Uso del ácido sulfúrico en las determinaciones de plaguicidas organoclorados: I. Calidad químico-analítica de la precipitación de grasa por el ácido sulfúrico concentrado en muestras con alto contenido de lípidos

many papers describe analytical methods for organochlorine pesticide residue determinations in environmental samples. gas chromatography with electron capture detection requires highly purified extracts, ie. with an efficient clean-up step. to achieve this purpose, different clean-up methods are employed. most organochlorine pesticides are resistant to sulfuric acid, a property used for the destruction of endogenous compounds and fat precipitation. both fat extract treatments that use sulfuric acid as a clean-up medium, and quantities of nonvolatile residues determined after the clean-up step, are described. samples of adipose tissues (human, bovine, pig and chicken), butter and margarine were studied. the analytical method allows good (higher than 90 %) organo-chlorine pesticide recovery and an extract ready for gas chromatography with a minimal amount of nonvolatile compounds (0.8 to 2.2 mg that constitutes 0.22 to 1.87 % of the analyzed sample) determined gravimetrically. the low quantity of nonvolatile residues present in cleaned-up extracts allows multiple sample gas chromatographies without diminishing column resolution and electron capture detector response. the analytical quality study (10 repetitions for each fat sample) shows a 4.8 to 12.5 % coefficient of variation, indicating an appropriate method for fat sample monitoring studies.