Method for determining limonene content in food contact grade plastic product

Abstract

The invention relates to the technical field of food contact grade plastic safety detection, and discloses a method for determining the content of limonene in a food contact grade plastic product, which comprises the following steps: S100, preparing a standard solution, S101, preparing an ethanol / water solvent (V: V = 1: 1), mixing 250mL of ethanol with 250mL of water, S102, preparing a mother solution (1000mu g / mL), accurately weighing 0.95-1.05 g (accurate to 0.001 g) of limonene in a 100mL volumetric flask containing 50mL of ethanol, and measuring the content of the limonene in the volumetric flask according to the standard solution. And fixing the volume to 100mL by using ethanol. According to the method for determining the content of limonene in the food contact grade plastic product, the ethanol / water mixed solvent is selected as the poising agent, so that plastic particles can be completely immersed in a liquid phase by the poising agent, and limonene can be transferred into the ethanol / water mixed solvent; the limonene emigrated from the plastic particles is more favorable for being distributed to a gas phase in a gas-liquid equilibrium state, so that the detection sensitivity is improved, and the distribution ratio of the limonene in the gas phase is further improved due to the addition of sodium chloride and a salting-out effect.

Description

Technical Field

[0001] The invention relates to the technical field of food contact grade plastic safety detection, in particular to a method for determining the limonene content in a food contact grade plastic product. Background Art

[0002] Limonene, also known as limonene, dipentene, and 1,8-terpenadiene, is an organic compound with a chemical formula of C10H16. It is a natural functional monoterpene, mainly used as a solvent and can also be used in organic synthesis. It can cause skin irritation and allergies, especially to infants and young children. Therefore, the content of limonene must be controlled for food contact grade plastics.

[0003] Conventionally, there are many methods for determining the content of limonene in food contact grade plastic products. For example, a method for detecting D-limonene in recycled PET bottles disclosed in Chinese patent CN108845049A includes the steps of taking a sample of the recycled PET bottle to be tested. The method can detect D-limonene in the recycled PET bottle. However, the conventional determination of limonene in plastic products often requires high costs and cannot be effectively quantitatively measured, which seriously affects the quality control and safety assessment of the product. Therefore, a method for determining the content of limonene in food contact grade plastic products is proposed to solve the above problems. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for determining the limonene content in food contact grade plastic products, which has the advantages of low cost and high-precision quantification, and solves the problem that the traditional method is high in cost and cannot effectively measure quantitatively.

[0005] In order to achieve the above-mentioned low cost and high precision purpose, the present invention provides the following technical solution: a method for determining the content of limonene in a food contact grade plastic product, comprising the following steps: S100) standard solution preparation: S101) preparing an ethanol / water solvent (V:V=1:1), taking 250 mL of ethanol and mixing it with 250 mL of water; S102) Prepare a mother solution (1000ug / mL), accurately weigh 0.95g-1.05g (accurate to 0.001g) of limonene into a 100mL volumetric flask containing 50mL of ethanol, and dilute to 100mL with ethanol; S103) Prepare a mother solution (10ug / mL), transfer 1mL of the mother solution into a 100mL volumetric flask containing 50mL of solvent, and dilute to 100mL with solvent; S104) Prepare a standard solution (0.ug / mL), transfer 1 mL of the mother solution into a 50 mL volumetric flask containing about 50 mL of solvent, dilute to 50 mL with solvent and set aside; S200) Standard curve drawing: S201) respectively transferring multiple volumes of standard solution into respective headspace bottles, and then respectively adding multiple volumes of ethanol / water solvent into respective bottles; S202) Add 1 g of NaCl to each volumetric flask, cover the flask with a cap and place it in the headspace heating position; S203) Conduct testing according to the headspace, chromatography and mass spectrometry conditions that meet the requirements; S204) using the mass of limonene as the horizontal coordinate (0ug, 0.2ug, 0.4ug, 1.0ug, 2.0ug) and selecting the peak area of ​​the quantitative ion as the vertical coordinate to fit the curve; S300) Test steps: S301) weigh the sample plastic particles into a headspace bottle, wherein the sample plastic particle sampling amount is 0.1g-1g, and the volume of the headspace bottle is 20mL; S302) Pipette 10 mL of gas-liquid balance agent into the headspace bottle. The gas-liquid balance agent is composed of ethanol-water solution. The density of ethanol-water solution is less than the concentration of plastic particles. By making the ratio of ethanol to water 1:1, it is ensured that PP and PE can be suspended in the balance solution. S303) adding NaCl to the headspace bottle, wherein the amount of NaCl added is 1 g to 3 g, so that the sample is suspended in the balance agent; S304) placing the headspace bottle into the headspace sampler and heating it for equilibrium, wherein the equilibrium temperature is 60°C-80°C and the equilibrium time is 20-30 minutes; S305) introducing the balanced gas phase into a gas chromatography-mass spectrometer for separation and determination; S306) Compare the measured frontal area with the curve to obtain the mass of limonene.

