Open Access

Thin-layer chromatography is a rapid and reliable working method for quantification of mycotoxins which is suitable for checking EC legislation aflatoxin limits for dried figs without an RP-18 pre-column cleaning step. We describe normal-phase chromatography on silica gel plates with 2.4:0.05:0.1:0.05 ( v/v ) methyl t -butyl ether-water-methanol-cyclohexane as mobile phase and reversed-phase chromatography on RP-18 plates with methanol-4% aqueous ZnSO 4 solution-ethyl methyl ketone 15:15:3 ( v/v ) as mobile phase. Sample pretreatment was by modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) extraction with tetrahydrofuran or acetone. NaCl was used as QuEChERS salt. Response was a linear function of amount chromatographed in the ranges 3 to 100 pg per zone for aflatoxins B 2 and G 2 , 10 to 350 pg per zone for the aflatoxins B 1 and G 1 , and 0.25 to 2.5 ng per zone for ochratoxin A. Quantification limits for the aflatoxins were between 13 and 35 pg per zone (equivalent to 1.5 and 2.4 ppb, taking the pre-treatment procedure into account). Ochratoxin A was detectable with a limit of quantification of 970 pg per zone, corresponding to 56 ppb in the sample. Normal phase and RP-18 separations work rapidly, reliably, and at low cost. They are also suitable for checking the content of the mycotoxins patulin, penicillic acid, zearalenone, and deoxynivalenol.

We present a video-densitometric quantification method for the triazine herbicides atraton, terbumeton, simazine, atrazine and terbutylazine. Triazine herbicides were separated on silica gel using methyl-t-butyl ether, cyclohexane (1+1, v/v) as mobile phase. The quantification was based on a bio-effective-linked analysis using chloroplast and 2,6-dichlorophenolindophenol. Within 1-2 minutes HILL-reaction inhibitor substances show blue-grey zones on a pale yellow-green background. To increase the contrast, the moist plate can be dipped into a solution of PEG-600 (10% PEG-600 in methanol) for 2s. Measurements were carried out using a 16 bit ST-1603ME CCD camera with 1.56 megapixels (from Santa Barbara Instrument Group, Inc., Santa Barbara, USA). A white LED was used for illumination purposes. The range of linearity covers more than one magnitude using the (1/R) - 1 expression data transformation. The method can be used for herbicide screenings in environmental samples, because not spectral sensitivity but herbicide activity is measured. The separation method is cheap, fast and reliable.