Sample preparation of atmospheric aerosol for the determination of carbonyl compounds

Particle characterization and quantification of organic and inorganic compounds from Chinese and Iranian aerosol filter samples using scanning laser desorption/ionization mass spectrometry

Besides their influence on climate and cloud formation, many organic and inorganic substances in aerosol particles pose a risk to human health. Namely, polycyclic aromatic hydrocarbons (PAH) and heavy metals are suspected to be carcinogenic or acutely toxic. The detection and quantification of such compounds is difficult if only small amounts of particulate matter (PM) are available. In addition, filter samples are often complex and time-consuming to prepare for chromatographic measurements and elemental analysis. Here, we present a method based on high-resolution atmospheric pressure laser desorption ionization mass spectrometry imaging (AP-LDI-MSI) and statistical analysis which allows the analysis and characterization of very small sample quantities (< 30 µg) without any sample preparation. The power and simplicity of the method is demonstrated by two filter samples from heavily polluted mega cities. The samples were collected in Tehran (Iran) and Hangzhou (China) in February 2018. In the course of the measurement, more than 3200 sum formulae were assigned, which allowed a statistical evaluation of colocalized substances within the particles on the filter samples. This resulted in a classification of the different particle types on the filters. Finally, both megacities could be distinguished based on characteristic compounds. In the samples from Tehran, the number of sulphur-containing organic compounds was up to 6 times as high as the samples from Hangzhou, possibly due to the increasing efforts of the Chinese government to reduce sulphur emissions in recent years. Additionally, quantification of 13 PAH species was carried out via standard addition. Especially, the samples from Tehran showed elevated concentrations of PAHs, which in the case of higher-molecular-weight species (> m/z 228) were mostly more than twice as high as in Hangzhou. Both cities showed high levels of heavy metals and potentially harmful organic compounds, although their share of total particulate matter was significantly higher in the samples from Tehran. The pre-treatment of the samples was reduced to a minimum with this method, and only small amounts of particles were required to obtain a comprehensive picture for a specific filter sample. The described method provides faster and better control of air pollution in heavily polluted megacities.

Electrochemical sensor based on polyoxometalate immobilized using a layer-by-layer assembly process to detect 2,4-dinitrophenylhydrazine

An electrochemical sensor for the detection of 2,4-dinitrophenylhydrazine was developed by utilizing the reversible redox properties of W-containing polyoxometalates.

Monitoring of Air-Dispersed Formaldehyde and Carbonyl Compounds as Vapors and Adsorbed on Particulate Matter by Denuder-Filter Sampling and Gas Chromatographic Analysis

Carbonyl compounds (CCs) are products present both as vapors and as condensed species adsorbed on the carbonaceous particle matter dispersed in the air of urban areas, due to vehicular traffic and human activities. Chronic exposure to CCs is a potential health risk given the toxicity of these chemicals. The present study reports on the measurement of the concentrations of 14 CCs in air as vapors and 2.5 µm fraction PM by the ENVINT GAS08/16 gas/aerosol sampler, a serial sampler that uses annular denuder, as sampling device. The 14 CCs were derivatized during sampling prior to gas-chromatographic separation and multiple detection by mass spectrometry, nitrogen-phosphorus thermionic, electron capture detection. Outdoor air multiple samples were collected in four locations in the urban area of Florence. The results evidenced that formaldehyde, acetaldehyde, and acetone were the more abundant CCs in the studied areas. The data collected was discussed considering the particle to vapor ratio of each CC found. The CCs pollution picture obtained was tentatively related to the nature and intensity of the traffic transiting by the sampling sites. This approach allowed to determine 14 CCs in both concentrated and diluted samples and is proposed as a tool for investigating outdoor and indoor pollution.

Determination of urine 3-HPMA, a stable acrolein metabolite in a rat model of spinal cord injury

Acrolein has been suggested to be involved in a variety of pathological conditions. The monitoring of acrolein is of significant importance in delineating the pathogenesis of various diseases. Aimed at overcoming the reactivity and volatility of acrolein, we describe a specific and stable metabolite of acrolein in urine, N-acetyl-S-3-hydroxypropylcysteine (3-HPMA), as a potential surrogate marker for acrolein quantification. Using the LC/MS/MS method, we demonstrated that 3-HPMA was significantly elevated in a dose-dependent manner when acrolein was injected into rats IP or directly into the spinal cord, but not when acrolein scavengers were co-incubated with acrolein solution. A nonlinear mathematic relationship is established between acrolein injected directly into the spinal cord and a correlated dose-dependent increase of 3-HPMA, suggesting the increase of 3-HPMA becomes less apparent as the level of injected acrolein increases. The elevation of 3-HPMA was further detected in the rat spinal cord injury, a pathological condition known to be associated with elevated endogenous acrolein. This finding was further validated by concomitant confirmation of increased acrolein-lysine adducts using established dot immunoblotting techniques. The noninvasive nature of measuring 3-HPMA concentrations in urine allows for long-term monitoring of acrolein in the same animal and ultimately in human clinical studies. Due to wide spread involvement of acrolein in human health, the benefits of this study have the potential to enhance human health significantly.

LC−MS Analysis of Carbonyl Compounds and Their Occurrence in Diesel Emissions

Liquid chromatography coupled with atmospheric pressure chemical ionization (APCI) ion trap mass spectrometry (ITMS) is applied to atmospheric aerosol relevant carbonyls. Characterization of positive and negative ion detection mass spectra are presented for 24 model compounds analyzed in their underivatized and O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) oxime forms. The addition of PFBHA derivatization enhanced the detection and sensitivity for many of the carbonyls investigated. For all but five of the carbonyls examined, a pseudomolecular (M + H)+ ion is the base peak in the APCI positive ion mass spectra of PFBHA oxime derivatives and is observed in four of the five exceptions. Application of the evaluated analysis methodology to heavy-duty diesel source emissions facilitated the quantification of 10 aliphatic carbonyls (5 C5-C9 ketones, 4 C6 unsaturated ketones, 1 C6 dicarbonyl) and 14 aromatic carbonyls (1 C9 aldehyde, 5 C8-C13 ketones, 8 C6-C14 quinones). Diesel truck engine emission factors spanning 0.55-540 microg km(-1) were measured for gas- and particle-phase carbonyls. Good agreement was observed for gas-phase emission factors with results obtained by gas chromatography with ITMS.

Determination of aldehydes and ketones in air samples using cryotrapping sampling

A cryotrapping sampling technique using glass traps cooled in liquid nitrogen for monitoring carbonyl compounds in air has been developed. Sampling was followed by derivatization by addition of acidified 2,4-dinitrophenyl hydrazine (DNPH) solution to the traps and an aliquot of the sample was analysed with a high performance liquid chromatograph system (HPLC), equipped with a diode array detector. The procedure was optimised concerning derivatization conditions and analytical parameters on formaldehyde, acetaldehyde, propanal, acetone, butanal and benzaldehyde. The technique was applied in monitoring their concentration in the urban atmosphere in Ljubljana.