How Robust is Your Assay?
There are many factors that characterize a good LC-MS/MS assay, such as having good sensitivity, selectivity, and reproducibility. But an often less appreciated feature is robustness. Conditions, such as temperature, humidity, and the age of columns or buffers used for the assay, can change over time and affect analytical performance. When this happens, can the assay still detect the analyte with a high degree of certainty? In other words, how robust is your assay to natural fluctuations within the environment and aging/declining components?
Right from the start, SCIEX instruments have been built to be robust and rugged. In fact, they had to be. Some of the first instruments to be marketed were actually mobile systems for environmental air quality monitoring. The SCIEX TAGA (Trace Atmospheric Gas Analyzer) quadrupole-based instruments could be driven to contamination sites for ambient air analysis. The precision-aligned ion rails within the systems needed to be immune to the effects of the transport. And then the ambient temperatures, pressures, and humidity were very different at every site and the systems and assays needed to be immune to these influences. As Tom Covey, Principal Research Scientist at SCIEX, stated about the TAGA 6000, “It was bomb-proof.”
While your typical LC-MS/MS instrument today is probably installed within a stationary building somewhere, the requirements for robustness are no less important. Liquid introduction to a mass spectrometer is inherently a more difficult task than sampling ambient air, and much of the success and robustness of the system comes down to the design of the ion source and the interface between atmospheric pressure and high vacuum. Two key developments that have provided the ruggedness and robustness for SCIEX instruments are the Curtain Gas™ interface and the Turbo V™ ion source (from which many subsequent sources have evolved).
Curtain Gas™ Interface
The Curtain Gas interface is one significant discovery that has been an integral part of virtually every SCIEX LC-MS/MS system since it was first introduced with the API III in 1989. This barrier of dry gas in front of the orifice entrance prevents solvent vapors and particles from entering the high vacuum region while still allowing charged analytes through. Clustering problems and clogging problems are greatly reduced, thereby greatly improving the sensitivity and robustness of the system. The Curtain Gas interface was a vitally important innovation for successful liquid introduction into a mass spectrometer and is still one of the main factors that contribute to the high degree of robustness and ruggedness for which SCIEX instruments have become known.
Turbo V™ Ion Source
Introduced more than 15 years ago, the Turbo V ion source is considered the gold standard for rugged and user-friendly source design. Its innovative architecture consists of strategically placed jets of heated gas directed at the sample spray. This greatly improves desolvation without disrupting the curtain gas flow and greatly boosts the robustness of the entire system. The success of the Turbo V ion source served as the inspiration and foundation upon which the more recently introduced IonDrive™ and OptiFlow® Turbo V sources were designed. Each of these sources benefits from the use of orthogonally placed jets of heated gas directed at the liquid sample spray to enable even more efficiency of desolvation at different liquid flow regimes. While robustness and ruggedness were built in from the start, plug-and-play simplicity and a “just put it on, and it works” engineering has become the norm for all present-day SCIEX sources based on the Turbo V.
These innovations and more have helped to provide SCIEX instrumentation with a built-in resistance against adverse conditions that can influences assay performance. They are some of the main reasons why our systems have become synonymous with the terms robust, rugged, and reliable. It’s become a part of our reputation. And that’s because it’s built-in.
- Douglas, D.J. & French, J.B. J Am Soc Mass Spectrom (1992) 3: 398. https://doi.org/10.1016/1044-0305(92)87067-9