阅读说明：本技术 一种pmma餐具吸附的橄榄油质量定量方法 (Method for quantitatively measuring olive oil adsorbed by PMMA tableware ) 是由 刘桂华 肖晶 李伟涛 董世蒙 孙文文 苏凤 刘君峰 于 2020-10-27 设计创作，主要内容包括：本发明涉及一种PMMA餐具吸附的橄榄油质量定量方法,包括以下步骤：S1:标准溶液的配制：S1.1:内标溶液的配置；S1.2:橄榄油标准储备液的配置；S2:迁移试验；S3:被试样吸收橄榄油的测定,包括以下步骤：S3.1溶解/沉淀法萃取：向烧瓶中加入内标溶液和迁移试验后的PMMA餐具样品,并加入四氢呋喃,连接冷凝器,煮沸回流30min,通过冷凝器加入正己烷,回流5min；冷却至室温,转移到离心管中用正已烷洗涤烧瓶,合并洗涤液到离心管中,离心后取上清液旋蒸至干；S3.2橄榄油甲酯化；S3.3气相色谱测定。本发明将萃取时间由原来的2天缩短为1h,显著提高检测效率；减少试验设备投入,显著降低检测成本的效果。(The invention relates to a method for quantifying the quality of olive oil adsorbed by PMMA tableware, which comprises the following steps: s1, preparation of a standard solution: s1.1, preparing an internal standard solution; s1.2, preparing an olive oil standard stock solution; s2 migration test; s3 measurement of olive oil absorption by a sample, comprising the following steps: s3.1 extraction by a dissolution/precipitation method: adding the internal standard solution and the PMMA tableware sample after the migration test into a flask, adding tetrahydrofuran, connecting with a condenser, boiling and refluxing for 30min, adding n-hexane through the condenser, and refluxing for 5 min; cooling to room temperature, transferring to a centrifuge tube, washing the flask with n-hexane, combining the washing solutions into the centrifuge tube, centrifuging, and taking the supernatant to dry by rotary evaporation; s3.2, methyl esterification of olive oil; s3.3 gas chromatography. The extraction time is shortened from the original 2 days to 1h, so that the detection efficiency is obviously improved; the investment of test equipment is reduced, and the detection cost is obviously reduced.)

1. A method for quantitatively measuring the olive oil adsorbed by PMMA tableware is characterized in that: the method comprises the following steps:

s1, preparing a standard solution, which comprises the following steps:

s1.1. preparation of internal standard solution: placing heptadecanoic acid triglyceride in a beaker, adding cyclohexane to dissolve, transferring into a volumetric flask, washing the beaker with cyclohexane, combining washing liquid into the volumetric flask, and fixing the volume with cyclohexane to obtain a target concentration of 2.0 mg/mL;

s1.2, preparing an olive oil standard stock solution: weighing blank olive oil obtained in a migration test, adding n-heptane to dissolve the blank olive oil, transferring the blank olive oil into a volumetric flask, washing the beaker with the n-heptane, combining washing liquid into the volumetric flask, and fixing the volume with the n-heptane to 100mg/mL of target concentration;

s2 migration test: adding olive oil preheated to 70 ℃ in advance into PMMA tableware, adding the olive oil into the position 1cm below the mouth edge, putting the PMMA tableware into an oven with the temperature stabilized at 70 ℃, taking out after placing for 2 hours, and discarding the olive oil;

s3 measurement of olive oil absorption by a sample, comprising the following steps:

s3.1 extraction by a dissolution/precipitation method: adding the internal standard solution and the PMMA tableware sample after the migration test into a flask, adding tetrahydrofuran, connecting a condenser, boiling and refluxing for 30 min; adding n-hexane through a condenser, and refluxing for 5 min; cooling to room temperature, transferring to a centrifuge tube, washing the flask with n-hexane, combining the washing solutions into the centrifuge tube, centrifuging, and taking the supernatant to dry by rotary evaporation;

s3.2 methyl esterification of olive oil: dissolving or completely dispersing the residue with n-heptane, adding potassium hydroxide-methanol solution into the flask, connecting with condenser, boiling and refluxing for 10 min; adding a boron trifluoride methanol solution through a condenser, and refluxing for 2 min; cooling to room temperature, adding a saturated sodium sulfate solution into the flask, fully oscillating, standing, layering, and filtering an upper-layer n-heptane solution through an organic microporous filter membrane to obtain a solution to be tested;

s3.3 gas chromatography determination: transferring 7 (0-5) mL olive oil standard stock solutions with different volumes into 7 flasks, adding an internal standard solution into each flask, spin-drying the solvent by using a rotary evaporator, performing methyl esterification according to S3.2 to obtain a liquid to be tested, sucking the liquid to be tested, injecting the liquid to be tested into a gas chromatograph, analyzing, and drawing a standard curve.

