Problems with a Nafion® membrane dryer for drying chromatographic samples

Burns, Walter F.; Tingey, David T.; Evans, R. C.; Bates, Emily H.

doi:10.1016/s0021-9673(01)90777-0

Cited by 46 publications

(15 citation statements)

References 13 publications

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“…There was a lack of comparison between the KPASS and the Cooler, but the KPASS was reported to have a higher and more stable water removal rate than a Nafion dryer [26]. A study on the water removal method using Nafion reported that recovery of the Nafion membrane to the polar material or the adsorbing material was inferior [28]. With insufficient heating, analytes absorbed and reacted with condensed water in the Nafion membrane [12,13,28].…”

Section: Resultsmentioning

confidence: 99%

Effects of Water Removal Devices on Ambient Inorganic Air Pollutant Measurements

Kim

Dinh

Lee

et al. 2019

IJERPH

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Water vapor is a pivotal obstacle when measuring ambient air pollutants. The effects of water vapor removal devices which are called KPASS (Key-compound PASSer) and Cooler. On the measurement of O3, SO2, and CO at ambient levels were investigated. Concentrations of O3, SO2, and CO were 100 ppb, 150 ppb, and 25 ppm, respectively. The amount of water vapor varied at different relative humidity levels of 30%, 50%, and 80% when the temperature was 25 °C and the pressure was 1 atm. Water vapor removal efficiencies and recovery rates of target gases were also determined. The KPASS showed a better performance than the Cooler device, removing 93.6% of water vapor and the Cooler removing 59.2%. In terms of recovery, the KPASS showed a better recovery of target gases than the Cooler. Consequently, it is suggested that the KPASS should be an alternative way to remove water vapor when measuring O3, SO2, and CO.

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Section: Resultsmentioning

confidence: 99%

Effects of Water Removal Devices on Ambient Inorganic Air Pollutant Measurements

Kim

Dinh

Lee

et al. 2019

IJERPH

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“…It is not known to what extent the identification of these two compounds in Atlanta and Detroit represents actual differences in the biogenic emissions between the various locations or artifacts caused by the collection or analysis of a subset of the samples. (With regard to p-cymene it is relevant to note that Burns et al [1983] found that the use of a Nation © membrane dryer to dry whole air samples before analysis can cause p-cymene artifacts. However, this cannot be an explanation for the p-cymene identification in the Atlanta data sets as a Nation© membrane dryer was not used in this case.…”

Section: Hydrocarbon Observationsmentioning

confidence: 99%

Ozone precursor relationships in the ambient atmosphere

et al. 1992

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The concentrations of ozone, nitrogen oxides, and nonmethane hydrocarbons measured near the surface in a variety of urban, suburban, rural, and remote locations are analyzed and compared in order to elucidate the relationships between ozone, its photochemical precursors, and the sources of these precursors. While a large gradient is found among remote, rural, and urban/suburban nitrogen oxide concentrations, the total hydrocarbon reactivity in all continental locations is found to be comparable. Apportionment of the observed hydrocarbon species to mobile and stationary anthropogenic sources and biogenic sources suggests that present-day emission inventories for the United States underestimate the size of mobile emissions. The analysis also suggests a significant role for biogenic hydrocarbon emissions in many urban/suburban locations and a dominant role for these sources in rural areas of the eastern United States. As one moves from remote locations to rural locations and then from rural to urban/suburban locations, ozone and nitrogen oxide concentrations tend to increase in a consistent manner while total hydrocarbon reactivity does not. hydrocarbon concentrations in four chemically distinct regimes of the atmospheric boundary layer, each having a distinct mix of anthropogenic and natural hydrocarbon and NOx emissions. These regimes are: I, the urban/suburban atmosphere, which is the regime most strongly impacted by anthropogenic emissions; II, the rural atmosphere, which is somewhat less impacted by anthropogenic emissions and more impacted by natural emissions than that of the urban atmosphere; III, the atmosphere over the remote, tropical forest which is essentially free of anthropogenic volatile organic compounds (VOC) and NOx emissions and strongly influenced by natural emissions; and IV, the remote, marine atmosphere, which is not only free of anthropogenic emissions but is also characterized by relatively small biogenic sources of VOC and NO x. Because we are most interested in the conditions that foster ozone episodes, our analysis concentrates on observations made during the daylight hours of the summer months.In the sections below we first briefly summarize the fundamentals of the photochemical smog mechanism and the nonlinearities inherent in this system and then discuss the concentrations of 03, NOx, and hydrocarbons typically observed in the four regimes listed above. PHOTOCHEMICAL SMOGWhile uncertainties remain in our understanding of tropospheric photochemistry, the basic set of reactions that lead to 03 production have been identified. These reactions, commonly referred to in the aggregate as the "photochemical smog" mechanism, involve the oxidation of hydrocarbons and other volatile organic compounds in the presence of nitrogen oxides (NOx) and sunlight [Haagen-Srnit, 1952; $einfeld, 1988]. Typical of this mechanism are reactions (R1) through (R7),RH + OH--> R + H20 (R2) R + 02 + M--> RO2 + M (R3) RO 2 + NO--> RO + NO 2 (R4) RO + 0 2 --> HO 2 + RCHO 6037

