Atom-trapping absorption spectrometry with water-cooled metal collector tubes

Water-cooled metal collector tubes for atom-trapping atomic absorption spectrometry in air—acetylene flames are discussed, particularly for the more volatile elements such as cadmium and selenium which may be less efficiently trapped at the hotter surface of a silica tube. It was found that a nickel tube gave 3 times greater sensitivity than silica for the determination of cadmium but was oniy half as sensitive for the determination of selenium. No atomic absorption signal for copper could be obtained with a nickel collector tube. A copper tube was 3–4 times more sensitive than nickel for cadmium and selenium. Similar effects were observed for cadmium solutions containing 1000 ppm copper or nickel, and for selenium solutions containing 1000 ppm copper, with silica atom-trap tubes, but in both cases better results were obtained when the analyte solution of cadmium or selenium contained the co-element (1000 ppm) than when the cadmium or selenium was measured with a silica tube previously metallized with the co-element.