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.

On-site determination of Pb2+ and Cd2+ in seawater by double stripping voltammetry with bismuth-modified working electrodes

To meet the urgent requirement of determining trace Pb2+ and Cd2+ in seawater on site, herein we developed a simple but novel electrochemical method, named as double stripping voltammetry, using only a portable heavy metal analyzer. The proposed method consisted of three steps: First, the targeted heavy metal ions in bulk solution were concentrated onto an ionic liquid-graphite-based paste working electrode (ILGPE), which exhibits a dramatic ability of accumulation, by electrodeposition in the presence of Bi3+. Second, the three-electrode arrangement, including the ILGPE loaded with the reduced products, was transferred into 1.0mL acetate buffer solution, followed by a stripping procedure. Third, the measurement was performed with the other stripping voltammetry procedure by using a glassy carbon electrode as working electrode. Under optimum conditions, the linear range values for Pb2+ and Cd2+ in seawater were 0.2-3.2 μg/L and 0.1-3.2 μg/L, respectively. The concentrations of Pb2+ and Cd2+ in five real samples collected from coastal sites of Qingdao City were determined on site, and the results were in good agreement with that obtained with the atomic absorption spectroscopy method. In addition, the analytical performance of working electrode modified with Bi film by in situ mode was investigated in comparison with that by ex situ mode. The results showed that the in situ mode was much better than the ex situ one.

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.

Characterisation of gold electrodes modified with self-assembled monolayers of l-cysteine for the adsorptive stripping analysis of copper

Electrochemical sensors for copper ions in environmental samples were prepared by modifying gold electrodes with l-cysteine by self-assembly. The adsorption of l-cysteine on gold electrodes was studied by electrochemical reductive desorption in 0.5 M KOH, and the interaction of l-cysteine with copper ions was investigated by cyclic voltammetry, chronoamperometry and X-ray photoelectron spectroscopy. At low concentrations the ratio of l-cysteine to bound Cu(II) is 2:1. At higher concentrations (0.1 M) copper reacts with adsorbed cysteine forming copper sulfide on the electrode surface. On a modified l-cysteine gold electrode, Osteryoung square wave voltammetric determination of Cu(II) with a detection limit below 5 ppb has been demonstrated.

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

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.

Association of genetic vatiation within UBL5 with phenotypes of metabolic syndrome

The BEACON gene was initially identified using the differential display polymerase chain reaction on hypothalamic mRNA samples collected from lean and obese Psammomys obesus, a polygenic animal model of obesity. Hypothalamic BEACON gene expression was positively correlated with percentage of body fat, and intracerebroventricular infusion of the Beacon protein resulted in a dose-dependent increase in food intake and body weight. The human homolog of BEACON, UBL5, is located on chromosome 19p in a region previously linked to quantitative traits related to obesity. Our previous studies showed a statistically significant association between UBL5 sequence variation and several obesity- and diabetes-related quantitative physiological measures in Asian Indian and Micronesian cohorts. Here we undertake a replication study in a Mexican American cohort where the original linkage signal was first detected. We exhaustively resequenced the complete gene plus the putative promoter region for genetic variation in 55 individuals and identified five single nucleotide polymorphisms (SNPs), one of which was novel. These SNPs were genotyped in a Mexican American cohort of 900 individuals from 40 families. Using a quantitative trait linkage disequilibrium test, we found significant associations between UBL5 genetic variants and waist-to-hip ratio (p = 0.027), and the circulating concentrations of insulin (p = 0.018) and total cholesterol (p = 0.023) in fasted individuals. These data are consistent with our earlier published studies and further support a functional role for the UBL5 gene in influencing physiological traits that underpin the development of metabolic syndrome.

The determination and characterisation of 2-naphthyloxycarbonyl chloride derivatised biogenic amines in pet foods

The need to monitor biogenic amines levels is essential for many areas of the food industry for two main reasons: the caustic nature and potential toxicity of these amines, and the potential to use amine levels as markers for freshness and quality in foodstuffs. Optimised analysis conditions used for the determination of biogenic amines derivatised with 2-napthyloxycarbonyl chloride has been applied to different pet food samples to assess the effectiveness of this method for complex sample matrices. Further to this, the use of high-resolution mass spectrometry has enabled the previously unconfirmed derivatised form of seven biogenic amines to be established. The derivatised forms identified include as mono substituted (tryptamine and histamine), bisubstituted (putrescine, cadaverine and tyramine), trisubstituted (spermidine) and tetrasubstituted (spermine). The methodology of biogenic amine determination was performed successfully to a range of pet food products highlighting the applicability to a variety of complex sample matrices.

