US EPA

4002043 

Journal Article 

Determination of phosphoric acid, dimethyl p-methylthiophenyl ester in cottonseed 

Westlake, WE; Lazzaro, CA; Gunther, FA 

1970 

Yes 

Bulletin of Environmental Contamination and Toxicology
ISSN: 0007-4861
EISSN: 1432-0800 

HAPAB/70/02077 

5 

1 

10-12 

English 

24185716 

10.1007/BF01545116 

WOS:A1970G093600003 

HAPAB A sensitive method has been developed for determining minute amounts of GC-6506 ( phosphoric acid, dimethyl p-methylthiophenyl ester ) in cottonseed. Seed samples were frozen and then ground in a Wiley mill. The ground product ( 25.0 g ) was transferred to an Omni-Mixer container and blended with 150 ml of hexane for 5 min at 85 v, filtered through 7-cm Whatman No. 2 filter paper in a Buchner funnel. This procedure was repeated twice using 100-ml protions of hexane. The container was rinsed with 100 ml of hexane. The extracts ( about 550 ml ) were combined and kept in tightly sealed bottles and later placed in a rotary vacuum evaporator at 60 C to remove the hexane. The oil was transferred to a separatory funnel to which 50 ml of a 65:35 acetonitrile-water mixture and a few grains of sodium chloride ( to aid phase separation ) were added. The mixture was shaken for 1 min. After several separations were completed, the combined lower phase ( acetonitrile-water ) was introduced in a 500-ml separatory funnel and mixed with 100 ml of 2% sodium chloride solution and 40 ml of methylene chloride and shaken. The methylene chloride was drawn off and the aqueous acetonitrile solution was extracted two more times with 20-ml portions of methylene chloride. The separated methylene chloride was treated with 10 g of anhydrous sodium sulfate. The funnel and the anhydrous sodium sulfate were washed with 25 ml of methylene chloride. The combined extracts were evaporated to near dryness, dried with an air jet and dissolved in 10 ml of a 3:1 hexane-ether mixture. The cleanup operation made use of a Shell-type chromatographic column, Florisil, hexane, hexane-ether mixture and acetone. The acetone eluate which contained the pesticide was assayed with gas chromatographs equipped with a flame photometric or a thermionic detector and 18-in stainless steel columns with Carbowax 20 M on Gas Chrom Q ( 60/80 mesh ). The Carbowax columns permitted the separation of GC-6506 from all other pesticides registered for use on cotton except malathion but the analytical procedures can be supplemented for malathion-associated assays by using a gas chromatograph equipped with a 6-ft stainless steel column, with 7% QF-1 and 9% OV-17 ( mixed 1:1 ) coated on Gas Chrom Q ( 80/100 mesh ). The parameters used for the gas chromatographic procedure are detailed. The procedures described permitted recoveries of 100% ( plus / minus 5% ) for the GC-6506 added to extracts from control samples at levels of 1.0, 0.1 and 0.05 ppm. ANALYSIS 70/11/00, 544 1970