VARIABILITY ASSOCIATED WITH ANALYTICAL METHODS USED TO MEASURE AFLATOXIN IN AGRICULTURAL COMMODITIES

A total of 1019 analytical precision estimates obtained from method-pe rformance (collaborative) studies for mycotoxins published through 199 1 were sorted by type of variance measurement, type of analytical meth od, and type of agricultural commodity, Precision estimates for total aflatoxin were sorted into 2 precision measurements (among-laboratorie s and within-laboratory), 3 analytical methods (thin-layer chromatogra phy [TLC], liquid chromatography [LC], and enzyme-linked immunosorbent assay [ELISA]), and 11 agricultural commodities. Sufficient data exis ted to study the analytical variability (precision) associated with 36 sorted combinations (of a possible 66). In all but one combination (w ithin-laboratory, barley and TLC), the variance (V) was a function of total aflatoxin concentration (C). A power function of the form V = aC (b), where a and b are constants, describes the relationship between v ariance and aflatoxin concentration, The coefficients a and b were det ermined from regression analysis, When results were pooled across all agricultural commodities, LC had the lowest analytical variability whi le ELISA had the highest, For a given method, among-laboratories varia bility was approximately double the within-laboratory variability. The se analytical variability estimates can be coupled with previously det ermined variability estimates of sampling and sample preparation to de termine the performance associated with specific test procedures used to inspect agricultural commodities for aflatoxin.