Method for determining residual quantity of chlorine-containing phenol in wood product for food contact by adopting automatic vortex-promoted derivatization-gas chromatography-mass spectrometry

Abstract

The invention provides a method for determining the residual quantity of chlorine-containing phenol in a wood product for food contact by adopting an automatic vortex-promoted derivatization-gas chromatography-mass spectrometry method, which comprises the following steps of: 1, firstly extracting a sample, 2, derivatizing the sample, 3, analyzing the re-determined sample, 4, determining the residual quantity of chlorine-containing phenol in the wood product for food contact by adopting an automatic vortex-promoted derivatization-gas chromatography-mass spectrometry method. And 5, adding target objects with different levels and contents into a blank matrix, then carrying out a recovery test, repeating the test for three times at each labeling level, carrying out quantitative analysis through an internal standard method, and calculating the average recovery rate. The method provided by the invention can meet the requirements of limited quantification of 19 kinds of chlorophenols, and is suitable for rapid detection and risk monitoring of the residual quantity of 19 kinds of chlorophenols in food-related wooden products.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of determination methods of residual amount of chlorinated phenol in wood products for contact, in particular, the determination of residual amount of chlorinated phenol in wood products for contact with food using automatic vortex-promoted derivatization-gas chromatography mass spectrometry. BACKGROUND

[0002] Currently, the tradition of long-term use of wood products for contact with food (such as wooden chopsticks, wooden cutting boards) has been widely used in the fields of construction, furniture and packaging due to its natural beauty, good mechanical properties and renewability. However, in order to improve the durability of wood products and prevent decay and insect damage, chlorinated phenolic compounds are often used as preservatives. Although these compounds have broad-spectrum antibacterial and insecticidal effects, their long-term and large-scale use has also brought significant environmental and health risks. Studies have shown that chlorinated phenol has strong toxicity and can cause cancer, teratogenicity and other hazards to the human body, and also causes serious pollution to soil and water. Especially in the case of direct contact between wood products and food or human body, residual chlorinated phenol may migrate into the environment or living organisms, further exacerbating its potential harm.

[0003] The current analysis method for the determination of pentachlorophenol in food contact materials, wood products and food simulators is gas chromatography-mass spectrometry. According to this method, higher content and more types of chlorinated phenol are still detected, so the detected products still have a high residual content of chlorinated phenol, and the detection effect is poor and the efficiency is low. Currently, there is no method for detecting 19 types in the prior art. SUMMARY

[0004] The present application provides a method for determining the residual amount of chlorinated phenol in wood products for contact with food using automatic vortex-promoted derivatization-gas chromatography mass spectrometry, which can meet the requirements of 19 types of chlorinated phenol for limited quantification and is suitable for rapid detection and risk monitoring of 19 types of chlorinated phenol in food-related wood products.

[0005] The present application adopts the following technical solution: a method for determining the residual amount of chlorinated phenol in wood products for contact with food using automatic vortex-promoted derivatization-gas chromatography mass spectrometry, which comprises the following steps: step one, first sample extraction, collect the wood sample for contact with food, then crush and sieve the wood sample to ensure uniformity of the wood sample particles, then weigh the sample and place it in a conical flask, then add an internal standard solution, then add an extraction solvent, ultrasonically extract in an ultrasonic cleaner, filter the extract with filter paper into a rotary flask, rotary evaporate to near dryness under water bath conditions, then dissolve with potassium hydroxide solution, and transfer to a first centrifuge tube;

[0006] Step two, then derivatize the sample: Add acetic anhydride solution to the first centrifuge tube in step one, then seal the tube. Place the sealed first centrifuge tube on an automatic vortex mixer for the first vortexing. Then add n-hexane to the first centrifuge tube for the second vortexing. After that, let it stand, open the first centrifuge tube, and transfer the upper layer of liquid from the first centrifuge tube to the second centrifuge tube. Add sodium sulfate aqueous solution to the second centrifuge tube and shake and wash once. Extract the upper layer of liquid from the second centrifuge tube as the sample to be tested again.

