Abstract: Using gas chromatography . Determination of fluroxypyr in vegetables and fruits by mass spectrometry . After extracting the sample with acetonitrile, the extract was blown dry with nitrogen, and methanol and concentrated H2SO4 were added for esterification. 10 mL of a 20 g/L Na2SO4 solution was added to the esterified product, and 5 mL of n-hexane was thoroughly mixed. The n-hexane phase was taken into the GC- MS. The detection limit of fluroxypyr was: 1.40 × 0.001 μg / g.
Key words: fluroxypyr; gas chromatography; mass spectrometry; esterification fluroxypyr, common name: fluroxypyr. Trade name: Starane, chemical name: 4-amino-3,5-dichloro-6-fluoro-pyridine-2-oxoacetic acid. Molecular formula: C7H5C12FN203.
It is mainly used in crop fields such as wheat to control broadleaf weeds. Due to its high herbicidal ability, low toxicity, low drift and low residue, fluroxypyr is widely used to control broadleaf weeds in cereal crops and some vegetables and fruits. In recent years, the EU has increased the detection and limit regulations for fluroxypyr residues in some cereals, vegetables, fruits and other plant products and animal-derived foods. The high allowable limit of fluroxypyrene in most agricultural products is 0.05 mg/kg. Previously reported in the literature, using GC-ECD and high performance liquid chromatography . As testing technology standards continue to increase, GC measurements are no longer sufficient to meet regulatory requirements. The author studied the gas chromatography-mass spectrometry method, which solved the quantitative problem while qualitatively, and was quick and simple, with high sensitivity and good accuracy.
1 Experimental part 1.1 Instrument and reagent temperament connection Agilent 6890GC/5973MSD with G1701BA ChemStation (Agilent Instrument Co., Ltd.); Homogenizer IKA T18 basic (Guangzhou Instrument Laboratory Technology Co., Ltd.); Nitrogen blower (homemade) ; six-hole water bath; rotary evaporator RE. 52A (Shanghai Yarong Biochemical Instrument Factory); Ultrasonic Cleaner SBS5200 (Beixinxin Ultrasonic (Shanghai) Co., Ltd.); Food Processor; Microporous Filter Mill: 0.45μm (Shanghai Xinya Purification Device Factory); Electronic Balance AE -200 type (inductive quantity 0.0001g, METTLER, Switzerland).
Acetonitrile, methanol and n-hexane are chromatographically pure reagents, concentrated 200 times and then into GC-MS, the test should have no interference peak; concentrated H2SO4 is excellent grade pure reagent; anhydrous sodium sulfate) AR), 550 ~ 600 °C for 4h, storage In the dryer; NaC1 (AR), baked at 350 ° C for 6h, stored in the dryer 盅.
The fluroxypyr was purchased from SIGMA-ALDSICH (purity: 9.7%) in Germany. It was firstly mixed with methanol to form a high-concentration solution of 10000 μg/mL, stored in a refrigerator, and diluted with methanol to a desired low-concentration solution before use.
1.2 Instrumental conditions Column: HP-5MS Phenyl Methym Siloxane 5% diphenyl-95% dimethylsiloxane capillary column (30.0m × 0.25mm i.d. × 0.25μm); carrier gas: He ( Purity 99.999%); Flow rate: 1.0 mL/min; Inlet temperature: 250 ° C; Injection method: pulse splitless injection, 20 psi, 1.0 min; column temperature: 70 ° C, 20 ° C / min 240 ° C (maintained 1.0 min), total injection time: 9.50 min; injection volume: 2 μL.
Ion source: EI (70 eV); ion source temperature: 230 ° C; quadrupole temperature: 150 ° C; interface temperature: 285 ° C; EM voltage: 1518 V; acquisition mode: SIM; solvent delay: 6.0 min; tuning mode: automatic tuning .
