Methods for the Determination of Inorganic Constituents in Water

Methods used for determining inorganic constituents in natural waters have undergone considerable change in the last decade. A majority of metal constituents are now determined by atomic absorption spectrophotometry (AAS). Various chelation and extraction procedures when used with AAS have lowered the detection limits to the microgram-per-liter range for many metal constituents. Aeration techniques have been developed which utilize AAS to determine such constituents as mercury, arsenic, and selenium. Vaporization techniques using graphite furnaces and similar devices linked with atomic absorption spectrophotometers provide for still lower detection limits and greater simplicity. These vaporization procedures require more research to limit interferences before they can be widely applied to the mass analysis of natural waters. Automated equipment is routinely used to analyze water samples. Colorimetric procedures have proven most useful but several potentiometric methods have recently been developed which also adapt themselves well to an automated approach. A procedure for determining fluoride using a potentiometric method has proven especially beneficial. An atomic absorption spectrophotometer has been joined with sampler and proportioning pump modules to produce automated determinations. Further potential development of the already mentioned instrumental techniques as well as anodic stripping voltammetry, X-ray fluorescence spectroscopy, emission spectroscopy, neutron activation analysis, and mass spectroscopy are described.