[0007] Step 3: Further analysis of the retested samples: Since the 19 chlorophenol-containing compounds and the derivatives of the internal standard solution in the retested samples are all weakly polar compounds, gas chromatography was selected for analysis. The capillary column of the gas chromatograph was programmed with segmented temperature ramp, helium was used as the carrier gas, and helium was injected in a split ratio of 10:1; the injection volume was 1 μL, and the mass spectrometry conditions were as follows: EI was used as the ion source, and the mass scan range was set to m / z 40-500. The 20 target compounds were well retained, and the peaks were symmetrical.

[0008] Step 4: After chromatographic analysis, the residual content of 19 chlorophenols in the wood sample was detected. The signal-to-noise ratio (S / N) of the 19 chlorophenol compounds was greater than 10, and the average recovery rate was greater than 90%. Therefore, according to the principle of quantification with a signal-to-noise ratio of 10, the detection limit values ​​of the 19 chlorophenol compounds were obtained.

[0009] Step 5: By adding different levels of the target analyte to the blank matrix, recovery tests were conducted. Each spiked level was repeated three times. Quantitative analysis was performed using the internal standard method, and the average recovery rate was calculated.

[0010] Furthermore, in step one of this invention, the wooden sample is pulverized to a particle size of 2 mm using a pulverizer and then sieved through a metal sieve. The sample weight is 1 g, and the weighing device is a Metter Toledo BAS224S electronic analytical balance. The conical flask has a capacity of 100 mL, and the volume of the internal standard solution added is 100 μL. The internal standard solution is prepared by weighing 10 mg of tetrachloro-o-methoxyphenol, dissolving it in n-hexane and making up to a final volume, and diluting it to a 2 mg / L solution. The extraction solvent is 30 mL of methanol. The ultrasonic cleaner is an Elma S100H ultrasonic generator, and the rotary evaporator is an IKA rotary evaporator. The water bath conditions during rotary evaporation are a 40°C water bath. The concentration of the potassium hydroxide solution is 2 mol / L, and the capacity is 20 mL. The capacity of the first centrifuge tube is 50 mL.

[0011] Furthermore, the methanol and potassium hydroxide solutions of this invention achieve analytical purity.

[0012] Furthermore, in step two of this invention, the volume of the acetic anhydride solution is 2 mL, the speed of the automatic vortex shaker is 2000 r / min, the first vortexing time is 10 min, the volume of added n-hexane is 5 mL, the second vortexing time is 5 min, the settling time is 5 min, the volume of the second centrifuge tube is 50 mL, the concentration of the sodium sulfate aqueous solution is 20 g / L, the volume is 20 mL, and the volume of the liquid extracted from the upper layer of the second centrifuge tube is 1 mL.

[0013] Furthermore, the acetic anhydride solution and sodium sulfate aqueous solution of the present invention have reached analytical purity.

[0014] Furthermore, the gas chromatograph in step three of this invention is a combination of an Agilent 7890B gas chromatograph and a 5977A MSD mass spectrometer detector. The capillary column used in the Agilent 7890B gas chromatograph is a DB-5MS capillary column with dimensions of 30m × 0.25mm × 0.25μm. The specific process of the segmented temperature ramp mode is as follows: the initial temperature is set to 60℃ and held for 1 min; then the temperature is increased to 150℃ at a rate of 15℃ / min and held for 3 min; subsequently, the temperature is increased to 300℃ at a rate of 30℃ / min and held for 5 min. The injection port temperature of the capillary column is set to 250℃, the helium purity is ≥99.999%, and the helium flow rate is 1.0mL / min.

[0015] Furthermore, the method for preparing the standard solution injected into the Agilent 7890B gas chromatograph of the present invention is as follows: 0.5 mL of a mixed standard of 19 chlorophenols is transferred to a 50 mL volumetric flask, dissolved in n-hexane and diluted to volume to obtain a mixed standard stock solution of chlorophenols. 1 mL of the mixed standard stock solution of chlorophenols is transferred to a 100 mL volumetric flask, diluted with n-hexane and diluted to volume. A certain volume of intermediate standard working solution is accurately pipetted and serially diluted with n-hexane to prepare a series of standard working solutions with concentrations of 1.0, 5.0, 10, 30, and 50 μg / L.

