Determination of anabolic steroids by differential pulse polarography

Determination of anabolic steroids often requires the use of elaborate techniques such as gas chromatography - mass spectrometry (GC-MS), gas liquid chromatography (GLC) and more recently high performance liquid chromatography (HPLC). Most of these methods employ derivatisation techniques prior to detection which makes them tedious and relatively time consuming. Other methods demand a great deal of skill. A simple and rapid analytical method, based on differential pulse polarography at a dropping mercury electrode has been developed for the determination of various anabolic steroids in a range of commercially available pharmaceutical preparations. Detailed investigation of the electrochemical behaviour of these steroids was made in order to elucidate the electrode processes involved, in addition to optimising the method. Several other analytical methods such as GC-MS, NMR, ultraviolet (UV), infrared (IR) spectroscopy were also used to confirm the products of the chemical and electrochemical reactions. Possible reactions are suggested. Various extraction procedures were examined for separation of selected steroids from the oil-based or pill matrix and their suitability for polarographic determination is discussed.

One-pot facile synthesis of platinum nanoparticle decorated reduced graphene oxide composites and their application in electrochemical detection of rutin

We report on the synthesis of platinum nanoparticle-reduced graphene oxide (PtNP-rGO) composites and their application as a novel architecture in electrochemical detection of rutin. PtNPs anchored over rGO are synthesized through a facile one-pot synthesis method, where the reduction of GO and in situ generation of PtNPs occurred concurrently. The characterization results of transmission electron microscopy (TEM) demonstrate that PtNPs with small particle sizes are dispersed on the rGO matrix. Electrochemical measurements reveal that a PtNP-rGO modified glass carbon electrode (GCE) directly catalyzes rutin oxidation and displays an enhanced current response compared with a bare GCE. Under the optimal experimental conditions, the peak current was linear with rutin concentration in the range of 5 × 10^-8 to 1 × 10^-5 M with the detection limit of 1 × 10^-8 M (S/N = 3) by differential pulse voltammetry. The proposed method was successfully applied to determine rutin in tablet samples with satisfactory results. This journal is

Trace metal speciation in the Pieman River catchment, western Tasmania

The Pieman River catchment has seen continuous mining of economic deposits of gold, silver, lead, copper, zinc and tin since the 1870’s. Tributaries of this river which receive mining effluent, either directly or from acid mine drainage (AMID), have total metal concentrations considerably above background levels and are of regulatory concern. The lower Pieman River is however classified as a State Reserve in which recreational fishing and tourism are the major activities. It is therefore important that water entering the lower Pieman River from upstream hydroelectric impoundments is of high quality. Metals in natural waters exist in a variety of dissolved, colloidal and particulate forms. The bioavailability and hence toxicity of heavy metal pollutants is very dependant on their physico form. Knowledge of the speciation of a metal in natural aquatic environments is therefore necessary for understanding its geochemical behaviour and biological availability. Complexation of metal ions by natural ligands in aquatic systems is believed to play a significant role in controlling their chemical speciation. This study has investigated temporal and spatial variation in complexation of metal ions in the Pieman River. The influence of pH, temperature, organic matter, salinity, ionic strength and time has been investigated in a series of field studies and in laboratory-based experiments which simulated natural and anthropogenic disturbances. Labile metals were measured using two techniques in various freshwater and estuarine environments. Diffusive gradients in thin-films (DGT) allowed in situ measurement of solution speciation whilst differential pulse anodic stripping voltammetry (DPASV) was used to measure labile metal species in water samples collected from the catchment. Organic complexation was found to be a significant regulating mechanism for copper speciation and the copper-binding ligand concentration usually exceeded the total copper concentration in the river water. Complexation was highly dependent on pH and at the river-seawater interface was also regulated by salinity, probably as a result of competitive complexation by major ions in seawater (eg. Ca 2+ ions). Zinc complexation was also evident, however total zinc concentrations in the water column often far exceeded the potential binding capacity of available ligands. In addition to organic complexation, Zn speciation may also be associated with adsorption by flocculated or resuspended colloidal Mn and/or Fe oxyhydroxides. Metal ion complexation and hence speciation was found to be highly variable within the Pieman River catchment. This presents major difficulties for environmental managers, as it is therefore not possible to make catchment-wide assumptions about the bioavailability of these metals. These results emphasise the importance of site-specific sampling protocols and speciation testing, ideally incorporating continuous, in situ monitoring.

Chemical and physical speciation of arsenic in a small pond receiving gold mine waste effluent

The chemical and physical speciation of arsenic in a small pond that receives wastewater from a gold mine operation in western Victoria, Australia was studied using differential pulse polarography. By using different sample pretreatments, distinction between the physical states (dissolved or particulate As), between the oxidation states (As(III) or As(V)), and between the degrees of lability (labile or strongly bound) was achieved. The results are interpreted in terms of the physicochemical properties with reference to the use of the pond as a settlement dam for gold mining effluent. The speciation of arsenic was found to vary markedly with the physicochemical properties of the water. A model for the behavior of arsenic in the pond is proposed.