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The fate of ivermectin (IVM) residues was studied throughout the processing of daily bulk milk from 30 ewes (taken up to 33 d following subcutaneous administration of 0 . 2 mg IVM/kg b.w.) in the following milk products: yoghurt made from raw and pasteurized milk; cheese after pressing ; 30-and 60-day ripened cheese; and whey, secondary whey and whey proteins obtained after cheese-making (albumin cheese). The concentration of the H 2 B 1a component of IVM was analysed in these dairy products using an HPLC method with fluorescence detection. The mean recovery of the method was, depending on the matrix, between 87 and 100%. Limits of detection in the order of only 0 . 1 mg H 2 B 1a /kg of product were achieved. Maximum concentrations of IVM were detected mostly at 2 d after drug administration to the ewes. The highest concentration of IVM was found on day 2 in 60-day ripened cheese (96 mg H 2 B 1a /kg cheese). Secondary whey was the matrix with the lowest concentration of IVM (< 0 . 6 mg H 2 B 1a / kg). Residue levels fell below the limits of detection between day 5 (for secondary whey) and day 25 (for all cheese samples). In the matrices investigated, linear correlations between daily concentrations of IVM, milk fat and solid content were evident. During yoghurt production, fermentation and thermal stability of IVM was observed. During cheese production, approximately 35 % of the IVM, present in the raw (bulk) milk samples, was lost. From the results it was concluded that the processing of ewes' milk did not eliminate the drug residues under investigation. The consequences of IVM in the human diet were discussed. Milk from treated animals should be excluded from production of fat products like cheese for longer after treatment with IVM than for lower fat products.

To prevent the illegal use of chloramphenicol (CAP), regulatory control of its residues in food of animal origin is essential. In Slovenia, the monitoring of CAP residues for statutory purpose started in 1991. The results of a 10-year period are presented. CAP residues were determined by capillary gas chromatography (GC) with electron capture detection (ECD) using meta-CAP as an internal standard (ISTD). Before chromatographic determination, analytes were derivatized by silylation. Overall, CAP recovery, adjusted for ISTD, was for bovine muscle tissue and raw cow's milk (in the region of 2-10 microg kg(-1)) 89 and 102%, respectively, and for whole eggs, 87% (in the region of 1-10 microg kg(-1)). The use of meta-CAP improved significantly the precision of the method. The detection limit for CAP was 1 microg kg(-1), which was sufficiently sensitive for routine use. A total of 1308 random samples of Slovenian origin were analysed from 1991 to 2000, covering all parts of the country. CAP was found only in one milk sample in 1997 at a concentration of 4.6 microg kg(-1).

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