Comparison of Analytical Techniques for the Determination of Various Types of Algal Toxins by LC-MS/MS

Changing the Paradigm for Water Pollution Monitoring
Oral Presentation

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Algal blooms have been observed in both marine and freshwater bodies across the country. In recent years, these blooms have become increasingly more common, in part due to nutrient loading from increasing agricultural runoff or perhaps even due to global climate change. Algal blooms themselves are typically not directly harmful; however, some species of algae produce chemical toxins that are harmful or even fatal to wildlife, livestock, and humans. Notably, algal toxins have made headlines in California with domoic acid contaminated shellfish, and in the Midwest with microcystin detections in drinking water sourced from Lake Erie. The potential for finding these toxins in places where humans swim, source their food and drinking water raises the need to monitor these water bodies for these algal toxins.

Analytical methodology for the determination of algal toxins generally employs LC-MS/MS or Enzyme Linked Immunosorbent Assays (ELISA), each of which present unique benefits and drawbacks. As part of the fourth Unregulated Compound Monitoring Rule (UCMR4), the EPA published a method for the determination of cylindrospermopsin and anatoxin-A by LC-MS/MS (EPA 545), and two methods for the determination of microcystins: an SPE-LC-MS/MS method (EPA 544), and an ELISA method (EPA 546). Method 546 tends to give a more accurate assessment of the total microcystins present in a sample, but is susceptible to false positives, while method 544 is less prone to false positives; it is more limited as to which types of microcystins can be quantified. This paper will describe the various analytical techniques available to measure these targets, including the three EPA methods, and how to minimize the inherent drawbacks of LC-MS/MS for this application.