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a b s t r a c tBackground: Microcystins (MCs) contaminate water bodies due to cyanobacterial blooms all over the world, leading to frequent exposure of humans to MCs through consumption of meat, fish, seafood, blue green algal products and water, accidental ingestion of contaminated water and scum during recre ational activities and inhalation of cyanobacterial aerosols. For monitoring of human exposure, sensitive screening methods are needed. However, during the analytical process of various matrices, such as human serum, some problems appear to regularly occur during sample preparation and storage, leading to MC loss and thus to underestimation of the true MC concentration. The aim of the current study was therefore to assess the pitfalls of the MC extraction method from human serum with more detail. Methods: Six MC congeners (MC LR, YR, RR, LA, LW, LF) and defined equimolar MC mixtures thereof were spiked into human serum, and quantified using the commercially available Adda ELISA subsequent to standard extraction (methanol extraction with subsequent SPE). To detect the potential influence of sample storage and preparation/storage materials, different types of material such as glass, standard polypropylene and surface treated polypropylene were compared. Results: Loss of MC during preparation and storage is largely dependent on (1) the handling of the stored material, (2) the 'surface' of the storage material and (3) the hydrophobicity of the MCs. Conclusions: The pitfalls described for MC analysis with the ELISA are primarily associated with sample preparation and clean up and thus also apply to other analytical techniques for MC detection beyond the ELISA used. It can be concluded that ELISA based methods are suitable tools for the detection of MCs in human sera and other samples.

A sensitive magnetic particle-based immunoassay to determine triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol] in drinking water and wastewater was developed. Rabbit antiserum was produced by immunizing the rabbit with 6-[5-chloro-2-(2,4-dichlorophenoxy)phenoxy]hexanoic acid-keyhole limpet hemocyanin. Horseradish peroxidase was conjugated with 4-[3-bromo-4-(2,4-dibromophenoxy)phenoxy]butyric acid via N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC). The triclosan antibody was coupled to magnetic particles via the NHS/EDC reaction. The antibodies were able to recognize some structurally related polybrominated biphenyl ethers but did not recognize various common pollutants that were less similar to the hapten. The ELISA could detect triclosan in standard solution (25% methanol/H2O v/v) at 20 ppt and its metabolite, methyl-triclosan, at 15 ppt. Water samples from different treatment stages were prepared to contain 25% methanol and analyzed directly without any sample extraction or preconcentration. The results showed that recoveries were >80% and the % CV was <10%, demonstrating the assay was both accurate and precise. Application of the triclosan ELISA to water treatment plants showed that tap water at various purification stages had low concentrations of triclosan (<20 ppt) and required an increased sample size for appropriate detection and measurement. Application of ELISA to the wastewater treatment plants (WWTP) demonstrated high concentrations of triclosan (in general, >3000 ppt in water entering the WWTP) with the levels decreasing as the water proceeded through the processing plant (<500 ppt at outflow sewage). The ELISA measurement was shown to be equivalent to the more specific GC-MS analysis on a number of wastewater treatment samples with a high degree of correlation, with the exception of a few samples with very high triclosan concentrations (>5000 ppt). Measurement of methyl-triclosan (in WWTP) using GC-MS demonstrated the levels of this compound to be low. In summary, a rapid, sensitive, accurate, and precise magnetic particle-based immunoassay has been developed for triclosan analysis, which can serve as a cost-effective monitoring tool for various water samples.