Determination of uronic acid in uronides by application of a new microgram-scale isotope dilution method for carbon dioxide.

Conditions studied earlier by Tracey [(1948) Biochem. J.43, 185] are used for acid decarboxylation in sealed tubes of uronide samples supplemented with 6-¹⁴C-labeled uronic acid. The specific activity of the CO₂ evolved is measured as the ratio of radioactivity to area of the CO₂ peak obtained in a gas chromatogram. By appropriate standardization, samples containing some 60 nmol of uronic acid can be analyzed with reproducibility and apparent accuracy of about ±2% (mean deviation). The techniques developed for uronic acid analysis should apply with minor modification to any problem requiring accurate measurement of CO₂ in small amounts.