Octadecyl immobilized silica beads packed microcolumn versus PTFE knotted reactor as Cd(OH)2 precipitate collection media coupled to ETAAS for cadmium determination

Octadecyl immobilized surface was proved to function as an effective medium for collecting cadmium hydroxide precipitate. A thorough comparison of precipitate collection and related analytical performances was made using a C18 microcolumn packed into a lab-on-valve system and a polytetrafluoroethylene knotted reactor (PTFE-KR) as the precipitate collection medium. Cadmium was isolated as hydroxide precipitate and collected onto the surface of the C18 microcolumn or the inner surface of the PTFE-KR. The precipitate was then quantitatively eluted with 20 μl nitric acid (1%), and the eluate was subsequently transported into the graphite tube of the ETAAS instrument for atomization. With a sampling volume of 600 μl, the detection limits (ng 1-1), enrichment factors, retention efficiencies (%), precisions (%, 0.05 ng 1-1), and sampling frequencies by using a C18 microcolumn/PTFE-KR were 1.7/3, 28/14, 93/48, 2.1/4.7, and 13/20, respectively. The procedure was validated by analyzing the cadmium contents in three certified references materials: river sediment (CRM 320), sea lettuce (CRM 279), and frozen cattle blood (GBW 09140). The results obtained were in good agreement with the certified values.