good uniformity, and the standard substance is accurately determined by liquid chromatography tandem mass spectrometry (LC-MS). The successful development of this standard substance ensures the accuracy, comparability and traceability of the measurement results of the relevant flame retardant residues, which has extremely significant social and economic benefits for food safety testing.

[0123] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0124] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a rice flour standard substance containing an organophosphorus flame retardant, characterized in that: include: Provide standard solutions containing several organophosphorus flame retardant standards; Mixing the standard solution with the diluent to obtain a solution to be immersed; Mixing the rice with the soaking liquid to be soaked, and after the soaking liquid is dried, obtaining soaked rice; The soaked rice is freeze-dried to obtain dry rice, wherein the moisture content of the dry rice is 10-20%; Grinding the dried rice to obtain rice powder; as well as The rice powder is sieved and mixed to obtain the rice powder standard material containing the organophosphorus flame retardant.

2. The method according to claim 1, characterized in that The solvent of the standard solution is methanol.

3. The method according to claim 1, characterized in that The diluent is water.

4. The method according to claim 1, characterized in that: The ratio of the diluent to the standard solution is 5-7:1, preferably 6:

1.

5. The method according to claim 1, characterized in that: The ratio of the rice to the liquid to be soaked is 1kg:200-300mL, preferably, 1kg:240-260mL.

6. The method according to claim 1, characterized in that The freeze-drying process conditions are: Prefreezing samples: placing the soaked rice in a prefreezing tray, setting the prefreezing temperature to -20 to -30°C; the prefreezing rate to 10-20°C / min; and rapid prefreezing for 2-4 hours to obtain the prefrozen rice; The first stage is sublimation drying: the pre-frozen rice is placed in a freeze drying oven with a pressure of 0.070 mbar, the shelf temperature is reduced at a rate of 5°C / time until it reaches -45 to -55°C, and the drying is continued for 5 hours; The second stage of sublimation drying: set the shelf temperature to below -50°C; automatically adjust the air permeation, the pressure is 0.070mbar, and the time is more than 2 hours; after the sample temperature drops below -50°C, restore the vacuum degree in the drying box and keep the temperature constant for 5 hours.

7. The method according to claim 1, characterized in that The grinding process was carried out at a rate of 15000 rpm for 2 min. Optionally, the sieving is performed using a 35 mesh screen.

8. The method according to claim 1, characterized in that The mixing time is 8-12 hours.

9. The method according to claim 1, characterized in that: The several organophosphorus flame retardants are no less than 5 organophosphorus flame retardants, Optionally, the organophosphorus flame retardant is at least five selected from dibutylphenyl phosphate (DBPHP), triethyl phosphate (TEP), tripropyl phosphate (TnPP), tributyl phosphate (TnBP), tris(2-chloroethyl) phosphate (TCEP), triphenyl phosphate (TPHP) and tricresyl phosphate (TMPP).

10. A rice flour standard substance containing an organophosphorus flame retardant, characterized in that: The rice flour standard substance is prepared by the method described in any one of claims 1-9.

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