C3 Aldehydes Research Articles

Computational Design of Optimized Modular Photovoltaic Electrochemical Reactor for Energy Efficient CO2‐to‐Cn Reduction Reaction with Bandgap Tunable Perovskite Tandem Cells

AbstractFor electrosynthesis of carbon fuels from CO2, engineered catalysts have improved the electrochemical (EC) reduction efficiency. However, most EC systems rely on a batch reactor, which is not relevant for Cn fuels with high n (n ≥ 3) due to low selectivity. For enhanced electron‐to‐fuel (ETF) efficiency, modular configurations are advantageous. The best configurations allowing high yield reduction of CO2 into Cn fuels are investigated. It is found that serial and parallel configurations exhibit four to five times higher ETF efficiency than simple batch reactor. The best photovoltaic (PV) tandem cells made of metal halide perovskite for the optimized EC modular systems are also found. These materials have a bandgap tunability covering most Cn fuels. With the computationally optimized tandem PVs, it is found that the [PV+EC] series configuration achieves up to 2.28% and 2.86% solar‐to‐fuel (STF) efficiency of C3 aldehydes and alcohols, which are greater than what has been reported in the literature. For C4 aldehydes and alcohols, the [PV+EC] parallel configuration achieves up to 0.17% and 0.21% STF efficiency, respectively. The present study on modules and materials design will provide a useful way to create EC production of Cn fuels that can help reach carbon neutrality.

Constraining emissions of volatile organic compounds from western US wildfires with WE-CAN and FIREX-AQ airborne observations

Abstract. The impact of biomass burning (BB) on the atmospheric burden of volatile organic compounds (VOCs) is highly uncertain. Here we apply the GEOS-Chem chemical transport model (CTM) to constrain BB emissions in the western USA at ∼ 25 km resolution. Across three BB emission inventories widely used in CTMs, the inventory–inventory comparison suggests that the totals of 14 modeled BB VOC emissions in the western USA agree with each other within 30 %–40 %. However, emissions for individual VOCs can differ by a factor of 1–5, driven by the regionally averaged emission ratios (ERs, reflecting both assigned ERs for specific biome and vegetation classifications) across the three inventories. We further evaluate GEOS-Chem simulations with aircraft observations made during WE-CAN (Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption and Nitrogen) and FIREX-AQ (Fire Influence on Regional to Global Environments and Air Quality) field campaigns. Despite being driven by different global BB inventories or applying various injection height assumptions, the model–observation comparison suggests that GEOS-Chem simulations underpredict observed vertical profiles by a factor of 3–7. The model shows small to no bias for most species in low-/no-smoke conditions. We thus attribute the negative model biases mostly to underestimated BB emissions in these inventories. Tripling BB emissions in the model reproduces observed vertical profiles for primary compounds, i.e., CO, propane, benzene, and toluene. However, it shows no to less significant improvements for oxygenated VOCs, particularly for formaldehyde, formic acid, acetic acid, and lumped ≥ C3 aldehydes, suggesting the model is missing secondary sources of these compounds in BB-impacted environments. The underestimation of primary BB emissions in inventories is likely attributable to underpredicted amounts of effective dry matter burned, rather than errors in fire detection, injection height, or ERs, as constrained by aircraft and ground measurements. We cannot rule out potential sub-grid uncertainties (i.e., not being able to fully resolve fire plumes) in the nested GEOS-Chem which could explain the negative model bias partially, though back-of-the-envelope calculation and evaluation using longer-term ground measurements help support the argument of the dry matter burned underestimation. The total ERs of the 14 BB VOCs implemented in GEOS-Chem only account for half of the total 161 measured VOCs (∼ 75 versus 150 ppb ppm−1). This reveals a significant amount of missing reactive organic carbon in widely used BB emission inventories. Considering both uncertainties in effective dry matter burned (× 3) and unmodeled VOCs (× 2), we infer that BB contributed to 10 % in 2019 and 45 % in 2018 (240 and 2040 Gg C) of the total VOC primary emission flux in the western USA during these two fire seasons, compared to only 1 %–10 % in the standard GEOS-Chem.

