Carbohydrate Interference and Its Correction in Pectin Analysis Using the m‐Hydroxydiphenyl Method

ABSTRACT The colorimetric assay using m‐hydroxydiphenyl for analysis of uronic acids is used to measure pectins in plant materials because of its relative insensitivity to the presence of nonuronide carbohydrates. Still, large amounts of these carbohydrates are often associated with pectins and it has been found that levels may be present which can interfere with this analysis. Concentrations of 5 nonuronide carbohydrates commonly associated with pectins were used to simulate and study this interference and recommendations are made to increase the accuracy of this method when high levels of these substances are present. The corrections suggested are appropriate for final sample dilutions that contain more than 200 μg/ml of nonuronide carbohydrate material.