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Chromatographs—Gas
Published in Béla G. Lipták, Analytical Instrumentation, 2018
Photoionization Detector The photoionization detector (PID) functions by irradiating the column effluent with high-energy ultraviolet (UV) light generated by a high-voltage discharge lamp containing a noble gas (e.g., krypton) (Figure 11z). The ions are collected at a polarized electrode, and the resulting current is measured with a FID-type electrometer. This detector is selective in that only compounds whose ionization potential is less than the UV radiation will be ionized. Compounds with aromatic ring structures give the highest sensitivities (as much as 10 times the FID), while compounds like methane and ethane with ionization potentials greater than 12.98 ev give no response with the commonly used PID tubes (9.5, 10.0, 10.2, 10.9, and 11.7 eV). The PID has a dynamic range of 107, extending from 2 pg to 30 μg. An advantage to this detector is that it does not require auxiliary gases as does the FID. This advantage is offset by the fact that it does not respond sensitively to many of the compounds of interest and it requires increased maintenance to maintain quantitative accuracy.
Chromatographic Methods
Published in Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus, Environmental Chemical Analysis, 2018
Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus
A detector which has much the same response as the FID, but which requires no support gases is the photoionization detector (PID). This detector exposes the effluent stream to ultraviolet (UV) light, thus ionizing the sample. The ions are collected on an electrode, with the resulting current amplified and measured with an electrometer. Figure 4.16 shows the detector. The range of compounds to which the detector is sensitive depends on the wavelength of the lamp used in the detector. Lamps can be purchased with wavelength peaks at 9.5, 10.0, 10.2, 10.7, and 11.7 eV. The 10.2 lamp is the most commonly used. The detector will respond to substances having ionization potentials below the lamp energy, and up to about 0.4 eV above it.
Analysis of Organic Pollutants by Gas Chromatography
Published in Pradyot Patnaik, Handbook of Environmental Analysis, 2017
Halogen-specific detectors, such as the electron capture detector (ECD) and Hall electrolytic conductivity detector (HECD) show the best response to compounds that contain halogen atoms. The nitrogen–phosphorus detector (NPD) in the nitrogen mode can determine most nitrogen-containing organics while the same detector in the phosphorus-specific mode can analyze organophosphorus compounds. The flame photometric detector (FPD) is also equally efficient for determining phosphorus compounds. The FPD, however, is primarily used to analyze sulfur-containing organics. The photoionization detector (PID) is sensitive to substances that contain the carbon–carbon double bond such as aromatics and olefins, as well as their substitution products.
Airborne exposures associated with the typical use of an aerosol brake cleaner during vehicle repair work
Published in Journal of Occupational and Environmental Hygiene, 2018
Michael Fries, Pamela R.D. Williams, Jerald Ovesen, Andrew Maier
Two hand-heldFigure 2 direct reading instruments, the ppbRAE 3000 (Honeywell, San Jose, CA) and Tiger Select (Ion Sciences, Stafford, TX), were used during the study to approximate THC concentrations near the mechanic's breathing zone while the aerosol brake cleaner was being applied. Both instruments were battery-operated and measured airborne concentrations using a photoionization detector (PID). The ppbRAE 3000 had a lamp energy of 10.6 electron volts (eV), while the Tiger Select had a lamp energy of 10.0 eV. The instruments were factory and field calibrated prior to being used in the study using isobutylene. Indoor wind speeds were measured using a VelociCalc Air Velocity Meter 9535 (TSI Inc., Shoreview, MN), which was factory calibrated prior to the study, and taped to a stationary pump stand in the work bay.
Particle and vapor emissions from vat polymerization desktop-scale 3-dimensional printers
Published in Journal of Occupational and Environmental Hygiene, 2019
A. B. Stefaniak, L. N. Bowers, A. K. Knepp, T. P. Luxton, D. M. Peloquin, E. J. Baumann, J. E. Ham, J. R. Wells, A. R. Johnson, R. F. LeBouf, F.-C. Su, S. B. Martin, M. A. Virji
Total volatile organic compound (TVOC) concentration was monitored using a real-time photoionization detector (PID) (RAE Systems, San Jose, CA or Ion Science Inc., Stafford, TX) with a 10.6 eV lamp. This instrument uses an ultraviolet light to ionize organic molecules (with an ionization potential below 10.6 eV); the positively charged ions are detected as changes in electrical current by the instrument. Measurements were logged on a 1-sec basis. The potential for chemical emissions from the printers to react with ozone to form secondary chemical compounds such as carbonyl compounds was evaluated by drawing air through liquid impingers at 4 L/min for three of the five trials per printer, followed by derivatization and analysis using GC-MS.[28]
Glove permeation of chemicals: The state of the art of current practice, Part 1: Basics and the permeation standards
Published in Journal of Occupational and Environmental Hygiene, 2019
Berardinelli et al.[40] in 1986 reported on the permeation of acetone through a whole neoprene latex glove. The glove was turned inside out, the acetone liquid added, the top of the glove tied off, and the hand clamped at the tie-off. A calibrated portable photoionization detector (PID) quantified the vapor from the permeated acetone from the outside. The thinnest parts of a glove which were between the fingers, back, and palm, had the shortest breakthrough time and produced the largest steady-state concentration. The thickest part of the gloves, the fingertips, had the longest breakthrough time and the lowest steady-state concentrations.