Analysis of Carbonyl Compounds in Ambient Air by a Microreactor Approach

Investigation of liquid chromatography-mass spectrometry analysis of a peptide aldehyde SJA6017 with identifying its hemiacetal, gem-diol, and enol ether

The quantitative analysis of SJA6017, a peptide aldehyde inhibitor of calpain (Calpain Inhibitor VI), has encountered challenges in preclinical drug studies. The complex reverse-phase HPLC chromatographic behavior exhibits two peaks, each containing multiple species. An liquid chromatography-mass spectrometry (LC-MS/MS) study proposed an explanation for this phenomenon, caused by the amide aldehyde structure of SJA6017. Four chemical species corresponding to the two HPLC peaks have been identified as SJA6017 and its methyl hemiacetal, methyl enol ether, and gem-diol. In many instances of preclinical studies, methanol is favored as a substitute for DMSO. The hemiacetal is formed when the amide-activated peptide aldehyde reacts with methanol, which can then be further dehydrated in the mass spectrometer ion source under high temperature to form the methyl enol ether. The hemiacetal and gem-diol can also be decomposed to SJA6017 in the ion source. Additionally, the amide-activated peptide aldehyde can easily hydrate to the gem-diol of SJA6017 during sample incubation or sample preparation. The hemiacetal and gem-diol of SJA6017 are stable enough to have different retention times in the liquid chromatography, which explains why SJA6017 appears as two peaks, each containing multiple species. An LC-MS/MS tandem quadrupole mass spectrometer quantitative analysis method is proposed, enabling the analysis of these types of samples. This work serves as both an illustrative example and a cautionary note for mass analysis, sample incubations, and sample preparations involving compounds of peptide aldehyde, including similar aldehyde-containing metabolites, especially when methanol is present. This study provides the information needed to understand peptide aldehyde behavior at various steps of preclinical in vitro studies in the presence of methanol. It has assisted in the development of the SJA6017 bioanalysis method and will also aid in the development of bioanalysis methods for similar peptide aldehydes.

Identification of volatile organic compounds and their sources driving ozone and secondary organic aerosol formation in NE Spain

Volatile organic compounds (VOCs) play a crucial role in the formation of ozone (O3) and secondary organic aerosol (SOA). We conducted measurements of VOC ambient mixing ratios during both summer and winter at two stations: a Barcelona urban background station (BCN) and the Montseny rural background station (MSY). Subsequently, we employed positive matrix factorization (PMF) to analyze the VOC mixing ratios and identify their sources. Our analysis revealed five common sources: anthropogenic I (traffic & industries); anthropogenic II (traffic & biomass burning); isoprene oxidation; monoterpenes; long-lifetime VOCs. To assess the impact of these VOCs on the formation of secondary pollutants, we calculated the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAP) associated with each VOC. In conclusion, our study provides insights into the sources of VOCs and their contributions to the formation of ozone and SOA in NE Spain. The OFP was primarily influenced by anthropogenic aromatic compounds from the traffic & industries source at BCN (38-49 %) and during winter at MSY (34 %). In contrast, the summer OFP at MSY was primarily driven by biogenic contributions from monoterpenes and isoprene oxidation products (45 %). Acetaldehyde (10-35 %) and methanol (13-14 %) also made significant OFP contributions at both stations. Anthropogenic aromatic compounds originating from traffic, industries, and biomass burning played a dominant role (88-93 %) in SOA formation at both stations during both seasons. The only exception was during the summer at MSY, where monoterpenes became the primary driver of SOA formation (41 %). These findings emphasize the importance of considering both anthropogenic and biogenic VOCs in air quality management strategies.

Characterization of organic contaminants associated with road dust of Delhi NCR, India

Hydrophobic organic contaminated polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and CHNS (carbon, hydrogen, nitrogen and sulphur species) are explosively associated with road dust particles. A few organic contaminants are toxic in nature and have an unpleasant effect on human health. The International Agency for Research on Cancer (IARC), the US Department of Health and Human Services (HHS) and the United States-Environmental Protection Agency has considered several PAHs and PCBs as carcinogens for human beings. In the proposed study, the anthropogenic contaminants present in road dust were assessed in six representative diversified sites i.e. industrial, commercial, office, residential, construction and traffic intersection in Delhi NCR, India. Roadside dust samples were gathered in premonsoon, monsoon and postmonsoon seasons and characterized for PAHs, PCBs and CHNS. The concentration of total PAHs (16 Nos) and PCBs (6 Nos) of the selected sites ranged from 0.27 µg/kg to 605.80 µg/kg and 0.01 µg/kg to 41.26 µg/kg, respectively. The Fourier transform infrared spectroscopy-attenuated total reflectance study suggested that the presence of O = C = O, Si-O, carbonyl, acidic or aliphatic esters group were associated with road dust particles. Hydrogen and sulphur concentrations were not detected in the selected road dust samples. Carbon and nitrogen concentrations varied from 2.24% to 16.82% and 0.69% to 14.5%, respectively, seasonally. In the premonsoon season, road dust was distinguishably contaminated as compared to monsoon and postmonsoon season, which might be due to movement of contaminated road dust from adjacent locations. It was perceived that Delhi NCR organic contamination in road dust was much below as compared to other countries. It may be concluded that due to the presence of significant amounts of carbon and nitrogen concentrations in the road dust, to a greater extent, road dust can be fertile and might be advantageous for green belt development to mitigate air pollution. The utilization of road dust will further bring down the burden of landfill sites and may lead towards sustainability.

