Phloroglucinol-based colorimetry of xylose in plasma and urine compared with a specific gas-chromatographic procedure

A commonly used method for xylose has several disadvantages, including use of thiourea which is a carcinogen. We examined an alternative colorimetric method in which phloroglucinol (1,3,5-trihydroxybenzene) is the chromogenic reagent and compared it with a specific gas-chromatographic procedure for use with blood and urine samples from subjects receiving xylose either orally or intravenously. Results by these methods correlated well, both for plasma (r² = 0.97) and urine (r² = 0.99). At concentrations >50 mg/L for plasma (slope = 1.005) and >350 mg/L for urine (slope = 0.99) the slopes were not significantly different from 1 or the intercepts different from zero. We recommend this method as a safer and more expedient alternative to the method currently used.