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Appendix: Screening studies of POPs in fish from the Paz watercourse Enzyme separation. Frozen samples of tissue were homogenised in special buffer (1,15% KCl solution in 0,01 M K+/Na+phosphate buffer) until homogeny solution. Samples were centrifuged by ultracentrifuge (12000 promptness/ min (10000 g)). Supernatant fractions were removed in flasks and stored on ice until incubation procedure. Incubation procedure. Supernatant fractions were added into flasks which contain: a) experiment flasks: aniline (5^mole/ 4 ml); glucose-6-phosphate (10^mole/ 4 ml); nicotinamide (50 ^mole/ 4 ml); magnesium chloride (25^mole/ 4 ml); b) control flasks: glucose-6-phosphate; nicotinamide; magnesium chloride (the same amounts of reagents). Flasks with incubation mixture and supernatant fraction have been incubated for 30 min at 37oC in thermostat. Activity measurement The reaction was stopped by 20% trichloracetic acid. Then, these samples were centrifuged by centrifuge (2500 - 3000 promptness/ min). After that supernatant fraction were removed in flasks. It was added 10% natrium carbonate, 2% phenol in 0,2 N NaOH solutions. Samples have been incubated for 30 min at 37oC in thermostat to allow colour to develop. Then samples were measured at 640 nm by spectrophotometer. Akvaplan-niva report APN 514-3365.02 54