Evaluation of air quality in indoor and outdoor environments: Impact of anti-COVID-19 measures

This study monitors the presence of 88 volatile organic compounds (VOCs) and semi-volatile organic compounds (semi-VOCs) at the gas phase of seven indoor settings in a school in the city of Tarragona, Spain, and five outdoor locations around the city. The VOCs and semi-VOCs monitored were solvents (∑Solvents), aldehydes (∑Aldehydes), emerging organic compounds (∑EOCs), and other VOCs and semi-VOCs (∑Others). Passive sampling campaigns were performed using Carbopack X tubes followed by thermal desorption coupled to gas chromatography with mass spectrometry (TD-GC-MS). Overall, 70 of the target compounds included in the method were determined in the indoor air samples analysed, and 42 VOCs and semi-VOCs in the outdoor air samples. Our results showed that solvents were ubiquitous throughout the school at concentrations ranging from 272 μg m^-3 to 423 μg m^-3 and representing 68%-83% of total target compounds (∑Total). The values of ∑Total in 2021 were three times as high as those observed at the same indoor settings in 2019, with solvents experiencing the greatest increase. A plausible explanation for these observations is the implementation of anti-COVID-19 measures in the indoor settings, such as the intensification of cleaning activities and the use of hydroalcoholic gels as personal hygiene. The ∑Total values observed in the indoor settings evaluated were twenty times higher than those found outdoors. ∑Solvents were the most representative compounds found indoors (74% of the ∑Total). The concentrations of VOCs and semi-VOCs observed in the outdoors were strictly related to combustion processes from automobile traffic and industrial activities, with ∑Others contributing 58%, ∑Solvents 31%, and ∑Aldehydes 11% of the ∑Total. EOCs, on the other hand, were not detected in any outdoor sample.

Lipid Peroxidation Produces a Diverse Mixture of Saturated and Unsaturated Aldehydes in Exhaled Breath That Can Serve as Biomarkers of Lung Cancer-A Review

The peroxidation of unsaturated fatty acids is a widely recognized metabolic process that creates a complex mixture of volatile organic compounds including aldehydes. Elevated levels of reactive oxygen species in cancer cells promote random lipid peroxidation, which leads to a variety of aldehydes. In the case of lung cancer, many of these volatile aldehydes are exhaled and are of interest as potential markers of the disease. Relevant studies reporting aldehydes in the exhaled breath of lung cancer patients were collected for this review by searching the PubMed and SciFinderⁿ databases until 25 May 2022. Information on breath test results, including the biomarker collection, preconcentration, and quantification methods, was extracted and tabulated. Overall, 44 studies were included spanning a period of 34 years. The data show that, as a class, aldehydes are significantly elevated in the breath of lung cancer patients at all stages of the disease relative to healthy control subjects. The type of aldehyde detected and/or deemed to be a biomarker is highly dependent on the method of exhaled breath sampling and analysis. Unsaturated aldehydes, detected primarily when derivatized during preconcentration, are underrepresented as biomarkers given that they are also likely products of lipid peroxidation. Pentanal, hexanal, and heptanal were the most reported aldehydes in studies of exhaled breath from lung cancer patients.

Catalytic role of formaldehyde in particulate matter formation

Formaldehyde (HCHO), the simplest and most abundant carbonyl in the atmosphere, contributes to particulate matter (PM) formation via two in-cloud processing pathways. First, in a catalytic pathway, HCHO reacts with hydrogen peroxide (H2O2) to form hydroxymethyl hydroperoxide (HMHP), which rapidly oxidizes dissolved sulfur dioxide (SO2,aq) to sulfate, regenerating HCHO. Second, HCHO reacts with dissolved SO2,aq to form hydroxymethanesulfonate (HMS), which upon oxidation with the hydroxyl radical (OH) forms sulfate and also reforms HCHO. Chemical transport model simulations using rate coefficients from laboratory studies of the reaction rate of HMHP with SO2,aq show that the HMHP pathways reduce the SO2 lifetime by up to a factor of 2 and contribute up to ∼18% of global sulfate. This contribution rises to >50% in isoprene-dominated regions such as the Amazon. Combined with recent results on HMS, this work demonstrates that the one-carbon molecules HMHP and HCHO contribute significantly to global PM, with HCHO playing a crucial catalytic role.