[0006] Preferably, the calculation formula in step S306 is: ,in : Volatile limonene content, mg / Kg; M: mass of sample particles, g.

[0007] Preferably, the chromatographic separation conditions in step S203 are: (1) Inlet temperature: 240℃~260℃; (2) Split / non-split: split ratio 45:1 to 55:1; (3) Chromatographic column: 5% Diphenyl, 30m*0.25mm*0.25um; (4) Carrier gas: He, flow rate: 1.0 mL / min; (5) Programmed temperature rise: Stage 1: 60°C to 65°C for 2 minutes. Stage 2: Raise the temperature to 90°C at a rate of 2.5°C / min to 3.5°C / min. Stage 3: Raise the temperature to 220°C at a rate of 18°C / min to 22°C / min and hold for 5 minutes.

[0008] Preferably, the mass spectrometry conditions in step S203 are: (1) Interface temperature: 280°C; (2) Ion source temperature, 230 °C; (3) Ionization method: EI; (4) Electron energy 70 eV; (5) Scanning mass range: 50~502; (6) Quantitative ion mass selection: 136; (7) Qualitative ion selection: 93, 79, 68.

[0009] Preferably, the measurement result in step S306 is reported to 0.1 mg / kg, and the reporting limit is 0.2 mg / kg.

[0010] Preferably, in step S201), 0 mL, 1 mL, 2 mL, 5 mL, and 10 mL of the standard solution are respectively transferred into respective headspace bottles, and then 10 mL, 9 mL, 8 mL, 5 mL, and 0 mL of the ethanol / water solvent are respectively transferred into respective bottles.

[0011] Compared with the prior art, the present invention provides a method for determining the content of limonene in food contact grade plastic products, which has the following beneficial effects: 1. By selecting an ethanol / water mixed solvent as a balancing agent, it can be ensured that the balancing agent can completely immerse the plastic particles in the liquid phase, which is conducive to the migration of limonene into the ethanol / water mixed solvent.

[0012] 2. Limonene migrated from plastic particles is more likely to be distributed to the gas phase under gas-liquid equilibrium, thereby improving detection sensitivity.

