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.
Comparison of indirect cathodic stripping voltammetric methods based on accumulation of mercury, copper(I) and nickel salts or complexes at a hanging mercury drop electrode: determination of 2-mercaptobenzothiazole
A preliminary study of the indirect cathodic stripping voltammetric determination of 2-mercaptobenzothiazole (MBT) based on accumulation of its mercury, copper(I) and nickel(II) salts or complexes was made as part of a wider study comparing these three related techniques of determining thiols. Detection limits for MBT using the copper(I) and nickel(II) methods ( <2 × 10–9 mol l–1) are considerably lower than that for the mercury method (about 3 × 10–7 mol l–1). The mercury method is susceptible to interference from copper(II) and large amounts of nickel(II), and seems generally to be less reliable for the determination of MBT. The change from accumulation as the mercury salt to accumulation as the copper(I) salt is illustrated in the presence of excess of MBT over copper(II) with increasing copper(II) concentrations, and with change of accumulation potential to more negative values from +100 mV. In the presence of a stoichiometric amount or excess of copper(II) over MBT, no mercury salt is accumulated at potentials more negative than +50 mV. Currents obtained for MBT with the nickel(II) method are much higher than those obtained previously with cysteine and penicillamine.
A survey of aquaculture production economics and management
Abstract The literature on production economics and management of fish culture has grown as aquaculture has matured as a commercial industry. Salmon, catfish, shrimp and trout are the focus of this literature survey as a reflection of the volume of research that has been completed on these species and their importance in US production and world trade. In addition, a discussion of low resource production systems is included that is dominated by tilapia and carp culture systems. A brief overview of the principles of aquaculture production economics and management is presented followed by a review of economic studies.