Exploring the detection of microcystin-LR using polar organic chemical integrative samplers (POCIS)

Abstract

Polar organic chemical integrative samplers (POCIS) were used in this study to explore passive sampling for the detection of microcystin-LR (MC-LR). POCIS were deployed in triplicate for a minimum of 28 days at the inlet and outlet of a 1 km², 4.2 km long lake in Atlantic Canada. POCIS results were compared to lake water grab sampling and followed a similar trend. Laboratory POCIS studies using lake water spiked with known MC-LR concentrations were used to estimate lake water concentrations over the deployment period by calculating POCIS sampling rate (R_s). The R_s for MC-LR in this lake water was found to be 0.045 (±0.001) and 0.041 (±0.001) L per day for initial concentrations of 0.5 and 1.0 μg L⁻¹. Estimated MC-LR concentrations from POCIS were generally higher than grab sampling results, especially at the outlet to the lake from late September to late October. This could possibly give a better picture of MC-LR concentrations in the lake; MC-LR concentrations can fluctuate substantially over short time periods. POCIS were able to detect MC-LR in the water stream when grab sampling resulted in non-detects (i.e., below detection limit of LC-MS/MS). The use of passive sampling for MC-LR could have beneficial implications for public health and toxicity testing by lowering detection limits for this chronically and acutely toxic chemical. The correlation of aqueous MC-LR concentrations to POCIS MC-LR concentrations needs further study.