Determination of the C-13 contents of organic acids and sugars in fruit juices: an inter-comparison study

The determination of the repeatability (r) and reproducibility (R) of the ( C-13/C-12) measurement in sugars and organic acids contained in different f ruit juices was conducted on an international basis involving 17 laboratori es. The mean values of r parts per thousand (R parts per thousand) for acid s and sugars are, respectively, equal to 0.58 (1.75) and 0.34 (0.71) and th e relatively large values observed for R of acid determinations are related to the preparation step. However, the least significant difference compute d for several pairs of natural and spiked juices indicate that the C-13 met hod can be applied for detecting fruit juice adulteration. (C) 1999 Elsevie r Science B.V. All rights reserved.