[0016] Furthermore, the electron energy of the ion source of the present invention is 70 eV, and the temperature of the ion source is set to 220°C.

[0017] Furthermore, in step five of this invention, three target compounds at different levels are added to the blank matrix. The levels of the three target compounds are L1 = 0.01 mg / kg, L2 = 0.02 mg / kg, and L3 = 0.05 mg / kg. When L1 = 0.01 mg / kg, the recoveries of the 19 chlorophenols are 105.4%-119.2%; when L1 = 0.02 mg / kg, the recoveries are 85.4%-109.3%; and when L1 = 0.05 mg / kg, the recoveries are 81.4%-118.5%. The relative standard deviation (RSD) of the 19 chlorophenols ranges from 0.8% to 9.7%, which meets the requirements of the analytical test for the detection method.

[0018] The present invention has the following beneficial effects: After adopting the above technical solution, the present invention has high extraction efficiency, simple and fast pretreatment, high sensitivity and recovery rate, good repeatability, and can meet the quantitative restriction requirements of 19 kinds of chlorophenols. It is suitable for rapid detection and risk monitoring of 19 kinds of chlorophenol residues in food-related wood products. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 To illustrate the present invention, linear regression was performed with mass concentration as the abscissa and peak area y as the ordinate, and linear relationships of 19 chlorophenol compounds were obtained in the range of 0.01-0.05 mg / L. Detailed Implementation

[0021] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0022] This invention provides a method for determining the residual amount of chlorophenol in wood products for food contact using an automated vortex-promoted derivatization-gas chromatography-mass spectrometry method, which includes the following steps:

[0023] Step 1: Sample extraction is performed by taking samples of the wood used for food contact. The wood samples are then crushed and sieved to ensure uniform particle size. The sample is then weighed and placed in an Erlenmeyer flask, followed by the addition of an internal standard solution and extraction solvent. The mixture is then ultrasonically extracted using an ultrasonic cleaner. After extraction, the extract is filtered through filter paper into a rotating flask and evaporated to near dryness under a water bath. The extract is then dissolved in potassium hydroxide solution and transferred to a centrifuge tube. In this embodiment, the wood sample in Step 1 is crushed to a particle size of 2 mm using a pulverizer and sieved through a metal sieve. The sample weight is 1 g, weighed using a Metter Toledo BAS224S electronic analytical balance. The Erlenmeyer flask has a capacity of 100 mL, and the internal standard solution is added in a volume of 100 μL. The internal standard solution is prepared by weighing 10 mg of tetrachloro-o-methoxyphenol, dissolving and diluting it with n-hexane to a concentration of 2 mg / L. The extraction solvent is 30 mL of methanol. An Elma ultrasonic cleaner is used. The S100H ultrasonic generator and the IKA rotary evaporator were used for rotary evaporation. The water bath conditions during rotary evaporation were 40°C. The concentration of the potassium hydroxide solution was 2 mol / L and the capacity was 20 mL. The capacity of the first centrifuge tube was 50 mL. The purity of the methanol and potassium hydroxide solution used in this embodiment reached analytical grade.

[0024] Step two, then derivatize the sample: Add acetic anhydride solution to the first centrifuge tube in step one, then seal the tube. Place the sealed first centrifuge tube on an automatic vortex mixer for the first vortexing. Then add n-hexane to the first centrifuge tube for the second vortexing. After completion, let it stand, open the first centrifuge tube, and transfer the upper layer liquid from the first centrifuge tube to the second centrifuge tube. Add sodium sulfate aqueous solution to the second centrifuge tube and shake and wash once. Extract the upper layer liquid from the second centrifuge tube as the sample for retesting. In this embodiment, the volume of acetic anhydride solution in step two is 2 mL, the speed of the automatic vortex mixer is 2000 r / min, the first vortexing time is 10 min, the volume of n-hexane added is 5 mL, the second vortexing time is 5 min, the standing time is 5 min, the volume of the second centrifuge tube is 50 mL, the concentration of the sodium sulfate aqueous solution is 20 g / L, the volume is 20 mL, and the volume of the upper layer liquid extracted from the second centrifuge tube is 1 mL. The purity of the acetic anhydride solution and sodium sulfate aqueous solution in this embodiment reaches analytical grade.