1.3 Sample processing Accurately weigh 25.00 g of sample processed in food processor; add 50.0mL acetonitrile; homogenize in high speed homogenizer for 2min; put 5~7.5g NaC1 in 100mL stopper cylinder, put A glass funnel with filter paper, filter the homogenized sample; collect about 40-50mL of filtrate; cover with a stopper and shake vigorously for 1min; let stand at room temperature for about 10min, let acetonitrile phase and water phase stratify; accurately absorb 10mL The acetonitrile phase solution was placed in a 50 mL beaker; it was heated with steam on a water bath at 80 ° C, and the inside of the cup was slowly blown with a stream of nitrogen, evaporated to dryness, and 2.0 mL of methanol, 2.0 mL of concentrated H 2 SO 4 was added to the concentrate, and thoroughly mixed. After that, esterification was carried out for 10 min on a 95 ° C water bath, and 10.0 mL of a 20 g/L Na 2 SO 4 solution, 5.0 mL of n-hexane was added to the esterified product, shaken, and the n-hexane phase was taken. A small amount of anhydrous Na 2 SO 4 was added, and the mixture was centrifuged. Measurement. Into the GC-MS analysis.
2 Results and discussion 2.1 Determination of esterification temperature and esterification time After experiment, select 10min, 95 °C is good esterification conditions.
2.2 The standard curve is drawn to the standard series of 5.0x0.001, 5.0 x0.01, 5.0 x0.1, 1.0, 5.0mg/L, with the concentration of fluroxypyr as the abscissa and the abundance of the response as the ordinate. The curve, Y (Response x0.00001) = 3.67p + 0.165, the linear relationship is good, the correlation coefficient r = 0.999.
2.3 Sample determination results 2.3.1 Qualitative determination According to the NIST02 library, the following conditions are met for the determination: the retention time of the library search target is the same as the retention time (RT) of the standard; the ion of the target is detected (181) 209, 211, 268, wherein 209 is a quantitative ion, and the other three are qualitative ions. The abundance ratio is ≥80% according to the standard.
2.3.2 Quantitative determination using external standard-standard curve method. Calculated by quantitative ion (209) by SIM method.
2.4 Sensitivity 2.4.1 Instrument Detection Limit of Detection (LOD) The lower limit of the peak of the analytical target can be clearly confirmed on the chromatogram, taking 3 times of the noise, ie LOD= P×3/( S/N); Zui low limit of quantitation (LOQ) on the chromatogram can clearly quantify the lower limit of the chromatographic bee of the analytical target, taking 10 times the noise, ie LOQ = P × 10 / (S / N). The Agilent Instrument ChemStation can measure S/N. If the injection is 0.010 mg/L and the instrument gives an S/N value of 20, then: LOD = 0.0015 mg/L; LOQ = 0.0050 mg/L.
2.4.2 Method detection limit (in the presence of matrix) Take the standard addition of garlic as an example. It can be seen that the recovery rate is between 82.0% and 86.0%, and the relative standard deviation RSD is <20%. It meets the requirements of pesticide residue analysis (ie, the recovery rate of spiked standard is between 70% and 120%).
2.5 Determination of recovery and precision Add recovery test: Add 0.O1 ~ 1.O0 mg / L of fluroxypyr standards to garlic samples, according to the instrument operating procedures.
2.6 Error Analysis Pesticide residue data acquisition includes three basic steps, namely sampling (S), sample preparation (SP) and analysis (A). As the analytical error of the laboratory, it is derived from SP and A, where the systematic error is: ΔR = ΔSp + ΔA. Errors are expressed by relative standard deviations: eg, decomposition of analytes in the sample storage and preparation stages, analysis of loss during extraction of the target material, matrix interference, conversion of derivative reactions, repeatability of analytical operations, and performance stability of the instrument. Whether the concentration of the standard is accurate or not.
references
[1] Li Benchang and so on. Manual for Practical Detection of Pesticide Residues (*Volume) Beijing: China Agricultural Science and Technology Press, 1995
[2] Cui Weideng. Hubei Plant Protection, 1997, (5): 23
[3] Sha Jiajun, Zhang Minheng, Jiang Yajun. New pesticide manual abroad. Beijing: Chemical Industry Press, 1992.341
[4] Bai Wei, Wang Mei, Gong Jinghong. Chromatography. 2003, 21 (3): 288
[5] Chen Daowen, Chen Rudong. Pesticide, 1995, (2)
[6] Pan Canping, Qian Chuanfan, Jiang Shuren. Modern pesticides, 2002, 12 (2): 12
Key words: fluroxypyr; gas chromatography; mass spectrometry; esterification fluroxypyr, common name: fluroxypyr. Trade name: Starane, chemical name: 4-amino-3,5-dichloro-6-fluoro-pyridine-2-oxoacetic acid. Molecular formula: C7H5C12FN203.
