Chemicals from Marine Fish Farms

Monitoring of chemicals from marine fish farms in Nordic environments - veterinary medicines, biocides and persistent organic contaminants

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Fish from Nordic fish farms have been criticized for containing "too high" concentrations of persistent organic pollutants (POPs) among others dioxin and PCB. These allegations have caused debate and may have a negative effect on the sale of products from Nordic fish farms in addition to giving a generally bad reputation that affects more or less all Nordic fish farms. It is generally agreed that the relatively high concentrations of POPs detected in fish from Nordic fish farms are caused by the high concentrations of POPs in the fish feed produced and used in the Nordic countries. Beside potential health effects caused by high POP contents in the fish fillet, the surrounding environment may be impacted as well, not only by excreted POPs but also by veterinary medicines used in the fish farms. In Nordic fish farms, veterinary medicines are mainly used therapeutically against different infectious diseases. The amount of veterinary medicines used varies from year to year and in some years, considerable amounts have been used. The major environmental concern in relation to the use of veterinary medicines is the potential occurrence of antibiotic resistance in the naturally occurring micro flora.



Method antibiotics

The sediment samples were frozen (-18°C) and stored until analysis if needed at -18°C. The sediment sample was mechanical homogenised. Before extraction each samples were spiked with surrogate internal standards resembling the compounds to be analysed. Chlortetracycline (mz = 479/444), ciprofloxacin (mz = 332/314) and erythromycin (mz = 360/342) was used as surrogate internal standard and 2 μg/L of each compound was spiked to each sample. Approx. 10 g sediment was dried at room temperature and extracted by pressurised liquid extraction (PLE), performed with an ASE 200 system equipped with a solvent selector, both from Dionex Sunnyvale, California, USA). The extraction procedure was optimised with regard to extraction solvent, pressure, temperature and number of cycles. Optimum extraction conditions were found to be 2,500 psig and 75°C and a three-step extraction procedure using two different extraction buffers - 0.2 mol L-1 aqueous citric acid buffer with pH adjusted to 4.7 with NaOH (two cycles) then 50% methanol:acetone (one cycle). 5 mL of both buffers was applied. The program for each cycle of the PLE-procedure was: 5 min heat (no pre-heat), 5 min static, 50% flush volume, and 60-s purge.


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