[0013] 3. The addition of sodium chloride further increases the distribution ratio of limonene in the gas phase due to the salting-out effect, further improving the detection sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a standard curve diagram of limonene according to an embodiment of the present invention; Figure 2 This is a diagram showing the measurement results of an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. Embodiment 1: A method for determining the content of limonene in a food contact grade plastic product, comprising the following steps: S100) standard solution preparation: S101) preparing an ethanol / water solvent (V:V=1:1), taking 250 mL of ethanol and mixing it with 250 mL of water; S102) Prepare a mother solution (1000ug / mL), accurately weigh 1.05g (accurate to 0.001g) of limonene into a 100mL volumetric flask containing 50mL of ethanol, and dilute to 100mL with ethanol; S103) Prepare a mother solution (10ug / mL), transfer 1mL of the mother solution into a 100mL volumetric flask containing 50mL of solvent, and dilute to 100mL with solvent; S104) Prepare a standard solution (0.ug / mL), transfer 1 mL of the mother solution into a 50 mL volumetric flask containing about 50 mL of solvent, dilute to 50 mL with solvent and set aside; S200) Standard curve drawing: S201) respectively transferring multiple volumes of standard solution into respective headspace bottles, and then respectively adding multiple volumes of ethanol / water solvent into respective bottles; S202) Add 1 g of NaCl to each volumetric flask, cover the flask with a cap and place it in the headspace heating position; S203) Conduct testing according to the headspace, chromatography and mass spectrometry conditions that meet the requirements; S204) using the mass of limonene as the horizontal coordinate (0ug, 0.2ug, 0.4ug, 1.0ug, 2.0ug) and selecting the peak area of ​​the quantitative ion as the vertical coordinate to fit the curve; S300) Test steps: S301) weigh the sample plastic particles into a headspace bottle, wherein the sample plastic particle sampling amount is 0.1g-1g, and the volume of the headspace bottle is 20mL; S302) Pipette 10 mL of gas-liquid balance agent into the headspace bottle. The gas-liquid balance agent is composed of ethanol-water solution. The density of ethanol-water solution is less than the concentration of plastic particles. By making the ratio of ethanol to water 1:1, it is ensured that PP and PE can be suspended in the balance solution. S303) NaCl is added to the headspace bottle, wherein the amount of NaCl added is 3 g, so that the sample is suspended in the balance agent; S304) placing the headspace bottle into the headspace sampler for heating and balancing, wherein the balancing temperature is 80°C and the balancing time is 30 minutes; S305) introducing the balanced gas phase into a gas chromatography-mass spectrometer for separation and determination; S306) Compare the measured frontal area with the curve to obtain the mass of limonene.

[0016] The calculation formula in step S306 is: ,in : Volatile limonene content, mg / Kg; M: mass of sample particles, g.

[0017] The chromatographic separation conditions in step S203 are: (1) Inlet temperature: 260°C; (2) Split / non-split: split ratio 55:1; (3) Chromatographic column: 5% Diphenyl, 30m*0.25mm*0.25um; (4) Carrier gas: He, flow rate: 1.0 mL / min; (5) Programmed temperature rise: Stage 1: 65°C for 2 minutes, Stage 2: Raise the temperature to 90°C at a rate of 3.5°C / min. Stage 3: Raise the temperature to 220°C at a rate of 22°C / min and maintain for 5 minutes.

[0018] The mass spectrometry conditions in step S203 are: (1) Interface temperature: 280°C; (2) Ion source temperature, 230 °C; (3) Ionization method: EI; (4) Electron energy 70 eV; (5) Scanning mass range: 50~502; (6) Quantitative ion mass selection: 136; (7) Qualitative ion selection: 93, 79, 68.

[0019] The measurement result in step S306 is reported to 0.1 mg / kg, and the reporting limit is 0.2 mg / kg.

