Cathodic stripping voltammetric determination at a hanging mercury drop electrode of the environmental heavy metal precipitant trimercapto-s-triazine (TMT).
Trimercapto-s-triazine (TMT) is available commercially for precipitating heavy metals in effluents prior to discharge and for recovering silver and copper. The TMT content of an effluent for discharge is normally monitored down to about 2 ppm by means of its UV absorption at 285 nm. Indirect cathodic-stripping voltammetric methods of determining TMT at sub-ppb levels in standard solutions are reported here. These methods might prove suitable for the determination of TMT in effluent at levels lower than is currently possible. TMT can be accumulated and determined indirectly at pH 9.0 as its mercury salt down to sub-ppb levels. Accumulation is made at 0 V and the mercury TMT reduction peak is at -0.47 V. Alternatively, by adding nickel(II), TMT can be determined optimally at pH 7.8, using the catalytic nickel peak at -0.73 V and accumulating between -0.10 and -0.60 V: at this pH the HgTMT peak at -0.47 V is small. At slightly higher pH (pH 8.6) the nickel TMT complex can be accumulated directly at -0.40 V, but at this pH, however, a slightly increased sensitivity can be achieved by accumulating TMT as its mercury salt, at -0.1 V in the presence of nickel(II), the nickel TMT complex being formed during the potential sweep on the release of the TMT when the mercury salt is reduced. Unlike many other thiols TMT is not accumulated as its copper(I) salt on addition of copper(II) to the solution.
Catalytic cathodic stripping voltammetry at a hanging mercury drop electrode of glutathione in the presence of nickel ion
Glutathione (GSH) catalyses the reduction of nickel ion and this effect is strongly enhanced if GSH is previously concentrated as a mercury thiolate on a hanging mercury drop electrode. During the subsequent cathodic scan, GSH is released by the reduction of mercury ion at about –0.4 V. The catalytic reduction of Ni2+ gives a cathodic peak at –0.6 V versus Ag—AgCl (3 mol l–1 KCl) reference electrode. By this means GSH can be determined by differential-pulse stripping voltammetry under the following conditions: pH = 7 (phosphate–acetate buffer); Ni2+, 1 mmol l–1; deposition potential, –0.1 to –0.3 V; scan rate, 10 mV s–1; pulse height, 50 mV; and pulse interval, 0.5 s. The detection limit is about 10 nmol l–1, i.e., ten times higher than for the similar determination of cysteine, owing to the particular characteristics of nickel ion complexation by GSH. The height of the catalytic peak is directly proportional to GSH concentration between 10 and 120 nmol l–1. Very small interferences are produced by Zn2+, NaCl, low concentrations of strong complexants and N-acyl derivatives of cysteine, Cu2+, cysteine and human serum albumin interfere slightly. A detailed discussion of the relationship between the structure of GSH and its behaviour in catalytic cathodic stripping voltammetry is presented.
An Optimization Approach to Occupant Safety and Fuel Economy in Vehicle Design
1. Abstract A major challenge in automotive design is the creation of safe vehicles with minimal environmental impact. This study presents a modeling framework for evaluating and optimizing body designs for improved occupant safety and fuel efficiency. Vehicle body mass is considered as the main link between safety and sustainability. The modeling framework includes frontal crash energy absorption, restraint system design and fuel economy. Preliminary results indicate a Pareto-optimal curve between safety and sustainability may exist when other factors are not taken into account. A more complete modeling framework that includes more sophisticated sustainability and safety metrics, cost and other market considerations, is suggested in order to support better design and regulatory decisions. 2. Keywords: Automotive body structures, fuel economy, occupant safety, optimal vehicle design, restraint systems