University of North Florida
Browse the Citations

Contact Info

Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Website: @unf

View Stuart Chalk's profile on LinkedIn


Classification: Environmental -> air -> outdoor

Citations 3

"Evaluation Of A Diffusive Sampling Method For The Determination Of Atmospheric Ammonia"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 1 Pages 19-26
Wolfgang Frenzel, Ewald Grimm and Gesa Gruetzmacher

Abstract: NH3 was collected in H3PO4 coated bottoms of glass phials followed by FIA. The samplers (3 at each site) were covered with a hydrophobic microporous membrane (PTFE tape) and hung upside down. After exposure, the tube-type samplers were opened under NH3-free air and 1 mL water was pipetted into each phial. After shaking, a 320 µL portion of the solution was pipetted into FIA system. Sample was mixed with a water carrier stream (1.4 ml/min) via an FIA manifold (schematic given) and 10 g/l NaCl in 1 M NaOH (0.4 ml/min) in a mixing coil. The resulting stream was mixed with an acceptor stream of 0.1 g/l bromocresol purple (0.6 ml/min) in a gas diffusion unit comprising channels (33 cm x 3 mm width x 0.1 mm depth). Detection was spectrophotometrically at 585 nm. The calibration range was linear from 0.5-100 µg/l (as NH3) and RSD were 1-3%. The standard deviation (n = 30) of the method was 0.33 ng and the sampling frequency was 20 samples/h. The detection limit under optimized conditions was 2.3 x 103:m3 s. The method was applied to outdoor and indoor measurements.
Ammonia Spectrophotometry Gas diffusion Optimization

"Determination Of Sulfur Dioxide In Southeast Asia By Flow Injection Analysis With On-line Reaction Column"
Anal. Sci. 1997 Volume 13, Issue suppl Pages 397-400

Abstract: Ambient air samples were collected in Southeast Asian cities (Beijing, Bangkok, Kuala Lumper and Jakarta etc.) by passive samplers. Sulfur dioxide (SO2) was analyzed as sulfate ion in solution by FIA with a BaSO4-immobilized on-line reaction column. The method was based on the reaction of sulfate ion with barium-dimethylsulfonazo-III complex. The results agreed with those obtained by ion chromatography. The results showed that the SO2 concentrations in theses cities were in the range of 24-140 ppb.
Sulfur dioxide Spectrophotometry Solid phase reagent Precipitation Indirect Method comparison

"An Automated Sampler For Collection Of Atmospheric Trace Gas Samples For Stable Isotope Analyses"
Agric. For. Meteorol. 2003 Volume 118, Issue 1-2 Pages 113-124
A. J. Schauer, C. -T. Lai, D. R. Bowling and J. R. Ehleringer

Abstract: Research focused on the isotopic composition of CO2 exchange between terrestrial ecosystems and the atmosphere has been historically constrained by the need for personnel to be present at remote field sites for sample collection. In practice, this has limited sampling frequency and duration, and potentially even biases sampling events to fair weather periods. We have developed an automated sampling system that can be installed and used for unattended collection of 100 mL air samples in remote areas. The sampler was designed with the primary goal of collecting samples for analysis of CO2 concentration and its isotopic composition in ecosystem-atmosphere flux research, but several other potential applications are also discussed.Laboratory tests examined potential artifacts associated with sampler components. These tests included evaluation of potential isotopic exchange between atmospheric CO2 and sampler component materials and the effects of sample exposure to these materials for up to 5 days and under a wide range of temperatures (10-50°C). Some of the rejected component materials influenced either CO2 mole fraction or CO2 isotopic content. Exposure of air at subambient CO2 concentrations to all sampler components in an intact system for 5 days resulted in a [CO2] value that was 0.9 µmol mol-1 higher than for an equivalent sample collected by the sampler but not stored. Associated exposure-induced errors in δ13C of CO2 were generally small, ranging between 0.03 and 0.17[permil] for 0 day versus 5 days exposure, respectively. These error values were within the sampling precision associated with a PreCon continuous flow mass spectrometer analysis. A more substantial exposure-induced error was observed for δ18O in CO2 (0.29 and 0.88[permil], respectively). The potential for isotopic exchange between CO2 and sampler components increased under a combination of elevated temperature and multiple-day storage treatments. These errors were small and of similar magnitude between 10 and 40°C, but unacceptably large at 50°C. Finally, we compared Keeling plots created with samples collected by the sampler with those collected simultaneously by a manual method and found no detectable differences between the two approaches. Based on these results, we conclude that sampler induced isotopic exchange for air samples held up to 5 days between 10 and 40°C is largely within the overall precision limits of a PreCon continuous flow mass spectrometer measurement.
Carbon dioxide Mass spectrometry Isotope ratio Apparatus Optimization Gas phase detection