Analysis of low molecular weight aldehydes in air samples by capillary electrophoresis after derivatization with 4-hydrazinobenzoic acid

4-hydrazinobenzoic acid as a derivatizing agent for aldehyde analysis by HPLC-UV and CE-DAD

Aldehydes are relevant analytes in a wide range of samples, in particular, food and beverages but also body fluids. Hydrazines can undergo nucleophilic addition with aldehydes or ketones giving origin to hydrazones (a group of stable imines) that can be suitably used in the identification of aldehydes. Herein, 4-hydrazinobenzoic acid (HBA) was, for the first time, used as the derivatizing agent in analytical methodologies using liquid chromatography aiming the determination of low-molecular aldehydes. The derivatization reaction was simultaneously performed along with the extraction process, using gas-diffusion microextraction (GDME), which resulted in a clean extract containing the HBA-aldehyde derivates. The corresponding formed imines were determined by both high-performance liquid chromatography (LC) with UV spectrophotometric detection (HPLC-UV) and capillary electrophoresis with diode array detection (CE-DAD). HBA showed to be a rather advantageous derivatization reagent due to its stability, relatively high solubility in water and other solvents, high selectivity and sensibility, reduced impurities, simple preparation steps and applicability to different separation and/or different detection techniques. Limits of detections (LODs) of the optimized methodologies (in terms of time and pH among other experimental variables) were all below 0.5 mg L^-1, using both instrumental techniques. Furthermore, for the first time, the HBA-aldehyde derivatives were analyzed by LC with mass spectrometry (LC-MS), demonstrating the possibility of identification by MS of each compound. The developed methodologies were also successfully applied in the analysis of formaldehyde and acetaldehyde in several alcoholic beverages. This was also the first time GDME was combined with CE, showing that it can be a valuable sample preparation tool for electrophoresis, in particular by eliminating the interference of ions and inorganic constituents present in the samples.

Simultaneous photodegradation of VOC mixture by TiO2 powders

Volatile and semi volatile organic compounds' concentration have dramatically increased in indoor environments in recent years. UV light promotes titanium dioxide, which oxidises various molecules; however, most of the studies report the degradation of a single VOC. Here, we investigate the photo-oxidation of 17 molecules in mixture to have a realistic test of TiO₂ efficacy. We compare P25, a nanometric catalyst, and 1077, a micrometric sample, that poses less health concerns. A proton-transfer-reaction mass spectrometer measured online the concentration of all the pollutants simultaneously. Aldehydes compete for the adsorption on both the catalyst's active sites and thus they degrade 70% and 55% with P25 and 1077 respectively. Considering the single pollutant oxidation, instead, aldehydes fully oxidize. Even though benzene is recalcitrant to degradation, P25 and 1077 reduced toluene's concentration to 97% and 96% in 55 min, respectively. Acetonitrile is refractory to photocatalysis.

Characterization of the variation of carbonyl compounds concentrations before, during, and after the renovation of an apartment at Niterói, Brazil

The present work reports the variation of 31 carbonyl compounds (CC) in an apartment located at Niterói City, Rio de Janeiro State, Brazil. Eight sampling campaigns were conducted through a 1-year period, and three areas (living room, kitchen, and bedroom) were evaluated before, during, and after the renovation activities and reoccupation of the apartment. Samples were collected using SEP-PAK cartridges impregnated with 2,4-dinitrophenylhydrazine, and the hydrazones were analyzed using rapid resolution liquid chromatography with UV detection. The lowest total concentration of CC (19.0 ± 1.5 μg m(-3)) was found before the renovation when the apartment was empty, but door varnishing resulted in highest contamination of the apartment (1386 ± 384 μg m(-3)); however, an important dispersion of CC was observed in the subsequent sampling (148 ± 1.8 μg m(-3)). After apartment reoccupation, the indoor contamination seemed to depend on the routine activities taken there, such as household product use and cooking activities, but apparently, local temperature increase favored the vaporization of the volatile CC from the building materials in the apartment. As far as we are concerned, this is the first study comparing the concentrations of 31 CC in residential areas before, during, and after renovation activities taken in Brazil.

Extraction and preconcentration of formaldehyde in water by polypyrrole-coated magnetic nanoparticles and determination by high-performance liquid chromatography

In this study, a simple and rapid extraction method based on the application of polypyrrole-coated Fe3 O4 nanoparticles as a magnetic solid-phase extraction sorbent was successfully developed for the extraction and preconcentration of trace amounts of formaldehyde after derivatization with 2,4-dinitrophenylhydrazine. The analyses were performed by high-performance liquid chromatography followed by UV detection. Several variables affecting the extraction efficiency of the formaldehyde, i.e., sample pH, amount of sorbent, salt concentration, extraction time and desorption conditions were investigated and optimized. The best working conditions were as follows: sample pH, 5; amount of sorbent, 40 mg; NaCl concentration, 20% w/v; sample volume, 20 mL; extraction time, 12 min; and 100 μL of methanol for desorption of the formaldehyde within 3 min. Under the optimal conditions, the performance of the proposed method was studied in terms of linear dynamic range (10-500 μg/L), correlation coefficient (R(2) ≥ 0.998), precision (RSD% ≤ 5.5) and limit of detection (4 μg/L). Finally, the developed method was successfully applied for extraction and determination of formaldehyde in tap, rain and tomato water samples, and satisfactory results were obtained.

