Highly sensitive determination of iodide by ion chromatography with amperometric detection at a silver-based carbon paste electrode

articleA silver-based solid carbon paste electrode was developed for use as a detector in ion chromatography (IC) for the sensitive determination of iodide in real samples. Micro- and nano-particles of silver were investigated for the fabrication of different electrodes. The iodide assay was based on IC with amperometric detection (IC-AD) at a silver composite electrode polarized at +0.080 V versus Ag/AgCl. Free iodide and organoiodide compounds were studied. The detection process was characterized by studying the redox behavior of iodide ions at both silver and silver composite electrodes by cyclic voltammetry (CV). The presence of iodide ions in solution was found to considerably facilitate metallic silver oxidation, with response currents directly related to iodide concentration. The calibration curve at the selected silver carbon paste electrode was linear in the concentration range comprised between 0.635 microg/L and 63.5 microg/L iodide. The relative standard deviation (R.S.D.) for successive injections was below 3% for all iodide standard solutions investigated. The limit of detection (LOD) was 0.47 microg/L (3.7 nmol/L) for an injection volume of 20 microL, i.e. 74 fmol injected. The IC-AD method was successfully applied to the determination of iodide in complex real samples such as table salts, sea products and iodide bound drug compounds. The analytical accuracy was verified by the assay of iodide in milk powder from an iodide certified reference material (CRM) Community Bureau of Reference (BCR) 150

Spatio-temporal variation in malaria transmission intensity in five agro-ecosystems in Mvomero district, Tanzania

Abstract. In Africa, malaria is predominantly a rural disease where agriculture forms the backbone of the economy. Various agro-ecosystems and crop production systems have an impact on mosquito productivity, and hence malaria transmission intensity. This study was carried out to determine spatial and temporal variations in anopheline mosquito population and malaria transmission intensity in five villages, representing different agro-ecosystems in Mvomero district, Tanzania, so as to provide baseline information for malaria interventions. The agro-ecosystems consisted of irrigated sugarcane, flooding rice irrigation, non-flooding rice irrigation, wet savannah and dry savannah. In each setting, adult mosquitoes were sampled monthly using Centers for Disease Control and Prevention (CDC) light traps from August 2004 to July 2005. A total of 35,702 female mosquitoes were collected. Anopheles gambiae sensu lato was the most abundant (58.9%) mosquito species. An. funestus accounted for 12.0 % of the mosquitoes collected. There was a substantial village to village variation and seasonality in the density of Anopheles mosquito population, with peaks in May towards the end of the warm and rainy season. Significantly larger numbers of anophelines were collected from traditional flooding rice irrigation ecosystem (70.7%) than in non-flooding rice irrigation (8.6%), sugarcane (7.0%), wet savannah (7.3%) and dry savannah (6.4%). The overall sporozoite rates for An. gambiae and An. funestus were 3.4% and 2.3%, respectively. The combined overall sporozoite rate (An. gambiae+An. funestus) was 3.2%. The mean annual entomological inoculation rate (EIR) for An. gambiae s.l. was 728 infective bites per person per year and this was significantl