Determination of creatinine in serum by high-performance liquid chromatography: a comparison of three ion-exchange methods.

Three ion-exchange high-performance liquid chromatographic methods for the determination of creatinine in serum have been compared. In method 1 a strong cation exchanger was used. In method 2 a reversed-phase column was given strong cation-exchange properties by the addition of N-methyloleoyl taurate to the mobile phase. In method 3 a weak cation exchanger was used. Elution was with a pH gradient in methods 1 and 2, and isocratic elution was used in method 3. The imprecision was similar for the three methods and varied between 0.9 and 2.5% as studied within-day and between 1.4 and 3.2% from day-to-day. The lowest coefficient of variation was obtained around the upper reference limit. Analytical recoveries were quantitative for the three methods. The method with N-methyloleoyl taurate showed no advantages over the conventional strong cation exchanger. With the weak cation exchanger no interferences were detected from compounds investigated, but with the strong cation exchanger a slight interference was obtained with uric acid. We prefer the weak cation-exchange method because of its simplicity, higher throughput and absence of interference from hitherto tested compounds.