[0025] Step 3: The retested sample was analyzed again. Since the 19 chlorophenol-containing compounds and the derivatives of the internal standard solution in the retested sample were all weakly polar compounds, gas chromatography was selected for analysis. The capillary column of the gas chromatograph was programmed with a segmented temperature ramp mode, helium was used as the carrier gas, and helium was injected in a split configuration with a split ratio of 10:1; the injection volume was 1 μL, and the mass spectrometry conditions were as follows: EI was used as the ion source; in this embodiment, the electron energy of the ion source was 70 eV, the temperature of the ion source was set to 220 °C, and the mass scan range was set to m / z 40-500. The 20 target compounds were well retained, and the peaks were symmetrical. The gas chromatograph used in step 3 of this embodiment was a combination of an Agilent 7890B gas chromatograph and a 5977A MSD mass spectrometer detector. The Agilent 7890B gas chromatograph uses a DB-5MS capillary column with dimensions of 30m × 0.25mm × 0.25μm. The segmented temperature ramp process is as follows: initial temperature set at 60℃, held for 1 min; then ramped to 150℃ at 15℃ / min, held for 3 min; subsequently ramped to 300℃ at 30℃ / min, held for 5 min. The capillary column inlet temperature is set to 250℃, helium purity ≥ 99.999%, and helium flow rate 1.0 mL / min. The standard solution preparation method for the Agilent 7890B gas chromatograph in this embodiment is as follows: 0.5 mL... Nineteen chlorophenols were mixed and added to a 50 mL volumetric flask, dissolved in n-hexane and diluted to volume to obtain a mixed chlorophenol standard stock solution. 1 mL of the mixed chlorophenol standard stock solution was transferred to a 100 mL volumetric flask, diluted with n-hexane and diluted to volume. A certain volume of intermediate standard working solution was accurately pipetted and serially diluted with n-hexane to prepare a series of standard working solutions with concentrations of 1.0, 5.0, 10, 30, and 50 μg / L.

[0026] Step 4: After chromatographic analysis, the residual content of 19 chlorophenols in the wood sample was detected. The signal-to-noise ratio (S / N) of the 19 chlorophenol compounds was greater than 10, and the average recovery rate was greater than 90%. Therefore, according to the principle of quantification with a signal-to-noise ratio of 10, the detection limit values ​​of the 19 chlorophenol compounds were obtained.

[0027] This invention uses mass concentration (μg / L) as the abscissa and peak area y as the ordinate for linear regression, obtaining linear relationships for 19 chlorophenol-containing compounds in the range of 0.01-0.05 mg / L. (See attached diagram). Figure 1 Linear correlation coefficient R 2 >, 0.999 (as shown in Table 1), Table 1

[0028]

[0029] Step 5 involves adding target analytes at different levels to the blank matrix and then conducting recovery tests. Each spiked level is repeated three times. Quantitative analysis is performed using the internal standard method, and the average recovery rate is calculated. The results are shown in Table 2. In step 5 of this embodiment, three levels of target analytes were added to the blank matrix. The added levels of the three target analytes were L1 = 0.01 mg / kg, L2 = 0.02 mg / kg, and L3 = 0.05 mg / kg. When L1 = 0.01 mg / kg, the recoveries of the 19 chlorophenols were 105.4-119.2%; when the spike was 0.02 mg / kg, the recoveries were 85.4-109.3%; and when the spike was 0.05 mg / kg, the recoveries were 81.4-118.5%. The relative standard deviation (RSD) of the 19 chlorophenols ranged from 0.8 to 9.7%, meeting the requirements of the analytical test for the detection method.

