Efficiency and Temperature Dependence of Water Removal by Membrane Dryers

Leckrone, Kristen J.; Hayes, John M.

doi:10.1021/ac9610220

Cited by 82 publications

(55 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Particles were then passed through a Nafion diffusion dryer before entering the DustTrak. 54,55 Continuous CO Monitor. One-hour averaged CO levels were measured using an electrochemical monitor, Langan Model T15 (Langan Products, Inc.).…”

Section: Methodsmentioning

confidence: 99%

Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O₃, PM₂₅, and CO

Chang¹,

Suh²,

Wolfson³

et al. 2001

Journal of the Air & Waste Management Association

View full text Add to dashboard Cite

While researchers have linked acute (less than 12-hr) ambient O 3 , PM 2.5 , and CO concentrations to a variety of adverse health effects, few studies have characterized short-term exposures to these air pollutants, in part due to the lack of sensitive, accurate, and precise sampling technologies. In this paper, we present results from the laboratory and field evaluation of several new (or modified) samplers used in the "roll-around" system (RAS), which was developed to measure 1-hr O 3 , PM 2.5 , and CO exposures simultaneously. All the field evaluation data were collected during two sampling seasons: the summer of 1998 and the winter of 1999.To measure 1-hr O 3 exposures, a new active O 3 sampler was developed that uses two nitrite-coated filters to measure O 3 concentrations. Laboratory chamber tests found that the active O 3 sampler performed extremely well, with a collection efficiency of 0.96 that did not vary with temperature or relative humidity (RH). In field collocation comparisons with a reference UV photometric monitor, the active O 3 sampler had an effective collection efficiency ranging between 0.92 and 0.96 and a precision for 1-hr measurements ranging between 4 and 6 parts per billion (ppb). The limits of detection (LOD) of this method were 9 ppb-hr for the chamber tests and ~16 ppb-hr for the field comparison tests. PM 2.5 and CO concentrations were measured using modified continuous monitors-the DustTrak and the Langan, respectively. A size-selective inlet and a Nafion dryer were placed upstream of the DustTrak inlet to remove particles with aerodynamic diameters greater than 2.5 µm and to dry particles prior to the measurements, respectively. During the field validation tests, the DustTrak consistently reported higher PM 2.5 concentrations than those obtained by the collocated 12-hr PM 2.5 PEM samples, by approximately a factor of 2. After the DustTrak response was corrected (correction factor of 2.07 in the summer and 2.02 in the winter), measurements obtained using these methods agreed well with R 2 values of 0.87 in the summer and 0.81 in the winter. The results showed that the DustTrak can be used along with integrated measurements to measure the temporal and spatial variation in PM 2.5 exposures. Finally, during the field validation tests, CO concentrations measured using the Langan were strongly correlated with those obtained using the reference method when the CO levels were above the LOD of the instrument [~1 part per million (ppm)].

show abstract

Section: Methodsmentioning

confidence: 99%

Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O₃, PM₂₅, and CO

Chang¹,

Suh²,

Wolfson³

et al. 2001

Journal of the Air & Waste Management Association

View full text Add to dashboard Cite

show abstract

“…The mass spectrometer capillary restricts the flow rate to the MS to ∼0.3 mL/min and the vacuum in the ion chamber of the mass spectrometer is ∼3 × 10 −6 mbar. To keep the system as dry as possible, the original NAFION tube, which removes water from the passing gas stream, was replaced by a longer version with a higher (∼40 mL/min) helium counter flow (Leckrone and Hayes, 1997). The GasBench interface also allows injecting square peaks of a mass spectrometer running gas through a second split system (reference split).…”

Section: Open Split Interface and Mass Spectrometrymentioning

confidence: 99%

Continuous-flow isotope ratio mass spectrometry method for carbon and hydrogen isotope measurements on atmospheric methane

Braß

Röckmann

2010

Atmos. Meas. Tech.

View full text Add to dashboard Cite

Abstract. We describe a continuous-flow isotope ratio mass spectrometry (CF-IRMS) technique for high-precision δD and δ 13 C measurements of atmospheric methane on 40 mL air samples. CH 4 is separated from other air components by utilizing purely physical processes based on temperature, time and mechanical valve switching. Chemical agents are avoided. Trace amounts of interfering compounds can be separated by gas chromatography after pre-concentration of the CH 4 sample. The purified sample is then either combusted to CO 2 or pyrolyzed to H 2 for stable isotope measurement. Apart from connecting samples and refilling liquid nitrogen as coolant the system is fully automated and allows an unobserved, continuous analysis of samples. The analytical system has been used for analysis of air samples with CH 4 mixing ratios between ∼100 and ∼10 000 ppb, for higher mixing ratios samples usually have to be diluted.

show abstract

“…Removal of water from the combustion gases is typically accomplished via a countercurrent drier based on a selectively permeable membrane of the sulfonated fluoropolymer Nafion TM . Construction and operation of these driers have been described in detail by Leckrone and Hayes [60]. Although they are more effective (producing a lower dew point) at colder temperatures, operation of Nafion driers at room temperature is generally adequate.…”

Section: Carbon Isotopesmentioning

confidence: 99%

Isotope‐ratio detection for gas chromatography

Sessions¹

2006

J of Separation Science

244

270

View full text Add to dashboard Cite

Isotope-ratio detection for gas chromatographyInstrumentation and methods exist for highly precise analyses of the stable-isotopic composition of organic compounds separated by GC. The general approach combines a conventional GC, a chemical reaction interface, and a specialized isotoperatio mass spectrometer (IRMS). Most existing GC hardware and methods are amenable to isotope-ratio detection. The interface continuously and quantitatively converts all organic matter, including column bleed, to a common molecular form for isotopic measurement. C and N are analyzed as CO 2 and N 2 , respectively, derived from combustion of analytes. H and O are analyzed as H 2 and CO produced by pyrolysis/reduction. IRMS instruments are optimized to provide intense, highly stable ion beams, with extremely high precision realized via a system of differential measurements in which ion currents for all major isotopologs are simultaneously monitored. Calibration to an internationally recognized scale is achieved through comparison of closely spaced sample and standard peaks. Such systems are capable of measuring 13 C/ 12 C ratios with a precision approaching 0.1? (for values reported in the standard delta notation), four orders of magnitude better than that typically achieved by conventional "organic" mass spectrometers. Detection limits to achieve this level of precision are typically a1 nmol C (roughly 10 ng of a typical hydrocarbon) injected on-column. Achievable precision and detection limits are correspondingly higher for N, O, and H, in that order.

show abstract

Efficiency and Temperature Dependence of Water Removal by Membrane Dryers

Cited by 82 publications

References 35 publications

Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O₃, PM₂₅, and CO

Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O₃, PM₂₅, and CO

Continuous-flow isotope ratio mass spectrometry method for carbon and hydrogen isotope measurements on atmospheric methane

Isotope‐ratio detection for gas chromatography

Contact Info

Product

Resources

About

Efficiency and Temperature Dependence of Water Removal by Membrane Dryers

Cited by 82 publications

References 35 publications

Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O3, PM25, and CO

Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O3, PM25, and CO

Continuous-flow isotope ratio mass spectrometry method for carbon and hydrogen isotope measurements on atmospheric methane

Isotope‐ratio detection for gas chromatography

Contact Info

Product

Resources

About

Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O₃, PM₂₅, and CO

Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O₃, PM₂₅, and CO