Rapid immunochromatographic test designed for use in the qualitative screening of free Microcystins and Nodularins in finished drinking water.
The Microcystins Strip Tests for Finished Drinking Water are rapid immunochromatographic tests designed for use in the qualitative screening of free Microcystins and Nodularins in finished drinking water. Chlorinated finished drinking water samples which are not tested immediately must be preserved (quenched) with sodium thiosulfate at the time of collection to remove residual chlorine. Source drinking water samples containing cyanobacterial cells may also be screened for the presence of free Microcystins and Nodularins using the Microcystins Strip Tests for Finished Drinking Water; an appropriate cell lysis procedure is required prior to analysis in order to screen for total Microcystins content (free and cell bound). The Microcystins Strip Tests provides only preliminary qualitative test results. If necessary, positive samples can be confirmed by ELISA, HPLC or other conventional methods.
The test is based on the recognition of Microcystins, Nodularins, and their congeners by specific antibodies. The toxin conjugate competes for antibody binding sites with Microcystins/Nodularins that may be present in the water sample. The test device consists of a vial containing specific antibodies for Microcystins and Nodularins labeled with a gold colloid and a membrane strip to which a conjugate of the toxin is attached. A control line, produced by a different antibody/antigen reaction, is also present on the membrane strip. The control line is not influenced by the presence or absence of Microcystins in the water sample and, therefore, should be present in all reactions.
In the absence of toxin in the water sample, the colloidal gold labeled antibody complex moves with the water sample by capillary action to contact the immobilized Microcystins conjugate. An antibody-antigen reaction occurs forming a visible line in the ‘test’ area. The formation of two visible lines of similar intensity indicates a negative test result, meaning the test did not detect the toxin at or above the cut-off point established for the toxin. If Microcystins are present in the water sample, they compete with the immobilized toxin conjugate in the test area for the antibody binding sites on the colloidal gold labeled complex. If a sufficient amount of toxin is present, it will fill all of the available binding sites, thus preventing attachment of the labeled antibody to the toxin conjugate, therefore preventing the development of a colored line. If a colored line is not visible in the test line region, or if the test line is lighter than the control line, Microcystins are present at a level of concern (>0.3 ppb). Semi-quantitative results can be obtained by comparing the sample test strip appearance to the appearance of test strips from solutions of known Microcystins concentrations (control solutions). Microcystins controls are available through Eurofins Abraxis (PN 422011).