Experimental and kinetic modeling studies of di-n-propyl ether pyrolysis at low and atmospheric pressures

The pyrolysis of di-n-propyl ether (DPE), a potential biofuel candidate, was studied under a temperature range of 850–1350 K in a flow reactor at low and atmospheric pressures. Synchrotron vacuum ultraviolet photoionization mass spectrometry was used for isomeric identification and mole fraction measurements of the pyrolysis products, especially the free radicals. Specific products were observed and measured for the unimolecular decomposition reactions of DPE. A detailed kinetic model of DPE pyrolysis was developed based on the n-propanol combustion model. Modeling analyses including the rate of production (ROP) and sensitivity analyses were performed to reveal the consumption pathways of DPE, as well as the formation and consumption pathways of intermediates and products. ROP and sensitivity analyses indicated that the consumption reaction of DPE was mainly controlled by the unimolecular decomposition reactions and H-abstractions at both low and atmospheric pressures. The pericyclic reaction, leading to n-propanol + propylene, was the most important unimolecular decomposition reactions, especially at low pressure. The H-abstraction reactions of DPE played crucial roles in its consumption. Further β-C–C and β-C–O scission reactions of the three primary radicals can produce some oxygenated and hydrocarbon products. Relatively high mole fractions of C1–C3 aldehydes and C1–C3 alkane, alkene, and alkyl radicals were observed, which demonstrated the structural feature of DPE. Comparison of the product distribution between DPE and n-propanol were also analyzed.

Inter-comparison of the Regional Atmospheric Chemistry Mechanism (RACM2) and Master Chemical Mechanism (MCM) on the simulation of acetaldehyde

Acetaldehyde (CH3CHO) is a key player of atmospheric chemistry, an important air pollutant, and hence a major target of air quality modeling and management. The Regional Atmospheric Chemistry Mechanism (RACM) is a highly lumped gas-phase chemical mechanism that has been widely applied in atmospheric chemistry modeling studies. A significant update of the latest version of RACM (RACM2) is the addition of CH3CHO as an explicit aldehyde species, facilitating the direct simulation of CH3CHO. In this study, we compared the performances of RACM2 and Master Chemical Mechanism (MCM; v3.3.1) on the simulation of CH3CHO. Zero-dimensional chemical box models based on these two independent mechanisms were prescribed to a polluted scenario to simulate the evolution of ozone (O3), hydroxyl radical (OH), C2H5O2 (ETHP) and CH3CHO, as well as their detailed chemical budgets. Overall, both mechanisms agreed with the simulation of O3 and OH, but the RACM2 model simulated significantly higher levels of ETHP and CH3CHO than the MCM model. The difference in the chemical kinetic data in both mechanisms is not the reason for this discrepancy. The oversimplification of the lumped peroxy acyl radicals (RCO3) and ≥C3 aldehydes chemistry of RACM2 should be responsible for its higher simulated ETHP and CH3CHO. We caution the use of RACM2 or any other highly aggregated chemical mechanism for the simulation of C2H5O2 and CH3CHO. Better methods are needed to represent the chemistry of peroxy acyl radicals and ≥C3 aldehydes for aggregated chemical mechanisms. More experiments are required to directly validate and further improve the current chemistry mechanisms.

Electroreduction of CO on Polycrystalline Copper at Low Overpotentials

Cu is the only monometallic electrocatalyst to produce highly reduced products from CO2 selectively because of its intermediate binding of CO. We investigate the performance of polycrystalline Cu for the electroreduction of CO in alkaline media (0.1 M KOH) at low overpotentials (−0.4 to −0.6 V vs RHE). We find that polycrystalline Cu is highly active at these potentials. The overall CO reduction rates are comparable to those of the nanostructured forms of the material, albeit with a distinct product distribution. While nanostructured forms of Cu favor alcohols, polycrystalline Cu produces greater amounts of C2 and C3 aldehydes, as well as ethylene.

Mechanisms for C[sbnd]C bond cleavage and formation during acrolein production on a mixed metal oxide catalyst

We report a reaction network detailing the mechanistic origins of 20 C2–C6 byproducts observed during the oxidation of propylene to acrolein at 623K on a molybdenum-based catalyst promoted with cobalt and nickel used in the industrial production of acrolein. The carbon backbone of propylene is preserved in the sequential oxidation of propylene to allyl alcohol, acrolein, and acrylic acid, as well as propylene oxidation to acetone and propanal via water-mediated pathways. Transient kinetic measurements in conjunction with co-feed experiments of C2 and C3 aldehydes and carboxylic acids show that decarbonylation and decarboxylation reactions, reactions of organic compounds with surface-adsorbed oxygen species, and total combustion reactions are the three mechanisms for CC bond cleavage. CC bond formation reactions that result in C4–C6 byproducts occur via: (i) the addition reaction of a propylene-derived surface allyl species with formaldehyde to form C4 products and with propylene and allyl alcohol to form C6 products, or (ii) the addition reaction of an acrolein (acrylic acid)-derived surface ethenyl intermediate with propylene to form pentadiene and with acrolein to form C5 cyclic oxygenates.

