Mass spectrometric thermal analysis

Appel, B. R., S. M. Wall, and R. L. Knights, "Characterization of Carbonaceous Materials in Atmospheric Aerosols by High Resolution Mass Spectrometric Thermal Analysis, Adv. Environ. Sci. Technol., 10, 353-365 (1980). 

Shulman GP (1965) Thermal degradation of polymers I. Mass spectrometric thermal analysis. Polym Lett 3 911... 

For mass spectrometric thermal analysis (MTA), a method previously described (16), any ion intensity can be recorded as a function of sample temperature. This method has been developed on a time-of-flight mass spectrometer (12). A small sample is introduced into a miniaturized furnace located within the ion source structure as shown in Fig. 1 by... 

The Kiselev-Zhuravlev constant aoH value of 4.6 was obtained with a deuterium-exchange method that distinguished between surface and bulk OH and with a mass spectrometric thermal analysis (MTA) method in conjunction with temperature-programmed desorption (TPD) (66). 

Names rejected by the ICTA committee were effluent gas detection, effluent gas analysis, thermovaporimetric analysis, and thermohygrometric analysis. Also, terms such as mass spectrometric thermal analysis (MTA) and mass spectrometric differential thermal analysis (MDTA) should be avoided. Unfortunately, new names for the techniques are constantly being created, such as thermal evolution analysis (TEA). The technique of TEA, according to Chiu (18), includes all techniques that monitor continuously the amount of volatiles thermally evolved from the sample upon programmed heating. 

Appel, B. R. 1981. Characterization of carbonaceous materials in atmospheric aerosols by high-resolution mass spectrometric thermal analysis. In G. M. Hidy, ed.. The aerosol characterization experiment. Wiley-Interscience, New York. 

Table 9.4 Experimental details of mass spectrometric thermal analysis ...

In Table IX a distinction is made between mass spectrometric thermal analysis, in which the sample is actually located in the mass spectrometer, and mass spectrometry coupled to either DTA, TG, or both. The latter type is most often used by commercial instrument manufacturers. The... 

Mass spectrometric analysis Mass spectrometric thermal analysis Mass spectraneter coupled to DTA or TG... 

Relatively few descriptions of direct mass spectral analysis of plastics compounds have appeared in the literature [22,37,63,240,243], Additives in PP were thermally desorbed into a heated reservoir inlet for 80 eV EI-MS analysis [240], Analysis of additives in PP compounds via direct thermal desorption ammonia CI-MS has been described [269] and direct mass spectrometric oligomer analysis has been reported [21],... 

To achieve sufficient vapor pressure for El and Cl, a nonvolatile liquid will have to be heated strongly, but this heating may lead to its thermal degradation. If thermal instability is a problem, then inlet/ionization systems need to be considered, since these do not require prevolatilization of the sample before mass spectrometric analysis. This problem has led to the development of inlet/ionization systems that can operate at atmospheric pressure and ambient temperatures. Successive developments have led to the introduction of techniques such as fast-atom bombardment (FAB), fast-ion bombardment (FIB), dynamic FAB, thermospray, plasmaspray, electrospray, and APCI. Only the last two techniques are in common use. Further aspects of liquids in their role as solvents for samples are considered below. 

Alternative approaches consist in heat extraction by means of thermal analysis, thermal volatilisation and (laser) desorption techniques, or pyrolysis. In most cases mass spectrometric detection modes are used. Early MS work has focused on thermal desorption of the additives from the bulk polymer, followed by electron impact ionisation (El) [98,100], Cl [100,107] and field ionisation (FI) [100]. These methods are limited in that the polymer additives must be both stable and volatile at the higher temperatures, which is not always the case since many additives are thermally labile. More recently, soft ionisation methods have been applied to the analysis of additives from bulk polymeric material. These ionisation methods include FAB [100] and LD [97,108], which may provide qualitative information with minimal sample pretreatment. A comparison with FAB [97] has shown that LD Fourier transform ion cyclotron resonance (LD-FTTCR) is superior for polymer additive identification by giving less molecular ion fragmentation. While PyGC-MS is a much-used tool for the analysis of rubber compounds (both for the characterisation of the polymer and additives), as shown in Section 2.2, its usefulness for the in situ in-polymer additive analysis is equally acknowledged. 

Table 6.10 reports the main areas of application of the various ionisation methods and the principal ions detected. A breakdown of MS techniques applied to various types of analytes is as follows thermally stable, low-MW Cl, El thermally instable, low-MW APCI (FLA, LC-MS), ESI and high-MW DCI, FD, FAB, LD, ESI (FLA, LC-MS, CZE-MS). Soft ionisation techniques such as FL, FAB and LD are useful for the detection of non-volatile, sometimes oligomeric, polymer additives. Recent developments in ionisation techniques have allowed the analysis of polar, ionic, and high-MW compounds, previously not amenable to mass-spectrometric analysis. Figure 6.4 shows the applicability of various atmospheric pressure ionisation techniques in terms of molar mass and polarity. 

Principles and Characteristics In the early mass-spectrometric ionisation techniques, such as El and Cl, the sample needs to be present in the ionisation source in its gaseous phase. Volatilisation by applying heat renders more difficult the analysis of thermally labile and involatile compounds, including highly polar samples and those of very high molecular mass. Although chemical derivatisation may be used to improve volatility and thermal stability, many compounds have eluded mass-spectrometric analysis until the emergence of fast atom bombardment (FAB) [72]. 

In direct insertion techniques, reproducibility is the main obstacle in developing a reliable analytical technique. One of the many variables to take into account is sample shape. A compact sample with minimal surface area is ideal [64]. Direct mass-spectrometric characterisation in the direct insertion probe is not very quantitative, and, even under optimised conditions, mass discrimination in the analysis of polydisperse polymers and specific oligomer discrimination may occur. For nonvolatile additives that do not evaporate up to 350 °C, direct quantitative analysis by thermal desorption is not possible (e.g. Hostanox 03, MW 794). Good quantitation is also prevented by contamination of the ion source by pyrolysis products of the polymeric matrix. For polymer-based calibration standards, the homogeneity of the samples is of great importance. Hyphenated techniques such as LC-ESI-ToFMS and LC-MALDI-ToFMS have been developed for polymer analyses in which the reliable quantitative features of LC are combined with the identification power and structure analysis of MS. 

Basile,F. Beverly,M. B. Abbas-Hawks,C. Mowry,C. D. Voorhees,K. J. FIadfield, T. L. Direct mass spectrometric analysis of in situ thermally hydrolyzed and methylated lipids from whole bacterial cells. Anal. Chem. 1998, 70,1555-1562. 

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