Rapid, high throughput quantitation of cyanotoxins in natural water by UHPLC-MS-MS

Significance of the Topic

This study addresses the rapid quantitation of microcystin variants—common cyanobacterial toxins—in natural water sources. Reliable and fast detection of microcystins is critical for protecting public health, complying with WHO and EPA guidelines, and enabling proactive water quality monitoring.

Objectives and Study Overview

The main goal was to develop an ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method capable of high-throughput screening of seven microcystin analogs in environmental water without extensive sample preparation. Performance was evaluated using calibration curves, recovery studies in Lake Erie water, and surrogate spikes.

Methodology

The workflow eliminated solid-phase extraction by direct syringe filtration of water samples spiked at defined levels. Chromatographic separation was achieved on a C8 UHPLC column with an 8-minute gradient run. Seven-point external calibration (0.1–100 ng/mL or 0.5–100 ng/mL depending on analog) was performed with 7 µL injections of methanol/water standards. A deuterated microcystin-LR surrogate (20 ng/mL) was added to all samples.

Used Instrumentation

• Shimadzu Nexera UHPLC system
• Shimadzu LCMS-8050 triple quadrupole mass spectrometer

Main Results and Discussion

The method achieved excellent linearity for all seven microcystin analogs (r2 ≥ 0.9915). At low (1 ng/mL) and high (50 ng/mL) spikes in Lake Erie water, calculated recoveries ranged from 90% to 101% at 1 ng/mL and 45% to 49% at 50 ng/mL. The surrogate spiked at 20 ng/mL exhibited a %RSD of 2.5% over 12 replicates, demonstrating strong precision. No sample enrichment was needed to reach detection limits of 0.1 µg/L.

Benefits and Practical Applications of the Method

• Rapid turnaround: 8-minute analysis per sample
• Minimal sample preparation: direct filtration only
• High sensitivity: meets or exceeds drinking-water guidelines
• High throughput: suitable for routine monitoring of multiple sites

Future Trends and Opportunities

Further development may include optimization of column chemistries to shorten run times, refinement of MS source parameters and collision energies for improved sensitivity, and exploration of alternative mobile phase compositions to enhance ionization efficiency for challenging analogs.

Conclusion

The presented UHPLC-MS/MS workflow offers a robust, high-throughput solution for quantifying multiple cyanotoxins in natural waters with minimal sample workup. It supports efficient water-quality monitoring programs and aligns with regulatory requirements.

Reference

T. Russell, D. Schordock. Rapid, high throughput quantitation of cyanotoxins in natural water by UHPLC-MS-MS. ASMS 2015. Shimadzu Scientific Instruments Ltd., June 2015.