Quantum Chemical Investigation on Photochemical Reactions of Nonanoic Acids at Air-Water Interface.

Photoinduced chemical reactions of organic compounds at the marine boundary layer have recently attracted significant experimental attention because this kind of photoreactions has been proposed to have substantial impact on local new particle formation and their photoproducts could be a source of secondary organic aerosols. In this work, we have employed first-principles density functional theory method combined with cluster models to systematically explore photochemical reaction pathways of nonanoic acids (NAs) to form volatile saturated and unsaturated C9 and C8 aldehydes at air-water interfaces. On the basis of the results, we have found that the formation of C9 aldehydes is not initiated by intermolecular Norrish type II reaction between two NAs but by intramolecular T1 C-O bond fission of NA generating acyl and hydroxyl radicals. Subsequently, saturated C9 aldehydes are formed through hydrogenation reaction of acyl radical by another intact NA. Following two dehydrogenation reactions, unsaturated C9 aldehydes are generated. In parallel, the pathway to C8 aldehydes is initiated by T1 C-C bond fission of NA, which generates octyl and carboxyl radicals; then, an octanol is formed through recombination reaction of octyl with hydroxyl radical. In the following, two dehydrogenation reactions result into an enol intermediate from which saturated C8 aldehydes are produced via NA-assisted intermolecular hydrogen transfer. Finally, two dehydrogenation reactions generate unsaturated C8 aldehydes. In these reactions, water and NA molecules are found to play important roles. They significantly reduce relevant reaction barriers. Our work has also explored oxygenation reactions of NA with molecular oxygen and radical-radical dimerization reactions.

Interdiffusion of small molecules into a glassy polymer film via coarse-grained molecular dynamics simulations

The interdiffusion of the C8, the C9 and the C10 aldehyde molecules into a glassy uncrosslinked polymer film composed of four components is studied by using coarse-grained (CG) molecular dynamics simulations. Effects of the aldehyde molecule size, water and temperature on the interdiffusion processes are probed. It is found that (i) the interdiffusion generally follows the smaller-the faster rule with the smallest C8 aldehydes diffusing fastest into the polymeric film, (ii) the water molecules significantly affect the adsorption and the initial interdiffusion of the aldehyde molecules onto/into the polymer film, (iii) the interdiffusions are strongly temperature dependent as the higher temperature enhances the initial dynamics of the aldehyde-polymer systems, (iv) the computed aldehydes diffusivities are highly concentration-dependent and increase with an increase in the concentration, and (v) the aldehydes density profiles scale as t0.5 in the polymer-rich regions, and are well described by the Fickian diffusion with a constant diffusivity. Here t is the time of diffusion. Even though only relative values of the diffusivity coefficients can be predicted via the CG simulations, this work suggests that this approach is very useful in guiding the design and the selection of polymeric films with a tailored barrier property. Furthermore, it enables one to analyze small molecules-polymer interdiffusions into a polymeric film that is difficult to study experimentally but is of technological importance.

Potassium modified alumina as a catalyst for the aldol condensation of benzaldehyde with linear C3–C8 aldehydes

Different types of catalysts based on potassium modified alumina were prepared. The source of potassium was either potassium carbonate or potassium hydroxide. The prepared materials were characterized by UV–Vis spectroscopy, X-ray diffraction, thermogravimetry, nitrogen physisorption and tested as catalysts in the aldol condensation of benzaldehyde with C3–C8 linear aldehydes. Some of the products may serve as important fragrant compounds—especially jasmine aldehyde (prepared from heptanal) or 2-hexylcinnamylaldehyde (from octanal). It was found that the reaction rate increased with the increasing amount of potassium loaded on the catalyst. The reaction rate increased with decreasing the length of the aldehyde chain. The selectivity to the autocondensation product increased when the pore diameter of catalyst was decreased. The aldol condensation of benzaldehyde with propanal performed using alumina modified by 3.6 mmol potassium/g of material resulted in 97% propanal conversion with 89% selectivity to 2-methylcinnamylaldehyde and 6% selectivity to 2-methylpent-2-enal. The aldol condensation of benzaldehyde with octanal performed using alumina modified by 1.5 mmol potassium/g of material resulted in 29% propanal conversion with 17% selectivity to 2-hexylcinnamylaldehyde and 82% selectivity to 2-hexyldec-2-enal.

