GB/T 5009.188-2003 Determination of thiophanate-methyl and carbendazim in vegetables and fruits

This standard specifies the determination method of thiophanate-methyl and carbendazim in vegetables and fruits. This standard is applicable to the determination of thiophanate-methyl and carbendazim in vegetables and fruits. GB/T 5009.188-2003 Determination of thiophanate-methyl and carbendazim in vegetables and fruits GB/T5009.188-2003 Standard download decompression password: www.bzxz.net

ICS67.040
National Standard of the People's Republic of China
GB/T5009.188--2003
Partially replaces GB/T5009.38-1996
Determination of thiophanate-methyl,carbendaziminvegetables and fruits
Promulgated on August 11, 2003
Ministry of Health of the People's Republic of China
Standardization Administration of the People's Republic of China
Implementation on January 1, 2004
GB/T5009.188-2003
This standard replaces the determination of thiophanate-methyl and carbendazim in 4.7 of GB/T5009.38-1996 "Analytical methods for hygienic standards of vegetables and fruits".
This standard is proposed and managed by the Ministry of Health of the People's Republic of China. This standard is drafted by the Food Hygiene Supervision and Inspection Institute of the Ministry of Health. 496
1 Scope
GB/T5009.188—2003
Determination of methyl thiophanate and carbendazim in vegetables and fruits This standard specifies the determination method of methyl thiophanate and carbendazim in vegetables and fruits. This standard is applicable to the determination of methyl thiophanate and carbendazim in vegetables and fruits. 2 Principle
Methyl thiophanate is extracted from the sample with methanol. At pH 1-2, it is extracted with dinitromethane. Methyl thiophanate is converted into carbendazim through a ring-closing reaction. After purification, it is quantitatively determined by ultraviolet spectrophotometry. After extraction, the absorbance of carbendazim can be directly measured for quantification. In order to eliminate the interference of various crops during quantification, the drawing method is used to obtain the corrected absorbance, and then a standard curve is drawn based on the relationship between the corrected absorbance and thiophanate-methyl or carbendazim. Carbendazim has the specific absorption of benzimidazole, and the plant components have little interference. 3 Reagents
3.1 Methanol
3.2 Diazomethane.
3.3 Triazine.
3.4 ​​Petroleum ether: boiling range 30℃~60℃. bZxz.net
3.5 Acetic acid-copper acetate solution: weigh 2g of copper acetate, add 100mL of glacial acetic acid, heat slightly to dissolve, and dilute with water to 200mL. 3.6 Hydrochloric acid (1+11): measure 90mL of hydrochloric acid, dilute to 1000mL with water. Sodium hydroxide solution (80g/L): weigh 8g of sodium hydroxide, dissolve in water and dilute to 100mL. 3.7
Ammonium hydroxide solution (1+7): Measure 10 mL of ammonia water and dilute to 80 mL with water. 3.9 Sodium chloride solution (100 g/L).
3.10 Thiophanate methyl standard solution: Accurately weigh 50.0 mg thiophanate methyl, place in a beaker, dissolve with chloroform and transfer to a 50 mL volumetric flask, and dilute to scale. This solution is equivalent to 1.0 mg thiophanate methyl per milliliter. 3.11 Thiophanate methyl standard working solution: Take 10.0 mL of thiophanate methyl standard solution and place in a 100 mL volumetric flask, add chloroform to dilute to scale, and this solution is equivalent to 100.0 g thiophanate methyl per milliliter. 3.12 Carbendazim standard solution: Accurately weigh 50.0 mg carbendazim and place in a beaker, dissolve with hydrochloric acid (1+11) and transfer to a 50 mL volumetric flask, and dilute to scale, and this solution is equivalent to 1.0 mg carbendazim per milliliter. 3.13 Carbendazim standard working solution: Take 10.0mL of carbendazim standard solution and place it in a 100mL volumetric flask. Add hydrochloric acid (1+11) to dilute to the mark. Each mL of this solution is equivalent to 100.0μg of carbendazim. 4 Instruments
