For the quantification of heavy metals, a calibration curve for each reference compound was constructed. The calibration curves for Pb and As were prepared in the range of 0.01–1.0 µg/g, for Hg 0.01–0.5 µg/g and for Cd 0.001–0.1 µg/g. All calibration curves showed good linear regression (r2 > 0.9996) within test ranges. Linearity was determined by calculating the regression plots by the least squares method and expressed as the correlation coefficient (r2). The regression equations and correlation coefficients (r2) of Pb was y = 0.06905 X + 0.00666 (r2 = 1.000), for Cd y = 0.00317X + 0.000027(r2 = 0.9996), for Hg y = 0.00329X + 0.00066(r2 = 0.9997) and for As it was y = 0.00098X + 0.00462 (r2 = 1.000).