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Colorimetric Determination of DDT in Milk and fatty Materials

, : Colorimetric Determination of DDT in Milk and fatty Materials. Industr. Engng Chem. Anal. Edn, Easton, Pa., 1-53

The analysis of milk for the presence of DDT is complicated by the large amounts of fatty matter that accompany the DDT when it is extracted in organic solvents, and in order to detect very small amounts of DDT, it is necessary to remove extraneous material and concentrate the DDT. In this paper, the authors describe a method by which concentrated sulfuric acid (in which fats are soluble and DDT is not) was used to eliminate all but a small residue of fatty material. The analysis was completed by nitration and colorimetric analysis as already described . The treatment may eliminate other interfering substances if they are soluble in sulfuric acid or easily sulphonatable. The method may be adapted for the analysis of biological tissues after they have been treated with sodium sulfate and extracted, the residue after evaporation of the solvent being dissolved in chloroform and treated with sulfuric acid as described. Bis(parachlorphenyl)-acetic acid is removed by the sulphuric-acid treatment and does not interfere in the analysis for DDT; if it is to be determined it should first be separated from the sample by means of its acidic properties. The procedure was tested for the detection of technical DDT and its dehydro-chlorinated derivative, l, l-dichlor-2, 2-bis(parachlorphenyl)ethylene, with 100 and 97-99 per cent. recovery, respectively. Since the derivative is not removed by the sulphuric-acid treatment, its presence to any appreciable extent in a sample may be detected by its effect on the absorption spectrum of the developed colour; it gives a red colour in the test, whereas DDT gives a blue one. It is expected that o, p'DDT and its dehydrochlorinated derivative would also be unaffected by the sulphuric-acid treatment. In tests of milk containing known amounts of technical DDT, concentrations as low as 1 part per million gave an easily discernible characteristic blue colour; milk with no added DDT gave only a yellow colour. Analysis of milk, butter, fat and lean meat samples from cows that had received DDT in their food all showed the characteristic colour.


DOI: 10.1021/ac60001a014

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