4.1 UV spectrophotometer.
4.2 Air condenser, or a 60cm long glass tube (homemade). 5 Analysis steps
5.1 Preparation of standard curve
5.1.1 Thiophanate-methyl standard curve: Pipette 0.0.10, 0.30, 0.50mL of thiophanate-methyl standard working solution (equivalent to 0, 10, 30, 50μg thiophanate-methyl) and place them in 30mL round-bottom centrifuge tubes respectively. After evaporating the solvent, add 10mL of acetic acid-copper acetate solution and 2 497
GB/T5009.188—2003
glass beads to each tube, connect the air condenser, boil slowly over low heat for 0.5h, remove it, wash the condenser and round-bottom centrifuge tube from the top of the condenser with 20mL of hydrochloric acid (1+11), and transfer them to a 125mL separatory funnel. , extract twice with dichloromethane, 10 mL each time, discard the dichloromethane layer, add 25 mL of sodium hydroxide solution (80 g/L) to the acid solution to pH 6.0-6.5 (pH test paper test), extract twice with difluoromethane, 20 mL each time, combine the dihydromethane extracts, wash once with 10 mL of water, let stand and separate, separate the dichloromethane layer into another dry separatory funnel, accurately add 10 mL of hydrochloric acid (1+11), shake for 5 minutes, let stand and separate, use a 1 cm quartz colorimetric cup for the hydrochloric acid extract, adjust the zero point of the spectrophotometer with hydrochloric acid (1+11), measure the absorbance at 250 nm to 300 nm, and draw an absorption spectrum with wavelength as the horizontal axis and absorbance as the vertical axis. Connect the absorbance reading points of 260nm and 290nm on the spectrum into a straight line, and set the absorbance of 282nm on the straight line as A, and the absorbance of 282nm on the absorption spectrum as A, and the difference between the two is △A (△A=A-A, which is the corrected absorbance). Then, with the corrected absorbance as the ordinate and the content of thiophanate methyl as the abscissa, draw a standard curve of the △A value of each thiophanate methyl standard point. 5.1.2 Carbendazim standard curve: Pipette 0, 0.10.0.30, 0.50mL of carbendazim standard working solution (equivalent to 0, 10.30, 50μg of carbendazim), place in a separatory funnel filled with 20mL of hydrochloric acid (1+11), extract twice with dichloromethane, 10mL each time, discard the dichloromethane layer, neutralize the aqueous solution with ammonium hydroxide (1+7) to pH 6.06.5 (pH test paper test), extract twice with dichloromethane, 20mL of the extract each time, wash once with 10mL of water, and proceed as described in 5.1.1 Thiophanate-methyl standard curve starting from "Put the dichloromethane layer into another dry separatory funnel and accurately add 10mL of hydrochloric acid (1+11)", draw the absorption spectrum, calculate the △A value, and draw the carbendazim standard curve.
5.2 Extraction and separation of samples
Weigh 50.0g of the chopped and mixed sample, add 50ml methanol and shake for 0.5h, filter with a Buchner funnel, wash the container and filter with methanol twice, 15mL~20mL each time, and after drying, transfer the filtrate to a beaker, wash the filtration bottle with about 10mL water, and add the washing liquid to the filtrate. After blowing off part of the methanol with air flow on a water bath, transfer it to a liquid separation bucket, add 30mL sodium chloride solution (100g/L), shake and extract twice with petroleum ether, 25mL each time, discard the petroleum ether, add hydrochloric acid to acidify to pH 1~2 (test with pH test paper), extract twice with dichloromethane, 25mL each time, combine the dichloromethane extracts, wash once with 25mL water, separate the dichloromethane layer and save it for thiophanate-methyl determination. The water washing liquid is combined with the water layer and saved for carbendazim determination. 5.3 Determination of thiophanate-methyl
After the dichloromethane extract is naturally evaporated, dissolve the residue in 10mL acetic acid-copper acetate solution in batches and transfer to a 30mL round-bottom centrifuge tube, add 2 glass beads, and operate according to 5.1.1 starting from "connecting the air condenser" to calculate the △A value of the sample, and then compare it with the standard curve of thiophanate-methyl to calculate the content in the sample. 5.4 Determination of carbendazim
Take the aqueous solution reserved for carbendazim determination in 5.2, neutralize it with ammonium hydroxide (1+7) to pH 6.0~6.5, and then operate according to 5.1.2 carbendazim standard curve starting from "extracting twice with dichloromethane" to calculate the △A value in the sample, and then compare it with the standard curve of carbendazim to calculate the content in the sample.
The main metabolite of thiophanate-methyl in plants is carbendazim, which is formed by the hydrolysis and ring closure of thiophanate-methyl. Therefore, the current residual amount of thiophanate-methyl is expressed as the sum of the residual amounts of these two compounds. 6 Result calculation
The content of thiophanate-methyl and carbendazim in the sample is calculated as follows: X=(mi+m)×1 000
mx1000
Wherein:
X-the content of thiophanate-methyl and carbendazim in the sample, in milligrams per kilogram (mg/kg); m1-—the mass of thiophanate-methyl in the test sample, in micrograms (μg); m?——the mass of carbendazim in the test sample, in micrograms (μg); m--the mass of the sample, in grams (g). The calculation result is expressed to two significant figures. 498
7 Precision
GB/T5009.188—2003
The absolute difference between two independent determination results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean. 8 Others
Wavelength/nm
Figure 1 Standard UV absorption spectrum of methyl thiophanate 0.16
AA,-10
AA2—307
AAs-507
—Concentration
A41=0. 0520.019=0.033
AA20.1120.022-0.090
AA30.1800.030=0.150
Figure 2 Standard curve of methyl thiophanate
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.