When performing electrospray ionization mass spectrometry, it is well understood that reducing chromatographic flow rates can improve sampling efficiency and therefore increase sensitivity.1 When operating in the nanoflow regime (50-500 nL/min) very high sampling efficiencies have been measured for favorable solvent conditions.2 This is particularly beneficial when sample amounts are limited, such as in proteomics applications, where nanoflow LC-MS is frequently used. One drawback to this approach is that typical run times are quite long; often 1-2 hour gradients are used to achieve optimal separations.
In other application areas, throughput and robustness are more important, such as with pharma bioanalysis studies. For the analysis of 100s of samples daily, analytical flow rates of 300-1000 µL/min are typically combined with gradients of less than 5-10 minutes. In recent years, there has been a resurgence in the interest in using microflow LC coupled to mass spectrometry as evolving research demands increasingly require more sensitivity while still maintaining good throughput and robustness.
This led SCIEX to develop the OptiFlow® Source, a single source that would cover the full spectrum of low flow rates for high sensitivity LC-MS analysis. Significant research was done to develop a low flow source that was sensitive, while maintaining high robustness and ease of use of higher flow sources. The ability to easily switch between flow regimes was also critical in the source design. Removing the barrier of switching helps researchers choose the right flow rate for every project.
REFERENCES
1.Covey, T. R., Schneider, B. B., Javaheri, H., Y., L. J. C., Ivosev, G., Corr, J. J., Kovarik, P., Electrospray and MALDI mass spectrometry: Fundamentals, instrumentation, practicalities, and biological applications. In ESI, APCI, and MALDI. A Comparison of the Central Analytical Figures of Merit: Sensitivity, Reproducibility, and Speed. Cole, R. B., Ed. Hoboken: John Wiley & Sons, Inc.: (2010); pp 443-490.
2.Schnieder BB, Javaheri H, Covey TR (2006) Ion Sampling Efficiency Under Conditions of Total Solvent Consumption. Rapid Comm Mass Spectrometry 20, 1538-1544.
3.SWATH Acquisition Performance Kit Standard Operating Protocol.
4.OptiFlow™ Interface for TripleTOF 6600 System - Switch from Nanoflow LC to Microflow LC in Minutes. SCIEX Technical Note RUO-MKT-02-7219-B.