Evaluation of the concentrations and distribution of carbonyl compounds in selected areas of a Brazilian bus terminal

This study describes the determination of 30 carbonyl compounds (CCs) in three areas (bus boarding platform, passenger circulation area, and a pastry shop) of the Presidente João Goulart Bus Terminal, located at Niterói City, RJ, Brazil, and in an open area 700 m distant from the terminal. Samples were collected using SEP-PAK cartridges impregnated with 2,4-dinitrophenylhydrazine, during May to July 2012. The hydrazones formed were analyzed using rapid resolution liquid chromatography with UV detection. The studied locations showed distinct profiles of distribution of CC. The circulation area, which is influenced by different pollution sources, presented an intermediate profile between that of the pastry shop and boarding platform. Formaldehyde and acetaldehyde were the most abundant CC, but acetaldehyde predominated in the pastry shop once it is a by-product of baking yeast fermentation. Samples taken in the pastry shop and circulation area showed significant concentrations of hexanaldehyde and nonanaldehyde emitted during cooking. The pastry shop showed the largest level of total CC among the studied areas followed by the circulation area, the boarding platform, and the open area.

Determination of vanillin in vanilla perfumes and air by capillary electrophoresis

The present study investigated capillary electrophoretic detection of vanillin in vanilla perfume and air. An UV-absorbance detector was used in a home-made capillary electrophoretic instrument. A fused silica capillary (outer diameter: 364 μm, inner diameter: 50 μm) was used as a separation capillary, and a high electric voltage (20 kV) was applied across the two ends of the capillary. Total length of the capillary was 70 cm, and the effective length was 55 cm. Experimental results showed that the vanillin peak was detected at about 600, 450, and 500 seconds when pH of running buffers in CE were 7.2, 9.3, and 11.5, respectively. The peak area of vanillin was proportional to its concentration in the range of 0-10(-2) mol/L. The detection limit was about 10(-5) mol/L. Vanillin concentration in a 1% vanilla perfume sample was determined to be about 3×10(-4) mol/L, agreed well with that obtained by a HPLC method. Furthermore, determination of vanillin in air by combination of CE and active carbon adsorption method was investigated.

Direct sampling in air of capillary electrophoresis

Capillary electrophoresis (CE) is usually off-line combined with an adsorption/desorption method to analyze gaseous or atmospheric samples. Here, we demonstrated direct sampling in the air of CE. The inlet end of a fused silica capillary filled with a pH 7.2 phosphate buffer was placed in the air for absorbing gaseous or volatile components, while the outlet end was immersed into a buffer vial at the low electric potential side. After a certain period of time, the inlet end was immersed into another buffer vial at the high electric potential side; CE was carried out by applying a high electric voltage of 20 kV. An UV-absorbance detector (wavelength, 254 nm) was used in CE. Evaporated vanillin in air was used as model gaseous sample. Experimental factors, such as a height difference between the inlet end and the outlet buffer, were investigated in detail. Fast detection of evaporated vanillin in indoor air was demonstrated.

Analysis of aldehydes in excipients used in liquid/semi-solid formulations by gas chromatography–negative chemical ionization mass spectrometry

Monitoring of low-molecular-weight aldehyde levels in excipients used in liquid/semi-solid based capsule (LFC) dosage forms plays a critical role in the development of these pharmaceutical products. A simple, sensitive and specific method based on gas chromatography coupled with mass spectrometry (GC-MS) utilizing an Rtx-5MS capillary column was developed and validated for the detection and quantification of C1-C8 aliphatic aldehydes in LFC excipients at sub-microg/g levels. The proposed procedure is based on the derivatization of aldehydes in 10:1 (v/v) acetonitrile:water with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by direct GC analysis of aldehyde-PFBHA-oxime derivatives with negative chemical ionization (NCI) MS detection. The method developed was successfully applied to the analysis of short chain aldehydes in 30 typical LFC excipients. An example case study on the formation and growth of aldehydes in these excipients under accelerated storage conditions is also reported.

Polymer-mediated extraction of the fluorescent compounds derived by Hantzsch reaction with dimedone for the sensitive determination of aliphatic aldehydes in air

An extraction method based on the thermo-responsive precipitation of a water-soluble polymer, poly(N-isopropylacrylamide) [PNIPAAm], was applied to the concentration of dimedone (5,5-dimethylcycrohexane-1,3-dion) derivatives for the highly sensitive determination of aldehydes in air. Aliphatic aldehydes including formaldehyde, acetaldehyde, propanal, 1-butanal, 1-heptanal, and 1-hexanal in air were well solubilized into the aqueous solution of dimedone and ammonium acetate by mixing the solution and air sample in a polyvinyl fluoride bag. Fluorescent derivatives of aldehydes that had formed by the Hantzsch reaction with dimedone were concentrated by polymer-mediated extraction. The recoveries of the fluorescent compounds increased with increasing the carbon number of aldehyde and were more than 80% for the derivatives from aldehydes having more than three carbon atoms under the optimal conditions. Microgram per m3 (sub-ppb) levels of the aliphatic aldehydes, propanal, 1-butanal, 1-heptanal, and 1-hexanal, in ambient air were successfully determined by HPLC separation with fluorometric detection. The sampling volume and time required were only 1l and 20 s, respectively.