It is mainly used in crop fields such as wheat to control broadleaf weeds. Due to its high herbicidal ability, low toxicity, low drift and low residue, fluroxypyr is widely used to control broadleaf weeds in cereal crops and some vegetables and fruits. In recent years, the EU has increased the detection and limit regulations for fluroxypyr residues in some cereals, vegetables, fruits and other plant products and animal-derived foods. The high allowable limit of fluroxypyrene in most agricultural products is 0.05 mg/kg. Previously reported in the literature, using GC-ECD and high performance liquid chromatography . As testing technology standards continue to increase, GC measurements are no longer sufficient to meet regulatory requirements. The author studied the gas chromatography-mass spectrometry method, which solved the quantitative problem while qualitatively, and was quick and simple, with high sensitivity and good accuracy.
1 Experimental part 1.1 Instrument and reagent temperament connection Agilent 6890GC/5973MSD with G1701BA ChemStation (Agilent Instrument Co., Ltd.); Homogenizer IKA T18 basic (Guangzhou Instrument Laboratory Technology Co., Ltd.); Nitrogen blower (homemade) ; six-hole water bath; rotary evaporator RE. 52A (Shanghai Yarong Biochemical Instrument Factory); Ultrasonic Cleaner SBS5200 (Beixinxin Ultrasonic (Shanghai) Co., Ltd.); Food Processor; Microporous Filter Mill: 0.45μm (Shanghai Xinya Purification Device Factory); Electronic Balance AE -200 type (inductive quantity 0.0001g, METTLER, Switzerland).
Acetonitrile, methanol and n-hexane are chromatographically pure reagents, concentrated 200 times and then into GC-MS, the test should have no interference peak; concentrated H2SO4 is excellent grade pure reagent; anhydrous sodium sulfate) AR), 550 ~ 600 °C for 4h, storage In the dryer; NaC1 (AR), baked at 350 ° C for 6h, stored in the dryer 盅.
The fluroxypyr was purchased from SIGMA-ALDSICH (purity: 9.7%) in Germany. It was firstly mixed with methanol to form a high-concentration solution of 10000 μg/mL, stored in a refrigerator, and diluted with methanol to a desired low-concentration solution before use.
1.2 Instrumental conditions Column: HP-5MS Phenyl Methym Siloxane 5% diphenyl-95% dimethylsiloxane capillary column (30.0m × 0.25mm i.d. × 0.25μm); carrier gas: He ( Purity 99.999%); Flow rate: 1.0 mL/min; Inlet temperature: 250 ° C; Injection method: pulse splitless injection, 20 psi, 1.0 min; column temperature: 70 ° C, 20 ° C / min 240 ° C (maintained 1.0 min), total injection time: 9.50 min; injection volume: 2 μL.
Ion source: EI (70 eV); ion source temperature: 230 ° C; quadrupole temperature: 150 ° C; interface temperature: 285 ° C; EM voltage: 1518 V; acquisition mode: SIM; solvent delay: 6.0 min; tuning mode: automatic tuning .
