ASTM D1688

ASTM D1688 – Standard Test Methods for Copper in Water

Description:

Significance and Use

4.1 Copper is found in naturally occurring minerals principally as a sulfide, oxide, or carbonate. It makes up approximately 0.01 % of the earth’s crust and is obtained commercially from such ores as chalcopyrite (CuFeS₂). Copper is also found in biological complexes such as hemocyanin.

4.2 Copper enters water supplies through the natural process of dissolution of minerals, through industrial effluents, through its use, as copper sulfate, to control biological growth in some reservoirs and distribution systems, and through corrosion of copper alloy water pipes. Industries whose wastewaters may contain significant concentrations of copper include mining, ammunition production, and most metal plating and finishing operations. It may occur in simple ionic form or in one of many complexes with such groups as cyanide, chloride, ammonia, or organic ligands.

4.3 Although its salts, particularly copper sulfate, inhibit biological growth such as some algae and bacteria, copper is considered essential to human nutrition and is not considered a toxic chemical at concentrations normally found in water supplies.

4.4 ICP-MS or ICP-AES may also be appropriate but at a higher instrument cost. See Test Methods D5673 and D1976.

Scope

1.1 These test methods cover the determination of copper in water by atomic absorption spectrophotometry. Section 34 on Quality Control pertains to these test methods. Three test methods are included as follows:

Test Method	Concentration Range	Sections
A—Atomic Absorption, Direct	0.05 to 5 mg/L	7 – 15
B—Atomic Absorption, Chelation-Extraction	50 to 500 μg/L	16 – 24
C—Atomic Absorption, Graphite Furnace	5 to 100 μg/L	25 – 33

1.2 Either dissolved or total recoverable copper may be determined. Determination of dissolved copper requires filtration through a 0.45-μm (11.10) membrane filter at the time of collection. In-line membrane filtration is preferable.

1.3 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.

1.4 Three former photometric test methods were discontinued. Refer to Appendix X1 for historical information.