493:, 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.
33:
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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)
169:(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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279:. The greater the concentration of the component, the more ions are produced, and the greater the current. The current is
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Lovelock, J. A. (1960). A Photoionization
Detector for Gases and Vapours. Nature 188, 401.
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291:The PID will only respond to components that have
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244:In a photoionization detector, high-energy
148:and other gases in concentrations from sub
144:Typical photoionization detectors measure
117:Learn how and when to remove this message
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172:Portable PIDs are used for monitoring:
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489:The PID is usually calibrated using
55:adding citations to reliable sources
300:Lamp types and detectable compounds
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537:https://doi.org/10.1038/188401a0
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42:needs additional citations for
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465:Some inorganics, including NH
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167:volatile organic compounds
146:volatile organic compounds
66:"Photoionization detector"
18:Photo-ionization detector
131:photoionization detector
441:Sulfides and mercaptans
612:Measuring instruments
209:Lower explosive limit
453:Esters and acrylates
438:Bromides and iodides
283:and displayed on an
228:facility maintenance
51:improve this article
310:Main photon energy
293:ionization energies
252:(VUV) range, break
248:, typically in the
197:Hazardous materials
617:Gas chromatography
497:Matrix gas effects
250:vacuum ultraviolet
221:Indoor air quality
162:gas chromatography
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154:parts per million
150:parts per billion
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481:Applications
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350:Most robust
333:Short-lived
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233:Table Tennis
211:measurements
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139:gas detector
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49:Please help
44:verification
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491:isobutylene
192:remediation
176:Industrial
156:(ppm). The
606:Categories
510:References
152:to 10 000
77:newspapers
473:S, and PH
456:Aldehydes
432:Aromatics
319:Comments
313:Fill gas
281:amplified
254:molecules
240:Principle
226:Cleanroom
205:detection
459:Alcohols
374:10.0 eV
355:10.2 eV
338:10.6 eV
324:11.7 eV
277:detector
199:handling
595:(1990).
585:(2007).
462:Alkanes
447:Ketones
435:Olefins
406:8.4 eV
390:9.6 eV
285:ammeter
265:ionized
258:charged
246:photons
235:rackets
203:Ammonia
178:hygiene
91:scholar
450:Ethers
273:signal
182:safety
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215:Arson
98:JSTOR
84:books
330:LiF
261:ions
190:and
180:and
70:news
469:, H
409:Xe
396:BaF
393:Xe
380:CaF
377:Kr
364:MgF
344:MgF
341:Kr
327:Ar
135:PID
133:or
53:by
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555:^
412:Al
141:.
129:A
475:3
471:2
467:3
418:3
416:O
414:2
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358:H
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