Air Sample Collection and Analysis

Solid-phase extraction (SPE) is widely used for isolating and concentrating analytes prior to chromatography measurement (Chapter 19). 

Air is ma.de up primarily of N2, O2, and Ar, which comprise 99.9% of dry air. There is a variable amount of water vapor, and many minor and trace gaseous components, as well as aerosol and particulate species. Table 26.1 lists some atmospheric gaseous components of environmental interest, along with representative concentrations in the troposphere. Typically, gaseous concentrations are expressed as mixing ratios, that is, volume/volume concentrations. A 1-ppm concentration represents 1 volume in 10 volumes of air. Such mixing ratios are independent of temperature and pressure. Environmental effects, though, may be quantitatively related to mass concentrations, and concentrations may be reported as mass per unit volume, usually mg/m of air, under specific conditions of temperature and pressure. Aerosols and particulates are reported in this way. 

Compound Approximate Concentrations (when present) (v/v) Representative Measurement 

Working with gases is different from liquids and solids. We deal with large volumes. The weight of analyte in the sample will generally be determined. 

Industrial emissions may be monitored as the gas leaves a stack or exhaust, where concentrations are much higher than when dispersed. Remote monitoring may be made to obtain an integrated measurement of emissions. 

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