Samples in solution are analysed in this laboratory and as such, solids must either be extracted or dissolved, as appropriate. The typically requires the use of concentrated acid mixtures. In addition to the instrumental techniques, standard wet chemistry methods such as titrations and pH measurements are carried out.
Atomic Absorption Spectrometry
ICENS operates a Perkin Elmer Model 5100PC Atomic Absorption spectrometer equipped for flame (air-acetylene or nitrous oxide - acetylene) and graphite furnace atomization. Background correction in flame measurements is achieved with deuterium and tungsten continuum sources. The transversely heated, platform based furnace is complemented by Zeeman Effect background correction for exceptional (sub ppb) detection limits. Autosamplers are used with both flame (AS-90) and furnace (AS-71) to give reproducible sample introduction. The instrument is used for the determination of some 19 elements in liquid samples such as natural waters, body fluids (blood and urine) and soil extracts.
At ICENS, AAS is being used for the measurement of essential nutrient elements (calcium, copper, iron, magnesium, manganese, potassium, sodium, and zinc) and the potentially hazardous arsenic, cadmium, lead, and mercury in foods. It provides an accurate, precise and reliable method for sequentially measuring a suite of these elements across the range of concentrations at which they exist in food crops. It is also increasingly being used on extracts performed under mild conditions, to provide estimates of bioavailability, and to analyse the soil porewaters - both important indicators of the likely effects of the elements in soils on plant and animal life. Autopsy and biopsy tissues are also being analysed and methods are being assessed for analysis of heavy metals in urine as indicators of human exposure. Since 2009 ICENS has also operated a Perkin Elmer Optima 7000 DV optical emission spectrometer which is contributing significantly to the analyses of further biological samples, as the health - related aspects of research accelerate.
Flow Injection Analysis
Flow Injection Analysis (FIA) automates traditional spectrophotometric techniques. It has the advantage of being able to analyse solutions containing high concentrations of dissolved solids and is particularly useful for brackish or seawater samples. In FIA, a small, precise volume of sample is injected into a continuously flowing carrier stream and merged with reagent streams on a manifold. This produces a coloured compound, the optical absorbance of which is measured with a flow-through detector to determine the concentration. ICENS operates a LaChat Quikchem 8000 two channel ion analyser, equipped with a random access autosampler. Nitrate/Nitrite, Phosphate, Silicate and ammonia are determined using colorimetric methods. Two ions can be determined simultaneously. Detection limits are in the sub-micromolar region and sampler throughput is approximately 60 samples per hour. The unit has also assisted nutrient analysis by graduate students carrying out environmental research at UWI and UTECH and in marine and freshwater analyses for organisations involved in environmental impact assessments. An important new application of FIA at ICENS is the measurement of creatinine in urine, an important parameter for use in evaluating heavy metal exposure in humans.