The Importance of Cannizzaro-Type Reactions during Electrocatalytic Reduction of Carbon Dioxide.

A seemingly catalytically inactive electrode, boron-doped diamond (BDD), is found to be active for CO2 and CO reduction to formaldehyde and even methane. At very cathodic potentials, formic acid and methanol are formed as well. However, these products are the result of base-catalyzed Cannizzaro-type disproportionation reactions. A local alkaline environment near the electrode surface, caused by the hydrogen evolution reaction, initiates aldehyde disproportionation promoted by hydroxide ions, which leads to the formation of the corresponding carboxylic acid and alcohol. This phenomenon is strongly influenced by the electrolyte pH and buffer capacity and not limited to BDD or formaldehyde, but can be generalized to different electrode materials and to C2 and C3 aldehydes as well. The importance of these reactions is emphasized as the formation of acids and alcohols is often ascribed to direct CO2 reduction products. The results obtained here may explain the concomitant formation of acids and alcohols often observed during CO2 reduction.

Guerbet alkylation of acetone by ethanol and reduction of product alkylate to alkane over tandem nickel/Mg,Al-hydrotalcite and nickel molybdate/γ-alumina catalyst systems

Single and double Guerbet alkylation of acetone with alcohols and hydrodeoxygenation of the produced alkylates were investigated. A flow-through tube reactor system, comprised of two subsequent fixed catalyst beds, was used. The first catalyst bed contained the catalyst for Guerbet coupling, namely activated hydrotalcite-supported nickel or palladium catalyst, whereas the second catalyst bed contained γ-alumina-supported nickel molybdate catalyst. The catalysts, pre-reduced in H2 flow at 450 °C, were contacted with a mixture of acetone and ethanol in flowing H2 at a total pressure of 21 bar and at a temperature in the range of 150–350 °C. The molar ratio of the acetone-ethanol mixture was 1:2. The WHSV of the mixture was varied between 1 and 3 gAE h−1 g cat. −1 . In the first reactor, C5–C19 mono- or dialkylated ketones were formed. C4, C6, C8 aldehydes and alcohols were also detected. The oxygenate products leaving the first catalyst bed were reduced by H2 to the corresponding alkanes in the second reactor. Catalytic alcohol coupling and ketone hydrodeoxygenation were separately studied using ethanol and 4-pentanone as a model reactant over the catalyst of the first and the second catalyst bed, respectively.

Comparison of conventional and green building materials in respect of VOC emissions and ozone impact on secondary carbonyl emissions

Building materials (BMs) are major contributors to indoor emission sources of volatile organic compounds (VOCs). In this study, 8 kinds of BMs (including conventional and green) for ceiling, cabinetry, and flooring commonly used indoors were tested in a 216 L chamber. Primary emissions of carbonyls (C1 to C8 aldehydes and ketones) at 48 h were 75–673 μg m−2 h−1 from conventional BMs, and 62–151 μg m−2 h−1 from green BMs. Primary emissions of BTEX at 48 h were 59–264 μg m−2 h−1 from conventional BMs, and 37–56 μg m−2 h−1 from green BMs. Ozone initiated molar yields of carbonyls were 0.10–2.36 from conventional BMs, and 0.13–0.86 from green BMs. Secondary emissions of carbonyls were 7–150 μg m−2 h−1 from conventional BMs, and 4–73 μg m−2 h−1 from green BMs. Green BMs had lower emissions than conventional analogs, especially for wooden flooring and gypsum board. BMs with mineral content are the most promising materials in this study, given moderately high ozone deposition velocity but generating the least byproducts. Secondary emissions determined in this study demonstrate that moderate indoor ozone concentrations may lead to increased concentrations of carbonyls, especially formaldehyde and acetaldehyde that potentially increase adverse chronic health effects.

