Determination of Trace Elements in Water Utilizaing Atomic Absorption Spectroscopy Measurement

A variety of flameless atomic absorption methods have been investigated for the possible determination of trace elements in water. The general applicability of each technique was determined and where applicable, procedures have been developed for the determination of trace elements in natural waters. Metals were preconcentrated by electrodeposition on a wire. The metals were then atomized for atomic absorption measurement by resistive heating of the wire. As little as 0.01 part per million (ppm) of mercury could be determined in this way. A mercury cold vapor cell was constructed in which the sample is treated with a reducing agent to reduce mercury to the elemental state and then argon gas is bubbled through the sample to carry mercury vapor into a quartz-ended tube where its atomic absorption is measured. Water vapor condensation and consequent light scattering in the absorption tube was minimized by heating the tube. As little as 5 x 10-8g or 0.5 part per billion (ppb) of mercury was determined in natural waters. A heated tube atomizer was designed for the determination of relatively volatile elements such as arsenic. The sample is placed in a vertical tube that is connected to a horizontal absorption tube. The system is evacuated and heated to 660°C with nichrome wire. Arsenic sublimes at 613°C and results in a significant absorbance at 1937Å, probably as As4. Ten micrograms of arsenic could be detected. A simple and inexpensive tantalum ribbon flameless atomizer cell was constructed in which a few microliters of sample were dried and atomized on a tantalum ribbon heated resistively. This is applicable to a large of elements, giving detection limits down to 10-13 number gram in favorable cases. Interference effects were studied. This system has been applied to the determination of traces of silver, zinc, cadmium, manganese, and lead in natural waters with no sample preparation required. A standard additions calibration is most satisfactory