Monoclonal antibody based electrochemical immunosensor for the determination of ochratoxin A in wheat

Competitive electrochemical enzyme-linked immunosorbent assays based on disposable screen-printed electrodes have been developed for quantitative determination of ochratoxin A (OTA). The assays were carried out using monoclonal antibodies in the direct and indirect format. OTA working range, 150 and detection limits were 0.05-2.5 and 0.1-7.5 mu g L-1, 0.35 (+/- 0.04) mu g L-1 and 0.9 (+/- 0.1) mu g L-1, 60 and 100 mu g L-1 in the direct and indirect assay format, respectively. The immunosensor in the direct format was selected for the determination of OTA in wheat. Samples were extracted with aqueous acetonitrile and the extract analyzed directly by the assay without clean-up. The 150 in real samples was 0.2 mu g L-1 corresponding to 1.6 mu g/kg in the wheat sample with a detection limit of 0.4 mu g/kg (calculated as blank signal -3 sigma). Within- and between-assay variability were less than 5 and 10%, respectively. A good correlation (r = 0.9992) was found by comparative analysis of naturally contaminated wheat samples using this assay and an HPLC/immunoaffinity clean-up method based on the AOAC Official Method 2000.03 for the determination of OTA in barley. (c) 2005 Elsevier B.V. All rights reserved.[...

A flow-through enzyme immunoassay for the screening of fumonisins in maize

The format of an existing flow-through enzyme immunoassay has been optimised for the detection of fumonisin B-1 (FB1) and B-2 (FB2) in maize. The visual detection limit i.e. the smallest mycotoxin concentration resulting in no colour development, is 1000 mug/kg. Assay validation was performed using samples spiked with respectively only FBI and a FB1 + FB2 mixture (ratio 1:1). Results showed that within-day and between-day coefficients of variation ranged from respectively 0.4-10.2% and 1.1-9.0%. Naturally contaminated samples were screened with the developed flow-through method and results were compared with fumonisin contamination values obtained by a validated HPLC method. The assay was demonstrated to be accurate and reliable giving no false compliant and only a low percentage of false non-compliant results. The described method offers a simple, rapid and cost-effective screening tool, thus contributing to a better consumers' health protection. (C) 2004 Elsevier B.V. All rights reserved

Evaluation of fumonisin contamination in cornflakes on the Belgian market by "flow-through" assay screening and LC-MS/MS analyses

A total of 205 cornflake samples collected in Belgian retail stores during 2003-2004 were surveyed for the natural occurrence of fumonisin B-1 (FB1), B-3 (FB3), and B-3 (FB3). These cornflake samples, originating from conventional as well as from organic production, were analyzed using an intralaboratory-validated LC-MS/MS method. Additionally, 90 cornflake samples were subjected to rapid screening using a flow-through enzyme immunoassay method to demonstrate the practicability of a screening test coupled to a validated confirmatory LC-MS/MS method for the management of food safety risks. FB1 concentrations ranged from not detected (nd) [LOD (FB1) = 20 mu g/kg] to 464 mu g/kg with mean and median concentrations of respectively 104 +/- 113 and 54 mu g/kg. For FB2 and FB3, the concentration ranges varied respectively from nd [LOD (FB2) = 7.5 mu g/kg] to 43 mu g/kg and from nd [LOD (FB3) = 12.5 mu g/kg] to 90 mu g/kg. Mean concentrations for FB2 and FB3 were respectively 12 +/- 8 and 21 +/- 15 mu g/kg, while the median concentration was 11 mu g/kg for FB2 and 19 mu g/kg for FB3. From the statistical tests (chi(2) and ANOVA model III), it could be concluded that the agricultural practice did not have any significant effect on the fumonisin concentrations but that the variation between different batches was significant (p < 0.0001)