Expanding EPA Method 544: Addition of Seven Microcystin Congeners for Analysis of Lake Erie Beach Samples, a Comparative Study with ELISA

Oral Presentation

Prepared by C. Soltis-Muth, D. Schordock
Northeast Ohio Regional Sewer District, 4747 East 49th Street, Cuyahoga Heights, OH, 44125, United States

Contact Information: soltis-muthc@neorsd.org; 216-641-6000


37 Lake Erie beach water samples from the summer of 2015 were analyzed for microcystins by EPA Method 544 utilizing solid phase extraction (SPE) and analysis on a Shimadzu LCMS-8050 Liquid Chromatograph Tandem Mass Spectrometer (LC/MS/MS). These same samples were lysed by a series of three freeze/thaw cycles and filtered. The resulting extracts were analyzed by ELISA and also by directly injecting into the LC/MS/MS with the same operating conditions as with EPA Method 544. In 19 cases, the ELISA result was greater than the sum of the individual microcystin results from EPA Method 544 (SPE & LC/MS/MS). In all except one of these 19 instances, the ELISA was also greater than the sum of the individual microcystin results from the direct inject LC/MS/MS method. This indicates that there may be additional microcystin congeners in these samples that are not being detected by EPA Method 544.

Seven additional microcystin congeners were added to the EPA Method 544 analysis. The beach water extracts from the summer of 2015 will be rerun to determine if the difference between the ELISA and EPA Method 544 results is due to microcystin congeners previously untested by the method.

Future work includes validating the SPE extraction procedure in EPA Method 544 with the additional microcystin congeners and continuing the ELISA and LC/MS/MS method comparison study into 2016.