Variability Associated with Analytical Methods Used To Measure Aflatoxin in Agricultural Commodities

Abstract

Abstract A total of 1019 analytical precision estimates obtained from method-performance (collaborative) studies for mycotoxins published through 1991 were sortedby type of variance measurement, type of analytical method, and type of agricultural commodity. Precision estimates for total aflatoxin were sorted into 2 precision measurements (among-labo ratories and with in-laboratory), 3 analytical methods (thin-layer chromatography [TLC], liquid chromatography [LC], and enzyme-linked immunosorbent assay [ELISA]), and 11 agricultural commodities. Sufficient data existed to study the analytical variability (precision) associated with 36 sorted combinations (of a possible 66). In all but one combination (within-laboratory, barley, and TLC), the variance (V) was a function of totalafla- toxin concentration (C). A power function of the form V = aCb, where a and b are constants, describes the relationship between variance and aflatoxin concentration. The coefficients a and b were determined from regression analysis. When results were pooled across all agricultural commodities, LC had the lowest analytical variability while ELISA had the highest. For a given method, among-labora tories variability was approximately double the with in-laboratory variability. These analytical variability estimates can be coupled with previously determined variability estimates of sampling and sample preparation to determine the performance associated with specific test procedures used to inspect agricultural commodities for aflatoxin.