Current power industry requirements place increasing emphasis on water and steam purity. Many of the contaminants present in plant systems exist at levels below the detection limits of available analytical methods. Evaporation of large volumes of water in a controlled environment provides a means of increasing the concentration of contaminants to a level that can be readily analyzed by current methodology. Since the continuous sample evaporator described in ASTM Tests for Particulate and Dissolved Matter in Water (D 1888-78) is no longer marketed, an improved version of the evaporator was designed, fabricated, and tested for low-level contaminant recovery.

The new instrument is capable of evaporating solutions from sample bottles or a sample line at rates approaching 500 cm³/h. The samples are concentrated in precleaned platinum dishes. A detailed description of the new evaporators and their operation is discussed.

Performance tests were conducted on both laboratory and field samples to define the limitations of the evaporation process for trace chemical analysis. These analyses included calcium, magnesium, iron, copper, potassium, sodium, chromium, nickel, manganese, zinc, lead, aluminum, silica, sulfate, chloride, phosphate, and nitrate. The laboratory studies showed that the evaporators were capable of chemical species recovery generally within ±20 percent of the absolute amount of synthetic species added. Evaporation and analyses of field samples obtained from operating power plants compared favorably with other concentrating techniques for most species. However, there are certain contaminants which cannot be determined accurately with current evaporation techniques and may require analysis by other available methods.