Determination of microcystins in fish by solvent extraction and liquid chromatography

A liquid chromatography electrospray mass spectrometry (LC/ESI/MS) method has been developed to identify and quantify microcystins in fish liver and intestine. Microcystins (MCs) were extracted from 500 mg sample with methanol–water (85:25, v/v) and the extracts concentrated to 250 μl. The parameters were optimized by a full factorial 23 design. Neither laborious pre-treatment nor clean up were necessary. MCs were separated using conventional C18 column and an acetonitrile–acidified water (pH 3) gradient. Negative samples (without MCs) were discriminated by liquid chromatography diode array detection (LC/DAD). The limits of detection (LOD) and the limits of quantification (LOQ) resulted equal for MC-RR, MC-YR, and MC-LR and were 0.1 and 0.5 μg g−1, respectively. MCs recoveries at three levels in spiked samples (0.5–3.0 μg g−1) were >92%, with relative standards deviations (RSDs) <16% for liver samples and >68% with RSDs <18% for intestine samples. The proposed method was applied to determine MC-LR in exposed fish to evaluate the bioaccumulation risk. The results showed the transference of MC-LR from cyanobacterial cells to fish tissues.