Atmospheric Monitoring With Chemical Ionisation Reaction Time-Of-Flight Mass Spectrometry (Cir-Tof-Ms) And Future Developments: Hadamard Transform Mass Spectrometry

Chemical ionisation reaction mass spectrometry (CIR-MS) is a more general version of proton transfer reaction mass spectrometry (PTR-MS) in which alternative chemical ionisation schemes are possible. This concept has been realised in a new instrument based on time-of-flight mass spectrometry (TOF-MS) and has been applied to the measurement of a range of trace atmospheric volatile organic compounds (VOCs) and oxygenated volatile organic compounds (OVOCs) (Blake et al., 2004 and Wyche et al., 2005). Initial results have demonstrated the instrument to be capable of recording the entire mass spectrum in "real time" (ca. 1min) with sensitivities in the order of 0.1 counts ppbV(-1) s(-1) in each unit mass channel. This article constitutes a brief overview of the CIR-TOF-MS instrument and several of its applications. A short account is also given of the "next generation" instrument which is under development. This new instrument will combine rapid beam modulation with Hadamard transformation of the detector output and should improve the detection sensitivity by more than an order of magnitude over the current CIR-TOF-MS instrument.