Volatile Organic Compounds (VOCs) are carbon-based compounds that occur naturally and vaporize at room temperature. Although some VOCs pose a minimal threat to humans and the environment, others pose a significant threat and must be reduced or eradicated. In fact, some VOCs are toxic enough for the Environmental Protection Agency to consider them Hazardous Air Pollutants (HAPs) - dangerous substances whose use is tightly regulated in the industrial sector. To detect dangerous VOCs in soil, water, and other substances, scientists use purge and trap equipment to facilitate the Gas Chromatography (GC) process. The purge and trap process for GC is outlined below:
The autosampler moves the sample to the column inlet
Gas bubbles through the sample to release the compounds
The compounds are released into the column
The column is heated and the compounds become vapor
The compounds travel into the chromatograph
This simple, yet effective process frees the sample of compounds that occur at low parts per billion (ppb) levels. Purge and trap analysis is used to test various substances for the presence of hazardous compounds. Three types of VOC testing that are commonly performed with purge and trap equipment include:
Beverage Testing
Beverages are created using food grade ingredients, but they often contain testable levels of VOCs. A natural ingredient that is improperly processed or formulated may release a trace amount of a VOC. According to researchers, more than 7,000 flavor volatiles have been established for foods and beverages. For example, an orange contains 203 VOCs; a baked potato has 259 VOCs; black tea possesses 541 VOCs; and the coffee bean contains a surprising 790 VOCs. It is important to remember, however, that not all VOCs are classified as HAPs.
Soil Testing
Soil testing is perhaps the best-known application for the purge and trap analysis of VOCs. Soil from fields, construction sites, Low Emissions Zones (LEZs), and brownfield sites is regularly tested for VOC containment. In some cases, the VOCs in soil pose little danger to humans or the environment, especially if the soil is located outdoors. However, VOCs classified as HAPs fall under EPA emission standards, and must be contained at appropriate levels.
Water testing
Industrial pollution is a common source of toxic compounds in wastewater and natural water bodies. In some cases, the presence of VOCs is detectable by smell alone, while in others a dangerous level of VOCs exists even after industrial filtration measures are taken. Analyzing water for VOCs is essential for the protection of human health, animals, and aquatic life.
Conclusion
Scientists use purge and trap equipment to analyze samples for the presence of low-level compounds, particularly VOCs. Purge and trap autosamplers are unique for how they operate. The autosampler places the sample in the injector, the compounds are separated from the sample and trapped in the concentrator, and then travel by carrier gas to the detector in the gas chromatograph. For help selecting the right autosampler for your analytical needs, contact a supplier of new and used laboratory equipment today.
Purge and trap equipment lets scientists perform purge and trap analysis on VOCs and other types of compounds.