Inês Maria Valente

Another glimpse over the salting-out assisted liquid–liquid extraction in acetonitrile/water mixtures

The use of the salting-out effect in analytical chemistry is very diverse and can be applied to increase the volatility of the analytes in headspace extractions, to cause the precipitation of proteins in biological samples or to improve the recoveries in liquid-liquid extractions. In the latter, the salting-out process can be used to create a phase separation between water-miscible organic solvents and water. Salting-out assisted liquid-liquid extraction (SALLE) is an advantageous sample preparation technique aiming HPLC-UV analysis when developing analytical methodologies. In fact, some new extraction methodologies like QuEChERS include the SALLE concept. This manuscript discusses another point of view over SALLE with particular emphasis over acetonitrile-water mixtures for HPLC-UV analysis; the influence of the salting-out agents, their concentration and the water-acetonitrile volume ratios were the studied parameters. α-dicarbonyl compounds and beer were used as test analytes and test samples, respectively. The influence of the studied parameters was characterized by the obtained phase separation volume ratio and the fraction of α-dicarbonyls extracted to the acetonitrile phase. Results allowed the distribution of salts within three groups according to the phase separation and their extractability: (1) chlorides and acetates, (2) carbonates and sulfates and (3) magnesium sulfate; of all tested salts, sodium chloride had the highest influence on the α-dicarbonyls fraction extracted.

Analysis of aldehydes in beer by gas-diffusion microextraction: Characterization by high-performance liquid chromatography–diode-array detection–atmospheric pressure chemical ionization–mass spectrometry

In this work, a recently developed extraction technique for sample preparation aiming the analysis of volatile and semi-volatile compounds named gas-diffusion microextraction (GDME) is applied in the chromatographic analysis of aldehydes in beer. Aldehydes-namely acetaldehyde (AA), methylpropanal (MA) and furfural (FA)-were simultaneously extracted and derivatized with 2,4-dinitrophenylhydrazine (DNPH), then the derivatives were separated and analyzed by high-performance liquid chromatography with spectrophotometric detection (HPLC-UV). The identity of the eluted compounds was confirmed by high-performance liquid chromatography-atmospheric pressure chemical ionization-mass-spectrometry detection in the negative ion mode (HPLC-APCI-MS). The developed methodology showed good repeatability (ca. 5%) and linearity as well as good limits of detection (AA-12.3, FA-1.5 and MA 5.4microgL(-1)) and quantification (AA-41, FA-4.9 and MA 18microgL(-1)); it also appears to be competitive in terms of speed and cost of analysis.

Increased sensitivity of anodic stripping voltammetry at the hanging mercury drop electrode by ultracathodic deposition.

An improved approach to the anodic stripping voltammetric (ASV) determination of heavy metals, using the hanging mercury drop electrode (HMDE), is reported. It was discovered that using very cathodic accumulation potentials, at which the solvent reduction occurs (overpotential deposition), the voltammetric signals of zinc(II), cadmium(II), lead(II) and copper(II) increase. When compared with the classical methodology a 5 to 10-fold signal increase is obtained. This effect is likely due to both mercury drop oscillation at such cathodic potentials and added local convection at the mercury drop surface caused by the evolution of hydrogen bubbles.

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.

An Overview on Cardamonin

Cardamonin, as shown by the increasing number of publications, has received growing attention from the scientific community due to the expectations toward its benefits to human health. In this study, research on cardamonin is reviewed, including its natural sources, health promoting aspects, and analytical methods for its determination. Therefore, this article hopes to aid current and future researchers on the search for reliable answers concerning cardamonins value in medicine.

Xanthohumol Modulates Inflammation, Oxidative Stress, and Angiogenesis in Type 1 Diabetic Rat Skin Wound Healing

Type 1 diabetes mellitus is responsible for metabolic dysfunction, accompanied by chronic inflammation, oxidative stress, and endothelium dysfunction, and is often associated with impaired wound healing. Phenol-rich food improves vascular function, contributing to diabetes prevention. This study has evaluated the effect of phenol-rich beverage consumption in diabetic rats on wound healing, through angiogenesis, inflammation, and oxidative stress modulation. A wound-healing assay was performed in streptozotocin-induced diabetic Wistar rats drinking water, 5% ethanol, and stout beer with and without 10 mg/L xanthohumol (1), for a five-week period. Wounded skin microvessel density was reduced to normal values upon consumption of 1 in diabetic rats, being accompanied by decreased serum VEGF-A and inflammatory markers (IL-1β, NO, N-acetylglucosaminidase). Systemic glutathione and kidney and liver H2O2, 3-nitrotyrosine, and protein carbonylation also decreased to healthy levels after treatment with 1, implying an improvement in oxidative stress status. These findings suggest that consumption of xanthohumol (1) by diabetic animals consistently decreases inflammation and oxidative stress, allowing neovascularization control and improving diabetic wound healing.

