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Water chemistry analyses provide information on the composition and properties of a given water sample. Techniques and the extent of analysis is dependent upon the nature of the water sample and the purpose of the analysis. A chemical analysis can be used to determine the profile of chemicals in water that might serve as a municipal drinking water supply. Wastewater produced by industries and other facilities are also subjected to analytical testing, which may be mandated by particular regulatory and government entities and/or legislation. Other laboratories utilize water analysis techniques for basic research purposes, such as hydrology, sedimentology, and geochemistry. Depending upon the particular requirements for an analysis, the equipment and methods being employed can vary and span across multiple areas of analytical chemistry and biology.

Drinking Water Quality

Water samples from the natural environment are routinely collected and analyzed as part of a pre-determined monitoring program by authorities to ensure that waters remain

In industrial process, the control of the quality of process water can be critical to the quality of the end product. Water is often used as a carrier of reagents and the loss of reagent to product must be continuously monitored to ensure that correct replacement rate. Parameters measured relate specifically to the process in use and to any of the expected contaminants that may arise as by-products. This may include unwanted organic chemicals appearing in an inorganic chemical process through contamination with oils and greases from machinery. Monitoring the quality of the waste water discharged from industrial premises is a key factor in controlling and minimising pollution of the environment. In this application monitoring schemes analyse for all possible contaminants arising within the process and in addition contaminants that may have particularly adverse impacts on the environment such as cyanide and many organic species such as pesticides. In then nuclear industry analysis focuses on specific isotopes or elements of interest. Where the nuclear industry makes waste water discharges to rivers which have drinking water abstraction on them, radio-isotopes which could potentially be harmful or those with long half-lives such as tritium will form part of the routine monitoring suite.

Research

Many aspects of academic research and industrial research, such as in pharmaceuticals, health products, and many others, relies on accurate water analysis to identify substances of potential use, to refine those substances and to ensure that when they are manufactured for sale that the chemical composition remains consistent. The analytical methods used in these area can be very complex and may be specific to the process or area of research being conducted and may involve the use of bespoke analytical equipment.

In environmental management, water analysis is frequently deployed when contamination is suspected and when a pollutant needs to be identified if remedial action is taken. The analysis can often enable the contaminator to be identified. Such forensic work can examine the ratios of various components and can "type" samples of oils or other mixed organic contaminants to directly link the pollutant with the source. In drinking water supplies the cause of unacceptable quality can similarly be determined by carefully targeted chemical analysis of samples taken throughout the distribution system. In manufacturing, off-spec products may be directly tied back to unexpected changes in wet processing stages and analytical chemistry can identify which stages may be at fault and for what reason.

Methodology

Water analysis can range from measuring physicochemical properties, such as pH and temperature, to quantifying various species and contaminants, like dissolved solids and trace metals. The analysis performed on a given water sample can depend on the nature of the sample (i.e. sampling location) and the purpose for analysis. Often, method protocols are established by different organizations for consistency in analysis results. These protocols can span across various laboratory techniques:

• Wet Chemistry: ??? Is something needed here???
• Electrochemistry: Various electrode equipment are capable of measuring properties like pH, specific conductance, and dissolved oxygen.
• Colorimetry/Spectrophotometry: ??? Is something needed here???
• Chromatography: ??? Is something needed here???
• Mass Spectrometry: Mass spectrometers, such as inductively-coupled plasma mass spectrometer (ICP-MS), are utilized to quantify metals in trace amounts such as arsenic, cadmium, and lead.

For example, the Environmental Protection Agency has a set of approved analytical methods to ensure compliance of wastewater samples with the Clean Water Act^[1]. Similarly, the EPA also outlines contaminants that should be analyzed for drinking water samples^[2]

Water analysis beyond

The methods defined in the relevant standards can be broadly classified as:

• Conventional wet chemistry including the
  chloramines. Nephelometers
  are used to measure solids concentrations as turbidity. These methods are generally robust and well tried and inexpensive, giving a reasonable degree of accuracy at modest sensitivity.
• Electro chemistry including pH, conductivity and dissolved oxygen using oxygen electrode. These methods yield accurate and precise results using electronic equipment capable of feeding results directly into a laboratory data management system
• Spectrophotometry is used particularly for metallic elements in solution producing results with very high sensitivity, but which may require some sample preparation prior to analysis and may also need specialised sampling methods to avoid sample deterioration in transit.
• Chromatography is used for many organic species which are volatile or which can yield a characteristic volatile component of after initial chemical processing.
• Ion chromatography is a sensitive and stable technique that can measure lithium, ammonium NH₄ and many other low molecular weight ions using ion exchange technology.
• Gas chromatography can be used to determine methane, carbon dioxide, cyanide, oxygen, nitrogen and many other volatile components at reasonable sensitivities.
• gas liquid chromatography
  for detecting trace organic chemicals.

Depending on the components, different methods are applied to determine the quantities or ratios of the components. While some methods can be performed with standard laboratory equipment, others require advanced devices, such as inductively coupled plasma mass spectrometry (ICP-MS).

References