Determination of chromium in urine samples by complexation–supercritical fluid extraction and liquid or gas chromatography

A method was developed for the determination of chromium as the Cr(acac)3 complex in urine using SFE and chromatography. Quantitative extractions were achieved when the experiments were carried out under 3000 p.s.i. of pressure, at a temperature of 120 °C, with 2.0 ml of methanol, 30 min of static extraction and 5 min of dynamic extraction. The chromium was quantified by GC–FID detection. The calibration graph of Cr(acac)3 solutions was linear between 0.50 and 43.0 μg ml−1 of chromium (DL 0.18 μg ml−1, R=0.9994). The same extracts were quantified by HPLC-340 nm detection. The calibration curve of the Cr(acac)3 solutions was linear over a range of 0.013 to 60.0 μg ml−1 (DL 0.02 μg ml−1, R=0.9999). This method was applied to urine samples from 60 diabetic patients and 21 healthy volunteers. Chromium concentration ranges were 2.5–29.5 μg l−1 for the diabetics and 5.9–12.3 μg l−1 for the normal subjects.