2. The method for quantitatively measuring the amount of olive oil adsorbed by PMMA tableware according to claim 1, wherein: and 3.3, during the measurement, sampling by adopting split sampling with the split ratio of 10:1, adopting nitrogen with the flow rate of 1.0mL/min as carrier gas, the temperature of a sample inlet is 220 ℃, the temperature of a detector is 250 ℃ in the detection process, and adopting nitrogen with the flow rate of 20mL/min as tail gas blowing.

3. The method for quantitatively measuring the amount of olive oil adsorbed by PMMA tableware according to claim 1, wherein: zeolite or glass beads are added in both steps S3.1 and S3.2.

4. The method for quantitatively measuring the amount of olive oil adsorbed by PMMA tableware according to claim 1, wherein: the internal standard solution of step S1.1 is stored in an environment at 4 ℃.

5. The method for quantitatively measuring the amount of olive oil adsorbed by PMMA tableware according to claim 1, wherein: and (3) respectively adopting a stepwise dilution method to prepare solutions of 7 olive oils with different volumes in the S3.3, wherein the adopted volumes are respectively 0.02mL, 0.1mL, 0.2mL, 0.5mL, 1mL, 2mL and 5mL of olive oil standard stock solutions.

6. The method for quantitatively measuring the amount of olive oil adsorbed by PMMA tableware according to claim 1, wherein: and the step S3.1 of dissolving/precipitating extraction and the step S3.2 of methyl esterification of the olive oil share the same set of reflux device when reflux is carried out.

Technical Field

The invention relates to the technical field of chemical detection, in particular to a quantitative method for the quality of olive oil adsorbed by PMMA tableware.

Background

The measurement of the total migration of food contact materials and products in olive oil requires accurate knowledge of the mass of olive oil adsorbed by the sample in the migration test for calculating the total migration detection result. According to the prior art, when the olive oil adsorbed by a sample is extracted, a Soxhlet extractor is adopted to reflux for 7-8 h, at least two times of extraction are needed, after the extraction is finished, a conversion solvent is dried in a spinning mode, saponification and methyl esterification are carried out, fatty acid methyl ester is determined by GC-FID, and the adopted standard curve is tested on a machine after the olive oil used in a migration test is synchronously saponified and subjected to methyl esterification.

The existing detection technology has the following defects and shortcomings:

1. the time consumption is long, the efficiency is low, the extraction time of the olive oil adsorbed by the sample is at least long, the efficiency is low, and the extraction time is at least 2 days; when the olive oil standard curve is manufactured, 2-200mg of olive oil needs to be weighed to manufacture the standard curve, and when the weighing mass is less than 10mg, the weighing difficulty is high, and the time consumption is long. 2. The detection cost is high. The Soxhlet extraction method needs to be provided with matched test equipment such as a Soxhlet extractor, a water bath, low-temperature condensing equipment and the like, and the equipment cost is high. In addition, the solvent with lower boiling point such as n-pentane, ether and the like is needed for Soxhlet extraction, and the solvent is continuously volatilized and lost in the reflux process; 3. the extraction equipment occupies a large area and is not beneficial to batch detection.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a method for quantitatively measuring the olive oil adsorbed by PMMA tableware, which has higher working efficiency.

The above object of the present invention is achieved by the following technical solutions:

a method for quantifying the quality of olive oil adsorbed by PMMA tableware comprises the following steps:

s1, preparing a standard solution, which comprises the following steps:

s1.1. preparation of internal standard solution: placing heptadecanoic acid triglyceride in a beaker, adding cyclohexane to dissolve, transferring into a volumetric flask, washing the beaker with cyclohexane, combining washing liquid into the volumetric flask, and fixing the volume with cyclohexane to obtain a target concentration of 2.0 mg/mL;

s1.2, preparing an olive oil standard stock solution: weighing blank olive oil obtained in a migration test, adding n-heptane to dissolve the blank olive oil, transferring the blank olive oil into a volumetric flask, washing the beaker with the n-heptane, combining washing liquid into the volumetric flask, and fixing the volume with the n-heptane to 100mg/mL of target concentration;

s2 migration test: adding olive oil preheated to 70 ℃ in advance into PMMA tableware, adding the olive oil into the position 1cm below the mouth edge, putting the PMMA tableware into an oven with the temperature stabilized at 70 ℃, taking out after placing for 2 hours, and discarding the olive oil;

s3 measurement of olive oil absorption by a sample, comprising the following steps:

s3.1 extraction by a dissolution/precipitation method: adding the internal standard solution and the PMMA tableware sample after the migration test into a flask, adding tetrahydrofuran, connecting a condenser, boiling and refluxing for 30 min; adding n-hexane through a condenser, and refluxing for 5 min; cooling to room temperature, transferring to a centrifuge tube, washing the flask with n-hexane, combining the washing solutions into the centrifuge tube, centrifuging, and taking the supernatant to dry by rotary evaporation;

s3.2 methyl esterification of olive oil: dissolving or completely dispersing the residue with n-heptane, adding potassium hydroxide-methanol solution into the flask, connecting with condenser, boiling and refluxing for 10 min; adding a boron trifluoride methanol solution through a condenser, and refluxing for 2 min; cooling to room temperature, adding a saturated sodium sulfate solution into the flask, fully oscillating, standing, layering, and filtering an upper-layer n-heptane solution through an organic microporous filter membrane to obtain a solution to be tested;

s3.3 gas chromatography determination: transferring 7 (0-5) mL olive oil standard stock solutions with different volumes into 7 flasks, adding an internal standard solution into each flask, spin-drying the solvent by using a rotary evaporator, performing methyl esterification according to S3.2 to obtain a liquid to be tested, sucking the liquid to be tested, injecting the liquid to be tested into a gas chromatograph, analyzing, and drawing a standard curve. By adopting the technical scheme, in the extraction process, the Soxhlet extraction method adopts a solvent cleaning mode, more olive oil adsorbed on the surface of the plastic is cleaned, if the adsorbed oil amount is larger, the cleaning is incomplete, and the dissolution/precipitation method is to completely dissolve the plastic, so that the oil adsorbed by the plastic is completely released, the extraction time is shortened to one hour from two days originally, and the work efficiency of the experiment is greatly improved.

The present invention in a preferred example may be further configured to: and 3.3, during the measurement, sampling by adopting split sampling with the split ratio of 10:1, adopting nitrogen with the flow rate of 1.0mL/min as carrier gas, the temperature of a sample inlet is 220 ℃, the temperature of a detector is 250 ℃ in the detection process, and adopting nitrogen with the flow rate of 20mL/min as tail gas blowing.

By adopting the technical scheme, the error in the detection process is reduced, so that a more accurate chromatogram can be manufactured.

The present invention in a preferred example may be further configured to: zeolite or glass beads are added in both steps S3.1 and S3.2.

By adopting the technical scheme, zeolite or glass beads can avoid the bumping phenomenon of the solution when the solution is heated.

The present invention in a preferred example may be further configured to: the internal standard solution of step S1.1 is stored in an environment at 4 ℃.

By adopting the technical scheme, the internal standard solution can be stored for about 30 days in the environment of 4 ℃, and the service life of the internal standard solution is prolonged.

The present invention in a preferred example may be further configured to: and the 7 kinds of olive oil with different volumes in the S3.3 are respectively prepared into solutions by adopting a stepwise dilution method, and the adopted volumes are 0.02mL, 0.1mL, 0.2mL, 0.5mL, 1mL, 2mL and 5mL of olive oil standard stock solutions.

By adopting the technical scheme, the traditional sampling method directly weighs by using a balance, needs manual methods for control, particularly weighs samples below 10mg, is difficult to weigh and long in time consumption, and is difficult to obtain specified weighing mass.

The present invention in a preferred example may be further configured to: and the step S3.1 adopts the same reflux device for the extraction by a dissolving/precipitating method and the step S3.2 adopts the same reflux device for the methyl esterification of the olive oil.

By adopting the technical scheme, the equipment between the two steps is shared, the investment of the equipment can be reduced, the detection precision of the equipment can be ensured, and the use is convenient.

In summary, the invention includes at least one of the following beneficial technical effects:

1. effectively shortens the detection time and improves the detection efficiency, and the dissolving/precipitating method can finish the extraction of the olive oil only in 1 h. The extraction time is shortened from the original 2 days to 1h, and the detection efficiency is obviously improved;

2. the investment of test equipment is reduced, and the detection cost is obviously reduced. The dissolving/precipitating method can share the same reflux device with the subsequent methyl esterification step, and no additional test equipment is needed.

3. The equipment sharing reduces the equipment occupation area, improves the detection capacity and is more favorable for batch detection.

Detailed Description

The present invention will be described in further detail below.

