Determination of creatinine in serum and urine by a rapid liquid-chromatographic method

We describe an HPLC ion-pair procedure for rapid and specific evaluation of creatinine in serum and urine. We used a 15 cm X 4.6 mm ODS column with a 50/50 (by vol) mixture of sodium decanesulfonic acid (10 mmol/L, pH 3.2) and methanol and measured absorbance at 236 nm. Serum (100 microL) or 30-fold-diluted urine (100 microL) was added to 400 microL of acetone. After centrifugation, the supernates (300 microL) were dried, reconstituted with the mobile phase, and injected into the HPLC. Assay precision was tested for concentrations of 10, 29, and 130 mg/L and yielded, respectively, 3.1%, 2.1%, and 1.1% for within-day CV and 2.8%, 2.1%, and 2.2% for total CV. Analytical recovery was 102 (+/- 6.7%). Linearity was demonstrated in the 0-200 mg/L range for serum and 0-3.5 g/L range for urine (r greater than or equal to 0.999). The detection limit for creatinine (signal-to-noise ratio = 3) was 0.5 mg/L. We used cimetidine for internal standardization. Correlation was good between this procedure and the Jaffé kinetic, the enzymatic (creatinine amidohydrolase), and the Fuller's earth alkaline picrate methods.