[0030] Table 2

[0031]

[0032] This invention involves purchasing various food contact wood samples from the market and testing for pentachlorophenol migration. Because a larger sample size is used for migration testing, the detection limit is lower. For example, for cutting boards, a small half or the entire board is soaked and tested. All samples met the requirements of GB 4806.12-2022 standard, indicating they are qualified products. When these products were then tested for residual chlorophenols in 19 different types using this method, 12 out of 30 batches of wooden cutting board samples tested positive for 1-2 types of chlorophenols. Of these, 4 samples had a content between 1-5 mg / kg, and 8 samples had a content between 0.01-1 mg / kg. Similarly, 5 out of 20 batches of bamboo skewers and chopsticks tested positive for 1-2 types of chlorophenols.

[0033] This invention establishes a GC / MS method for analyzing the residues of 19 chlorophenols in wood products using methanol as the extraction solvent. This method features high extraction efficiency, simple and rapid pretreatment, high sensitivity and recovery rate, and good reproducibility. It meets the quantitative requirements of relevant regulations for the 19 chlorophenols and is suitable for rapid detection and risk monitoring of the residues of these 19 chlorophenols in food-related wood products.

[0034] Not limited to this, any variations or substitutions conceived without inventive effort should be included within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope defined in the claims.

Claims

1. A method for determining the residual amount of chlorophenol in wood products for food contact using an automated vortex-promoted derivatization-gas chromatography-mass spectrometry method, characterized in that... It includes the following steps: Step 1: Sample extraction is performed by taking samples of the wood used for food contact. The wood samples are then crushed and sieved to ensure uniform particle size. The samples are then weighed and placed in an Erlenmeyer flask, and an internal standard solution is added, followed by the extraction solvent. The mixture is then extracted using an ultrasonic cleaner. After extraction, the extract is filtered through filter paper into a rotary flask and evaporated to near dryness under a water bath. The solution is then dissolved in potassium hydroxide solution and transferred to a centrifuge tube. Step two, then derivatize the sample: Add acetic anhydride solution to the first centrifuge tube in step one, then seal the tube. Place the sealed first centrifuge tube on an automatic vortex mixer for the first vortexing. Then add n-hexane to the first centrifuge tube for the second vortexing. After that, let it stand, open the first centrifuge tube, and transfer the upper layer of liquid from the first centrifuge tube to the second centrifuge tube. Add sodium sulfate aqueous solution to the second centrifuge tube and shake and wash once. Extract the upper layer of liquid from the second centrifuge tube as the sample to be tested again. Step 3: Further analysis of the retested samples: Since the 19 chlorophenol-containing compounds and the derivatives of the internal standard solution in the retested samples are all weakly polar compounds, gas chromatography was selected for analysis. The capillary column of the gas chromatograph was programmed with segmented temperature ramp, helium was used as the carrier gas, and helium was injected in a split ratio of 10:1; the injection volume was 1 μL, and the mass spectrometry conditions were as follows: EI was used as the ion source, and the mass scan range was set to m / z 40-500. The 20 target compounds were well retained, and the peaks were symmetrical. Step 4: After chromatographic analysis, the residual content of 19 chlorophenols in the wood sample was detected. The signal-to-noise ratio (S / N) of the 19 chlorophenol compounds was greater than 10, and the average recovery rate was greater than 90%. Therefore, according to the principle of quantification with a signal-to-noise ratio of 10, the detection limit values ​​of the 19 chlorophenol compounds were obtained. Step 5: By adding different levels of the target analyte to the blank matrix, recovery tests were conducted. Each spiked level was repeated three times. Quantitative analysis was performed using the internal standard method, and the average recovery rate was calculated.

2. The method for determining the residual amount of chlorophenol in food contact wood products using automated vortex-promoted derivatization-gas chromatography-mass spectrometry according to claim 1, characterized in that... In step one, the wooden sample was pulverized to a particle size of 2 mm using a pulverizer and sieved through a metal sieve. The sample weight was 1 g, and the weighing equipment was a Metter ToledoBAS224S electronic analytical balance. The conical flask had a capacity of 100 mL, and the volume of the internal standard solution added was 100 μL. The internal standard solution was prepared by weighing 10 mg of tetrachloro-o-methoxyphenol, dissolving it in n-hexane, and diluting it to a concentration of 2 mg / L. The extraction solvent was 30 mL of methanol. The ultrasonic cleaner was an Elma S100H ultrasonic generator, and the rotary evaporator was an IKA rotary evaporator. The water bath conditions during rotary evaporation were 40°C. The concentration of the potassium hydroxide solution was 2 mol / L, and the volume was 20 mL. The capacity of the first centrifuge tube was 50 mL.

