SIFT-MS uses ultra-soft, precisely controlled chemical ionization (CI) coupled with mass spectrometric detection to rapidly quantify VOCs and permanent gases to low part-per-trillion concentrations by volume (pptv).
Eight chemical ionization agents (reagent ions) are applied in Syft instruments: H3O+, NO+, O2+, O–, O2–, OH–, NO2–, and NO3–. These eight reagent ions react with analyte VOCs and inorganic gases in very well controlled ion-molecule reactions, but they do not react with the major components of air (N2, O2, and Ar).
This enables SIFT-MS to analyze air at trace and ultra-trace levels without preconcentration.
Rapid switching of eight reagent ions provides unsurpassed selectivity compared to other direct MS techniques.
There are three fundamental components of the SIFT-MS technique:
- Reagent ion generation and selection. The eight SIFT-MS reagent ions are formed by microwave discharge through moist or dry air at low pressure. One reagent ion is selected at any particular time using the first quadrupole mass filter.
- Analyte ionization. The selected reagent ion is injected into the flow tube and excess energy is removed through collisions with the carrier gas. The sample is then introduced at a known flow rate and the reactive compounds it contains are ionized by the reagent ion to form well-characterized product ions.
- Analyte detection and quantitation. Product ions and unreacted reagent ions are sampled into a second quadrupole mass spectrometer. Utilizing Syft’s compound library, the software instantaneously calculates each analyte’s absolute concentration.