[0020] In step S201), 0 mL, 1 mL, 2 mL, 5 mL, and 10 mL of the standard solution are respectively transferred into the respective headspace bottles, and then 10 mL, 9 mL, 8 mL, 5 mL, and 0 mL of the ethanol / water solvent are respectively transferred into the respective bottles. Example 2: A method for determining the content of limonene in a food contact grade plastic product, comprising the following steps: S100) standard solution preparation: S101) preparing an ethanol / water solvent (V:V=1:1), taking 250 mL of ethanol and mixing it with 250 mL of water; S102) Prepare a mother solution (1000ug / mL), accurately weigh 1g (accurate to 0.001g) of limonene into a 100mL volumetric flask containing 50mL of ethanol, and dilute to 100mL with ethanol; S103) Prepare a mother solution (10ug / mL), transfer 1mL of the mother solution into a 100mL volumetric flask containing 50mL of solvent, and dilute to 100mL with solvent; S104) Prepare a standard solution (0.ug / mL), transfer 1 mL of the mother solution into a 50 mL volumetric flask containing about 50 mL of solvent, dilute to 50 mL with solvent and set aside; S200) Standard curve drawing: S201) respectively transferring multiple volumes of standard solution into respective headspace bottles, and then respectively adding multiple volumes of ethanol / water solvent into respective bottles; S202) Add 1 g of NaCl to each volumetric flask, cover the flask with a cap and place it in the headspace heating position; S203) Conduct testing according to the headspace, chromatography and mass spectrometry conditions that meet the requirements; S204) using the mass of limonene as the horizontal coordinate (0ug, 0.2ug, 0.4ug, 1.0ug, 2.0ug) and selecting the peak area of ​​the quantitative ion as the vertical coordinate to fit the curve; S300) Test steps: S301) weigh the sample plastic particles into a headspace bottle, wherein the sample plastic particle sampling amount is 0.55 g and the volume of the headspace bottle is 20 mL; S302) Pipette 10 mL of gas-liquid balance agent into the headspace bottle. The gas-liquid balance agent is composed of ethanol-water solution. The density of ethanol-water solution is less than the concentration of plastic particles. By making the ratio of ethanol to water 1:1, it is ensured that PP and PE can be suspended in the balance solution. S303) NaCl is added to the headspace bottle, wherein the amount of NaCl added is 2 g, so that the sample is suspended in the balance agent; S304) placing the headspace bottle into the headspace sampler for heating and balancing, wherein the balancing temperature is 70°C and the balancing time is 25 minutes; S305) introducing the balanced gas phase into a gas chromatography-mass spectrometer for separation and determination; S306) Compare the measured frontal area with the curve to obtain the mass of limonene.

[0021] The calculation formula in step S306 is: ,in : Volatile limonene content, mg / Kg; M: mass of sample particles, g.

[0022] The chromatographic separation conditions in step S203 are: (1) Inlet temperature: 250°C; (2) Split / non-split: split ratio 50:1; (3) Chromatographic column: 5% Diphenyl, 30m*0.25mm*0.25um; (4) Carrier gas: He, flow rate: 1.0 mL / min; (5) Programmed temperature rise: Stage 1: 62.5℃ for 2 minutes, Stage 2: Raise the temperature to 90°C at a rate of 3.5°C / min. Stage 3: Raise the temperature to 220°C at a rate of 20°C / min and maintain for 5 minutes.

[0023] The mass spectrometry conditions in step S203 are: (1) Interface temperature: 280°C; (2) Ion source temperature, 230 °C; (3) Ionization method: EI; (4) Electron energy 70 eV; (5) Scanning mass range: 50~502; (6) Quantitative ion mass selection: 136; (7) Qualitative ion selection: 93, 79, 68.

[0024] The measurement result in step S306 is reported to 0.1 mg / kg, and the reporting limit is 0.2 mg / kg.

[0025] In step S201), 0 mL, 1 mL, 2 mL, 5 mL, and 10 mL of the standard solution are respectively transferred into the respective headspace bottles, and then 10 mL, 9 mL, 8 mL, 5 mL, and 0 mL of the ethanol / water solvent are respectively transferred into the respective bottles.

