Volatile Organic Compounds (VOC) Analyzers

Volatile organic compound (VOC) analyzers are used to detect concentrations of heavy hydrocarbons in gas or liquid media. They can be used to detect alkanes, isoalkanes, cycloalkanes, alkenes and aromatics as well as benzene, toluene, xylenes, cyclohexane, ethane, ethyelene, and lead. VOC analyzers use many different detection methods. Examples include gas chromatography (GC), high-resolution gas chromatography (HRGC), mass spectrometry (MS), atomic absorption spectrometry (AAS), electron capture detection (ECD), photoionization detection (PID) and flame ionization detection (FID). Portable VOC analyzers are usually hand-held devices such as photoionization detectors (PIDs) and flame ionization detectors (FIDs). A photoionization detector uses an ultraviolet (UV) lamp to irradiate incoming gas from either a sparger or flare. The UV energy ionizes the molecules, producing an ionic current which is measured by an electrometer. A flame ionization detector (FID) is similar to a flame thermocouple detector, but measures the ions from the flame instead of the heat generated. Larger, rack-mounted or benchtop volatile organic compound (VOC) analyzers may use analytical methods such as HRGC/FID, GC/FID, GC/MS, HRGC/FID, HRGS/MIS, GC/FID or GC/MS.

Specifications for volatile organic compound (VOC) analyzers include precision or accuracy, response time, sample flow rate, span drift, range or linear range, power consumption, physical dimensions, operating temperature, relative humidity, and electrical outputs. Precision or accuracy is plus (+) or minus (-) percentage (%) of the total reading. Response is measured in seconds to 90% response. The span drift for a VOC analyzer is also expressed as a percentage, but measured over 24 hours. Range is measured in parts per million (ppm) or parts per billion (ppb). Dimensions include length, width, and height. Operating temperature is measured in degrees Fahrenheit or degrees Celsius, but relative humidity is expressed as a percentage. VOC analyzers provide several types of electrical outputs. Analog voltage outputs are a simple, usually linear function of the measurement. Analog current outputs such as a 4 - 20 mA current loop are useful for sending signals over long distances. Digital, serial outputs such as RS232 and RS485 are also available.

Volatile organic compound (VOC) analyzers differ in terms of features. Some devices include integral software such as Microsoft CE (Microsoft Corp.), or can be interfaced to a programmable logic controller (PLC). Others are network-ready or network-capable, or feature a paperless chart recorder or solid-state data storage device. Touch screen VOC analyzers and devices that are designed to measure highly reactive volatile organic compounds are also available from some suppliers of volatile organic compound (VOC) analyzers.

• Detection of Volatile Organic Compounds (VOC's) with a Spectrally Filtered Cooled Mid-Wave Infrared Camera
  The world's petrochemical industry is constantly seeking methods for the detection of Volatile Organic Compounds (VOC's) such as benzene, propane and methane. Leaks of such materials all too often...
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