Increasing the robustness of SIFT-MS volatilome fingerprinting by introducing notional ion concentrations

Selected-ion-flow-tube-mass-spectrometry (SIFT-MS) is an analytical technique for volatile detection and quantification. SIFT-MS can be applied in a ‘white box’ approach, measuring concentrations of target compounds, or as a ‘black box’ fingerprinting technique, scanning all product ions during a full scan. Combining SIFT-MS full scan data acquired from multi-batches or large-scale experiments remains problematic due to signal fluctuation over time. The standard approach of normalizing full scan data to total signal intensity was insufficient. This study proposes a new approach to correct SIFT-MS fingerprinting data. In this concept, all the product ions from a full scan are considered individual compounds for which notional concentrations can be calculated. Converting ion count rates into notional ion concentrations accounts for any changes in instrument parameters. The benefits of the proposed approach are demonstrated on three years of data from both multi-batches and long-term experiments showing a significant reduction of system-induced fluctuations providing a better focus on the changes of interest.