Biovalidation of an SPE-HPLC-UV-fluorescence method for the determination of valsartan and its metabolite valeryl-4-hydroxy-valsartan in human plasma

A simple and fast method for the simultaneous determination of the antihypertensive drug Valsartan and its metabolite in human plasma has been validated. The proposed method deals with SPE, followed by an HPLC separation coupled with fluorimetric and photometric detection. The optimization of the SPE-HPLC method was achieved by an experimental design. The separation was performed on an RP C18 Atlantis 100 mmx3.9 mm column. The mobile phase consisted of a mixture of ACN 0.025% TFA and phosphate buffer (5 mM, pH = 2.5) 0.025% TFA and was delivered in gradient mode at a flow rate of 1.30 mL/min. The eluent was monitored with a fluorescence detector at 234 and 378 nm excitation and emission wavelengths, respectively, and at 254 nm using a photometric detector. The full analytical validation was performed according to the Food and Drug Administration (FDA) 'guidance for industry: bioanalytical method validation' and the recoveries obtained for Valsartan and its metabolite ranged from 94.6 to 108.8%. The validated method was successfully applied to 12 plasma samples obtained from patients under antihypertensive treatment with Valsartan.     

Influence of the organic compounds addition in the polymer free volume,gas sorption and diffusion

Three low molecular compounds were added to a glassy polymer, poly(amino-ether) resin, in order to change its free volume and to study the subsequent effect in transport properties. Free volume characterization was carried out using the positron annihilation lifetime spectroscopy technique. Two electrobalances were used to obtain carbon dioxide sorption kinetic. Diffusion coefficient variation is in good agreement with the additive antiplasticizer character, i.e. the reduction of the free volume fraction. However, solubility is affected by other variables too, as the balance of the interactions between penetrant, additive and polymer as well as the effect of coming closer the sorption temperature to the glass transition temperature in the sorption mode.     

Ultracompact polarization converter with a dual subwavelength trench built in a silicon-on-insulator waveguide

The design and fabrication of an ultracompact silicon-on-insulator polarization converter is reported. The polarization conversion with an extinction ratio of 16 dB is achieved for a conversion length of only 10 μm. Polarization rotation is achieved by inducing a vertical asymmetry by forming in the waveguide core two subwavelength trenches of different depths. By taking advantage of the calibrated reactive ion etch lag, the two depths are implemented using a single mask and etching process. The measured converter loss is -0.7 dB and the 3 dB bandwidth is 26 nm.     

In situ detection of aromatic compounds with biosensor <Emphasis Type="Italic">Pseudomonas putida</Emphasis> cells preserved and delivered to soil in water-soluble gelatin capsules

While many types of bacteria have been engineered to produce an optical output in response to given analytes in a culture, their use for extensive, in situ monitoring of distinct chemical species in soil is hampered by a dearth of practicable spreading schemes. In this work, we report and validate a comprehensive system for the long-term preservation of Pseudomonas putida cells genetically designed for biosensing benzene, toluene, ethylbenzene, and xylenes (BTEX) in soil, along with a procedure to formulate, spread, and vigorously activate such bacteria at the desired site and occasion. To this end, various known lyoprotectants were tested for promoting the long-term maintenance of biosensor cells with quite variable outcomes. While a formulation of inositol and maltodextrines was optimal for preservation of freeze-dried BTEX-sensing bacteria, adsorption of P. putida cells to corncob powder (an abundant residue of the corn industry) endowed the resulting material with a lasting viability at ambient conditions. In any case, the thereby preserved bacterial biomass acquired physical and mechanical properties adequate for formulating the biosensor agent in water-soluble but otherwise hard dry gelatine capsules with a long shelf life. When such capsules were spread in a soil microcosm and subsequently liquefied with water or high humidity, the released microorganisms formed spots that gave an intense luminiscent signal upon exposure to effectors of the sensor circuit implanted in the chromosome of the P. putida strain. We argue that the procedures described here can facilitate implementation of wide-area biological detection strategies for revealing the location of toxic or perilous chemicals.     

Catalytic activity of a nickel on alumina catalyst in the CO2 reforming of methane

The kinetics of the CO₂-reforming of methane over a stable Ni/γ-Al₂O₃ catalyst has been studied in the range of 773-873 K, at normal pressure and various CO₂/CH₄ molar ratios. An Eley-Rideal type model gives good agreement with the experimental observations and the kinetic parameters are statistically significant. This revised version was published online in June 2006 with corrections to the Cover Date.