Donald V. Kenny

MS/MS analysis of the products of toluene photooxidation and measurement of their mutagenic activity

Products of the photooxidation of toluene from an irradiated 5.1 ppm toluene/0.9 ppm NO/sub x/ mixture were identified by use of a triple-quadrupole MS/MS operated in an atmospheric pressure ionization mode. The reaction was carried out in a flow-mode 22.7-m/sup 3/ Telfon smog chamber. The steady-state reactant and product mixture was continuously transferred to the mass spectrometer inlet at 144 L/min. By using structurally similar standards, semiquantitative MS/MS analyses for many of the ring fragmentation products were conducted. Quantitative analyses by chromatographic methods and semiquantitative analyses by MS/MS were conducted for a variety of ring fragmentation products. The following products were found with yields of 1% (C/C) or greater: methylglyoxal, glyoxal, benzaldehyde, methylbutenedial, hydroxy-methylbutenedial, peroxyacetyl nitrate, oxoheptadienal, CH/sub 3/COOH, HCHO, hexadienal, and hydroxyoxo-heptadienal. The mutagenic activity of the steady-state product mixture was measured by using the Ames assay Salmonella typhimurium strain TA 100. The mutagenic activity data are discussed relative to our earlier findings that resulted from different reaction conditions.

Transformations, lifetimes, and sources of NO2, HONO, and HNO3 in indoor environments

Recent research has demonstrated that nitrogen oxides are transformed to nitrogen acids in indoor environments, and that significant concentrations of nitrous acid are present in indoor air. The purpose of the study reported in this paper has been to investigate the sources, chemical transformations and lifetimes of nitrogen oxides and nitrogen acids under the conditions existing in buildings. An unoccupied single family residence was instrumented for monitoring of NO, NO2, NOy, HONO, HNO3, CO, temperature, relative humidity, and air exchange rate. For some experiments, NO2 and HONO were injected into the house to determine their removal rates and lifetimes. Other experiments investigated the emissions and transformations of nitrogen species from unvented natural gas appliances. We determined that HONO is formed by both direct emissions from combustion processes and reaction of NO2 with surfaces present indoors. Equilibrium considerations influence the relative contributions of these two sources to the indoor burden of HONO. We determined that the lifetimes of trace nitrogen species varied in the order NO approximately HONO > NO2 > HNO3. The lifetimes with respect to reactive processes are on the order of hours for NO and HONO, about an hour for NO2, and 30 minutes or less for HNO3. The rapid removal of NO2 and long lifetime of HONO suggest that HONO may represent a significant fraction of the oxidized nitrogen burden in indoor air.

Eddy correlation fluxes of trace gases using a tandem mass spectrometer

Abstract This paper describes a field evaluation of a tandem mass spectrometer (TAGA) for use in measuring turbulence fluxes of trace gases. Measurements were made over a two-day period in a fallow farm field west of Columbus, OH. The results show that for weakly adsorbing species such as acetone, the effective time constant for the TAGA is

Observations of dimethyl sulfide over the western North Atlantic Ocean using an airborne tandem mass spectrometer

An atmospheric sampling tandem mass spectrometer has been evaluated for aircraft monitoring of dimethyl sulfide (DMS) and then used for DMS monitoring during portions of six flights over the western North Atlantic Ocean. Laboratory evaluations demonstrated that the mass spectrometer is highly selective for DMS, and responds linearly over a wide range of mixing ratios. The detection limit for DMS is 1–2 ppt in dry air. However, the response is suppressed in the presence of water vapor, so the sample air must be dried or the response must be corrected for this effect. There appeared to be no consistent effect of altitude/pressure on instrument response. The mass spectrometer was installed on the Battelle Gulf stream G-1 research aircraft and used to monitor DMS and a number of other chemicals during flights over the western North Atlantic Ocean in August and September, 1992. DMS mixing ratios ranged from <2 ppt to 332 ppt, and were highly variable both horizontally and vertically. Vertical profiles indicated that there are times when the marine boundary layer is stratified by one or more temperature inversions, and that DMS emitted by surface seawater can be confined near the surface within a shallow layer a few hundred meters deep. Under such circumstances, the DMS photooxidation products may be removed rapidly by deposition, lessening the potential for cloud nucleation. The mean DMS mixing ratio in the boundary layer below the lowest observed temperature inversion was 61 ppt, with a range of 7–332 ppt. DMS measurements in the free troposphere were lower than the boundary layer values, but high enough to suggest significant transport from the boundary layer to the free troposphere. Significant horizontal variability was observed during constant altitude flights in the boundary layer. In one case the DMS mixing ratio was observed to vary with the ocean depth under the flight path, with higher mixing ratios observed over the shallower coastal shelf and undersea banks. In several cases we also observed an apparent association between atmospheric DMS mixing ratio at low elevation and sea surface temperature.

