Methamidophos extraction

Kicuchi and Saito used carbon Empore disks in combination with SDB-XD Em-pore disks to extract polar (methamidophos, acephate and trichlorfon) and nonpolar pesticides (diazinon, chloroneb and simazine) from water. The water sample (500 mL) was passed through the disk and the disk simultaneously eluted with 30 mL of acetone-ethyl acetate (1 1). The samples were concentrated and analyzed by GLC/MS. 

Currently, the use of water insoluble solvents such as ethyl acetate that do not require partition is preferred. Unfortunately, using ethyl acetate, lower recoveries are observed for the most polar pesticides. If the raw extract is saturated with sodium sulphate, satisfying recoveries are observed for methamidophos, acephate and omethoate (Holland and Malcolm, 1992). 

The QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) method allows the extraction of a wide variety of pesticides from polar and basic (methamidophos, acephate, omethoate, imazalil and thiabendazole) to less polar, such as pyrethrins. Samples of homogenized grape (lOg) are extracted with 10 mL of acetonitrile. After shaking for 1 min, 4 g of anhydrous MgS04 and 1 g of NaCl are added and mixed. One milliliter of the acetonitrile aliquot is transferred to a 1.5 mL vial... 

A small number of OPPs with similar properties (water solubility, Aiow) is missing in the methods described in literature or is incidentally taken into consideration, and includes acephate,methamidophos, omethoate, vamidothion, oxydemeton-methyl, and monocrotophos. These compounds are thermally labile or very polar. Moreover, acephate, methamidophos, monocrotophos, and omethoate are extremely water-soluble and not extractable using the more... 

The compounds trapped on the sorbent are extracted either by Soxhlet with a hexane/diethylether (1 1, v/v) mixture, or by ultrasonic extraction with an acetone/toluene (10 90, v/v) mixture for 30 min. The extraction method using PFE can also be used, according to EPA method 3545A. The extract is dried, hltered, and evaporated in order to obtain a hnal volume of 1 ml. Desorption efficiencies using acetone/toluene (10 90) of the analytes from the XAD-2 sorbent and the quartz microhber prehlters are equivalent to >90%, except for methamidophos (68%) and dichrotophos (86%). " ... 

Analyses are done by GC-FPD using a DB-1 capillary column (30 m X 0.32 mm X 0.25 /rm thick), as described in NIOSH 5600 for OPPs. This method enables determination of 19 OPPs with quantihcation limits in the liquid extract of between 0.07 and 1.0 mg/1 methamidophos, mevinphos, ethoprop, dicrotophos, monocrotophos, phorate, fonofos, terbufos, disulfoton, diazinon, parathion-methyl, ronnel, malathion, parathion-ethyl, chlorpyriphos, fenamiphos, ethion, sulprofos, and azinphos-methyl. 

Tomaszewaska and Hebert (2003) reported a method for the analysis of ( , -dimethyl hydrogen phosphorothioate (0,5-DMPT) in urine. 0,5-DMFT is a specific metabolite of methamidophos, The urine sample was extracted with a CIS column, and the sample was lyophilized at low temperature to prevent loss of highly volatile and thermally unstable metabolite (0,5-DMPT). The lyophilized residue was derivattzed using MTBSTFA and 1% terl-butyl-dimethylchlorosilane in acetonitrile. After filtration, the derivatized product was analyzed with GC/FPD (pulse FPD) in the phosphorus mode. The limit of detection for the method is reported as 0.004 ppm, with a mean recovery of 108%. 

Valverdegarcia, A., Fernandez-Alba, R Aguera, A., and Contreas, M. (1995). Extraction of methamidophos residue.s from vegetables with supercritical fluid carbon dioxide. 7. AOAC/nt. 78, 867-873. 

We should also mention that LiChrolut EN was successfully used for SPE pre-concentration of 90 pesticides from water—acetone extracts of fresh frxtits and vegetables with a subsequent pesticide analysis by GC-MS [285]. Only the most polar pesticides (methamidophos, acephate, and omethoate) could not be determined by this technique. Finally, a simple, fast, and sensitive method of determining a mycotoxine potuline (a metabolite of many moulds Penicillium and Aspergillus) in fruits and fruit juices was developed [286]. The method includes SPE pre-concentration of the toxin on Purosep 200 and its quantification by normal-phase FIPLC and provides recoveries over 90%, with LOD five times lower than the allowed tolerance Hmit, 50 Xg/kg. 

Tamarindus indica Tamarindus indica extract. See Tamarind (Tamarindus indica) extract Tamaron . See Methamidophos TAME. Seet-Amyl methyl ether T-Amine WR-500. See 2-Dimethylamino-2-methyl-1-propanol... 

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