Carbonyl Compounds In Ambient Air Research Articles

Analysis of Carbonyl Compounds in Ambient Air by a Microreactor Approach.

Aldehydes including formaldehyde, acetaldehyde, and acrolein are toxic organic components of air pollution that cause lung cancer and cardiovascular disease with chronic exposure. The commonly used method for determining the levels of carbonyl compounds based on the derivatizing agent 2,4-dinitrophenylhydrazine is of limited use for ketones and unsaturated aldehydes because of issues such as low capture efficiencies, unstable derivatives, and long sample collection times. This work details the analysis of carbonyls in ambient air by a microreactor approach. The microreactor is fabricated on a silicon wafer and has thousands of micropillars in a microfluidic channel for uniformly distributing the air flow through the channel. The surfaces of the micropillars are coated with a quaternary ammonium aminooxy reagent, 2-(aminooxy)ethyl-N,N,N-trimethylammonium iodide (ATM), for chemoselective capture of carbonyl compounds by means of oximation reactions. ATM–carbonyl adducts are eluted from the microreactor and directly analyzed by Fourier transform ion cyclotron resonance mass spectrometry and ultrahigh-performance liquid chromatography–mass spectrometry. More than 20 carbonyls were detected in ambient air samples. Acetone, 2-butanone, acetaldehyde, and formaldehyde were the most abundant carbonyls in ambient air of the studied urban areas.

Determination of carbonyl compounds in smoke samples: strategies for sampling and standardization

There are significant drawbacks to the calibration procedure recommended in the normalized Spanish or American methods used to determine carbonyl compounds in ambient air by quantifying hydrazones that form with 2,4-dinitrophenylhydrazine. The impurities present in 2,4-dinitrophenylhydrazine, as well as the lack of quantitativity and the slow kinetics of some derivatization reactions can lead to considerable errors in quantification. This work proposes two alternative systems for sampling biomass smoke in order to analyze aldehydes and ketones. The standardization process used by both systems requires standard solutions to be reacted with 2,4-dinitrophenylhydrazine under experimental conditions similar to those used to collect the sample. The resulting calibration curve slopes differ between 8% and 74% from the curves used in methods that employ commercial standard hydrazone solutions. The detection limits reached by using the proposed methods are between 0.07 and 0.47 mg L(-1). Both methods are complementary for smoke samples that have significant differences in the concentrations of aldehydes or ketones.

Characteristics of carbonyl compounds in ambient air of Shanghai, China

The levels of carbonyl compounds in Shanghai ambient air were measured in five periods from January 2007 to October 2007 (covering winter, high-air-pollution days, spring, summer and autumn). A total of 114 samples were collected and eighteen carbonyls were identified. Formaldehyde, acetaldehyde and acetone were the most abundant carbonyls and their mean concentrations of 19.40 ± 12.00, 15.92 ± 12.07 and 11.86 ± 7.04 μg m−3 respectively, in the daytime for five sampling periods. Formaldehyde and acetaldehyde showed similar diurnal profiles with peak mixing ratios in the morning and early afternoon during the daytime. Their mean concentrations were highest in summer and lowest in winter. Acetone showed reversed seasonal variation. The high molecular weight (HMW, ≥C5) carbonyls also showed obvious diurnal variations with higher concentrations in the daytime in summer and autumn, while they were all not detected in winter. Formaldehyde and acetaldehyde played an important role in removing OH radicals in the atmosphere, but the contribution of acetone was below 1%. The carbonyls levels in high-air-pollution days were reported. More carbonyl species with higher concentrations were found in high-air-pollution days than in spring. These carbonyls were transported with other pollutants from north and northwest in March 27 to April 2, 2007 and then mixed with local sources. Comparing with Beijing and Guangzhou, the concentrations of formaldehyde and acetaldehyde in Shanghai were the highest, which indicated that the air pollution in Shanghai was even worse than expected.

Gas chromatographic approach for the determination of carbonyl compounds in ambient air

In this study, an effort was made to apply gas chromatography (GC) with a flame ionization detector (FID) to the determination of gaseous carbonyls (without derivatization) at sub ppb level. A GC system interfaced with a multi-function thermal desorber system (TD) was hence tested for the collection and analysis of gaseous carbonyls. During this study, the calibration properties of five carbonyl compounds – acetaldehyde, propionaldehyde, butyraldehyde, isovaleraldehyde, and valeraldehyde – were evaluated by varying the operation conditions of the TD system (i.e., sample transfer approaches and sorbent types of cold trap). The results were generally discernible between compounds (light and heavy carbonyls) and/or between selected concentration levels. Most interestingly, the GC detection properties of the lighter aldehydes (acetaldehyde and propionaldehyde) varied significantly, as they were sensitively affected by the types of cold trap combination. However, the heavier aldehydes – butyraldehyde, isovaleraldehyde, and valeraldehyde – maintained highly constant trends for GC calibration. According to this study, a GC-based quantification of aldehydes can be completed by an optimized setup of TD system.

