Method 545 (Microcystins and Nodularin) is used for the analysis of cylindrospermopsins and anatoxin-a. This method requires the freezing of the sample at -40C. The freezing and thawing are performed three times to ensure that all algal cells are ruptured prior to the filtration of the sample. Once the sample is filtered the filtrate is injected into liquid chromatograph, where the analytes are separated based on polarity, and passed through two mass spectrometers in tandem for identification based on the molecular masses of the fragmented compounds. In addition, this analysis provides a high precise quantitation of these compounds.