Intestinal microbiota associated with differential feed conversion efficiency in chickens

Analysis of model systems, for example in mice, has shown that the microbiota in the gastrointestinal tract can play an important role in the efficiency of energy extraction from diets. The study reported here aimed to determine whether there are correlations between gastrointestinal tract microbiota population structure and energy use in chickens. Efficiency in converting food into muscle mass has a significant impact on the intensive animal production industries, where feed represents the major portion of production costs. Despite extensive breeding and selection efforts, there are still large differences in the growth performance of animals fed identical diets and reared under the same conditions. Variability in growth performance presents management difficulties and causes economic loss. An understanding of possible microbiota drivers of these differences has potentially important benefits for industry. In this study, differences in cecal and jejunal microbiota between broiler chickens with extreme feed conversion capabilities were analysed in order to identify candidate bacteria that may influence growth performance. The jejunal microbiota was largely dominated by lactobacilli (over 99% of jejunal sequences) and showed no difference between the birds with high and low feed conversion ratios. The cecal microbial community displayed higher diversity, and 24 unclassified bacterial species were found to be significantly (<0.05) differentially abundant between high and low performing birds. Such differentially abundant bacteria represent target populations that could potentially be modified with prebiotics and probiotics in order to improve animal growth performance.

Industry self regulation of television food advertising : responsible or responsive?

Introduction. This study evaluated the impact of the Australian Food and Grocery Council (AFGC) self-regulatory initiative on unhealthy food marketing to children, introduced in January 2009. The study compared patterns of food advertising by AFGC and non-AFGC signatory companies in 2009, 2007 and 2006 on three Sydney commercial free-to-air television channels.

Methods. Data were collected across seven days in May 2006 and 2007, and four days in May 2009. Advertised foods were coded as core, non-core and miscellaneous. Regression for counts analyses was used to examine change in rates of advertisements across the sampled periods and differential change between AFGC-signatory or non-signatory companies between 2007 and 2009.

Results. Of 36 food companies that advertised during the 2009 sample period, 14 were AFGC signatories. The average number of food advertisements decreased significantly from 7.0 per hour in 2007 to 5.9 in 2009. There was a significant reduction in non-core food advertising from 2007 to 2009 by AFGC signatories compared with non-signatory companies overall and during peak times, when the largest numbers of children were viewing. There was no reduction in the rate of non-core food advertisements by all companies, and these advertisements continue to comprise the majority during peak viewing times.

Discussion. While some companies have responded to pressures to reduce unhealthy food advertising on television, the impact of the self-regulatory code is limited by the extent of uptake by food companies. The continued advertising of unhealthy foods indicates that this self-regulatory code does not adequately protect children.

Estimation of accumulated lethality under pressure-assisted thermal processing

A study was conducted to develop an integrated process lethality model for pressure-assisted thermal processing (PATP) taking into consideration the lethal contribution of both pressure and heat on spore inactivation. Assuming that the momentary inactivation rate was dependent on the survival ratio and momentary pressure-thermal history, a differential equation was formulated and numerically solved using the Runge-Kutta method. Published data on combined pressure-heat inactivation of Bacillus amyloliquefaciens spores were used to obtain model kinetic parameters that considered both pressure and thermal effects. The model was experimentally validated under several process scenarios using a pilot-scale high-pressure food processor. Using first-order kinetics in the model resulted in the overestimation of log reduction compared to the experimental values. When the n th-order kinetics was used, the computed accumulated lethality and the log reduction values were found to be in reasonable agreement with the experimental data. Within the experimental conditions studied, spatial variation in process temperature resulted up to 3.5 log variation in survivors between the top and bottom of the carrier basket. The predicted log reduction of B. amyloliquefaciens spores in deionized water and carrot purée had satisfactory accuracy (1.07-1.12) and regression coefficients (0.83-0.92). The model was also able to predict log reductions obtained during a double-pulse treatment conducted using a pilot-scale high-pressure processor. The developed model can be a useful tool to examine the effect of combined pressure-thermal treatment on bacterial spore lethality and assess PATP microbial safety. © 2013 Springer Science+Business Media New York.