Analytical methods for pesticides and plant growth regulators
PESTAB. Cycocel plant growth regulant, containing 2-chloroethyl trimethylammonium, chloride (chlormequat) produces varied responses in a wide variety of plant species. Generally, treated plants are compact and sturdy and have shortened internodes. Effects on flowering, fruit set, and tolerance to stress conditions have also been reported. Cycocel has a relatively low mammalian toxicity with single oral LD50 for rats of 670 mg/kg. The chemical is available at several concentrations in aqueous solution. The active ingredient in the technical material and in formulations is determined gravimetrically after precipitation with sodium tetraphenylboron. A colorimetric procedure calls for reacting the Cycocel with dipicrylamine and measuring the resulting chlormequat dipicrylamine salt at 415 nm. For residue analysis, extraction from the prepared sample is carried out with methanol, water-methanol, chloroform-methanol, or acid methanol solvent, the choice depending on the type of sample under study. The residue extract is then purified by cleanup procedures appropriate to sample type. Quantitation is achieved by spectrophotometric measurement of the yellow dipicrylamine-chlormequat complex at 415 nm. Sample handling and extraction procedures are discussed for apples, pears, potatoes, tomatoes, grapes, sugar beets, black currants, wine, cottonseeds, sugar cane, refined sugar, mature grains, wheat straw, green wheat foliage, muscle, fat, liver, kidney, and milk. The sensitivity of the method for a crop depends on the size of the control value. The apparent control for all crops tested ranged from a high of 0.27 ppm for wheat straw to a low of 0.006 ppm for milk.