H. Anson Moye

Dynamic Fluorogenic Labelling of Pesticides for High Performance Liquid Chromatography: Detection of N-Methylcarbamates with o-Phthalaldehyde

Abstract A post-column fluorogenic labelling reaction between o-phthalaldehyde (OPA) and methylamine, a hydrolysis product of the N-methylcarbamate and carbamoyl Florida Agricultural Experiment Station Journal Series No. 654. oxime pesticides, is described which provides a highly sensitive and selective detection mechanism for the high performance liquid chromatography of these pesticides. Separations were achieved by reverse phase, with solvent programming of water-dioxane mixtures. As little as 1 ng of the pesticides could be detected, with the last eluting carbamate, mesurol, requiring from 22 to 54 minutes, depending upon column and program contour. Chromatography was performed with a modular instrument and with a commercially available fully cabineted instrument.

A Versatile Fluorogenic Labelling Reagent for Primary and Secondary Amines: 9-Fluorenylmethyl Chloroformate

Abstract Both primary and secondary amines may be readily labelled with the 9-fluorenylmethoxy carbonyl group by the reaction with 9-fluorenylmethyl chloroformate (FMOCCI). The reaction proceeds rapidly under alkaline aqueous conditions, allows for simple elimination of excess reagent by partitioning, improves chroatographic resolution of amino acid-like compounds by anion exchange liquid chromatography and introduces a fluorophore with a large quantum yield which is essentially unaffected by solvent-solute interactions.

Postcolumn formation of fluorophores from nitrogenous pesticides by UV photolysis

The ultraviolet (UV) photolysis of several classes of nitrogenous pesticides was examined with a view to photo-induced fluorescence detection in flow-injection analysis (FIA) and liquid chromatography. The solvents evaluated as typical reversed-phase mobile phases included water, methanol, and 1:1 mixtures of methanol/water and acetonitrile/water, and methanol/acetonitrilelwater mixtures. Acetone, acetophenone, the surfactant triton X-100, and the photocatalyst titanium dioxide were assessed as photosensitizers to enhance the UV photolysis and fluorescence responses. FIA and liquid chromatographic separations of several pesticides were followed by post-column UV photolysis for the fluorescence detection. Ultraviolet photolysis produces some fluorescent products. The type of photolytic solvent seems to play a significant role. The presence of photosensitizers also affects the fluorescence response of some pesticides. The photochemical transformation products of some of the pesticides are suggested. Analytical figures of merit were evaluated for determination of several pesticides in ground water. The post-column UV photolysis approach for fluorescence detection in liquid chromatography was assessed for several nitrogenous pesticides in ground water samples at ng/g concentrations.

A Fluorometric Enzyme Inhibition Detector for Carbamate Pesticide Analysis by High Speed Liquid Chromatography

Abstract A fluorometric enzyme inhibition detector has been developed for the detection of carbamate pesticides after separation using high speed liquid chromatography. Housefly head cholinesterase was found to have the greatest sensitivity toward the carbamates, together with horse plasma and bovine erythrocyte cholinesterases. The substrate N-methyl indoxyl acetate is used for monitoring of enzyme activity.

A rapid gas chromatographie procedure for the analysis of oxalate ion in urine

A specific, precise, rapid and sensitive method for the analysis of oxalic acid in urine is described. This microanalytical procedure can detect concentrations of urinary oxalic acid as low as 4 mg/l with a relative standard deviation of replicates of less than 5% (24-h urine collections). 10% BCl3:2-chloroethanol is used to derivatize 0.1 ml of urine after evaporation to dryness or lyophilization. The bis-2-chloroethyl ester of oxalic acid formed is extracted into ethyl acetate/isopropyl ether (1:3, v/v) and is detected by electron capture gas chromatography at the 50 pg level. The total analysis time for 35 samples in 8 h per GC column. A series of determinations of urinary oxalic acid in 21 kidney stone-forming patients resulted in values ranging from 10.6 to 42.0 mg/24 h with a mean recovery of added oxalic acid of 98.2% (range 84.0-111.3%).