Wastewater is a term used to describe spent or used water discharged from residential homes, industry, farms, hospitals and other sources of anthropogenic origin. Wastewater contains dissolved or suspended solids and is composed of a complex mixture of chemical contaminants as well as microorganisms, paper fibres, plant material, proteins, pharmaceuticals, hair colorants, emulsified oils and hundreds of industrial chemicals.
Analysis of contaminants in wastewater, often required at trace or ultra trace concentrations is difficult due to the complex composition of wastewater. Therefore analytical techniques used to determine trace contaminants in wastewater need to be specific and allow analytes to be detected without interference from other compounds present in the sample (often at concentrations considerably higher than the compounds of interest).
At the point of analysis, it is essential that a sample is still representative of the whole from which it was taken. This is an
obvious statement, but one which can often be overlooked. Regardless of how modern the analytical instrumentation, or how sophisticated the extraction process, or how experienced the operator, all of this is irrelevant if the concentration of the target analyte has changed since the sample was taken
Analyte concentrations can change with time. Sample degradation through bacterial activity, volatility, chemical interactions and exposure to air or light can all cause changes to the composition of a sample. Consequently, establishing the length of time that an analyte remains stable, without statistically significant changes in concentration, is extremely important. It is essential to analyse the sample within the stability timeframe, or to highlight any samples that have deviated from this target.
When considering a stability testing protocol, there are a number of factors that must be taken into account. Although it sounds counterintuitive, it might be advisable to start by deciding what criteria you are going to assess your data against. Once this has been established, factors such as number of replicates, frequency of testing and matrix types may become more obvious, as these are often dictated by the mathematical processing at the end.
Reference : http://www.ehs-news.com/
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