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The Irish finfish-farming section has increased from 20 tonnes in 1980 to 15,440 in 1997. The sales value of the 15,440 tonnes was £37.5 M where exports were worth approximately £30 M of this. This increasing intensity of fish farming has inevitably been paralleled by increases in disease, which has force the mariculturist to increase the use of chemicals. A major concern with the use of chemicals in mariculture is residues, which may remain in the fish tissue after harvesting and resulting in exposure to the consumer. Under Council Directive 96/23/EC Member States are required to monitor on a routine basis, veterinary drug residues in animals and animal products. The aim of this monitoring plan is to ascertain that residues, where present are below the maximum residue limit (MRL), and that no residues are present for analytes which do not have an established MRL. In consistence with this Directive, HPLC methods were optimised and validated according to the criteria set out in Commission Decision 93/256/EEC for the qualitative and quantitative analysis in farmed salmon tissue, of oxytetracycline (OTC), oxolinic acid (OA), sulphadiazine (SD), sulphamethoxazole (SMX) and trimethoprim (TMP). All methods were found to be linear from 50-150% of the respective MRLS, while recoveries were within the required 70-110% range for OTC, OA, SD and SMX. The precision obtained at 100ugky-1 was 2.1% RSD (n=5), 1.5% RSD (n=8), 9.7% RSD (=6) AND 8.4% RSD (N=6) for OA, OTC, SD and SMX respectively. The limit of detection (LOD) based on S/N=3, was found to be 10.0ugkg-1, 20.1ugkg-1, 1.0ugkg and 2.6ugkg-1 respectively, for OA, OTC,SD and SMX. Based on S/N=5, the limit of quantification (LOQ) in tissue samples was 11.3ugkg-1, 37.6ugkg-1, 1.6ugkg-1 and 8.2ugkg-1 for OA, OTC, SD and SMX respectively. In addition to the above chemical ivermectin and cypermethrin were examined using size exclusion chromatography (SEC) as a possible screening and clean-up technique. A SEC method capable of screen 16 samples in one overnight run, for residues of SD, SMX and OA in tissue, at 50ugkg-1 was developed. Additionally SEC was developed as a cleanup technique to increase sample throughput for ivermectin analysis.
Behan, Patrice. Chemical analysis of veterinary drug residues in salmon tissue. Dublin : Dublin Institute of Technology, 1999.