Physicochemical properties and encapsulation of silicon in double emulsions for healthier food applications.

This article analyses the potential use of double emulsions as silicon delivery systems with reference to the influence of the composition of the inner aqueous phase (W1, containing NaCl and sodium caseinate or gelatin) on silicon encapsulation and physicochemical properties of food-grade W1/O/W2. Irrespective of W1, DEs initially showed a well-defined monomodal distribution, with the widest range registering in the sample with gelatin. All samples developed a bimodal distribution during storage (3 ± 2 °C). Heating increased the range of droplet size distribution. DEs exhibited high physical stability (creaming), decreasing over storage; this behaviour was generally unaffected by W1 composition, which maintained similar stability (95-96%) at the end of storage. Viscosity was generally unaffected by formulation, storage time or heating treatment. Si encapsulation efficiency (72.4 and 78.3%) was not affected by W1 composition, while Si encapsulation stability was generally unaffected by either storage or heating. These DEs can be used as potential ingredient (with lower fat content, better fatty acid profile and with the potential Si health benefits) for the development of healthier foods including meat products.

Multiparametric optimization of a new high-sensitive and disposable mercury (II) electrochemical sensor.

An electrochemical sensor for mercury (II) determination was developed by modifying the surface of a commercial screen-printed carbon electrode (SPCE) with a polystyrene sulfonate-NiO-carbon nanopowder composite material. Mercury measurements were performed by differential pulse anodic stripping voltammetry (DPASV). Sensor composition and measurement conditions were optimized using a multivariate experiment design. A screening experiment by using a Plackett-Burman design was first performed in order to determine the main contributing factors to the electrochemical response. The most important factors were employed to establish the interactions between different experimental variables and get the best conditions for mercury determination. For this purpose, a five level central composite design and a response surface methodology were used. The optimized method using the developed NiO-PSS-SPCE sensor presents a very low limit of detection of 0.021 µg L(-1) and a linear response over two concentration ranges with two different slopes, from 0.05 to 2.0 µg L(-1) and between 2.0 and 75 µg L(-1). The sensor was successfully applied to mercury determination in water samples.

Interaction of organic contaminants with natural clay type geosorbents: potential use as geologic barrier in urban landfill.

The aim of this work is to characterize the capability of several clay materials as preservative of organic pollution for use as landfill barrier. Interaction of representative organic pollutants with different polarity and water solubility (atrazine, benzamide, methomyl, paraquat and toluene) with several clay materials coming from several locations of Spain were studied. Batch suspension method was used to study the pesticide adsorption onto the clay sorbents in solution conditions that simulate the composition of a young leachate in its aerobic acetogenic stage (pH=5 and I=0.15) The obtained data of the analytes sorption were modelized by several sorption isotherm models, and the best fitted data were got with a generalized Langmuir adsorption isotherm. The higher maxima adsorptions were observed for paraquat (50-62 mmol kg(-1)) and toluene (19-34 mmol kg(-1)) whereas more hydrophobic compounds present lower adsorption (0.7-2.5 mmol kg(-1)). Paraquat is the compound that presents the higher bonding coefficients. Therefore these clays could be used as components of the multibarriers in controlled urban landfill.

Evaluation of the capability of different chromatographic systems for the monitoring of thimerosal and its degradation products by high-performance liquid chromatography with amperometric detection.

Several liquid chromatographic systems using electrochemical detection on carbon electrodes were compared for the analysis of thimerosal and its degradation products, thiosalicylic acid and dithiodibenzoic acid. The studied separation systems included reversed-phase ion-suppressed chromatography, reversed-phase ion-pair chromatography and ion chromatography. Amperometry and coulometry were evaluated as electrochemical detection techniques. The best method for thimerosal determination in ophthalmic solutions in terms of selectivity and sensitivity was ion-pair chromatography.

HPLC analysis of thimerosal and its degradation products in ophthalmic solutions with electrochemical detection.

A reverse-phase high-performance liquid chromatographic assay using amperometric detection on a glassy-carbon electrode has been developed for analysis of thimerosal and its main degradation products, thiosalicylic acid and dithiodibenzoic acid, in ophthalmic formulations. A potential value of 0.9 V vs. Ag/AgCl was chosen for simultaneous detection of thimerosal and thiosalicylic acid, obtaining limits of detection of 1.0 and 0.2 ng injected, respectively. A potential value of 1.2V was applied for simultaneous determination of all three compounds studied, obtaining in this case limits of detection of 3,4 and 4 ng injected for thimerosal, thiosalicylic acid and dithiodibenzoic acid, respectively. The results obtained reveal the utility of the HPLC method in quality control of commercial products containing thimerosal with good detectability.