We often talk about the speed of a Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) analysis and what a key benefit this is. Yet for lab techs who have not had direct experience it is difficult to fully appreciate the power that this brings to the laboratory, not only to enhance sample throughput but, just as importantly, to facilitate method development.
We encountered a good example of this recently when a customer visited with samples of two VOCs that he had no means of quantifying. Neither of the compounds in question (halocarbons) were in Syft’s Compound Library and we had no experience in the analysis of these compounds. Furthermore, these compounds had a very low proton affinity so could not be measured by the many techniques, like PTR-MS, that utilise the chemical ionisation agent H3O+.
SIFT-MS utilises multiple reagents ions, and a quick scan was sufficient to confirm that O2+ readily ionises these compounds. Furthermore, the information gathered during these scans was sufficient to allow the compounds to be added to Syft’s compound library. Doing so required a knowledge of the reaction rate between these compound and SIFT’s reagent ions. In this case these rates were estimated on the basis of similar compounds already in the library.
Once in the library, the stable and well-defined ionisation conditions that are unique to SIFT enable a quantitative analysis to be routinely performed. This was done for the known-concentration samples our customer had bought along: a 2 ppb and 400 ppb sample of each of the two compounds. The results of all measurements were within 20% of the expected concentration.
The simplicity with which a trace-level quantitative measurement can be performed on new compounds is remarkable. But perhaps more remarkable still is the that this entire process: performing a preliminary scan of the compounds; adding them to the Syft Compound Library; and performing a quantitative measurement, took less than ten minutes!
For fast and robust method development in the laboratory, the power of SIFT-MS is hard to beat.