Saturday 29 April 2017

Revisiting the Schönbein ozone measurement methodology

Geophysical Research Abstract

Trough the XIX century the Schönbein method gained a lot of popularity by its easy way to measure tropospheric ozone. Traditionally it has been considered that Schönbein measurements are not accurate enough to be useful. Detractors of this method argue that it is sensitive to meteorological conditions, being the most important the influence of relative humidity. As a consequence the data obtained by this method have usually been discarded. Here we revisit this method taking into account that values measured during the 19th century were taken using different measurement papers. We explore several concentrations of starch and potassium iodide, the basis for this measurement method. Our results are compared with the previous ones existing in the literature. The validity of the Schönbein methodology is discussed having into account humidity and other meteorological variables.

Friday 28 April 2017

Optimization of selective pressurized liquid extraction of organic pollutants in placenta to evaluate prenatal exposure

Journal of Chromatography A

The early exposure to organic pollutants (OPs) related to dietary habit or environmental exposure is a concern of growing interest in environmental health. When OPs enter the body, they can accumulate in fatty tissue and even travel through the bloodstream being able to cross the placenta and reach the fetus through the substance exchange between the mother and the child. Epidemiologic and clinical data affirm that these chemicals increase the risk of adverse effects during childhood. This article reviews and addresses one of the most relevant analytical methods for determining OPs in placenta. We discuss and critically evaluate procedures, such as solid-liquid and selective pressurized liquid extraction (SPLE). Clean-up of extracts was performed by solid-phase extraction (SPE) using EZ-POP cartridges. Detection of OPs was carried out by gas chromatography (GC) coupled to tandem mass spectrometry (MS/MS). Recoveries ranged from 52% to 94% by SPLE with estimated quantification limits between 0.15 and 2.2 ng/g for organochlorine pesticides (OCPs), between 0.083 and 0.50 for organophosphate pesticides (OPPs), between 0.025 and 0.15 ng/g for polychlorinated biphenyl (PCBs), between 0.015 and 0.10 ng/g for polybromodiphenyl ethers (PBDEs), between 0.33 and 0.66 ng/g for pyrethroids and between 0.022 and 0.87 ng/g for polycyclic aromatic hydrocarbons (PAHs). Most of the target OPs were detected in twenty real placenta samples studied, with pyrethroids, PAHs and OPPs representing most of the 90% of OPs with means of 13–18 ng/g versus PCBs, OCPs, and PBDEs with means <4.0 ng/g. The rsults of this work indicate a prenatal exposure to OPs in Galicia.

Saturday 1 April 2017

Physico-chemical characterization and evaluation of bio-efficacies of black pepper essential oil encapsulated in hydroxypropyl-beta-cyclodextrin

Food Hydrocolloids

Encapsulation of essential oils with cyclodextrins can protect their active compounds from environmental conditions and improve their aqueous solubility, hence increasing their functional capabilities as additives. The purpose of this study was to characterize the physico-chemical properties and bio-efficacies, antioxidant and antibacterial activities, of the encapsulated black pepper essential oil in hydroxypropyl-β-cyclodextrin (HPβCD), in comparison with the major ingredient in the oil, β-caryophyllene. The difference in encapsulation efficiency of the pure compound and the black pepper oil results from the presence of other components in the black pepper oil such as limonene, δ-3-carene and pinene. Although the inclusion complexes increase their stability, they gave slightly lower antioxidant activity as a result of the HPβCD was blocking the functional groups of active compounds during reaction with DPPH radicals. Instead, after encapsulated in HPβCD, the antibacterial activity of black pepper oil was improved by 4 times against both S. aureus and E. coli.