Development of an SI-traceable transmission curve reference material to improve comparability of proton transfer reaction mass spectrometry measurements

Abstract. Since its inception more than two decades ago proton-transfer-reaction mass-spectrometry (PTR-MS) has established itself as a powerful technique for the measurements of volatile organic compounds (VOCs) providing high time resolution, high sensitivity measurements without any sample pre-treatment. As this technology has matured and its application become more widespread there is a growing need for accurate and traceable calibration to ensure measurement comparability. As a result of the large number of VOCs detectable with PTR-MS it is impractical to have a calibration standard or standards that cover all observable compounds. However, recent work has demonstrated that quantitative measurements of uncalibrated compounds are possible provided that the transmission curve is sufficiently constrained. To enable this, a novel multi-component gas reference material containing 20 compounds that spans the molecular weight range of 32 to 671 has been developed. This development and the compositional evolution of this reference material are described along with an evaluation of the accuracy and stability. This work demonstrates that for the majority of components the accuracy is < 5 % (most < 3 %; < 10 % for hexamethylcyclotrisiloxane (D3-siloxane) and 1,2,4-trichlorobenzene (1,2,4-TCB)) with stabilities of > 2 years (> 1 year for acetonitrile, methanol and PFTBA).