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A procedure is described for the detection of five sulfonamides in muscle and kidney of swine, chicken and cattle. The method consists of an extraction with dichloromethane, cleaning up of the extracts on a Sep-Pak silica disposable column, and analysis by thin-layer chromatography on a silica plate with chloroform/n-butanol as an eluent. The sulfonamides were visualized by spraying with a fluorescamine solution. In spiked tissues the presence of the sulfonamides at concentrations of 0.05 mg/kg and higher is easily demonstrated. Direct detection of sulfonamides in tissue extracts of kidneys and lean tissues under the same chromatographic conditions is also described. This method, in which the Sep-Pak cleaning up procedure is omitted, has been successfully applied to spiked swine and cattle kidneys, chicken liver and breast tissue.

A comparison is made between lysinoalanine (LAL) determinations both with an automatic amino acid analyzer (AAA) and with thin layer chromatography-densitometry (TLC) in different types of food and food ingredients, taken from the Dutch market. Generally there is a reasonable agreement between the LAL content obtained by both methods. However, some results indicate that a single technique is not always conclusive about the real identity of the ninhydrin-positive compound at the same position as LAL on the chromatogram. By TLC for instance, in yeast a content of about 800 mg of LAL/kg in protein is found, but according to the AAA method no LAL is present. In heated milk and milk products the LAL content determined by the TLC method is also higher than that found by the AAA method. This is caused by a preceding unknown ninhydrin-positive compound in TLC, occurring in all heated milk products and practically coinciding with LAL. In the AAA technique similar interferences of unknown ninhydrin-positive compounds could be avoided by choosing a suitable elution temperature; however, application of this temperature modification to foaming agents gave no satisfactory results.

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