A CLEANUP METHOD FOR ANALYSTS OF TRACE AMOUNTS OF MICROCYSTINS IN LAKE WATER

A clean-up method using high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS) was developed to p ursue trace amounts of microcystins in lake water. The method consiste d of the combined usage of octadecyl silanized (ODS) silica gel and si lica gel cartridges. In the first clean-up process, the retention beha vior of microcystin RR on ODS silica gel cartridge was carefully obser ved together with microcystin LR, and 10% water-methanol was chosen as the best solvent system to elute microcystins from the ODS silica gel cartridge. Because many impurities still remained in the desired frac tion from the raw water even after the clean-up with ODS silica gel, a n additional clean-up process was developed using various cartridges. As a result of extensive experiments, the second clean-up process usin g silica gel cartridge was established, and the impurities were effect ively eliminated. The present method including a tandem cartridge syst em allowed a precise analysis of microcystins in water samples from th ree different lakes at a 0.02 ppb level.