Search Results (6)

This work presents a novel application of gas-diffusion microextraction (GDME) for the extraction and identification of volatile carbonyl compounds from a dry-process fibreboard (MDF) by combining high-performance liquid chromatography with diode array detection (HPLC–DAD) and mass spectrometry (MS). GDME is a simple, inexpensive, and environmentally friendly technique that allows the simultaneous extraction and derivatization with 2,4-dinitrophenylhydrazine (DNPH) of selected volatiles. The extraction conditions were optimized using design of experiments through a 2⁴ full fractional design followed by a Box–Behnken design, resulting in 35 min of extraction at 45 °C using 500 µL of DNPH 0.15%. The analysis of commercial MDF samples with different characteristics, such as thickness or colour, showed a distinct emission profile of volatile carbonyls. The principal emitting compounds found were formaldehyde, acetaldehyde, acetone, butanal, pentanal, hexanal, heptanal, octanal, and nonanal. A total of 25 compounds were identified using MS, including saturated and unsaturated aldehydes, ketones, dicarbonyls, and benzaldehyde-derivatives. This method can be a valuable tool for the qualitative evaluation of VOCs released from wood-based panels and for the assessment of indoor-air quality. Full article

Chitosan is a linear biopolymer composed of D-glucosamine and N-acetylglucosamine units. The percentage of D-glucosamine in the polymeric chain can vary from one sample to another and is expressed as the degree of deacetylation (DDA). Since this parameter has an impact on many properties, its determination is often critical, and potentiometric titration is a common analytical technique to measure the DDA. Cross-linking with glutaraldehyde is one of the most explored modifications of chitosan; however, the determination of the DDA for the resulting reticulated chitosan resins can be challenging. In this paper, we report a new, rapid, and efficient method to determine the DDA of glutaraldehyde-cross-linked chitosan resins via HPLC. This method relies on the use of 2,4-dinitrophenylhydrazine (DNPH) as a derivatizing agent to measure the level of reticulation of the polymer (LR) after the reticulation step. In this study, we prepare three calibration curves (with an R² value over 0.92) for three series of reticulated polymers covering a large range of reticulation levels to demonstrate that a correlation can be established between the LR established via HPLC and the DDA obtained via titration. The polymers are derived from three different chitosan starting materials. These standard calibration curves are now used on a routine basis in our lab, and the HPLC method has allowed us to change our DDA analysis time from 20 h to 5 min. Full article

Quantitative and qualitative analyses of chemical species out of CI engine tailpipe emissions fueled with pure diesel and diesel methanol blends, trapped in dinitro phenylhydrazine (DNPH) solutions, were performed. The formed hydrazine was studied using high-performance liquid chromatography (HPLC) accompanied by a detector for ultraviolet (UV). A set of carbonyl-DNPH derivative standards was developed and compared with engine tailpipe gases produced by both fuel modes. An understanding of carbonyl chemical compounds such as formaldehyde, acetaldehyde, and acrolein (HCHO, CH₃CHO, and H₂ = CHCHO, respectively) is essential for researchers to know how these chemicals affect human health and the environment. In both fuel modes, acetaldehyde was the main combustible product 25 ppm followed by formaldehyde 17 ppm, croton aldehydes 16 ppm, acrolein 12 ppm, and iso-valerdyhyde 10 ppm. In addition to these species, only a few other chemical species were detected in the exhaust gas. According to this study, carbonyl compounds from blended fuel contribute 15–22% of pure diesel fuel emissions. As shown by the results, engine operating conditions and fuel mode have a strong impact on the total amount of carbonyls released by the engine. Engine performance was highly influenced by different fuel modes and engine speeds. Using pure diesel, the regulated emissions, HC, CO, and NOx, registered high concentrations at a lower speed (1500 rpm) and NOx presented with the highest concentration of 4 g/kWh followed by CO with 1 g/kWh and HC with 0.5 g/kWh. Full article

