Determination of fumonisin B1 in botanical roots by liquid chromatography with fluorescence detection: single-laboratory validation.

The accuracy, repeatability, and reproducibility characteristics of a published method for measuring levels of fumonisin B1 (FB1) in botanical root products were determined by an AOAC single-laboratory validation procedure. Replicates of 10 test portions of each powdered root product (black cohosh, echinacea, ginger, ginseng, valerian, dong quai, and turmeric) at each spiking level (FB1 at 0, 50, 100, and 200 ng/g) were analyzed on 3 separate days. Test samples were extracted with methanol-acetonitrile-water (25 + 25 + 100, v/v/v). The extracts were centrifuged, the supernatants diluted with phosphate-buffered saline (PBS) containing 1% Tween 20 and filtered, and the filtrates applied to an immunoaffinity column containing antibodies specific for fumonisins. After the column was washed sequentially with PBS and water, the toxin was eluted from the column with 80% methanol, and the eluate dried by lyophilization. The residue was reconstituted with 50% acetonitrile. FB1 was derivatized with a mixture of o-phthaldialdehyde and mercaptoethanol by using an LC autoinjector. Separations were performed with an RP-LC column, and the FB1 derivative was quantified by fluorescence detection. All root products were found to contain FB1 at <10 ng/g. Average within- and between-day recoveries of FB1 from the botanical roots ranged from 67 to 95% and from 68 to 100%, respectively. Total RSD values for within- and between-day repeatability ranged from 5.5 to 26.4%. HorRat values were <1.3 for all of the matrixes examined. The method meets the AOAC method performance criteria at levels of >50 ng/g for the seven botanical roots tested.