posted on 2022-10-04, 18:06authored byAi Jia, Yingbo C. Guo, George D. Di Giovanni, Matthew D. Prescott, Wei L. Li, Eduardo A. Garcia
Two commonly used methods for cyanotoxin analysis are
enzyme-linked
immunosorbent assay (ELISA) and liquid chromatography–tandem
mass spectrometry (LC-MS/MS). Each method has its advantages and disadvantages,
and discrepancies are commonly observed between the two methods due
to various factors including the ELISA antibody cross-reacting to
different cyanotoxin congeners. However, reliable cyanotoxin monitoring
methods and accurate interpretation of results are needed for water
utilities to guide recreational water planning and drinking water
treatment operations. In this study, we explored an innovative “effective
concentration-equivalent concentration” (EC-EQ) approach to
improve the interpretation of ELISA results and the comparison to
LC-MS/MS results. The precision of ELISA results was first improved
by reporting the sample ECs and EQs derived from their ELISA dose
curves. Concentrations of each cyanotoxin as measured by LC-MS/MS
were then combined with their respective ELISA cross-reactivities
to calculate their theoretical ELISA responses. Finally, instead of
comparing the results from the two methods directly, the equivalent
concentration based on one single reference cyanotoxin was used for
reporting and comparison. This integrated mass balance-based approach
provides a more reliable interpretation of results by considering
the reactivity differences between toxins as well as their mixture
effects. This approach has been successfully applied to microcystin
(one main group of cyanotoxins) standard mixtures and cyanobacterial
bloom samples to interpret and compare their ELISA and LC-MS/MS detection
results. The study provides guidance to utilities on how to obtain
more accurate cyanotoxin monitoring results and better understand
the discrepancy between the two methods.