Effects of Polarity Switching in High Speed LCMS Analysis

Significance of the Topic

High-speed liquid chromatography coupled with mass spectrometry (LC-MS) has transformative potential for laboratories focused on research, development, quality control and environmental monitoring. Enhancing analysis throughput reduces bottlenecks and allows chemists to prioritize interpretation and method development. A major barrier to adopting ultra-high-speed LC-MS is the inherent delay during polarity switching in electrospray ionization, which compromises peak shape and quantitation when measuring both positive and negative ions simultaneously.

Aims and Study Overview

This technical report evaluates the impact of rapid polarity switching on quantitative performance and sensitivity in high-speed LC-MS analysis. It introduces Shimadzu’s solutions—the LCMS-8030 triple quadrupole and LCMS-2020 single quadrupole systems—integrated with the Nexera UHPLC platform to achieve 15 millisecond switching. Key objectives include comparing conventional and ultra-fast switching, assessing effects on peak shape and repeatability, and demonstrating applicability to multi-residue pesticide screening.

Methodology and Instrumentation

The principle of electrospray ionization polarity switching involves alternately applying positive and negative high voltages to the ionization probe. Conventional circuits employ parallel high-voltage supplies with switching times of several hundred milliseconds. Shimadzu’s innovation arranges positive and negative supplies in series with bypass circuitry, enabling instantaneous activation of either polarity. Polarity switching time was measured at 15 ms on the LCMS-8030 and LCMS-2020, compared to ~500 ms in standard configurations.

Instrumentation

• Nexera UHPLC system
• LCMS-8030 triple quadrupole MS/MS
• LCMS-2020 single quadrupole MS
• Electrospray ionization probe with high-speed switching circuit

Main Results and Discussion

Ultra-fast 15 ms polarity switching yielded near-ideal chromatographic peaks with minimal data loss during mode transitions. Quantitative repeatability improved dramatically, with relative standard deviation (%RSD) of 2.2% versus 36.9% for conventional 500 ms switching. Sensitivity analyses for representative compounds showed no loss of signal intensity when high-speed switching was employed. A demonstration run analyzing 316 pesticide residues (286 positive-ion MRM channels and 30 negative-ion channels) produced sharp, well-resolved peaks, validating the method’s robustness for complex multi-residue screening.

Benefits and Practical Applications

Ultra-high-speed polarity switching enables:

• Simultaneous positive and negative ion detection without compromising peak shape
• Enhanced quantitation precision and reproducibility
• Uncompromised sensitivity for trace-level analytes
• Significantly increased sample throughput in routine analyses

This advancement is particularly valuable in pesticide monitoring, pharmaceutical impurity profiling, metabolomics, and other fields requiring rapid, comprehensive LC-MS screening.

Future Trends and Potential Applications

Further integration of ultra-fast polarity switching is expected to accelerate method development in high-throughput laboratories. Emerging applications include automated multi-laboratory QC, large-scale environmental screening, and real-time process monitoring. Combining this capability with high-resolution mass analyzers or ion mobility separations could unlock advanced workflows for isomer differentiation and non-targeted screening.

Conclusion

Shimadzu’s implementation of 15 ms polarity switching in the LCMS-8030 and LCMS-2020 systems overcomes a critical throughput limitation in high-speed LC-MS. The series-arranged high-voltage circuit with bypass enables simultaneous dual-polarity detection, delivering superior peak shapes, quantitation precision and sensitivity. Adoption of this technology promises to expand the utility of ultra-high-speed LC-MS across diverse analytical laboratories.

Reference

Shimadzu Corporation. Technical Report C146-E176 “Effects of Polarity Switching in High Speed LCMS Analysis.” First Edition July 2012.