Electrothermal atomic absorption spectrometric determination of gold by vapor formation and in situ trapping in graphite tubes

Gold was determined in ore samples following generation, separation, collection on a graphite cuvette inner wall, and atomization of its volatile species formed by combining an acidified sample solution with an aqueous sodium tetrahydroborate solution at room temperature. A detection limit of 2.6 microg L(-1) (3sigma) was obtained with a 5.0 mL sample volume. Precision of replicate measurements was typically 10% RSD. The overall efficiency of the volatile species generation, transport, and trapping process was 0.4%. Atomization of gold from Pd, Ir, Cu, Ag, and W coated graphite cuvettes, following by trapping of the gaseous volatile gold species on these surfaces, has been investigated. Pd coating was found to decrease the sensitivity. Five microg of Ir, 20 microg of Cu, 20 microg of Ag, and 5 microg of W were chosen as optimum masses. W treatment was the best one for sensitivity enhancement, having an improvement factor of 2.4. Silanization of glass surfaces significantly decreased memory effects; improved peak shapes were thus obtained for flow injection vapor generation atomic absorption spectrometry (FI-VGAAS). The method described in this study was used for the determination of gold in an ore reference material, Gold Ore (MA-1b), Canadian Reference Materials Program.     

Development of an adsorptive catalytic stripping voltammetric method for the determination of an endocrine disruptor pesticide chlorpyrifos and its application to the wine samples

A very sensitive voltammetric method for the determination of an endocrine disruptor Chlorpyrifos (CP) insecticide at ng mL⁻¹ level was described. The pesticide was accumulated at a hanging mercury drop electrode (HMDE) and a well-resolved reduction peak was observed at −1.2 V (vs. Ag/AgCl) in pH: 2.0 media containing 5% aqueous ethanol solution. A systematic investigation of the solution parameters and operational parameters which affect the stripping response were carried out with differential pulse voltammetry. With an accumulation potential of −0.5 V and an accumulation time of 60 s, the detection and quantification limits were found to be 0.14 and 0.45 ng mL⁻¹, respectively. The remarkable sensitivity of the method was attributed to a catalytic process as concluded from cyclic voltammetry. The degree of interference from diverse ions and some other pesticides on the differential pulse stripping signal for CP was evaluated. The method developed was adapted for wine samples. The matrix effect of red wine was eliminated by means of liquid–liquid extraction (LLE) followed by solid-phase extraction (SPE) with satisfactory recovery values. This method offers a very sensitive and inexpensive way for determining CP residues in red wines.     

Torsion of a nonhomogeneous transversely isotropic half space

The statical Reissner Sagoci problem for a transversely isotropic, nonhomogeneous elastic solid is investigated. The modulus of rigidity of the medium is assumed to be variable as a power of the radial coordinate in the form $\text{r}{}^{\mathrm{\beta }}\text{(β ? 0)}$. The expressions for stresses, displacement and torque are given.     

Effect of processing conditions on the quality of naturally fermented Turkish sausages (sucuks)

Effects of temperature and different fat levels on the quality of Turkish sausages (sucuks) were studied during the ripening period. Sausage batters prepared at 10%, 20% and 30% fat levels were processed at 20-22 and 24-26 °C. A high ripening temperature and low fat level caused fast dehydration. Fat level affected water activity, colour, total viable and lactic acid bacteria counts of the sausages. Increasing fat content and ripening temperature resulted in high lightness (L*) and yellowness (b*) and low redness (a*) at the end of ripening. The sausages with 10% fat resulted in higher redness values. Growth of total viable and micrococci-staphylococci bacteria was affected by ripening temperature. Sausages ripened at 24-26 °C had a rapid increase in micrococci-staphylococci counts.