Quantitative analysis of limonin in grapefruit juice using an enzyme-linked immunoassay: interlaboratory study.

Eleven laboratories participated in an interlaboratory study of an enzyme-linked immunoassay for limonin in grapefruit juice. Participating laboratories received training and practice samples until familiar with the procedure. Laboratories then received 8 sample pairs of grapefruit juice as blind duplicates. Samples were refrigerated and analyzed within 4 days of receipt. Results from 1 laboratory and 6 individual samples were excluded from the statistical analysis. Method performance was measured by the one-way component of variance analysis. Repeatability relative standard deviations (RSDr) ranged from 7.0 to 15.6%. Reproducibility relative standard deviations (RSDR) ranged from 12.9 to 29.4%.