Liquid-chromatographic method for estimating urinary sugars: applicability to studies of intestinal permeability

Sugars of exogenous origin excreted in the urine can be rapidly quantified by "high-pressure" liquid chromatography. A simple extraction with an ion-exchange resin is used to prepare the sample for analysis. Aliquots (20 microL) are chromatographed on a cation-exchange column at 85 degrees C, with water as the mobile phase. Sugars are detected with a refractive index detector. Lactulose, rhamnose, and mannitol all give discrete peaks and a linear response up to 5 g/L, with analytical recoveries from urine of 80, 62, and 80%, respectively. Precision is good, the CVs for lactulose, rhamnose, and mannitol being 2.9, 4.0, and 5.6%, respectively. The only endogenous compound consistently present in the chromatograms is urea, which does not interfere. However, glucosuria, if present, could interfere with the lactulose estimation. This method may be a simple, labor-saving means of quantifying urinary sugars in the clinical laboratory.