A rapid gas-liquid chromatography method for the determination of lactulose and mannitol in urine: clinical application in studies of intestinal permeability.

OBJECTIVE: The purpose of this study was to develop a gas-liquid chromatography method for the determination of the urinary excretion of two nonmetabolizable sugars (lactulose and mannitol) to estimate the intestinal permeability. METHODS: Two internal standards (alpha-methyl-D-glucopyranosyde and sucrose) were added to the urine samples prior to derivatization with the aid of a solution of pyridine, [N, O-bis (trimethylsilyl)]-acetamide and chlorotrimethylsilan. Sample preparation was simpler and faster than in other previous methods and the four sugars were resolved within 27 min. RESULTS: The inclusion of internal standards reduced the coefficient of variation from 9.44% to 4.78%. The method provided better sensitivity, range of analysis, and linearity than a previously published HPLC method reducing variances in the recovery of lactulose and mannitol added to urine. The clinical application of this method was tested in preterm infants fed human milk or cow's milk based formula and in breast fed term infants. CONCLUSION: The method described here for the determination of urinary lactulose and mannitol is more rapid, simpler, and more accurate than other previously published methods.

Determination of pantothenic acid in infant milk formulas by high performance liquid chromatography.

A reverse-phase liquid chromatographic method was adapted for the assay of pantothenic acid in infant milk formulas. Sample preparation consisted of deproteination with acetic acid and sodium acetate solutions, followed by centrifugation and filtration. The chromatographic system included a C-18 column and a mobile phase consisting of a sodium phosphate buffer and acetonitrile (97:3, vol/vol). The column effluent was monitored by UV detection at 197 nm. The system was linear from 50 to 800 ng. The recoveries of pantothenic acid from augmented samples ranged from 89 to 98%, and the coefficients of variation ranged from 1.17 to 3.20%. The results obtained with the HPLC and a microbiological method were highly correlated for starting infant formula, follow-up infant formula, and formula for infants of low birth weight from four different manufactures. All formulas analyzed contained pantothenic acid at concentrations higher than those declared on their nutritional labels and were in compliance with international recommendations.