The invention discloses a method for quantifying the quality of olive oil adsorbed by PMMA tableware, which comprises the following steps:

s1, preparing a standard solution, which comprises the following steps:

s1.1. preparation of internal standard solution: placing 1.0g (error is 0.1mg) of heptadecanoic acid triglyceride (purity is more than or equal to 98%) in a 100mL beaker, adding cyclohexane to dissolve, transferring into a 500mL volumetric flask, washing the beaker with cyclohexane for 3 times, combining the washing solution into the volumetric flask, and fixing the volume with cyclohexane, wherein the prepared internal standard solution is placed in an environment with the temperature of 4 ℃ for storage, the quality guarantee period is about 30 days, and the concentration of the internal standard solution is 2.0 mg/mL;

s1.2, preparing an olive oil standard stock solution: weighing 5.0g (error is 0.1mg) of migration test in a 50mL beaker, adding n-heptane to dissolve, transferring into a 50mL volumetric flask, washing the beaker with n-heptane for 3 times, combining washing liquid into the volumetric flask, and fixing the volume with n-heptane, wherein the concentration of the olive oil standard stock solution is 100 mg/mL;

s2 migration test: adding olive oil preheated to 70 ℃ in advance into PMMA tableware, adding the olive oil into the position 1cm below the mouth edge, putting the PMMA tableware into an oven with the temperature stabilized at 70 ℃, taking out after placing for 2 hours, and discarding the olive oil;

s3 measurement of olive oil absorption by a sample, comprising the following steps:

s3.1 extraction by a dissolution/precipitation method: adding 10.0mL of internal standard solution and PMMA tableware sample after the migration test into a flask, adding 50mL of tetrahydrofuran, adding zeolite or glass beads to prevent bumping, connecting a condenser, boiling and refluxing for 30min to dissolve the PMMA tableware sample and release adsorbed olive oil; adding 50mL of n-hexane into the mixture through a condenser, and refluxing for 5min to precipitate a polymer; cooling to room temperature, transferring to a centrifuge tube, washing the flask with n-hexane, combining the washing solutions into the centrifuge tube, centrifuging, taking the supernatant, and performing rotary evaporation to dryness by using a rotary evaporator;

s3.2 methyl esterification of olive oil: dissolving or completely dispersing the residue with 10.0mL of n-heptane, adding 10.0mL of potassium hydroxide-methanol solution, in this example, the concentration of potassium hydroxide-methanol solution is 11.0g/L, connecting with a condenser, boiling under reflux for 10 min; 5.0mL of boron trifluoride in methanol was added through a condenser and refluxed for 2 min. The reflux device adopted by the device and the reflux device of S3.1 are the same set of reflux device; cooling to room temperature, adding 15-20 mL of saturated sodium sulfate solution into the flask, fully oscillating, standing, layering, and filtering an upper layer of n-heptane solution through an organic microporous filter membrane to obtain a solution to be tested;

s3.3 gas chromatography determination: adopting a stepwise dilution method to prepare solution, respectively transferring 0.02mL, 0.1mL, 0.2mL, 0.5mL, 1mL, 2mL and 5mL of olive oil standard stock solution into 7 flasks, then adding an internal standard solution into each flask, using a rotary evaporator to spin dry the solvent, carrying out methyl esterification according to S3.2 to obtain a liquid to be tested, respectively measuring the corresponding olive oil quality in each liquid to be tested by 2.0mg, 10mg, 20mg, 50mg, 100mg, 200mg and 500 mg, respectively sucking the liquid to be tested, injecting the liquid to be tested into a gas chromatograph for analysis, and drawing a standard curve;

the gas chromatography reference conditions were as follows:

a) a chromatographic column: polyethylene glycol quartz capillary column, 30.0m × 250 μm × 0.25 μm, or analytical column with similar performance;

b) carrier gas: nitrogen, flow rate: 1.0 mL/min;

c) sample inlet temperature: 220 ℃;

d) and (3) sample introduction mode: split-flow sample injection with a split-flow ratio of 10: 1;

e) sample introduction volume: 1.0 μ L;

f) temperature rising procedure: the initial temperature is 120 ℃, the temperature is kept for 1min, the temperature is raised to 220 ℃ at the speed of 20 ℃/min, and the temperature is kept for 10 min;

g) detector temperature: 250 ℃;

h) hydrogen flow rate: 30 mL/min;

i) air flow rate: 350 mL/min;

j) tail blowing: nitrogen, flow rate: 20 mL/min.

The standard curve is drawn by an internal standard method, the ratio of the sum of peak areas of all fatty acid methyl esters (C16:0, C16:1, C18:0, C18:1 and C18:2) of the olive oil to the peak area of the internal standard is adopted as the ordinate, and the corresponding quality of the olive oil is adopted as the abscissa.

The olive oil extraction can be completed by adopting a dissolution/precipitation method for only 1 hour. The extraction time is shortened from the original 2 days to 1h, and the detection efficiency is obviously improved;

and the dissolving/precipitating method can share the same reflux device with the subsequent methyl esterification step, so that additional test equipment is not needed, the investment of the test equipment is reduced, and the detection cost is obviously reduced.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.