Recent reports have suggested that (1) formaldehyde levels (measured as a hydrazone derivative using the DNPH derivatization method) in Electronic Nicotine Delivery Systems (ENDS) products were underreported because formaldehyde may react with propylene glycol (PG) and glycerin (Gly) in the aerosol to form hemiacetals; (2) the equilibrium would shift from the hemiacetals to the acetals in the acidic DNPH trapping solution. In both cases, neither the hemiacetal nor the acetal would react with DNPH to form the target formaldehyde hydrazone, due to the lack of the carbonyl functional group, thus underreporting formaldehyde. These reports were studied in our laboratory. Our results showed that the aerosol generated from formaldehyde-fortified e-liquids provided a near-quantitative recovery of formaldehyde in the aerosol, suggesting that if any hemiacetal was formed in the aerosol, it would readily hydrolyze to free formaldehyde and, consequently, form formaldehyde hydrazone in the acidic DNPH trapping solution. We demonstrated that custom-synthesized Gly and PG hemiacetal adducts added to the DNPH trapping solution would readily hydrolyze to form the formaldehyde hydrazone. We demonstrated that acetals of PG and Gly present in e-liquid are almost completely transferred to the aerosol during aerosolization. The study results demonstrate that the DNPH derivatization method allows for an accurate measurement of formaldehyde in vapor products. Full article

In leathers, formaldehyde is currently analyzed according to EN ISO 17226-1 standard, by reversed phase liquid chromatography after off-line precolumn derivatization with 2,4 dinitrophenylhydrazine (DNPH) in strong acidic conditions. We first demonstrate that this standard is not adapted to leather retanned with resins likely to release formaldehyde by hydrolysis. Indeed, formaldehyde content may be largely overestimated due to concomitant resin hydrolysis (in harsh acidic conditions) that releases formaldehyde during the derivatization step and during the waiting time on autosampler before analysis. Therefore, we thoroughly studied the derivatization step in order to propose new derivatization conditions. Replacing orthophosphoric acid by less acidic buffer solutions is not enough to avoid hydrolysis. A derivatization without adding acid is realized by solubilizing DNPH in acetonitrile instead of orthophosphoric acid. These conditions lead to a complete derivatization of formaldehyde in 3 h at 50 °C (in a water bath) while avoiding the hydrolysis of co-extracted dicyandiamide and melamine resins. The as-obtained leather extracts are stable over time. Formaldehyde contents found with this method agree with the formaldehyde content measured immediately at the end of derivatization reaction in standard conditions or with formaldehyde content measured by a home-designed flow injection analysis with acetylacetone online derivatization and UV detection. Full article

The health risks of cigarette smoking have been reported to increase continuously, while it is estimated to be responsible for the death toll of more than seven million people globally each year. In an effort to reduce the risk involved in cigarette smoking, nicotine-free inhalators have been developed as smoking-cessation aids. To evaluate the feasibility of nicotine-free inhalators in such respect, we investigated the composition of volatile organic compounds (VOCs) released from the consumption of nicotine-free inhalators of which major components include natural essential oils and traditional Chinese medicinal herbs. Vapor samples from nicotine-free inhalators were generated and collected for analysis using an e-cigarette auto-sampler. The vapor samples were captured onto a multi-bed sorbent tube sampler and a 2,4-dinitrophenylhydrazine (DNPH) cartridge for the quantitative analysis with the aid of thermal desorption-gas chromatography/mass spectrometry and high-performance liquid chromatography, respectively. A total of 29 VOCs were determined in vapor samples at concentrations below 0.2 ppm. Concentrations of (+)-isomenthone and acrolein slightly exceeded the derived no-effect level (DNEL) or sensory irritation level. However, VOCs were below the concentration exposure limit, according to the Occupational Safety and Health Administration (OSHA). According to our study, most of the aroma compounds and VOCs released from nicotine-free inhalator were lower than the DNEL or sensory irritation level. Consequently, it is found that nicotine-free inhalators could be safe to use in reference to toxic guidelines for inhalation exposure. However, if the use of nicotine-free inhalators is over prolonged period, it can also increase the risk of exposure to potentially toxic compounds. Full article