Fourier transform infrared spectroscopy atmospheric studies

Other combinations of chromatography techniques with MS which may be useful in environmental studies are the coupling of high performance liquid chromatography (LC) with MS [84,384,504,506,530,585-593],LC with MS-MS [181, 594 - 599], LC with atmospheric pressure chemical ionization MS (LC-APCI-MS) [600], and Fourier transform infrared spectroscopy-fast atom bombardment coupled to LC-MS (FTIR-FAB-LC-MS) [514]. 

Table 1 lists many of the short-lived species detected in the gas phase with Fourier transform infrared spectroscopy. Two prominent groups are those headed by Bernath, now at the University of Waterloo, and by Howard at the National Oceanic and Atmospheric Administration (NO AA). The former group has used IR emission to study unstable diatomics produced in discharge sources or furnaces. The molecules studied in this group tend to be of astrophysical interest. The research team at NOAA mainly studies short-lived molecules of atmospheric significance. They employ a long flow tube fitted with White cell optics and coupled to a Bomem DA3.002 spectrometer. They usually make the transient they are interested in by performing a carefully controlled series of chemical reactions. 

Fourier transform infrared spectroscopy (FTIR) and mass spectroscopy were used to study the photo-oxidation of both poly(alpha-methylstyrene) (PMS) and polystyrene (PS) films which had been irradiated at different temperatures and with different radiation sources under an oxygen atmosphere. The oxidised films were treated with ammonia or sulphur tetrafluoride and photolysis carried out under vacuum. Photoproducts from both polymers were broadly similar, but aromatic ketone concentration was higher from the PMS and a new ketone was also identified from this source. Routes for formation of identified photoproducts are proposed. 13 refs. 

H. Niki, P. D. Maker, C. M. Savage, and L. P. Breitenbach, Fourier transform infrared spectroscopic studies of atmospheric chemistry, in Spectroscopy in Chemistry and Physics Modern Trends, F. J. Comes, A. Muller, and W. J. Orville-Thomas, Eds., Elsevier, New York, 1980 and J. Mol. Struct., 59, 1 (1980). 

Towards this goal, there have been extensive studies that have compared PTR-MS measurements of atmospheric VOCs with those obtained by other atmospheric analytical techniques, such as GC-MS [17], GC-FID [21-26], atmospheric pressure chemical ionization mass spectrometry (AP-CIMS) [27], differential optical absorption spectroscopy (DOAS) [24,28] and Fourier transform infrared (FTIR) spectroscopy [17,29], in addition to offline sampling methods coupled to GC analysis [30-34], These studies have shown that PTR-MS is capable of accurately measuring concentrations of VOCs providing that there is no contribution to the miz of interest in a mass spectram by interfering species. If other compounds are present in the atmospheric sample which can lead to ions (protonated parent compounds, cluster ions or fragment ion species) at the nominal mJz of the protonated VOC of interest, then the lack of specificity associated with PTR-MS requires that the actual identity of the compound still needs to be confirmed by other analytical techniques, such as GC-MS. 

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