ASTM D4691

ASTM D4691 – Standard Practice for Measuring Elements in Water by Flame Atomic Absorption Spectrophotometry

Description:

Significance and Use

5.1 Elemental constituents in water and wastewater need to be identified to support effective water quality monitoring and control programs. Currently, one of the most widely used and practical means for measuring concentrations of elements is by atomic absorption spectrophotometry.

5.2 The major advantage of atomic absorption over atomic emission is the almost total lack of spectral interferences. In atomic emission, the specificity of the technique is almost totally dependent on monochromator resolution. In atomic absorption, however, the detector sees only the narrow emission lines generated by the element of interest.

Scope

1.1 This practice covers general considerations for the quantitative determination of elements in water and waste water by flame atomic absorption spectrophotometry. Flame atomic absorption spectrophotometry is simple, rapid, and applicable to a large number of elements in drinking water, surface waters, and domestic and industrial wastes. While some waters may be analyzed directly, others will require pretreatment.

1.2 Detection limits, sensitivity, and optimum ranges of the elements will vary with the various makes and models of satisfactory atomic absorption spectrometers. The actual concentration ranges measurable by direct aspiration are given in the specific test method for each element of interest. In the majority of instances the concentration range may be extended lower by use of electrothermal atomization and conversely extended upwards by using a less sensitive wavelength or rotating the burner head. Detection limits by direct aspiration may also be extended through sample concentration, solvent extraction techniques, or both. Where direct aspiration atomic absorption techniques do not provide adequate sensitivity, the analyst is referred to Practice D3919 or specialized procedures such as the gaseous hydride method for arsenic (Test Methods D2972) and selenium (Test Methods D3859), and the cold vapor technique for mercury (Test Method D3223).

1.3 Because of the differences among various makes and models of satisfactory instruments, no detailed operating instructions can be provided. Instead the analyst should follow the instructions provided by the manufacturer of a particular instrument.

1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversion to inch-pound units that are provided for information only and are not considered standard.