Gas-diffusion microextraction.

Gas-diffusion microextraction (GDME) is an innovative technique that combines the advantages of membrane-aided gas-diffusion with microextraction concepts. GDME makes uses of a novel portable and low-cost device that comprises a small, commercially available, semi-permeable membrane. Furthermore, if derivatization is integrated into the GDME concept, considerable enrichment factors can be obtained. It may become a powerful tool for any analyst who intends to quantify volatile and semi-volatile analytes in various kinds of matrices. The analysis of vicinal diketones in beer was used as a case study to show GDME applicability and capabilities. Vicinal diketones were derivatized with o-phenylenediamine and then determined by HPLC-UV. Obtained results showed good repeatability and precision with extraction periods at the minute time span.

Jatrophane Diterpenes from Euphorbia mellifera and Their Activity as P-Glycoprotein Modulators on Multidrug-Resistant Mouse Lymphoma and Human Colon Adenocarcinoma Cells

Three new macrocyclic jatrophane diterpenes, named euphomelliferine (1) and euphomelliferenes A (2) and B (3), and one new tetracyclic triterpene, 19(10→9)-abeo-8α,9β,10α-tirucalla-5,25-diene-3β,24-diol (6, C-24 epimers), were isolated from the methanolic extract of Euphorbia mellifera. A known ingenane (7) and two jatrophane diterpenes (4 and 5) were also isolated. Their structures were elucidated by extensive spectroscopic methods, including 1D and 2D homo- and heteronuclear NMR experiments. Jatrophane diterpenes 1-3 and 5 were evaluated for their effects on the reversion of multidrug resistance (MDR) mediated by P-glycoprotein, by using the rhodamine-123 exclusion test, on human MDR1 gene-transfected mouse lymphoma cells (L5178Y MDR) and on human colon adenocarcinoma cells (COLO 320). The apoptosis-inducing activity of these compounds was also tested on COLO 320 cells, using the annexin-V/propidium iodide assay. Diterpenes 1 and 2 displayed significant MDR reversing activity, in a dose-dependent manner, on both cancer cell models. The tested compounds did not induce apoptosis in the COLO 320 cells.

New application of the QuEChERS methodology for the determination of volatile phenols in beverages by liquid chromatography

The QuEChERS methodology has been used for the determination of pesticides in solid samples. However, this technique can be equally useful for other applications, namely for liquid samples. This work presents a new application of QuEChERS to the analysis of important ageing markers in beverages, the volatile phenols, by liquid chromatography with fluorimetric and UV detection. The sample preparation methodology comprises two sequential steps: (1) salting-out liquid-liquid extraction and (2) dispersive solid-phase extraction for extract clean-up. The methodology showed good repeatability (ca. 3%) and reproducibility (ca. 6%) with recovery levels above 90% and limits of detection varied in the range of 0.001-0.055 mg L(-1). A variable amount of phenols was found in the analysed samples (beers, wines and fruit juices), being 4-ethylphenol and 4-ethylguaiacol the compounds found in higher amounts, varying in the range of 0.12-1.11 mg L(-1) and 0.13-1.23 mg L(-1), respectively.

Development of a membraneless extraction module for the extraction of volatile compounds: application in the chromatographic analysis of vicinal diketones in beer.

A membraneless extraction module (MLEM) for the sample preparation of volatile compounds and its use for the chromatographic analysis of vicinal diketones in beer are reported. The extraction process is based on the same principles of gas diffusion (GD) and pervaporation (PV); however it does not use a membrane. This module has a lower chamber where the sample continuously flows, while volatile compounds evaporate to the headspace. Inside the module there is a suspended small reactor, where a small volume of a suitable acceptor solution is placed. This extraction module was tested in the determination of vicinal diketones (VDKs) in beer (CV=5%; LOD=4 microg L(-1)), showing applicability with real samples. Several parameters of the extraction process, such as temperature, sample flow and extraction time, were studied and optimized. This module proved to be a good tool for the sampling of volatile compounds, since the extraction is made without using a membrane avoiding all the robustness problems related with its use.