[0026] Embodiment 3: A method for determining the content of limonene in a food contact grade plastic product, comprising the following steps: S100) standard solution preparation: S101) preparing an ethanol / water solvent (V:V=1:1), taking 250 mL of ethanol and mixing it with 250 mL of water; S102) Prepare a mother solution (1000ug / mL), accurately weigh 0.95g (accurate to 0.001g) of limonene into a 100mL volumetric flask containing 50mL of ethanol, and dilute to 100mL with ethanol; S103) Prepare a mother solution (10ug / mL), transfer 1mL of the mother solution into a 100mL volumetric flask containing 50mL of solvent, and dilute to 100mL with solvent; S104) Prepare a standard solution (0.ug / mL), transfer 1 mL of the mother solution into a 50 mL volumetric flask containing about 50 mL of solvent, dilute to 50 mL with solvent and set aside; S200) Standard curve drawing: S201) respectively transferring multiple volumes of standard solution into respective headspace bottles, and then respectively adding multiple volumes of ethanol / water solvent into respective bottles; S202) Add 1 g of NaCl to each volumetric flask, cover the flask with a cap and place it in the headspace heating position; S203) Conduct testing according to the headspace, chromatography and mass spectrometry conditions that meet the requirements; S204) using the mass of limonene as the horizontal coordinate (0ug, 0.2ug, 0.4ug, 1.0ug, 2.0ug) and selecting the peak area of ​​the quantitative ion as the vertical coordinate to fit the curve; S300) Test steps: S301) weigh the sample plastic particles into a headspace bottle, wherein the sample plastic particle sampling amount is 0.1g-1g, and the volume of the headspace bottle is 20mL; S302) Pipette 10 mL of gas-liquid balance agent into the headspace bottle. The gas-liquid balance agent is composed of ethanol-water solution. The density of ethanol-water solution is less than the concentration of plastic particles. By making the ratio of ethanol to water 1:1, it is ensured that PP and PE can be suspended in the balance solution. S303) NaCl is added to the headspace bottle, wherein the amount of NaCl added is 1 g, so that the sample is suspended in the balance agent; S304) placing the headspace bottle into the headspace sampler for heating and balancing, wherein the balancing temperature is 60°C and the balancing time is 20 minutes; S305) introducing the balanced gas phase into a gas chromatography-mass spectrometer for separation and determination; S306) Compare the measured frontal area with the curve to obtain the mass of limonene.

[0027] The calculation formula in step S306 is: ,in : Volatile limonene content, mg / Kg; M: mass of sample particles, g.

[0028] The chromatographic separation conditions in step S203 are: (1) Inlet temperature: 240°C; (2) Split / non-split: split ratio 45:1; (3) Chromatographic column: 5% Diphenyl, 30m*0.25mm*0.25um; (4) Carrier gas: He, flow rate: 1.0 mL / min; (5) Programmed temperature rise: Stage 1: 60℃ for 2 minutes, Stage 2: Raise the temperature to 90°C at a rate of 2.5°C / min. Stage 3: Raise the temperature to 220°C at a rate of 18°C / min and maintain for 5 minutes.

[0029] The mass spectrometry conditions in step S203 are: (1) Interface temperature: 280°C; (2) Ion source temperature, 230 °C; (3) Ionization method: EI; (4) Electron energy 70 eV; (5) Scanning mass range: 50~502; (6) Quantitative ion mass selection: 136; (7) Qualitative ion selection: 93, 79, 68.

[0030] The measurement result in step S306 is reported to 0.1 mg / kg, and the reporting limit is 0.2 mg / kg.

[0031] In step S201), 0 mL, 1 mL, 2 mL, 5 mL, and 10 mL of the standard solution are respectively transferred into the respective headspace bottles, and then 10 mL, 9 mL, 8 mL, 5 mL, and 0 mL of the ethanol / water solvent are respectively transferred into the respective bottles. The beneficial effects of the present invention are: By selecting an ethanol / water mixed solvent as a balancing agent, it can be ensured that the balancing agent can completely immerse the plastic particles in the liquid phase, which is conducive to the migration of limonene into the ethanol / water mixed solvent. The limonene migrated from the plastic particles is more conducive to distribution to the gas phase under a gas-liquid equilibrium state, thereby improving the detection sensitivity. In addition, the addition of sodium chloride further improves the distribution ratio of limonene in the gas phase due to the salting-out effect, further improves the detection sensitivity, ensures the effective suspension of the plastic particles and the good separation of limonene, and further improves the sensitivity and accuracy of the detection. The present invention is suitable for the detection of various food contact grade plastics and has strong versatility and broad application prospects.

[0032] Although 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 appended claims and their equivalents.

