EXPANSION OF DYNAMIC-RANGE OF FLAME ATOMIC-ABSORPTION SPECTROMETRY BYAN EFFICIENT FLOW-INJECTION DILUTION SYSTEM BASED ON DISPERSION OF MICROLITER-VOLUME SAMPLES

An automatic on-line flow injection dilution system for flame atomic a bsorption spectrometry was developed based on the injection of low- an d submicroliter sample volumes and their dispersion in a mixing coil. Precise control of volumes was possible using computer-controlled step per motor-driven peristaltic pumps and small-bore Neoprene pump tubes. A more than 1000-fold dilution with a precision of better than 2% (rs d) (n = 15) was achieved using a sample volume of 0.7 muL and a mixing coil of 160-cm length and 1.3-mm i.d. Precision improved to 0.5-0.6% (rsd) when sampling times longer than 2 s were used. Sampling frequenc ies of 60-100/h, even for the highest dilutions, made the system highl y compatible with routine application. A concentration of 7.2% Mg in a n aluminum alloy was determined directly in the solution of 1 g of all oy in 100 mL.