Abstract
Ronstar EC (emulsifiable concentrate) was applied at rates of 4.48 or 8.96 kg ai/ha as a broadcast spray during the winter, in late spring, and in mid-summer to plots in commercial hop fields. Residues of oxadiazon, the active ingredient, and its 4 metabolites (methoxy, alcohol, acid, and phenol) were determined at harvest (1 month after last treatment) in green and dry hops and in hop foliage, by using gas-liquid chromatography after column chromatographic cleanup. Drying the cone increased residues of oxadiazon, but resulted in loss of the methoxy and alcohol metabolites. Oxadiazon residues in hop foliage ranged from 0.058 to 0.163 ppm. Measurable amounts of metabolites were also found in the foliage.
ABSTRACT
The 17-oxosteroids were estimated in the urine of 27 patients with Cushing's syndrome by gas-liquid chromatography (G. L. C.). The values of the various steroid fractions are compared with those of normal subjects, patients with thyrotoxicosis and obese subjects. The effect of the age of the patients on the diagnostic value of the invidual 17-oxosteroids and their ratios is discussed.
Techniques developed for use with gas-liquid chromatography for the examination of evidence collected at the scene of suspected arson fires and firebombings are discussed. Both solvent extraction and vapor phase examinations are employed. Internal standards are used for the identification of specific components in actual samples to allow confirmation of hydrocarbon type, e.g., gasoline and kerosene. Operating parameters and solvent selection criteria are included. Results obtained from known materials and residual hydrocarbons in actual samples are compared.
Abstract
A rapid and specific method is described for the determination of microamounts of methyl, propyl, and butyl p-hydroxybenzoic esters (parabens) in pharmaceuticals and cosmetics. The method involves the direct extraction of parabens into benzene or chloroform followed by derivatization with phosphorochloridate. The diethyl phosphate ester derivatives are cleaned up on a Florisil minicolumn and finally measured by gas-liquid chromatography on 5% OV-210 on Gas-Chrom Q. A flame photometric detector or a KCl thermionic detector may be used. The concentration response was linear up to 40 ng parabens. The reproducibility and margin of error were tested with fortified samples. This method may be applied to the estimation of other phenol derivatives.
Structure determination of methyl esters of unsaturated fatty acids by gas-liquid chromatography of the aldehydes formed by triphenyl phosphine reduction of the ozonides
