Speciation of Organics

As seen in Chapter 9.C.2, a very wide variety of organics are found in particles in ambient air and in laboratory model systems. The most common means of identification and measurement of these species is mass spectrometiy (MS), combined with either thermal separation or solvent extraction and gas chromatographic separation combined with mass spectrometry and/or flame ionization detection. For larger, low-volatility organics, high-performance liquid chromatography (HPLC) is used, combined with various detectors such as absorption, fluorescence, and mass spectrometry. For applications of HPLC to the separation, detection, and measurement of polycyclic aromatic hydrocarbons, see Wingen et al. (1998) and references therein. 

Solvent extraction of the sample is also frequently used in the analysis of particulate matter. Through the appropriate choice of solvents, the organics can be separated into acid, base, and neutral fractions, polar and nonpolar fractions, and so on. This grouping of compounds according to their chemical properties using extraction techniques simplifies the subsequent analysis. Each fraction can then be analyzed by GC-MS, with the GC retention time and the mass spectrum used for identification and measurement. 

Other types of mass spectrometry have also been used to examine ambient particulate samples. One such technique is secondary ion mass spectrometry (SIMS) in which the surface of the sample is bombarded with a beam of ions or neutral atoms that cause ejection of fragments from the surface. The fragments may be neutral atoms or molecules, positively or negatively charged species, electrons, or photons. The 

In addition to these chemical artifacts, physical artifacts can also occur. For example, the problems of particle bounce (e.g., see Wedding et al., 1986) and reentrainment in impactors were discussed earlier. In addition, air turbulence is known to have a significant effect on the overall sampling efficiency of particle inlets (e.g., Wiener et al., 1988 Francois et al., 1995). 

In short, care must be taken in sampling and analysis of airborne particles, as well as in the data interpretation, to minimize or at least recognize potential artifact problems. Such problems, along with a need to understand not only the bulk composition of a collection of airborne particles but also that of individual particles, have contributed to the development of realtime and single-particle analysis techniques discussed in the following section. 

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Chemical Speciation of Organics and of Metals at Biological Interphases... 

Escher, B. and Sigg, L. (2004). Chemical speciation of organics and metals at biological interphases. In Physicochemical Kinetics and Transport at Biointerfaces. eds. van Leeuwen, H. P. and Koster, W., Vol. 9, IUPAC Series on Analytical and Physical Chemistry of Environmental Systems, Series eds. Buffle, J. and van Leeuwen, H. P., John Wiley Sons Ltd, Chichester, pp. 205-269. 

Relatively little is known about the speciation of organic compounds, and organic reductants in particular, when adsorbed to metal oxides. It is known that surface coverage is higher for bidentate organic ligands, such as catechol and salicylate, than... 

Illustrative Example 8.1 Assessing the Speciation of Organic Acids and Bases in Natural Waters... 

Schulton and Sorge [274] used laser Raman spectroscopy to provide detailed information on the location, elemental composition and chemical speciation of organic compounds in soil. 

Olivas, R.M., Donard, OXF., Gilon, N. and PotinGautier, M. (1996) Speciation of organic selenium compounds by high-performance liquid chromatography inductively coupled plasma mass spectrometry in natural waters./. Anal. At. Spectrom., 11, 1171-1176. 

I. Feldmann, N. Jakubowski, D. Stuewer, C. Thomas, Speciation of organic selenium compounds by reversed-phase liquid chromatography and inductively coupled plasma mass spectrometry, J. Anal. Atom. Spectrom., 15 (2000), 371D376. 

Escher BI, Sigg L. 2004. Chemical speciation of organics and of metals at biological interfaces. In Van Leeuwen HP, Koster W, editors, Physicochemical kinetics and transport at biointerfaces. Vol. 9. Chichester (UK) John Wiley, p 205-271. 

Microbiological specifications and microbial test methods for each topical product should be well-established to ensure that they are consistent with any described in the relevant application or USP. In general, product specifications should cover the total number of organisms permitted, as well as specific organisms that must not be present. These specifications must be based on use of specified sampling and analytical procedures. Where appropriate, the specifications should describe action levels where additional sampling or speciation of organisms is necessary. 

Several methods have been described for the determination of inorganic mercury together with speciation of organic mercurials (see below). 

Separation, Preconcentration and Speciation of Organic Phosphorus in Environmental Samples... 

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