The analysis of gas and vapors in the field is an important part of the environmental characterization and remediation process. The purpose of this article is to familiarize the reader with some of the analytical instrumentation currently used to determine the composition of gaseous samples. Although this section deals with portable instruments, on‐site measurements warrant a brief mention. These measurements are often conducted with conventional analytical instruments operating from recreational vehicles. The samples have to be collected and transported to the instrument, and the first part of this article gives an overview of some of the techniques, such as canister and solid adsorbents, used for this purpose. Identification of compounds collected on‐site or directly in the field can be done by gas chromatography (GC) and mass spectrometry (MS). A more comprehensive description of these laboratory‐based techniques is found in a previous version of this article. An important part of the portable section covers direct‐reading instruments such as gas sensors, electrochemical devices, ionization detectors, and colorimetric detectors. These instruments provide a limited amount of information and, most of the time, require prior knowledge of the content of the sample. However, they are small, portable, and cheaper than laboratory analytical instruments and therefore they have found a market. Portable instruments include miniaturized gas chromatographs and mass spectrometers. These instruments do not offer the high performance of their laboratory counterparts, but they give more information about the sample than direct‐reading instruments. The next step in process measurement sophistication is to combine these techniques. The most popular hyphenated technique is coupling of a gas chromatograph with a mass spectrometer, but there are also powerful and lesser‐known techniques such as GC combined with ion mobility spectrometry (IMS). IMS has found a market in military applications for the detection of chemical warfare agents. It offers less resolution than MS but operates at atmospheric pressure and is therefore truly portable. When combined with GC, it offers some interesting features which are described later.
