In order to study the nature and role of food contaminating factors, some modern techniques are used to detect their levels in food, to determine the safe dose of toxicants using knowledge of toxicology, to evaluate the safety of food, and to elucidate whether a certain food is safe for consumption. Source: Food Safety Testing Technology (Chemical Industry Press)
Operation method
Techniques for the determination of organophosphorus pesticide residues
Principle
Organophosphorus pesticides (organophosphorus pesticides, referred to as OPPs) are organic compounds that contain C-P bonds or C-O-P, C-S-P, C-N-P bonds. -P bond of organic compounds, currently in common use there are four major categories: 1. phosphate esters of phosphoric acid in the three hydrogen atoms replaced by an organic group to generate compounds called phosphate esters. 2. phosphorothioate class of phosphoric acid molecules in the replacement of oxygen atoms by sulfur atoms to generate compounds for the phosphorothioate, phosphorothioate in the replacement of hydrogen atoms by an organic group, which is to become the phosphorothioate esters. 3. phosphonate class and phosphorothioate class of phosphoric acid, phosphoric acid and phosphoric acid. Phosphoric acid esters and phosphorothioate esters in a hydroxyl group is replaced by an organic group! That is, in the molecule to form a P-C bond is called "phosphonic acid", phosphonic acid in the hydrogen atom of the hydroxyl group is replaced by an organic group that is phosphonate, or phosphonate in the oxygen atom is replaced by a sulfur atom, that is, phosphonothioate. 4. Phosphoramidites and thiophosphoramidites phosphoric acid molecule of the hydroxyl group is replaced by an amino group to produce phosphoramidite; or the remaining oxygen atom in the phosphoramidite molecule is replaced by a sulfur atom, which becomes phosphoramidothioate.
Materials and Instruments
Grain Oilseed Move 1. Extraction Method 1 (Homogenized extraction) Weigh about 20 g (0.1 g) of the sample into a 250 mL stoppered conical flask, add 20 mL of water, shake and leave for 1 h. Then add 100 mL of acetone and homogenize the extract for 3 min at high speed, and then filter the extract into a 250 mL pear shaped flask. The residue was extracted again with 50 mL of acetone, and the filtrate was combined and concentrated to about 20 mL in a 40 ℃ water bath with rotation for purification. Method 2 (ASE rapid solvent extraction) Weigh about 20 g (accurate to 0.1 g) of the sample in the sample cell, sealed, according to the specified conditions [ASE extraction conditions extraction solvent: dichloromethane; pressure: 1500 psi (l psi = 6894.76 Pa); temperature: 50 ℃; extraction volume: 60 mL; static time: 5 min] for the extraction and purification. 2. 2. Liquid-liquid partition purification The concentrated extract was transferred to a 250 mL dispensing funnel, 150 mL of aqueous sodium chloride and 50 mL of dichloromethane were added (no need to add dichloromethane for ASE extraction), shaking for 3 min, static layering, and the dichloromethane phase was collected. The aqueous phase was then extracted twice with 2×50 mL dichloromethane, and the dichloromethane phase was combined. It was dehydrated by an anhydrous sodium sulfate column, collected in a 250 mL pear-shaped vial, concentrated to near dryness by spinning in a water bath at 40 C. 5 mL of cyclohexane-ethyl acetate (1 + 1) was added to dissolve the residue and filtered through a 0.45 um filter membrane. 5 mL of the solution to be purified was purified by GPC. 3. Purification by gel chromatography Combine the collected liquids from the fraction collector in a 500 mL pear shaped bottle, rotate and concentrate in a water bath at 40 ℃ until nearly dry, add 2 mL of n-hexane to dissolve the residue, and leave it to be purified by SEP. Gel chromatography (GPC) conditions: clean-up column: 700 mm×25 mm, Bio BeadsS-X3, or equivalent; mobile phase: cyclohexane-ethyl acetate (1 + 1); flow rate: 5.0 mL/min; sample quantification loop: 5.0 mL; pre-rinse volume: 50 mL; elution volume: 200 mL; collection volume: 90 ~ 190 mL. 4. Solid phase extraction cleanup Common Problems For more product details, please visit Aladdin Scientific website.
Acetone Dichloromethane Sodium chloride aqueous
Stoppered conical flasks Filter flasks Gel columns Dispensing funnels Fraction collectors
The column was pre-drenched with 6 mL of hexane, the sample solution was poured into the column, washed with 2 mL of hexane, and then eluted with 20 mL of hexane-ethyl acetate (2 + 3). All the eluate was collected in a 50 mL pear-shaped bottle, concentrated to dryness by spinning in a water bath at 40 ℃, dissolved with n-hexane and concentrated to 2.0 mL for determination and confirmation by gas chromatography-mass spectrometry (GC-MS). 5. Determination Ionization mode: EI; Ionization energy: 70 eV; Measurement mode: selected ion monitoring mode; Solvent delay: 5 mD;