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“…However, the reported efficiency of humidity reduction by nafion tubing is highly variable, ranging from 58% to 98% depending on ambient humidity [14, 15]. For this reason many applications must flow additional drying gas into the nafion tubing in order to maintain the efficiency [16], which adds complexity into the device, and also makes it unsuitable for personal use that requires portability.…”

Section: Introductionmentioning

confidence: 99%

“…For this reason many applications must flow additional drying gas into the nafion tubing in order to maintain the efficiency [16], which adds complexity into the device, and also makes it unsuitable for personal use that requires portability. A more serious issue with the nafion approach is that it removes not only unwanted humidity, but also partially or completely (75% to >90%) remove many wanted analytes, such as low-molecular-weight, polar, oxygenated compounds, including some ketones, alcohols, aldehydes, and water-soluble ethers [14]. These analytes are of high clinical significance for different diseases.…”

Section: Introductionmentioning

confidence: 99%

Online Sample Conditioning for Portable Breath Analyzers

et al. 2012

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Various innovative chemical sensors have been developed in recent years to sense dangerous substances in air and trace biomarkers in breath. However, in order to solve real world problems, the sensors must be equipped with efficient sample conditioning that can, e.g., control the humidity, which is much less discussed in literatures. To meet the demand, a miniaturized mouthpiece was developed for personal breath analyzers. A key function of the mouthpiece is to condition the humidity in real breath samples without changing the analyte concentrations and introducing substantial backpressure, which is achieved with optimized packing of desiccant particles. Numerical simulations were carried out to determine the performance of the mouthpiece in terms of various controllable parameters, such as the size, density and geometry of the packing. Mouthpieces with different configurations were built and tested, and the experimental data validated the simulation findings. A mouthpiece with optimized performance reducing relative humidity from 95% (27,000 ppmV) to 29% (8000 ppmV) whereas retaining 92% nitric oxide (50ppbV to 46ppbV) was built and integrated into a handheld exhaled nitric oxide sensor, and the performance of exhaled nitric oxide measurement was in good agreement with the gold standard chemiluminescence technique. Acetone, carbon dioxide, nitric oxide, oxygen and ammonia samples were also measured after passing through the desiccant mouthpiece using commercial sensors to examine wide applicability of this breath conditioning approach.

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Problems with a Nafion® membrane dryer for drying chromatographic samples

Cited by 46 publications

References 13 publications

Effects of Water Removal Devices on Ambient Inorganic Air Pollutant Measurements

Effects of Water Removal Devices on Ambient Inorganic Air Pollutant Measurements

Ozone precursor relationships in the ambient atmosphere

Online Sample Conditioning for Portable Breath Analyzers

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