Recent advances in capillary electrophoresis and capillary electrochromatography of pollutants

Recent advances in the CE and CEC separation, detection, and sample preparation methodologies applied to the determination of a variety of compounds having current or potential environmental relevance have been overviewed. The reviewed literature has illustrated the wide range of CE applications, indicating the continuing interest in CE and CEC in the environmental field.

A Sensitive Method for the Quantification of Acrolein and Other Volatile Carbonyls in Ambient Air

Acrolein, an unsaturated aldehyde found in both indoor and outdoor air, is considered one of the greatest noncancer health risks of all organic air pollutants. Current methods for determining acrolein often employ sorbent-filled cartridges containing a carbonyl derivatizing agent (e.g., dinitrophenylhydrazine). These methods are of limited use for unsaturated compounds due to the formation of unstable derivatives, coelution of similar compounds, long sample collection times, and ozone interferences that result in poor sensitivity, selectivity, and reproducibility. The goal of this research was to develop an analytical method for determining ppt concentrations of acrolein and other carbonyls in air with short sampling times (10 min). The method uses a mist chamber to collect carbonyls by forming water-soluble carbonyl-bisulfite adducts. The carbonyls are then liberated from the bisulfite, derivatized, and quantified by gas chromatography/electron capture negative ionization mass spectrometry. The method was applied to determine atmospheric acrolein concentrations at three sites in northern California reflecting hemispheric background concentrations, biogenic-dominated regions, and urban environments. The resulting acrolein concentrations were 0.056, 0.089, and 0.29 microg/m3, respectively, which are all above the EPA Reference Concentration of 0.02 microg/m3. The minimum detection limit of 0.012 microg/m3 is below that of other published methods. Methacrolein, methyl vinyl ketone, crotonaldehyde, glyoxal, methyl glyoxal, and benzaldehyde were also quantified.

Rapid and sensitive method for the determination of acetaldehyde in fuel ethanol by high-performance liquid chromatography with UV–Vis detection

A high-performance liquid chromatography (HPLC) method for the determination of acetaldehyde in fuel ethanol was developed. Acetaldehyde was derivatized with 0.900 mL 2,4-dinitrophenylhydrazine (DNPHi) reagent and 50 microL phosphoric acid 1 mol L(-1) at a controlled room temperature of 15 degrees C for 20 min. The separation of acetaldehyde-DNPH (ADNPH) was carried out on a Shimadzu Shim-pack C18 column, using methanol/LiCl((aq)) 1.0 mM (80/20, v/v) as a mobile phase under isocratic elution and UV-Vis detection at 365 nm. The standard curve of ADNPH was linear in the range 3-300 mg L(-1) per injection (20 microL) and the limit of detection (LOD) for acetaldehyde was 2.03 microg L(-1), with a correlation coefficient greater than 0.999 and a precision (relative standard deviation, RSD) of 5.6% (n = 5). Recovery studies were performed by fortifying fuel samples with acetaldehyde at various concentrations and the results were in the range 98.7-102%, with a coefficient of variation (CV) from 0.2% to 7.2%. Several fuel samples collected from various gas stations were analyzed and the method was successfully applied to the analysis of acetaldehyde in fuel ethanol samples.

Analysis of methylglyoxal in water and biological matrices by capillary zone electrophoresis with diode array detection

We describe a new method for the determination of methylglyoxal in water and biological matrices, using o-phenylenediamine as derivatizing agent and solid-phase extraction followed by capillary zone electrophoresis with diode array detection. 25 mM sodium phosphate running buffers at pH 2.2, 30 kV, and 25 degrees C allowed the best instrumental conditions for the optimum separation of methylglyoxal in a suitable analytical time (< 10 min), using an uncoated fused-silica capillary of 75 microm inner diameter and an effective length of 45.1 cm with an extended light path and the wavelength set to 200 nm. Under optimized instrumental conditions, good reproducibility of the migration time (< 1.1%), precision (< 5%), an excellent linear dynamic range from 0.1 to 3.6 mg/L (r(2) = 0.9997), and low limits of detection (7.2 microg/L) were obtained for methylglyoxal measurements, using the internal standard methodology. Assays on laboratory-spiked tap and ground water samples allowed a remarkable accuracy, presenting yields of 95.0 +/- 4.3 and 94.0 +/- 1.1%, respectively, and good performance to determine methylglyoxal in beer and yeast cells suspensions matrices was also obtained at trace level. The present methodology is a cost-effective alternative for routine quality control analysis, showing to be reliable, sensitive, and with a low sample volume requirement to monitor methylglyoxal in water and biological matrices.