Briefly, 100-200 mg of thawed muscle/fin-clip was loaded in nickel boat and analysed. No pre-treatment of muscle samples was made, and fin-clips were only washed with deionized water prior to analysis. Final concentration of the sample was calculated as a mean of two independent measurements and it is expressed as wet weight (ww) concentration. For calibration of the instrument, MERCK calibration solutioneCertiPUR was used.