ONLINE CHROMATOGRAPHIC-SEPARATION OF CR(I II) CR(VI) AND PRECONCENTRATION OF CR(III) USING KH PHTHALATE AND THEIR DETERMINATION IN VARIOUS SAMPLES BY FLAME ATOMIC-ABSORPTION SPECTROMETRY/

A method has been developed for on-line liquid chromatographic separat ion of Cr(III) on a reverse phase C18 column in the presence of KH pht halate. KH phthalate, newly introduced into the chromatographic techni que by us, is so much selective for Cr(IU) in contrast to many complex -forming agents mentioned in the literature that in its presence pract ically no ion is sorbed on the C18 column except Cr(III). This is why practically no interference caused by the matrix was observed during t he detection of Cr(III). Cr(III) sorbed on the column was eluted into the flame of an atomic absorption spectrometer using a mixture of meth anol and water (80-20 %v/v). With 100 mu 1 of sample solution, the det ection limits (3 sigma) were found to be 0.024 ng/l and 0.075 ng/l for the separation of Cr(III) and Cr(VI) with FAAS detection and the time needed for separation was less than 60 s. In the case of the preconce ntration of Cr(III) from 5 mi sample solution the detection limit (3 s igma) was 0.73 ng/ml, the accuracy of the measurement was 3.8 RSD% for the preconcentration of 20 ng/ml Cr(III). The sensitivity of the meth od permitted determination of Cr(III) and Cr(VI) in surface waters and various samples of natural origin below ng/ml concentrations. After r eduction of Cr(VI) to Cr(III) with ascorbic acid and its preconcentrat ion we were able to determine the total chromium content of various sa mples.