The concentration of promacyl declined in cattle dipping fluid, and laboratory experiments were undertaken to establish the cause of breakdown and devise ways of overcoming it. Promacyl declined more quickly in dipping fluid at 15–26°C than at 35°C, with concentrations of the metabolite promecarb increasing as the temperature decreased. Promacyl did not break down in distilled water, other than by hydrolysis at 50°C. The degradation rate of promacyl in dipping fluid increased with the addition of ammonium nitrate and by saturation with air, but it remained unchanged with the addition of copper sulphate, magnesium chloride, urea and chlorhexidine diacetate. When samples which were already breaking down were recharged with promacyl the rate of depletion remained unaltered. Samples inoculated with dip solution already showing promacyl breakdown had increased rates of promacyl degradation (P<0.05). Calcium hypochlorite prevented promacyl breakdown, but only for a short time. Breakdown could be prevented by the addition of the bactericides 2,4‐benzisothiazolin‐2‐one or dichlorophen, or by reducing the pH to <5.0. Data indicated that breakdown of promacyl was due to microbial action.
A simple and reliable method has been developed for determining chlordimeform. A preliminary cleanup converts chlordimeform to its hydrochloride and removes ultraviolet-absorbing impurities. The aqueous acid phase containing chlordimeform. HCl is diluted and passed through a silica gel column. The column effluent is used as the reference solution and a portion not eluted through silica gel is used as the sample solution in the spectrophotometer. The absorbance at 240 nm is measured, and chlordimeform concentration is determined from the calibration graph. The method applied to solutions of acaricides gives good results in the range of 0.02–0.06% w/v chlordimeform; higher concentrations may be determined by appropriate dilutions.
Infrared (IR) and gas chromatographic methods have been developed for determining the acaricide amitraz (N-(2,4-dimethylphenyl)-N - [[(2,4- dimethylphenyl)imino]methyl] - N - methanimidamide) in cattle dip solutions. Extraction with petroleum ether, followed by IR and gas-liquid chromatography (GLC) gave coefficients of variation of 3.4 and 3.6%, respectively, for 0.010-0.035% amitraz. Dilution of the dip sample with acetone and determination by GLC gave a coefficient of variation of 3.6% in the same range. Recovery of amitraz from fortified dip samples was 97–100%.
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