Gas-diffusion microextraction combined with HPLC-DAD for the comprehensive analysis of volatile carbonyl compounds in wood-based panels.

This work presents a novel application of gas-diffusion microextraction (GDME) combined with high-performance liquid chromatography with diode-array detection (HPLC-DAD) for the comprehensive analysis of volatile carbonyl compounds released from wood-based panels. GDME is a simple, fast, and environmentally friendly technique that allows the simultaneous extraction and derivatization of volatile carbonyls directly from solid samples. Commercial particleboards were analysed together with particleboard panels specifically produced using controlled conditions, materials, and reagents, to evaluate the differences in the emission profile of volatile carbonyl compounds. The effect of different production parameters, such as the type of wood particle, resin, and moisture content, on the emission profile of volatile carbonyls from particleboards was investigated using principal component analysis (PCA). The results showed that GDME-HPLC-DAD could successfully differentiate particleboards according to their emission of carbonyl compounds, such as formaldehyde, furfural, benzaldehyde, and other aliphatic carbonyls. Besides the differences on the emission of formaldehyde caused by the type of resin used, UF (urea-formaldehyde) and mUF (UF fortified with melamine), it was found that pine (Pinus pinaster Ait.) particleboards exhibit higher emissions of compounds such as acetaldehyde or hexanal when compared to the higher emissions of compounds such as furfural or benzaldehyde on the recycled particleboards.

A new electroanalytical methodology for the determination of formaldehyde in wood-based products.

A new electroanalytical methodology was developed for the sensitive and selective determination of formaldehyde in wood-based products (WBPs), featuring an extraction process using a Headspace Liquid Acceptor System (HLAS), and detection by square-wave voltammetry (SWV) on unmodified screen-printed carbon electrodes (SPCEs). HLAS, here presented for the first time, captures and derivatizes formaldehyde released from the sample by using the acetylacetone reagent as acceptor solution. The product of formaldehyde with acetylacetone, in the presence of ammonium salt, is 3,5-diacetyl-1,4-dihydrolutidine (DDL) which we have found to be electrochemically active at unmodified SPCEs, generating a selective oxidation peak at +0.4 V. Detection and quantification limits of 0.57 and 1.89 mg kg-1 were obtained, together with intra- and inter-day precisions below 10% (as relative standard deviation, RSD). The methodology was used to determine formaldehyde content in seven WBPs, with similar results being obtained by the developed HLAS-SPCE method and the European standard method EN 717-3, with a profound reduction of total analysis time. The developed HLAS-SPCE combines the use of a new sample preparation procedure for volatiles with, as far as we know, the first determination of formaldehyde (as the derivative product, DDL) on unmodified SPCEs, offering a promising alternative for the determination of formaldehyde in WBPs and other samples.

GDME-based methodology for the determination of free formaldehyde in cosmetics and hygiene products containing formaldehyde releasers.

Formaldehyde is often applied in the industrial production of different products, such as textiles, insulation materials, or cosmetics, due to its preservative and disinfectant properties. However, formaldehyde is classified by the International Agency for Research on Cancer as carcinogenic, and there are numerous studies about the pernicious health effects that frequent exposure to formaldehyde can pose to human health. In the cosmetic industry, compounds called formaldehyde releasers are added during production, with the intent of releasing small amounts of formaldehyde over time. Although there are many methods available for the determination of formaldehyde, they are usually not suitable for the determination of free formaldehyde in cosmetics with formaldehyde releasers in their composition, as they can promote the accelerated release of formaldehyde. In this work, the gas-diffusion microextraction (GDME) technique was used for the extraction of formaldehyde from cosmetic and personal hygiene products. Acetylacetone was used as the derivatization reagent which was later used for the spectrophotometric determination of formaldehyde. The developed methodology exhibits limits of detection (1.98 mg kg-1) and quantification (6.60 mg kg-1) perfectly adequate for the determination of formaldehyde in these samples. Formaldehyde values between 6.9 ± 0.3 and 365 ± 15 mg kg-1 were found in samples containing the formaldehyde releasers DMDM hydantoin, Diazolidinyl urea, and Bronopol. Furthermore, mass spectrometry studies were performed in order to unbiasedly ensure the presence of formaldehyde in every extract. GDME proved to be an economical, simple, and robust alternative for the extraction of free formaldehyde in personal hygiene and cosmetic samples. Graphical abstract ᅟ.

Determination of Carbonyl Compounds in Cork Agglomerates by GDME-HPLC-UV: Identification of the Extracted Compounds by HPLC-MS/MS.

A new approach is proposed for the extraction and determination of carbonyl compounds in solid samples, such as wood or cork materials. Cork products are used as building materials due to their singular characteristics; however, little is known about its aldehyde emission potential and content. Sample preparation was done by using a gas-diffusion microextraction (GDME) device for the direct extraction of volatile aldehydes and derivatization with 2,4-dinitrophenylhydrazine. Analytical determination of the extracts was done by HPLC-UV, with detection at 360 nm. The developed methodology proved to be a reliable tool for aldehyde determination in cork agglomerate samples with suitable method features. Mass spectrometry studies were performed for each sample, which enabled the identification, in the extracts, of the derivatization products of a total of 13 aldehydes (formaldehyde, acetaldehyde, furfural, propanal, 5-methylfurfural, butanal, benzaldehyde, pentanal, hexanal, trans-2-heptenal, heptanal, octanal, and trans-2-nonenal) and 4 ketones (3-hydroxy-2-butanone, acetone, cyclohexanone, and acetophenone). This new analytical methodology simultaneously proved to be consistent for the identification and determination of aldehydes in cork agglomerates and a very simple and straightforward procedure.

