An improvement of the method commonly used for the determination of ivermectin is proposed. An automatic system is used for the solid-phase extraction column purification stage in order to provide more efficient and fast sample preparation, prior to separation and quantification by HPLC. Some tests were performed to obtain recovery and repeatability data. The mean recovery for spiked samples (five replicates twice at three concentration levels) was more than 90% in the concentration range 7.5-30 ng g-1. The tests for accuracy (five replicates at three concentration levels) gave a standard error of -2.0% at the highest and -19.2% at the lowest concentration. Concerning repeatability data (five replicates twice at three concentration levels), in the concentration range 7.5-30 ng g-1 the RSD varied from 9.29 to 2.15%. The described method was used in a survey on the presence of ivermectin in food-producing animals in two regions of southern Italy; no positives out of 250 liver samples were found.

The possibility of using automated equipment for solid phase extraction of isoniazid from milk has been investigated. This equipment provides two noteworthy advantages: it shortens the time of analysis and avoids SPE column plugging, stabilizing flow rates. After setting the correct programme on software controlling the equipment, some validation parameters have been determined to obtain recovery and repeatability data. The mean recovery for spiked samples resulted in the range 75-95%, the standard error ranged from -5 to -20% while the RSD varied from 2 to 22%. Therefore the method can be considered reliable and fast.