Quantitative fluorodensitometric determination and survey of aflatoxins in nutmeg

A study is presented for the quantitative fluorodensitometric analysis of aflatoxins in spices, in particular nutmeg (Semen myristicae). Samples were extracted with chloroform, followed by silica gel column cleanup according to the AOAC officail first action method, 26.019(a), and by 2-dimensional thin layer chromatography according to the antidiagonal technique. The method includes a confirmatory test for aflatoxins by hemiacetal formation. The concentrations of aflatoxins in samples were determined by measurement of the fluorescent intensities of the separated aflatoxin spots from sample and standards on the same chromato-plate with a reflectance flying-spot sensitometer. With such a technique, a coefficient of variation value of 5.22 plus or minus 1.24% (P = 99%) was calculated for a series of 5 standard B-1 spots and averaged for 13 TLC plates, demonstrating the precision of the chromatographic and densitometric procedures. An average recovery of 108.4 plus or minus 5.8% (P = 95%) was obtained for 11 spiked nutmeg extracts (5.0-20.0 mu-g B-1 added/kg), whereas an average recovery of 92.6 plus or minus 4.9 (P = 95%) was established for 13 spiked nutmeg samples (5.0-20.0 mu-g B-1 added/kg). The coefficient of variation of the complete analytical procedure for ground nutmeg was 8.80%. In a survey on the occurrence of aflatoxins in 40 commercial nutmeg samples (covering 12 different brands) in The Netherlands, aflatoxins were detected in 30 ground samples (32 ground samples analyzed) in concentrations ranging from 1.0 to 23.2 mu-g B-1/kg or 2.7 to 36.5 mu-g B-1 + B-2 + G-1 + G-2/kg, whereas no aflatoxins were present in whole nutmeg kernels (8 samples analyzed). The lowest level of detection was 1.0 mu-g B-1/kg. In addition, 50 commercial spices consisting of 19 different types of commodities other than nutmeg wer assayed for aflatoxins according to the same procedure. No aflatoxins were detected in these samples, with the exception of 1 sample of bay leaf which contained 5.1 mu-g B-1/kg.