Reduced solvent and reagent amounts: effect on carbonyl dinitrophenylhydrazone measurements at low concentrations

This work aims to advance towards a more affordable laboratory procedure for sample treatment to determine carbonyl compounds by derivatization with 2,4-dinitrophenylhydrazine (DNPH). The proposal is based on reducing the amount of DNPH and solvents. A simple addition of standard carbonyls in a solution containing DNPH to prepare hydrazone standards is described and evaluated. Tedious recrystallization steps are avoided. Formaldehyde, acetaldehyde, acetone, tolualdehyde and hexanal, as carbonyl models, were quantified using a DNPH concentration of 400 μg mL^-1 and 3.8 mM H₂SO₄ and by keeping for 24 hours at room temperature. Analytical coefficients of variation between 10 and 25% were found from the analysis of blanks under intermediate conditions (two different devices, very different concentrations of DNPH and analysis on two days). From these values of relative standard deviations and background levels, quantification limits were estimated between 15 and 40 ng mL^-1. The reduction of reagent amounts allows the operator to better control the background levels in the use of DNPH, as well as making the method more cost-effective and easy to use. In short, it leads to a more sustainable adaptation of the classical method. The versatility in analytical application was tested to estimate the levels of formaldehyde, acetaldehyde and acetone in very different types of environmental samples. In particular, outdoor and indoor samples were collected in filters and impregnated cartridges, respectively. Moreover, tars in 2-propanol and particulate matter from gasification processes were also tested.

The impact of surface Cu2+ of ZnO/(Cu1-x Zn x )O heterostructured nanowires on the adsorption and chemical transformation of carbonyl compounds

The surface cation composition of nanoscale metal oxides critically determines the properties of various functional chemical processes including inhomogeneous catalysts and molecular sensors. Here we employ a gradual modulation of cation composition on a ZnO/(Cu1-x Zn x )O heterostructured nanowire surface to study the effect of surface cation composition (Cu/Zn) on the adsorption and chemical transformation behaviors of volatile carbonyl compounds (nonanal: biomarker). Controlling cation diffusion at the ZnO(core)/CuO(shell) nanowire interface allows us to continuously manipulate the surface Cu/Zn ratio of ZnO/(Cu1-x Zn x )O heterostructured nanowires, while keeping the nanowire morphology. We found that surface exposed copper significantly suppresses the adsorption of nonanal, which is not consistent with our initial expectation since the Lewis acidity of Cu2+ is strong enough and comparable to that of Zn2+. In addition, an increase of the Cu/Zn ratio on the nanowire surface suppresses the aldol condensation reaction of nonanal. Surface spectroscopic analysis and theoretical simulations reveal that the nonanal molecules adsorbed at surface Cu2+ sites are not activated, and a coordination-saturated in-plane square geometry of surface Cu2+ is responsible for the observed weak molecular adsorption behaviors. This inactive surface Cu2+ well explains the mechanism of suppressed surface aldol condensation reactions by preventing the neighboring of activated nonanal molecules. We apply this tailored cation composition surface for electrical molecular sensing of nonanal and successfully demonstrate the improvements of durability and recovery time as a consequence of controlled surface molecular behaviors.

Association of aldehyde exposure with cardiovascular disease

The effect of aldehyde exposure on the cardiovascular system remains unclear. The objective of this study was to determine whether aldehyde exposure is associated with the prevalence of cardiovascular disease (CVD). We analyzed associations between aldehydes and CVD using data from 1962 adult participants in the National Health and Nutrition Examination Survey (NHANES) from 2013 to 2014. Multivariable logistic regression and restricted cubic spline models were used to examine the association between aldehydes and CVD. The prevalence of CVD was 10.3%. After adjusting for confounding factors, including age, sex, education level, race, diabetes mellitus, smoking, alcohol use, hypertension, body mass index, the poverty-income ratio, physical activity, energy intake, high-density cholesterol (HDL) and low-density cholesterol (LDL), compared with the lowest quartiles, the odds ratios (ORs) with 95% confidence intervals (CIs) for CVD across the quartiles were 0.52 (0.31, 0.87), 0.73 (0.43, 1.22), and 1.13 (0.68, 1.86) for benzaldehyde and 1.48 (0.87, 2.52), 1.70 (1.01, 2.92), and 2.13 (1.19, 3.86) for isopentanaldehyde. There was no significant association between other aldehydes and CVD. The restricted cubic spline plot showed a J-curve relationship between benzaldehyde and CVD. The inflection point for the curve was found at a benzaldehyde level of 0.98 ng/ml. The ORs (95% CIs) for CVD were 0.51 (0.31, 0.86) and 1.58 (1.15, 2.17) on the left and right sides of the inflection point, respectively. Our results demonstrate a J-curve relationship between benzaldehyde and CVD. Isopentanaldehyde is positively associated with CVD. Further study is warranted to verify this association and to elucidate its underlying mechanisms.