Abstract: In ICP-AES analysis the slopes of the calibration curves obtained by weighted linear reg-ression are slightly larger than those obtained by unweighted method for most elements inves-tigated, and use of weighted linear regression minimizes curvature of calibration curves. Alt-hough the regression coefficients of weighted regression equations are smaller than those ofunweighted equations, the weighted calibration curves are better than the unweighted ones.It indicates that the residual standard deviations and intercepts should be considered when thecalibration curves by weighted and unweighted linear regressions are compared. Intercepts ofcalibration curves containing zero standard are nearer to origin than those of nonzero-contai-ning standard series. Use of zero-containing calibration curves improves the accuracy of ana-lysis when the concentration of the elements are low.

Key words: inductively coupled plasma, calibration, weighting, linear regression