Analysis of urinary pseudouridine by micellar electrokinetic capillary chromatography.

We describe a capillary electrophoresis procedure, using uridine as an internal standard, for the analysis of urinary pseudouridine following solid-phase extraction. This method retains the advantages of existing chromatographic techniques but has superior resolving power and is technically less demanding. The standard curves were linear and reproducible with a detection limit of 60 fmol; chromatographic analysis was complete in under 10 min. Injection variability was < 5% and multiple independent analyses of the same urine sample for pseudouridine concentration gave coefficients of variation of < 10%. The mean (SD) urinary pseudouridine level in 18 healthy subjects was 16.1 (2.1) nmol/mumol creatinine. For a limited group of subjects where samples were taken more frequently, intra-individual variation averaged 27.5% reflecting variable excretion.