Oxylipins generation inLactobacillus helveticusin relation to unsaturated fatty acid supplementation

Oxylipins are regarded as unsaturated fatty acids (UFAs) oxidation products, whose accumulation in plants and fungi is associated with stress. The aim of this study was to investigate if a metabolic pathway from UFAs to oxylipins was present also in lactic acid bacteria (LAB). A strain of Lactobacillus helveticus, incubated in the presence of oleic, linoleic and linolenic acids released, after 2h, fatty acid oxidation products, mainly C6 , C8 , C9 aldehydes and alcohols. An experiment with total carbon labelled linoleic acid, in the presence or not of an oxidative stress, demonstrated that oxylipins, such as hexanal, octanal, nonanal, 2-octenal, 2-octanal, originated mainly from the oxidation of this fatty acid. Since lipoxygenase, dioxygenase and cytochrome P450 genes have never been found in L.helveticus, a possible pathway for linoleic conversion and oxylipins formation could include, as a first step, the transient formation of hydroxylated linoleic acids by fatty acids hydratases. However, the sequence of steps from the linoleic acid to the C6 and C8 aldehydes needs to be more deeply investigated. Due to the multiple role of oxylipins which are flavouring agents, antimicrobial compounds and interspecific signalling molecules, the knowledge of the mechanisms involved in their biosynthesis in food related bacteria could have an important biotechnological impact, also allowing the overproduction of selected bioactive molecules.

Synthesis of 2-Ethylhexanal from Propylene in a Single Pot Using an Ecofriendly Multifunctional Catalyst Synthesized by Intercalation of HRhCO(TPPTS)3 Complex in the Interlayer Space of Hydrotalcite

Catalytic activity of HRhCO(TPPTS)3 intercalated hydrotalcite (Mg/Al molar ratio =3.5) as a multifunctional catalyst [HT(3.5)-INT] was studied for synthesis of C8 aldehydes (2-ethylhex-2-enal and 2-ethylhexanal) from propylene in a single pot. The effect of catalyst amount, partial pressure of propylene, and aldol temperature (T2) on the selectivity of 2-ethylhexanal and 2-ethylhex-2-enal was studied in detail to optimize the reaction parameters. The highest selectivity for C8 aldehydes (49%) was obtained at 1200 mg of catalyst and 10 atm partial pressure of propylene. Reusability experiments revealed that the HRhCO(TPPTS)3 intercalated hydrotalcite shows activity even after fourth cycle for hydroformylation reaction; however, selectivity of C8 aldehydes decreased after the second cycle. Rates of the product formation were determined individually for hydroformylation of propylene, aldol condensation of n-butanal, and hydrogenation of 2-ethylhex-2-enal catalyzed by [HT(3.5)-INT] using propylene, n-butanal, and 2-ethylhex-2-enal as reactants. Reaction conditions were maintained identical to those used for the single-pot synthesis of C8 aldehydes from propylene. The calculated rates of reaction for the single-pot synthesis of C8 aldehydes were compared with the rates of reaction determined individually.

Analysis for wine C5–C8 aldehydes through the determination of their O-(2,3,4,5,6-pentafluorobenzyl)oximes formed directly in the solid phase extraction cartridge

A method for the determination of wine carbonyl compounds with 5–8 carbon atoms including 3-methylbutanal, E-2-hexenal, E-2-heptenal, E-2-octenal and phenylacetaldehyde has been developed. Aldehydes are retained in a solid phase extraction cartridge and derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine takes place in the same cartridge at room temperature (25 °C) in 15 min. The corresponding oximes are further eluted and determined by gas chromatography–mass spectrometry. Isolation, derivatization and elution conditions were examined. Recoveries from red wines are all >94%, and are consistent from wine to wine. For white wines, recoveries for E-2-heptenal, E-2-octenal and phenylacetaldehyde are 80–85%, but are consistent from wine to wine. Precision (measured as relative standard deviation) is <7% in all cases. Method detection limits ranged from 0.12 to 0.70 μg L −1 and linearity holds at least up to 60 μg L −1 with r 2 in the range 0.9957–0.9997. The method has been applied to the determination of these components in several wine samples. Results show that phenylacetaldehyde, E-2-octenal and 3-methylbutanal can be found at concentrations above their corresponding odor thresholds in normal wines.