Direct Sampling and Analysis of Volatile Organic Compounds in Air by Membrane Introduction and Glow Discharge Ion Trap Mass Spectrometry with Filtered Noise Fields

Two direct air sampling interfaces have been evaluated in the laboratory for monitoring toxic air pollutants in real time by ion trap mass spectrometry in both single mass spectrometry and tandem mass spectrometry (MS/MS) modes. The mass spectrometer is the research-grade Finnigan MAT ion trap (ITMSTM) equipped with the Teledyne filtered noise field (FNF) module to eject unwanted ions and isolate only ions of interest. This results in enhanced sensitivity and selectivity for analyte ions of interest. MS/MS operation, for characterization of individual compounds with high sensitivity and specificity, is achieved by applying a supplementary RF signal to the end-caps of the ion trap. The direct air sampling interfaces are a semi-permeable helium-purged tubular membrane and an atmospheric sampling glow discharge ionization (ASGDI) source. Nonpolar and polar volatile organic compounds (VOCs) are measured at trace levels in air, using an environmental test chamber as the source of the target compound mixtures at known concentrations. Experiments conducted with the combination systems permit a comparison of the two direct air sampling interfaces for monitoring VOCs continuously in real time and illustrate the power of the FNF method to isolate ions with unit mass resolution and to perform MS/MS measurements.

Continuous airborne measurements of gaseous formic and acetic acids over the western North Atlantic

A tandem mass spectrometer modified for aircraft applications was used to measure gas-phase formic and acetic acid mixing ratios over the western North Atlantic during late summer 1992. The sensitive, specific, and essentially real-time measurements provided by the mass spectrometer allow a true spatial evaluation of these compounds in the study area. Formic and acetic acid mixing ratios showed substantial vertical variation, varying by factors of up to 13 and 6, respectively, within 2-km profiles extending from the boundary layer into the free troposphere. Substantial horizontal variation was also observed at constant altitudes within both the boundary layer and free troposphere. Mixing ratios of the two acids were correlated (r²>0.70) throughout the study region.

Evaluation of NO2 Measurement Methods for Indoor Air Quality Applications

Measurement of nitrogen dioxide (NO2) and other oxidized nitrogen compounds in indoor environments can present some measurement difficulties not normally encountered in sampling outdoor air. This paper examines three methods that are in current use for monitoring indoor nitrogen dioxide. The methods include ozone-based and luminol-based chemiluminescence, and an electrochemical technique. We have examined these methods for accuracy, linear dynamic range, and interferences. Each of the methods was subject to interference. For indoor measurements, nitrous acid probably represents the most significant interference for the ozone-based chemiluminescence and electrochemical monitors.

Continuous determination of dimethylsulfide at part-per-trillion concentrations in air by atmospheric pressure chemical ionization mass spectrometry☆

Abstract Highly sensitive and specific continuous measurement of dimethylsulfide (DMS) in air has been demonstrated using triple quadrupole mass spectrometry with atmospheric pressure chemical ionization. Detection limits of 2 parts per trillion and 4 parts per trillion by volume in air are achieved for DMS using positive ion detection with benzene charge exchange and hot wire excitation, respectively. Either of these ionization modes provides sensitivity sufficient for continuous direct monitoring of dimethylsulfide in the atmosphere, with time response of approximately 1 s. This capability may be applicable to study the effect of oceanic DMS emissions on global climate. Detection limits in continuous monitoring were also determined for hydrogen sulfide (1 ppbv) and for methyl mercaptan, carbonyl sulfide, and carbon disulfide (≈ 10 ppbv).

Design and Evaluation of a Breath-Analysis System for Biological Monitoring of Volatile Compounds

To ensure the health and safety of workers, integrated industrial hygiene methodologies often include biological monitoring of the workers to help understand their exposure to chemicals. To this end, a field-portable breath-analysis system was developed and tested to measure selected solvents in exhaled air. The exhaled breath data were evaluated using a physiologically based pharmacokinetic (PBPK) model to relate exposure to tissue dose. The system was designed to monitor workers every time they entered or left a work environment—a vast improvement over current 8-hour integrated monitoring strategies. The system combines (1) chemical dosimeters to measure airborne contaminant levels (analyzed in the field/workplace); (2) real-time breath analysis to quantitate exposure; and 3) PBPK models to estimate internal target tissue dose. To evaluate the system, field tests were conducted at two locations: (1) at an incinerator in Tennessee monitoring benzene and toluene exposures; and (2) a waste repackaging faci...