RAPID GAS-CHROMATOGRAPHIC ASSAY OF LACTULOSE AND MANNITOL FOR ESTIMATING INTESTINAL PERMEABILITY

We developed a gas-chromatographic method to determine urinary mannito l and lactulose. The procedure for purification of urine by a resin wa s optimized for purification of analytes and high recovery; the aliquo t of resin chosen (500 mg) was kept in contact with the urine for 1 mi n. The recoveries of mannitol and lactulose were >85% at concentration s that include both normal and pathological values. Sugars were conver ted to oximes before the silylation step to avoid multiple peaks for t he anomeric forms. The calibration was linear over the range 0.1-1 mu g of sugar injected. Analytical recovery of the sugars ranged from 90% to 95.3% for mannitol and from 90.4% to 95.8% for lactulose. The mean within-day imprecision (CV) was 6.2% for mannitol and 4.7% for lactul ose; the between-day CV was 6.7% for mannitol and 5.1% for lactulose. A lactulose/mannitol ratio of 0.035 completely differentiated 28 norma l children and 28 children with active gluten-sensitive enteropathy, w hose mean ratios were 0.022 (SD 0.007) and 0.084 (SD 0.054), respectiv ely.