Cyclic voltammetric behaviour of dimensionally stable anodes in the presence of C1 - C3 aldehydes

This work describes the cyclic voltammetry study of three aliphatic aldehydes: formaldehyde, acetaldehyde and propionaldehyde at dimensionally stable anodes (DSA®). Electrodes of nominal composition Ti/Ru0.3M0.7O2 (where M = Ti ou Sn) were used in 0.5 mol dm-3 H2SO4 in a filter-press cell. Both electrodes exhibit behaviour typical of such materials in the presence of formaldehyde. However, with acetaldehyde and propionaldehyde non-typical behaviour is observed. This is characterised by a fall in the normalised faradaic anodic charge (qnf) and also a decrease in the current density associated with the oxygen evolution reaction (OER). A possible reaction mechanism, considering the direct oxidation of the aldehyde at the electrode surface, is suggested.

The polar selectivities of non-polar reversed phases

To reduce the influence of surface silanol groups on the retention of basic solutes reversed phases (RP) have been introduced with polar groups embedded in the anchored alkyl chain. The retention times of strongly basic solutes on such phases are much shorter than on conventional RP columns, and they are eluted with symmetrical peaks. The polar embedded groups, usually amide or carbamate groups, contribute to the retention of polar solutes; thus, e.g. analytes with phenolic groups are much more strongly retarded on shielded RP columns. This polar selectivity is shown to improve the separation of the dinitrophenylhydrazones of C3 aldehydes and ketones and result in better selectivity in the determination of flavonids in wine. Different selectivities for classical RP columns and shielded phases with methanol and acetonitrile as organic modifiers are demonstrated.

A new fluorescent probe for sensitive detection of carbonyl compounds: sensitivity improvement and application to environmental water samples

The use of 2-aminooxy- N-[3-(5-dimethylamino-naphtalene-1-sulfonylamino)-propyl]-acetamide (dansylacetamidooxyamine, DNSAOA, 2) as a new molecular probe for trace measurement of carbonyl compounds (i.e. aldehydes and ketones) in water samples is reported. 2 can be considered as an evolution of the parent N-(5-dimethylamino-1-naphtalenesulphonamido)-3-oxopentane-1,5-dioxyamine (dansyloxyamine, DNSOA, 1) molecule that was initially proposed in a recent paper. An updated procedure for the synthesis of 2 leading to higher purity of such oxyamino probes and a subsequent better sensitivity of the method was described. The reactivity behaviour of 2 with solutions containing small amounts of formaldehyde, acetaldehyde, propionaldehyde and acetone is also described: even for concentrations less than 1 μM, C1–C3 aldehydes can be fully derivatized within 10 h and only one calibration curve is needed. Longer reaction times are nevertheless required for accurate measurements of the less reactive acetone. Very low limits of detection (LODs), mainly depending on the initial purity of the probe, have been obtained: 10 nM of formaldehyde and 5 nM of the other carbonyls can be detected. The limit of quantification (LOQ) of the method is close to 25 fmol. 2 was used in measuring the carbonyl content of snow, ice and cloud-water samples. The first data concerning acetaldehyde in alpine and polar snow, and a first estimation of acetone in cloud-water droplets are reported here.

Low level determination of formaldehyde in water by high-performance liquid chromatography

Low levels of formaldehyde in water were determined by derivatization with 2,4-dinitrophenylhydrazine at an optimized pH (1.5–2.5), solid-phase extraction with C18 adsorption cartridges and analysis by reversed-phase high-performance liquid chromatography with ultraviolet detection. A novel procedure for the removal of formaldehyde present as an impurity in blank water was responsible for lowering the detection limit to 0.1 µg l–1 for a 200 ml sample. A strong anion-exchange resin, in the hydrogen sulfite form, was used to adsorb formaldehyde and any other aldehyde impurities present in blank water. The use of C18 adsorption cartridges also minimized background effects. The recovery of C1—C3 aldehydes spiked into purified blank water was 83–93% with a relative standard deviation of 1.4–6.4%.

Determination of low boiling aldehydes in air and exhaust gases by using annular denuders combined with HPLC techniques

An improved procedure for the HPLC determination of C1−C3 aldehydes in environmental samples is described. These air pollutants are quantitatively collected on annular denuders coated with 2,4-Dinitrophenylhydrazine and analyzed as hydrazone derivatives by HPLC with UV absorbance and voltammetric detection. Collection efficiencies of aldehydes are reported and compared with other available methods. Practical examples of the application of the method are given.