Immunochemical detection of aminoglycosides in milk and kidney

In 1996, the European Union established provisional maximum residue limits (MRL) for gentamicin, neomycin, streptomycin and dihydrostreptomycin in milk and tissue (0.1-5 mg kg-1). For the detection of these four aminoglycosides, three enzyme linked immunosorbent assays (ELISA) for applications in milk and kidney were developed. The screening of defatted and diluted milk resulted in limits of determination (LDM) of < 0.01 mg l-1. Kidney samples were deproteinized with a trichloroacetic acid solution (3%) and after filtration and the addition of buffer, aliquots were used in the ELISA. The LDM of the four aminoglycosides in kidney were < 0.05 mg kg-1. The ELISA were found suitable for the semi-quantitative screening of milk and kidney for the presence of the four aminoglycosides far below the MRL levels. In randomly taken milk samples (n = 776) and in kidneys derived from healthy pigs (n = 124), the aminoglycoside residues found were far below their established MRL. In eight out of the 94 kidney samples obtained from diseased animals after emergency slaughter, aminoglycoside residues were above the MRL.