PRECISION AND LINEARITY OF INORGANIC ANALYSES BY ION CHROMATOGRAPHY

The repeatability of the measurements of peak areas for calibration so lutions and the precision of anion and cation determinations (3-600 mu M) in freshwater are discussed on the basis of 2 years of measurement s on calibration solutions and stabilized internal standards. Anion me asurements show higher repeatability of the measurements of peak areas for calibration solutions (R.S.D. 2-5%) and precision (R.S.D. 2-8%) t han those of cations (R.S.D. 2-10% and 2-15%, respectively). Results f or the calibration technique show that multi-point (6-8 concentrations ), quadratic or cubic regressions permit a correct quantification over a wide range (1.5-2 orders of magnitude) of concentrations. Thanks to the repeatability of the measurements of peak areas for calibration s olutions, only two calibrations, at the beginning and end of a batch o f 20-30 samples, are adequate. These conditions give better results th an calibrations performed with 2-3 points and repeated every 8-10 samp les.