Claims

1. A method for determining the content of limonene in food contact grade plastic products, characterized in that: The following steps are involved: S100) standard solution preparation: S101) preparing an ethanol / water solvent (V:V=1:1), taking 250 mL of ethanol and mixing it with 250 mL of water; S102) Prepare a mother solution (1000ug / mL), accurately weigh 0.95g-1.05g (accurate to 0.001g) of limonene into a 100mL volumetric flask containing 50mL of ethanol, and dilute to 100mL with ethanol; S103) Prepare a mother solution (10ug / mL), transfer 1mL of the mother solution into a 100mL volumetric flask containing 50mL of solvent, and dilute to 100mL with solvent; S104) Prepare a standard solution (0.ug / mL), transfer 1 mL of the mother solution into a 50 mL volumetric flask containing about 50 mL of solvent, dilute to 50 mL with solvent and set aside; S200) Standard curve drawing: S201) respectively transferring multiple volumes of standard solution into respective headspace bottles, and then respectively transferring multiple volumes of ethanol / water solvent into respective bottles; S202) Add 1 g of NaCl to each volumetric flask, cover the flask with a cap and place it in the headspace heating position; S203) Conduct testing according to the headspace, chromatography and mass spectrometry conditions that meet the requirements; S204) using the mass of limonene as the horizontal coordinate (0ug, 0.2ug, 0.4ug, 1.0ug, 2.0ug) and selecting the peak area of ​​the quantitative ion as the vertical coordinate to fit the curve; S300) Test steps: S301) weigh the sample plastic particles into a headspace bottle, wherein the sample plastic particle sampling amount is 0.1g-1g, and the volume of the headspace bottle is 20mL; S302) Pipette 10 mL of gas-liquid balance agent into the headspace bottle. The gas-liquid balance agent is composed of ethanol-water solution. The density of ethanol-water solution is less than the concentration of plastic particles. By making the ratio of ethanol to water 1:1, it is ensured that PP and PE can be suspended in the balance solution. S303) adding NaCl to the headspace bottle, wherein the amount of NaCl added is 1 g to 3 g, so that the sample is suspended in the balance agent; S304) Place the headspace bottle into the headspace sampler for heating and balancing, wherein the balancing temperature is 60°C-80°C and the balancing time is 20-30 minutes. ; S305) introducing the balanced gas phase into a gas chromatography-mass spectrometer for separation and determination; S306) Compare the measured frontal area with the curve to obtain the mass of limonene.

2. The method for determining the content of limonene in a food contact grade plastic product according to claim 1, characterized in that: The calculation formula in step S306 is: ,in : Volatile limonene content, mg / Kg M: mass of sample particles, g.

3. The method for determining the content of limonene in a food contact grade plastic product according to claim 1, characterized in that: The chromatographic separation conditions in step S203 are: (1) Inlet temperature: 240℃~260℃; (2) Split / non-split: split ratio 45:1 to 55:1; (3) Chromatographic column: 5% Diphenyl, 30m*0.25mm*0.25um; (4) Carrier gas: He, flow rate: 1.0 mL / min; (5) Programmed temperature rise: Stage 1: 60°C to 65°C for 2 minutes. Stage 2: Raise the temperature to 90°C at a rate of 2.5°C / min to 3.5°C / min. Stage 3: Raise the temperature to 220°C at a rate of 18°C / min to 22°C / min and hold for 5 minutes.

4. The method for determining the content of limonene in a food contact grade plastic product according to claim 1, characterized in that: The mass spectrometry conditions in step S203 are: (1) Interface temperature: 280°C; (2) Ion source temperature, 230 °C; (3) Ionization method: EI; (4) Electron energy 70 eV; (5) Scanning mass range: 50~502; (6) Quantitative ion mass selection: 136; (7) Qualitative ion selection: 93, 79, 68.

5. The method for determining the content of limonene in a food contact grade plastic product according to claim 1, characterized in that: The measurement result in step S306 is reported to 0.1 mg / kg, and the reporting limit is 0.2 mg / kg.

6. The method for determining the content of limonene in a food contact grade plastic product according to claim 1, characterized in that: In the step S201), 0 mL, 1 mL, 2 mL, 5 mL, and 10 mL of the standard solution are respectively transferred into the respective headspace bottles, and then 10 mL, 9 mL, 8 mL, 5 mL, and 0 mL of the ethanol / water solvent are respectively transferred into the respective bottles.

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