3. The method for determining the residual amount of chlorophenol in food contact wood products using automated vortex-promoted derivatization-gas chromatography-mass spectrometry according to claim 2, characterized in that... The methanol and potassium hydroxide solutions reached analytical grade purity.

4. The method for determining the residual amount of chlorophenol in food contact wood products using automated vortex-promoted derivatization-gas chromatography-mass spectrometry according to claim 1, characterized in that... In step two, the volume of acetic anhydride solution is 2 mL, the speed of the automatic vortex mixer is 2000 r / min, the first vortexing time is 10 min, the volume of added n-hexane is 5 mL, the second vortexing time is 5 min, the settling time is 5 min, the volume of the second centrifuge tube is 50 mL, the concentration of sodium sulfate aqueous solution is 20 g / L, the volume is 20 mL, and the volume of the liquid extracted from the upper layer of the second centrifuge tube is 1 mL.

5. The method for determining the residual amount of chlorophenol in wood products for food contact using automated vortex-promoted derivatization-gas chromatography-mass spectrometry according to claim 4, characterized in that... The acetic anhydride solution and sodium sulfate aqueous solution reached analytical grade purity.

6. The method for determining the residual amount of chlorophenol in wood products for food contact using automated vortex-promoted derivatization-gas chromatography-mass spectrometry according to claim 1, characterized in that... In step three, the gas chromatograph used was a combination of an Agilent 7890B gas chromatograph and a 5977A MSD mass spectrometer detector. The Agilent 7890B gas chromatograph used a DB-5MS capillary column with dimensions of 30 m × 0.25 mm × 0.25 μm. The specific process of the segmented temperature ramp mode was as follows: the initial temperature was set to 60°C and held for 1 min; then the temperature was increased to 150°C at a rate of 15°C / min and held for 3 min; subsequently, the temperature was increased to 300°C at a rate of 30°C / min and held for 5 min. The injection port temperature of the capillary column was set to 250°C, the helium purity was ≥99.999%, and the helium flow rate was 1.0 mL / min.

7. The method for determining the residual amount of chlorophenol in food contact wood products using automated vortex-promoted derivatization-gas chromatography-mass spectrometry according to claim 6, characterized in that... The method for preparing standard solutions injected into the Agilent 7890B gas chromatograph is as follows: Transfer 0.5 mL of a mixture of 19 chlorophenol-containing standards to a 50 mL volumetric flask, dissolve and dilute with n-hexane to obtain a chlorophenol-containing mixed standard stock solution. Transfer 1 mL of the chlorophenol-containing mixed standard stock solution to a 100 mL volumetric flask, dilute and dilute with n-hexane, accurately pipette a certain volume of intermediate standard working solution, and dilute stepwise with n-hexane to prepare a series of standard working solutions with concentrations of 1.0, 5.0, 10, 30, and 50 μg / L.

8. The method for determining the residual amount of chlorophenol in food contact wood products using automated vortex-promoted derivatization-gas chromatography-mass spectrometry according to claim 6, characterized in that... The electron energy of the ion source is 70 eV, and the temperature of the ion source is set to 220℃.

9. The method for determining the residual amount of chlorophenol in wood products for food contact using automated vortex-promoted derivatization-gas chromatography-mass spectrometry according to claim 1, characterized in that... In step five, three target analytes at different levels were added to the blank matrix. The levels of the three target analytes were L1 = 0.01 mg / kg, L2 = 0.02 mg / kg, and L3 = 0.05 mg / kg. When L1 = 0.01 mg / kg, the recoveries of the 19 chlorophenols were 105.4%–119.2%; when L1 = 0.02 mg / kg, the recoveries were 85.4%–109.3%; and when L1 = 0.05 mg / kg, the recoveries were 81.4%–118.5%. The relative standard deviations (RSDs) of the 19 chlorophenols ranged from 0.8% to 9.7%, which met the requirements of the analytical test for the detection method.

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