Evaluation of the Abraxis Strip Test for Microcystins™ for use with wastewater effluent and reservoir water

Rapid tests for the microcystin-type cyanobacterial toxins that are designed to be able to be used in the field have recently become available. The tests provide a semi-quantitative result over a relatively narrow concentration range (10-fold) and are available with detection limits relevant for drinking water and recreational water compliance testing (1 μg/L and 10 μg/L, respectively). The aim of this research was to assess the applicability of these tests for the determination of microcystin-related toxicity in treated effluent from the Western Treatment Plant and potable source water from Tarago Reservoir, both near Melbourne, Australia. Accuracy, precision, cross-reactivity, matrix effects and inter-operator variability were assessed. The claimed mLR concentration response range of the tests was confirmed within reasonable limits, although the false negative and false positive rates were significant for spike concentrations below 2.5 μg/L (Recreational Strip Test). Inter-operator variability was reasonably high (CV = 23%) and this was exacerbated by the use of untrained scorers. Contributing to this was significant inter-assay variability in test band intensity (CV = 28%). The strip tests responded to all 8 microcystin analogues tested and also to a mixture of another 7 analogues contained in a Certified Bloom Material. Cross-reactivity was always greater than 50%. Matrix effects due to the test waters or to cyanobacterial cell material were also relatively minor, being of the order of 2-fold at the maximum. Overall, these Strip Tests were found to be reliable for relatively rapid detection of microcystins around the upper limits of their response ranges, as recommended by the manufacturer. While the Recreational Water Strip test was less reliable in the lower ranges, it can be used in conjunction with the Drinking Water Strip test to reduce uncertainty around the 1 μg/L concentration. Despite limitations, both strip tests provide near real-time information which can assist with day to day operational decisions. When results indicate microcystin concentrations near compliance limits it is recommended that use of the test kits should be supported by accurate quantitative toxin testing together with traditional algal cell counts, and possibly emerging qPCR methods for species and toxin gene detection.

► The Abraxis Strip Test for Microcystins was evaluated for water industry use.
► Various sources of assay variability were identified and quantified.
► The assay is reasonably accurate and reliable in a range of matrices.
► The assay is relatively rapid and can be applied away from the lab.
► It will be a useful addition to the cyanotoxin assays available to the water industry.