Determination of Microcystins in Drinking Water by Ultra High Performance Liquid Chromatography/Triple Quadrupole Mass Spectrometry

Significance of the topic

Microcystins are potent hepatotoxins produced by cyanobacteria. Because they are chemically stable and resist degradation, they can accumulate in drinking water and pose serious health risks. Regulatory agencies, including the WHO, set strict limits on microcystin levels, making rapid and sensitive analysis essential for water safety.

Objectives and overview of the study

This study aimed to establish a straightforward, high‐throughput method using ultra‐high performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC‐ESI‐MS/MS) for simultaneous determination of ten microcystin variants in drinking water without complex sample pretreatment.

Methodology and Instrumentation

• Sample preparation: Tap water samples were filtered directly and injected without further cleanup.
• UHPLC conditions: Shimadzu Nexera system with XR‐ODSIII column (50 × 2.0 mm, 1.6 µm) at 40 °C; mobile phases—0.1 % formic acid in water (A) and acetonitrile (B); gradient from 30 % B to 80 % B over 1.5 min, held until 4 min, then returned to 30 % B by 4.1 min; total run time 5.5 min; flow rate 0.4 mL/min; injection volume 20 µL.
• MS/MS conditions: Shimadzu LCMS-8040 triple quadrupole with ESI in positive mode; desolvation line 250 °C, heat block 400 °C, nebulizing gas 3 L/min, drying gas 15 L/min; optimized multiple reaction monitoring (MRM) transitions for each microcystin.

Key results and discussion

• Chromatographic performance: Baseline separation of ten microcystins achieved in 5.5 min.
• Calibration: Linear response over 0.02–50 µg/L for most analytes (r > 0.999).
• Precision: Retention time RSD 0.077–0.369 %; peak area RSD 0.843–9.672 % at 1 and 10 µg/L.
• Sensitivity: Limits of quantitation (LOQs) ranged 0.02–0.5 µg/L, validated by spiking experiments in tap water with no detectable matrix interference.

Benefits and practical applications of the method

This rapid, high‐sensitivity UHPLC‐ESI‐MS/MS protocol supports routine monitoring and regulatory compliance in drinking water quality control labs, offering robust performance with minimal sample preparation.

Future trends and potential applications

• Automated, on‐line sampling and analysis for near real‐time water monitoring.
• Extension to additional cyanotoxins and other environmental matrices (e.g., surface water, wastewater).
• Integration with high‐resolution mass spectrometry for broad‐scope screening of known and emerging toxins.

Conclusion

A reliable UHPLC‐ESI‐MS/MS method was developed for fast and accurate quantification of ten microcystins in drinking water. The approach meets regulatory requirements and enhances laboratory throughput for water quality assessment.

References

• Yao J., Hao H., Huo Y., Dong H., Watanabe K., Huang T., Kawano S., Hashi Y. Determination of Microcystins in Drinking Water by UHPLC/Triple Quadrupole MS. Shimadzu Application Note WP-033, June 2013.
• World Health Organization. Guidelines for Drinking‐water Quality, 4th Edition, 2011.