482:, and other analytes may produce a relatively greater or lesser response on a concentration basis. Although many PID manufacturers provide the ability to program an instrument with a correction factor for quantitative detection of a specific chemical, the broad selectivity of the PID means that the user must know the identity of the gas or vapor species to be measured with high certainty. If a correction factor for benzene is entered into the instrument, but hexane vapor is measured instead, the lower relative detector response (higher correction factor) for hexane would lead to underestimation of the actual airborne concentration of hexane.
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ions formed in close proximity and/or 2) absorption of UV light without ionization. The signal produced by a PID may be quenched when measuring in high humidity environments, or when a compound such as methane is present in high concentrations of ≥1% by volume This attenuation is due to the ability of water, methane, and other compounds with high ionization energies to absorb the photons emitted by the UV lamp without leading to the production of an ion current. This reduces the number of energetic photons available to ionize target analytes.
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years later, in 1976. A PID is highly selective when coupled with a chromatographic technique or a pre-treatment tube such as a benzene-specific tube. Broader cuts of selectivity for easily ionized compounds can be obtained by using a lower energy UV lamp. This selectivity can be useful when analyzing mixtures in which only some of the components are of interest.
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Response to stand-alone PIDs is generally linear from the ppb range up to at least a few thousand ppm. In this range, response to mixtures of components is also linearly additive. At the higher concentrations, response gradually deviates from linearity because of recombination of oppositely charged
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The first commercial application of photoionization detection was in 1973 as a hand-held instrument for the purpose of detecting leaks of VOCs, specifically vinyl chloride monomer (VCM), at a chemical manufacturing facility. The photoionization detector was applied to gas chromatography (GC) three
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similar to or lower than the energy of the photons produced by the PID lamp . As stand-alone detectors, PIDs are broad band and not selective, as these may ionize everything with an ionization energy less than or equal to the lamp photon energy. The more common commercial lamps have photons energy
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or digital concentration display. The ions can undergo numerous reactions including reaction with oxygen or water vapor, rearrangement, and fragmentation. A few of them may recapture an electron within the detector to reform their original molecules; however only a small portion of the airborne
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upper limits of approximately 8.4 eV, 10.0 eV, 10.6 eV, and 11.7 eV. The major and minor components of clean air all have ionization energies above 12.0 eV and thus do not interfere significantly in the measurement of VOCs, which typically have ionization energies below 12.0 eV.
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or as hand-held portable instruments. Hand-held, battery-operated versions are widely used in military, industrial, and confined working facilities for health and safety. Their primary use is for monitoring possible worker exposure to
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Smith, P.A., Jackson Lepage, C., Harrer, K.L., and P.J. Brochu: Handheld photoionization instruments for quantitative detection of sarin vapor and for rapid qualitative screening of contaminated objects. J. Occ. Env. Hyg. 4:729-738
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analytes are ionized to begin with so the practical impact of this (if it occurs) is usually negligible. Thus, PIDs are non-destructive and can be used before other sensors in multiple-detector configurations.
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Stauffer, E., Dolan, J. A., Newman, R. (2008). Detection of
Ignitable Liquid Residues at Fire Scenes. In E. Stauffer, J. A. Dolan and R. Newman (Editors), Fire Debris Analysis, pp. 131-161. Academic Press,
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Nyquist, J.E., Wilson, D.L., Norman, L.A., and R.B. Gammage: Decreased sensitivity of photoionization detector total organic vapor detectors in the presence of methane. Am. Ind. Hyg. Assoc. J., 51:326-330
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The 10.6 eV lamp is the most common because it has strong output, has the longest life and responds to many compounds. In approximate order from most sensitive to least sensitive, these compounds include:
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With a gas chromatograph, filter tube, or other separation technique upstream of the PID, matrix effects are generally avoided because the analyte enters the detector isolated from interfering compounds.
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Poole, C. F., Gas
Chromatography: Detectors. in P. Worsfold, C. Poole, A. Townshend, and M. Miro (Editors), Encyclopedia of Analytical Science (Third Edition). Academic Press (2016) pages 135-147.
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detector is an efficient and inexpensive detector for many gas and vapor analytes. PIDs produce instantaneous readings, operate continuously, and are commonly used as detectors for
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PID lamp photon emissions depend on the type of fill gas (which defines the light energy produced) and the lamp window, which affects the energy of photons that can exit the lamp:
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Haag, W.R. and Wrenn, C.: The PID Handbook - Theory and
Applications of Direct-Reading Photoionization Detectors (PIDs), 2nd. Ed., San Jose, CA: RAE Systems Inc. (2006)
158:(VOCs) such as solvents, fuels, degreasers, plastics and their precursors, heat transfer fluids, lubricants, etc. during manufacturing processes and waste handling.
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Driscoll, J.N., and J.B. Clarici: Ein neuer
Photoionisationsdetektor für die Gas-Chromatographie. Chromatographia, 9:567-570 (1976).
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when they absorb the UV light, resulting in ejection of electrons and the formation of positively charged ions. The ions produce an
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Lovelock, J. A. (1960). A Photoionization
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233:In a photoionization detector, high-energy
137:and other gases in concentrations from sub
133:Typical photoionization detectors measure
106:Learn how and when to remove this message
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161:Portable PIDs are used for monitoring:
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478:The PID is usually calibrated using
44:adding citations to reliable sources
289:Lamp types and detectable compounds
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526:https://doi.org/10.1038/188401a0
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31:needs additional citations for
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454:Some inorganics, including NH
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156:volatile organic compounds
135:volatile organic compounds
55:"Photoionization detector"
120:photoionization detector
430:Sulfides and mercaptans
601:Measuring instruments
198:Lower explosive limit
442:Esters and acrylates
427:Bromides and iodides
272:and displayed on an
217:facility maintenance
40:improve this article
299:Main photon energy
282:ionization energies
241:(VUV) range, break
237:, typically in the
186:Hazardous materials
606:Gas chromatography
486:Matrix gas effects
239:vacuum ultraviolet
210:Indoor air quality
151:gas chromatography
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38:Please help
33:verification
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480:isobutylene
181:remediation
165:Industrial
145:(ppm). The
595:Categories
499:References
141:to 10 000
66:newspapers
462:S, and PH
445:Aldehydes
421:Aromatics
308:Comments
302:Fill gas
270:amplified
243:molecules
229:Principle
215:Cleanroom
194:detection
448:Alcohols
363:10.0 eV
344:10.2 eV
327:10.6 eV
313:11.7 eV
266:detector
188:handling
584:(1990).
574:(2007).
451:Alkanes
436:Ketones
424:Olefins
395:8.4 eV
379:9.6 eV
274:ammeter
254:ionized
247:charged
235:photons
224:rackets
192:Ammonia
167:hygiene
80:scholar
439:Ethers
262:signal
171:safety
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204:Arson
87:JSTOR
73:books
319:LiF
250:ions
179:and
169:and
59:news
458:, H
398:Xe
385:BaF
382:Xe
369:CaF
366:Kr
353:MgF
333:MgF
330:Kr
316:Ar
124:PID
122:or
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118:A
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