Flow injection analysis of free glycerol in biodiesel using a copper electrode as an amperometric detector

The main goal of this work was to develop a simple analytical method for quantification of glycerol based on the electrocatalytic oxidation of glycerol on the copper surface adapted in a flow injection system. Under optimal experimental conditions, the peak current response increases linearly with glycerol concentration over the range 60-3200 mg kg(-1) (equivalent to 3-160 mg L(-1) in solution). The repeatability of the electrode response in the flow injection analysis (FIA) configuration was evaluated as 5% (n = 10), and the detection limit of the method was estimated to be 5 mg kg(-1) in biodiesel (equivalent to 250 mu g L(-1) in solution) (S/N = 3). The sample throughput under optimised conditions was estimated to be 90 h(-1). Different types of biodiesel samples (B100), as in the types of vegetable oils or animal fats used to produce the fuels, were analysed (seven samples). The only sample pre-treatment used was an extraction of glycerol from the biodiesel sample containing a ratio of 5 mL of water to 250 mg of biodiesel. The proposed method improves the analytical parameters obtained by other electroanalytical methods for quantification of glycerol in biodiesel samples, and its accuracy was evaluated using a spike-and-recovery assay, where all the biodiesel samples used obtained admissible values according to the Association of Official Analytical Chemists. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.

Oscillatory electro-oxidation of glycerol on platinum

This paper describes the experimental study of the oscillatory electro-oxidation of glycerol on platinum under galvanostatic control. The system was investigated in both acidic and alkaline media and for different glycerol concentrations. In acidic supporting electrolyte, the oscillatory behavior is rather simple and the main features such as period, amplitude and waveform are barely affected by the glycerol concentration. A more complex picture including the presence of different temporal patterns and strong dependence with glycerol concentration emerges in alkaline medium. In both media, the composite oscillations visit two clearly discernible potential windows, and potential oscillations in alkaline media are observed only when the working electrode is kept stationary. The mechanistic implications of our findings are discussed in connection with available data obtained under close-to-equilibrium conditions. (C) 2012 Elsevier Ltd. All rights reserved.

Biotechnological Utilization of Biodiesel-Derived Glycerol for the Production of Ribonucleotides and Microbial Biomass

Ten yeast strains were evaluated concerning their capabilities to assimilate biodiesel-derived glycerol in batch cultivation. The influence of glycerol concentration, temperature, pH and yeast extract concentration on biomass production was studied for the yeast selected. Further, the effect of agitation on glycerol utilization by the yeast Hansenula anomala was also studied. The yeast H. anomala CCT 2648 showed the highest biomass yield (0.30 g g(-1)) and productivity (0.19 g L-1 h(-1)). Citric acid, succinic acid, acetic acid and ethanol were found as the main metabolites produced. The increase of yeast extract concentration from 1 to 3 g L-1 resulted in high biomass production. The highest biomass concentration (21 g L-1), yield (0.45 g g(-1)) and productivity (0.31 g L-1 h(-1)), as well as ribonucleotide production (13.13 mg g(-1)), were observed at 700 rpm and 0.5 vvm. These results demonstrated that glycerol from biodiesel production process showed to be a feasible substrate for producing biomass and ribonucleotides by yeast species.

Physical properties of edible films based on bovine myofibril proteins

Myofibril proteins have excellent filmogenic properties. The objective of this article was to study the effect of the thermal treatment, of the pH and of the plasticizer concentration (Cp) of the filmogenic solution (FS), using over some physical properties of edible films, using a surface and response methodology (SRM). Films were made of lyophilized myofibril proteins (LMP) extracted from bovine muscle, employing the technique of solubility obtained from diluted saline solutions. The films were elaborated from FS containing 1 g of LMP/100g of FS and from Cp of 50 g to 79 g of glycerin/100 g of LMP. The LMP was dispersed in water under moderate agitation, and the pH was kept at 2.5-3.5 with the use of acetic acid. The FS were submitted to thermal treatment at different temperatures for 45 minutes. Films were dried in ventilated oven at 37 degrees C/18hr, conditioned at 75% of relative humidity at 25 degrees C/48 hr before analysis of: mechanical properties by puncture test; apparent opacity by spectrophotometer; solubility by immersion in water; and water vapor permeability by the gravimetric method. In general, films showed good appearance, translucent, easily handled and touchable, except for the films formed with pH 2.5 and at a low temperature (35 degrees C), with a medium thickness of 0.400 +/- 0.005 mm. The pH of the FS significantly affected all the physical properties under study. The temperature of the thermal treatment of the FS greatly affected the force at the rupture, solubility and water vapor permeability. This treatment can promote intermolecular interactions through the formation of disulphide bonds; however a very intense treatment can reverse this effect by irreversible structural alterations in the proteins. The glycerol concentration affected considerably all the properties under study, with the exception of the apparent opacity. Plasticizer increases the mobility of macromolecules with consequences in all physical properties.

Development and optimization of biodegradable films based on achira flour

The influence of glycerol concentration (C-g), process temperature (T-p), drying temperature (T-s), and relative humidity (RH) on the properties of achira flour films was initially assessed. The optimized process conditions were C-g of 17g glycerol/100g flour, T-p of 90 degrees C, T-s of 44.8 degrees C, and RH of 36.4%. The films produced under these conditions displayed high mechanical strength (7.0 MPa), low solubility (38.3%). and satisfactory elongation values (14.6%). This study showed that achira flour is a promising source for the development of biodegradable films with good mechanical properties, low water vapor permeability, and solubility compared to films based on other tubers. (c) 2011 Elsevier Ltd. All rights reserved.

Enhancement of Electrical Conductivity in Plasticized Chitosan Based Membranes

Plasticized natural macromolecules-based polymer electrolyte samples were prepared and characterized. The plasticization of chitosonium acetate with glycerol increased the ionic conductivity value from 3.0 x 10(-7) S/cm to 1.1 x 10(-5) S/cm. The conductivity temperature relationship of the samples exhibits either VTF or Arrhenius type depending on the glycerol concentration in the sample. The dielectric studies evidencing the relaxation process in the plasticized sample at low frequency region are due to the electric polarization effect. Moreover, the samples were transparent in the Vis region, showed thermal stability up to 160 degrees C and good surface uniformity.