Analysis of Aliphatic and Aromatic Carbonyl Compounds in Ambient Air by LC/MS/MS

A sensitive liquid chromatograph/tandem mass spectrometric technique (LC/MS/MS) was applied to determine aliphatic and aromatic carbonyl compounds in ambient air. Traces of the carbonyl compounds were sampled by passing through a Sep-Pak DNPH-silica cartridge. Their derivatives were thus eluted with acetonitrile, separated by reversed-phase liquid chromatography and determined by quadrupole tandem mass spectrometry in an atmospheric pressure chemical ionization (APCI) mode with multiple reaction monitoring (MRM). The detection limits (DL) of the carbonyl compounds were 0.8 - 15 ng/m3. A number of the carbonyl compounds were detected at n.d.- 14 microg/m3 levels. The precursor ion scanning analysis was applied to identify the unknown compounds.

Determination of Aldehydes and Ketones in Ambient Air by Micellar Electrokinetic Capillary Chromatography

Abstract A new analytical method was developed for determining 14 aldehydes and ketones of environmental interest in ambient air. The method uses 2,4-dinitrophenylhydrazine (DNPH)-coated silica cartridges for sampling, acetonitrile for preconcentration, and micellar electrokinetic capillary chromatography for separation and quantitation. With hydrodynamic sampling of 8.5 cm cartridge for 30 s, applied voltage of 25 kV, detection at 360 nm, and separation in a 60 cm long, 50 μm id fused silica column at ambient temperature (25° ± 1°C) within an electrophoretic buffer (20 mM borate/50 mM sodium dodecyl sulfate at pH 9.2 in 20% [v/v] methanol), baseline separation was obtained for DNPH derivatives of formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde, butanone, crotonaldehyde, isobutyraldehyde/butyra(dehyde, 2-pentenaldehyde, isovaleraldehyde, valeraldehyde, benzaldehyde, and hexaldehyde. Detection limits [signal-to-noise (S/N) ratio = 2] ranged from 0.10 to 0.77 mg/L, the working range was 0.3-86 mg/L, and the precision as indicated by the relative standard deviation ranged from 2.3 to 6.6% (n = 3). With 1 h sampling at 0.25 L/min and a 1000-fold enrichment, most carbonyl compounds in ambient air can be determined with de- tection limits ranging from 0.008 to 0.1 mg/m3 and a working range of 0.04-11 μg/m3. The developed method was successfully applied to the determination of carbonyl compounds in a chemical laboratory and at street level.

An artifact in air carbonyls sampling using C 18 DNPH-coated cartridge

A sampling artifact is observed when collecting carbonyl compounds in ambient air using 2,4-dinitrophenylhydrazine (DNPH)-coated C 18 cartridges. While lower carbonyls (C 1–C 4) are not significantly affected, ca. 80% of C 5–C 8 carbonyl concentrations are due to artifact formation. Furthermore, several high molecular weight carbonyls, containing up to 18 carbons, were artificially produced during sampling probably due to reactions between ambient ozone and C 18 sorbent matrix. The use of ozone trap is recommended for carbonyls sampling with DNPH-coated solid sorbents. The most suitable sampling system is a DNPH-coated silica gel cartridge connected to an upstream crystalline KI trap.

Structure Elucidation of 2,4-Dinitrophenylhydrazone Derivatives of Carbonyl Compounds in Ambient Air by HPLC/MS and Multiple MS/MS Using Atmospheric Chemical Ionization in the Negative Ion Mode

Ion trap multiple fragmentation mass spectrometry (MS(n)()) combined with high-performance liquid chromatography (HPLC) has been used for the structure elucidation and identification of 2,4-dinitrophenylhydrazone derivatives of carbonyl compounds in ambient air samples. Atmospheric pressure chemical ionization in the negative ion mode was the most suitable detection method. Different measures are described to decrease the MS background originating from the HPLC system. Low-picogram quantities were detectable in extracted mass chromatograms generated from full-scan records. Fragment ions produced by MS/MS allowed identification of substructures of the carbonyls. Detailed fragmentation paths were studied by MS(3) to MS(4) using reference compounds. A fragmentation scheme was established which enabled a structure confirmation and identification with 1-10 ng by HPLC/MS/MS. The identification of a compound coeluting with n-pentanal-DNPH and of a dimerization byproduct are given as examples.