ONLINE SEPARATION AND PRECONCENTRATION OF CADMIUM, LEAD AND NICKEL INA FULLERENE (C-60) MINICOLUMN COUPLED TO FLOW-INJECTION TUNGSTEN COILATOMIC-ABSORPTION SPECTROMETRY

A how system was coupled to a tungsten coil electrothermal atomizer (1 50 W) for on-line separation and preconcentration of cadmium, lead and nickel based on the formation of DDC complexes and sorption into a mi nicolumn packed with fullerene C-60 Three way solenoid valves used for sample and reagents management as well as the tungsten coil power sup ply were controlled by a computer running a programme written in Visua l Basic, which was employed in synchronism with the original software of the atomic absorption spectrometer. The fullerene column (5 mm leng th, 2 mm i.d.) was inserted into the tip of the autosampler arm, and e lution was performed by sampling 35 mu l of methanol from the autosamp ler cup. With 3.0 ml of sample (loading time of 60 s) enrichment facto rs ranging from 100 to 150 were achieved. The detection limits for cad mium, lead and nickel were 2.2, 23;and 75 ng1(-1), respectively. No in terference effects were observed on cadmium, lead and nickel preconcen tration in the presence of up to 10(6) fold concentrations of sodium, potassium, calcium or magnesium. Application of t-test to the results obtained by the proposed method and the certified values of cadmium, l ead and nickel in five water reference materials did not reveal signif icant differences at the 5% probability level. (C) 1998 Elsevier Scien ce B.V. All rights reserved.