Comparison of ICP-MS and photometric detection of an immunoassay for the determination of ochratoxin A in wine

An immunoassay was developed for ochratoxin A (OTA) detection in wine and two completely different detection methods were compared: ICP-MS and photometry. For labelling, we applied secondary antibodies conjugated with gold nanoparticles for ICP-MS and with horseradish peroxidase for photometric detection, respectively. Detection limits of the assay were determined as 0.003 mu g L(-1) for both detection methods. OTA in wine was determined below the EU limit value of 2 mu g kg(-1). The measurement range was between 0.01 and 1 mu g L(-1) for ICP-MS and photometric detection. Assay precision detected by ICP-MS and photometry were similar showing that precision of the detection method has only a minor effect on total assay precision. By using BSA as a buffer additive to minimize nonspecific binding, we could also confirm that OTA strongly binds to BSA. In a comparison study of several additives, casein was found to be preferable.