What is Vietnam Standard TCVN 8347:2010 on aquatic animals and animal products - determination of organophosphorus pesticide residues by using gas chromatography about?
- What are the reagents and test materials used for the determination of organophosphorus pesticide residues by using gas chromatography in Vietnam?
- What are the equipment and instruments used in the determination of organophosphorus pesticide residues in Vietnam?
- What are the regulations for preparing samples and cleaning extracts in using gas chromatography for determination of organophosphorus pesticide residues in Vietnam?
What are the reagents and test materials used for the determination of organophosphorus pesticide residues by using gas chromatography in Vietnam?
According to Section 3 of Vietnam Standard TCVN 8347:2010, the reagents and test materials used for the determination of organophosphorus pesticide residues by using gas chromatography in Vietnam are only analytical purity reagents and distilled water or water of equivalent purity, unless otherwise stated as follows:
Sodium sulfate, granular, dried overnight at 350 0C and kept in glass bottles.
- Hexan used for GC.
- Ethyl acetate used for HPLC
- Helium-carrying gas used for GC
- Glass wool, SUPELCO, 2-0411 or equivalent.
- Silicagel, particle size 60 mesh (silica-60), Merck, Darmstadt, Germany or equivalent.
- Activated silicagel: Weigh a quantity of silicagel, rinse with diclomethane and put it in a porcelain cup and store in a drying cabinet at 120 0C for 12 h. Then, cover the mouth of the porcelain cup with tin foil and leave it in the drying cabinet at 120 0C before using.
- Xelite.
- Solution wash: A mixture of acetonitrine (GC) and acetone (GC) in a volume ratio of 9:1 is mixed before use.
- OP pesticide standards (Promochem, Wesel, Germany or equivalent): dimethoate, chlorfenvinphos (E+Z isomer), chlorpyrifos, methidathion and phosmet, purity greater than 99%.
- OP pesticide standard solution in acetone: Prepare OP pesticide standard solutions in acetone from standard substances. Depending on the concentration of pesticides in the standard tube, use the appropriate rated bottle and the amount of acetone (type used for GC).
NOTE: Standards must be stored at a temperature of – 20 0C.
- Recovery standard: Mix the standards of OP in acetone to have concentrations in the range of 0.005 mg/ml to 50 mg/ml.
- Intermediate standard solution: Dilutes the initial standards in acetone that are intermediate by standard solutions.
- Working standard solution: Dilutes intermediate standards in hexane that are working standards. Working standards are used to pump into the GC.
What are the equipment and instruments used in the determination of organophosphorus pesticide residues in Vietnam?
According to Section 4 of Vietnam Standard TCVN 8347:2010, the following ordinary and specific equipment and instruments of laboratories shall be used for the determination of organophosphorus pesticide residues in as follows:
- Analytical balance, which can weigh accurately to 0.1 mg.
- Glass cup with beak.
- Crusher.
- High speed mixer.
- Her camera spins in a vacuum.
- Drying cabinet.
- Kiln.
- Gas chromatographer, equipped with electron (ECD) and nitơ-phospho (NPD) detector.
- Column chromatography, with lock valve, length 150 mm, inner diameter 5 mm and length 50 mm, inner diameter 20 mm.
- Capillary column (for GC machine), HP Ultra 2 type, column stuffing containing 5 % methylsilicol, length 25 m, inner diameter 0.2 mm, stationary phase thickness 0.33 mm or equivalent.
What are the regulations for preparing samples and cleaning extracts in using gas chromatography for determination of organophosphorus pesticide residues in Vietnam?
According to Section 5 of Vietnam Standard TCVN 8347:2010, the preparation of test samples, white samples and samples to determine the recovery and cleaning of extracts is specified as follows:
- Sample preparation
+ Weigh 5 g of the sample that has been crushed by a crusher, accurate to 0.1 mg, and then put in a glass cup with a mine. Add 1 g of xelite, 30 g of anhydrous sodium sulfate and grind well.
Continue to add 150 ml of washing solution and mix the mixture for 3 min in a high-speed mixer to extract pesticides from the sample. After that, strain the solution with filter paper.
+ The extracted product is concentrated on the machine she rotates to about 5 ml, then she continues to dry on the machine she spins in vacuum mode at a temperature of 40 0C. Mix the sediment to obtain 1 ml of hexane and then clean the extract according to 5.4 Vietnam Standard TCVN 8347:2010.
White sample preparation: A white sample is defined as an aquatic sample that has been determined not to contain OP-based pesticides.
Prepare white samples in the same way as for test samples as prescribed in 5.1 Vietnam Standard TCVN 8347:2010.
- Sample preparation for determination of recovery: Add 1 ml of recovery standard solution with content from 0.005 mg/ml to 50 mg/ml to 5 g of white sample, mix the sample well with a crusher; prepare samples in the same way as for test samples as prescribed in 5.1 Vietnam Standard TCVN 8347:2010
- Extract cleansing
+ Column preparation: Prepare columns, including glass wool, 1.3 g activated silicagel, 1 g anhydrous sodium sulfate. Before proceeding with the analysis, put in the column 5 ml of ethyl acetate and then 5 ml of hexane.
+ Clean the extract
++ Transfer obtained solution according to 5.1.2, 5.2 and 5.3 of Vietnam Standard TCVN 8347:2010 into prepared chromatography columns.
++ Wash the solution in columns with 5 ml of hexane, then with 2 ml of hexane-ethyl acetate mixture in a volume ratio of 95:5; next, rinse with 8 ml of hexane-ethyl acetate mixture in a volume ratio of 50:50 and then separate for fraction 1. After that, continue to wash the solution with 5 ml of ethyl acetate and then separate to take fraction 2. The washing speed should always be adjusted to 10 drops/min.
++ Collect the extraction segments into the round-bottom glass vessels of the vacuum spinning machine; proceed her on the camera she spins until dry; then, add exactly 1 ml of hexane to each bottle, shake to dissolve and then suck to pump into the GC machine according to subsection 5.5 of Vietnam Standard TCVN 8347:2010.
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