1.3 Sample processing Accurately weigh 25.00 g of sample processed in food processor; add 50.0mL acetonitrile; homogenize in high speed homogenizer for 2min; put 5~7.5g NaC1 in 100mL stopper cylinder, put A glass funnel with filter paper, filter the homogenized sample; collect about 40-50mL of filtrate; cover with a stopper and shake vigorously for 1min; let stand at room temperature for about 10min, let acetonitrile phase and water phase stratify; accurately absorb 10mL The acetonitrile phase solution was placed in a 50 mL beaker; it was heated with steam on a water bath at 80 ° C, and the inside of the cup was slowly blown with a stream of nitrogen, evaporated to dryness, and 2.0 mL of methanol, 2.0 mL of concentrated H 2 SO 4 was added to the concentrate, and thoroughly mixed. After that, esterification was carried out for 10 min on a 95 ° C water bath, and 10.0 mL of a 20 g/L Na 2 SO 4 solution, 5.0 mL of n-hexane was added to the esterified product, shaken, and the n-hexane phase was taken. A small amount of anhydrous Na 2 SO 4 was added, and the mixture was centrifuged. Measurement. Into the GC-MS analysis.
2 Results and discussion 2.1 Determination of esterification temperature and esterification time After experiment, select 10min, 95 °C is good esterification conditions.
2.2 The standard curve is drawn to the standard series of 5.0x0.001, 5.0 x0.01, 5.0 x0.1, 1.0, 5.0mg/L, with the concentration of fluroxypyr as the abscissa and the abundance of the response as the ordinate. The curve, Y (Response x0.00001) = 3.67p + 0.165, the linear relationship is good, the correlation coefficient r = 0.999.
2.3 Sample determination results 2.3.1 Qualitative determination According to the NIST02 library, the following conditions are met for the determination: the retention time of the library search target is the same as the retention time (RT) of the standard; the ion of the target is detected (181) 209, 211, 268, wherein 209 is a quantitative ion, and the other three are qualitative ions. The abundance ratio is ≥80% according to the standard.
2.3.2 Quantitative determination using external standard-standard curve method. Calculated by quantitative ion (209) by SIM method.
2.4 Sensitivity 2.4.1 Instrument Detection Limit of Detection (LOD) The lower limit of the peak of the analytical target can be clearly confirmed on the chromatogram, taking 3 times of the noise, ie LOD= P×3/( S/N); Zui low limit of quantitation (LOQ) on the chromatogram can clearly quantify the lower limit of the chromatographic bee of the analytical target, taking 10 times the noise, ie LOQ = P × 10 / (S / N). The Agilent Instrument ChemStation can measure S/N. If the injection is 0.010 mg/L and the instrument gives an S/N value of 20, then: LOD = 0.0015 mg/L; LOQ = 0.0050 mg/L.
2.4.2 Method detection limit (in the presence of matrix) Take the standard addition of garlic as an example. It can be seen that the recovery rate is between 82.0% and 86.0%, and the relative standard deviation RSD is <20%. It meets the requirements of pesticide residue analysis (ie, the recovery rate of spiked standard is between 70% and 120%).
2.5 Determination of recovery and precision Add recovery test: Add 0.O1 ~ 1.O0 mg / L of fluroxypyr standards to garlic samples, according to the instrument operating procedures.
2.6 Error Analysis Pesticide residue data acquisition includes three basic steps, namely sampling (S), sample preparation (SP) and analysis (A). As the analytical error of the laboratory, it is derived from SP and A, where the systematic error is: ΔR = ΔSp + ΔA. Errors are expressed by relative standard deviations: eg, decomposition of analytes in the sample storage and preparation stages, analysis of loss during extraction of the target material, matrix interference, conversion of derivative reactions, repeatability of analytical operations, and performance stability of the instrument. Whether the concentration of the standard is accurate or not.
references
[1] Li Benchang and so on. Manual for Practical Detection of Pesticide Residues (*Volume) Beijing: China Agricultural Science and Technology Press, 1995
[2] Cui Weideng. Hubei Plant Protection, 1997, (5): 23
[3] Sha Jiajun, Zhang Minheng, Jiang Yajun. New pesticide manual abroad. Beijing: Chemical Industry Press, 1992.341
[4] Bai Wei, Wang Mei, Gong Jinghong. Chromatography. 2003, 21 (3): 288
[5] Chen Daowen, Chen Rudong. Pesticide, 1995, (2)
[6] Pan Canping, Qian Chuanfan, Jiang Shuren. Modern pesticides, 2002, 12 (2): 12
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