STEPWISE DETERMINATION OF ALUMINUM AND CHROMIUM IN WATER AND BIOMEDICAL SAMPLES BY HPLC-UV, BASED ON THEIR DIFFERENT KINETICS WITH 8-HYDROXYQUINOLINE

ABSTRACT

A reversed-phase high performance liquid chromatographic (RP-HPLC) method, with spectrophotometric detection for determination of trace amounts of aluminum (Al) and chromium (Cr) in water and biomedical samples, has been developed using 8-hydroxylquinoline (8-HQ) as a precolumn reagent based on the differential chelation kinetics of these two ions. The analysis is achieved with a Spherisorb ODS 2 column, with an eluent consisting of 4.0 mmol L⁻¹ acetate buffer (pH 6.0) and 3.2 mmol L⁻¹ 8-HQ in 57% (v/v) methanol–water, at a flow rate of 1.0 mL min⁻¹. On the basis of the fact that the peaks of Al and Cr chelates appear at the same retention time, the procedure is divided into two stages:

1.	(1) determining Al concentration by peak area after precolumn chelation at ambient temperature;
2.	(2) measuring total peak area of Al and Cr after reaction at 90°C for 30 min, and the concentration of Cr being determined by the difference between Al peak area and the total area.

The response of both Al and Cr is linear from 0.002 to 0.6 µg mL⁻¹ with a detection limit of 0.001 µg mL⁻¹. The analysis is free from interference from common ions except 10-fold excess of cobalt. The values obtained by this method are in good agreement with those of ICP-AES or GF-AAS. The proposed method has been successfully applied to the direct determination of Al and indirect determination of Cr in natural water, serum, synthetic renal dialysate, parenteral solution, and pharmaceutical-grade organic acid with the recoveries of over 90%.

ACKNOWLEDGMENTS

This project is supported by the National Natural Science Foundation of China (No. 29777013) and the Analysis and Test Fund of CMANU. The authors thank Waters Collaborating Model Laboratory in CMANU for technical support.