Application of gas-diffusion microextraction to solid samples using the chromatographic determination of α-diketones in bread as a case study.

Gas-diffusion microextraction (GDME) was applied to the extraction of vicinal diketones in bread samples aimed at the determination of these compounds by high-performance liquid chromatography with ultraviolet detection (HPLC-UV). For the first time, GDME was used for direct chemical determination in solid samples, i.e. avoiding any sample preparation prior to extraction. Different extraction parameters were studied and optimized, namely temperature, time and chemical composition of the acceptor solution where o-phenylenediamine was used as a derivatizing agent, originating quinoxalines that could be determined at 315 nm. GDME demonstrated to be a good tool for the sampling of volatile compounds in solid samples with suitable method features for butane-2,3-dione (diacetyl, DC), pentane-2,3-dione (PN) and hexane-2,3-dione (HX): low LODs (6.0, 8.6 and 12 µg kg(-1), for DC, PN and HX respectively) and LOQs (20, 29 and 38 µg kg(-1), for DC, PN and HX respectively), r(2) above 0.990, and CV around 5%. The developed methodology was applied to the determination of different bread samples and was used to reveal the decrease of α-diketones in bread during the timeframe of a week.

Analysis of biogenic amines in wines by salting-out assisted liquid-liquid extraction and high-performance liquid chromatography with fluorimetric detection.

Biogenic amines are nitrogenous organic compounds of low molecular weight that are either formed or metabolized in cells of living organisms and can be found in several food products, being produced mainly by amino acid decarboxylation. When ingested in high concentrations they can induce several health problems in humans. In alcoholic beverages, and especially in wine, they are formed during the vinification process as a result of the action of microorganisms. In this work it is proposed a new methodology for the determination of biogenic amines in wines, which includes a sample preparation approach based on salting-out assisted liquid-liquid extraction, the use of dansyl chloride for the derivatization and chromatographic separation by high-performance liquid chromatography with fluorimetric detection. The salting-out effect is used to promote phase separation between water and a water-miscible organic solvent, while improving the extraction of organic or inorganic species. Several extraction parameters were optimized, such as the dansyl chloride concentration, pH and the effects caused by the order in which the extraction and derivatization were performed. Extraction of amines, and consequent detection, depends on the presence of dansyl chloride in solution prior to extraction. The results showed the possibility to simultaneously perform the extraction and the derivatization, making sample preparation easier and less time-consuming. The methodology was successfully applied to the determination of biogenic amines in five wines (white, red and rosé). This method has the potential to be a good alternative to existing methods since it is cheaper, easier and simplifies the sample preparation step.

Are hot-spots occluded from water?

Protein-protein interactions are the basis of many biological processes and are governed by focused regions with high binding affinities, the warm- and hot-spots. It was proposed that these regions are surrounded by areas with higher packing density leading to solvent exclusion around them - "the O-ring theory." This important inference still lacks sufficient demonstration. We have used Molecular Dynamics (MD) simulations to investigate the validity of the O-ring theory in the context of the conformational flexibility of the proteins, which is critical for function, in general, and for interaction with water, in particular. The MD results were analyzed for a variety of solvent-accessible surface area (SASA) features, radial distribution functions (RDFs), protein-water distances, and water residence times. The measurement of the average solvent-accessible surface area features for the warm- and hot-spots and the null-spots, as well as data for corresponding RDFs, identify distinct properties for these two sets of residues. Warm- and hot-spots are found to be occluded from the solvent. However, it has to be borne in mind that water-mediated interactions have significant power to construct an extensive and strongly bonded interface. We observed that warm- and hot-spots tend to form hydrogen bond (H-bond) networks with water molecules that have an occupancy around 90%. This study provides strong evidence in support of the O-ring theory and the results show that hot-spots are indeed protected from the bulk solvent. Nevertheless, the warm- and hot-spots still make water-mediated contacts, which are also important for protein-protein binding.

Relative cardiovascular and gastrointestinal safety of non-selective non-steroidal anti-inflammatory drugs versus cyclo-oxygenase-2 inhibitors: implications for clinical practice.

Non-steroidal anti-inflammatory drugs (NSAIDs) are frequently used in clinical practice, and are considered a first-line option for pain management. However, non-selective NSAIDs (nsNSAIDs) and new generation NSAIDs named cyclo-oxygenase-2 inhibitors (coxibs) are very different from one another and their cardiovascular and gastrointestinal safety profiles may influence prescribing. This article resulted from a search of MEDLINE/Pubmed, Cochrane Library, Bandolier, Medscape and Trip database, up to June 2011. Key words included non-steroidal anti-inflammatory, coxib and safety, with the purpose of reviewing the gastrointestinal and cardiovascular safety issues of NSAIDS and the main aspects that differentiate both classes. Selective coxibs are associated with a more favourable gastrointestinal safety profile than nsNSAIDs. In terms of the risk of cardiovascular events, there seems to be a class effect for all NSAIDs with the possible exception of naproxen. The proper usage guidelines for NSAIDs detail the importance of risk factors for each patient in addition to the differences between classes. Patients with high cardiovascular or gastrointestinal risk should avoid using NSAIDs. These medications should be used at the minimum effective dose and for the shortest time possible in all patients.