Intern. J. Environ. Anal. Chem. Vol. 83, No. 12, December 2003, pp. 1009–1019 PRECONCENTRATION PROCEDURES FOR TRACE CADMIUM DETERMINATION IN NATURAL AQUEOUS SYSTEMS PRIOR TO ZEEMAN ETAAS KATARINA C ˇ UNDEVA a , TRAJC ˇ E STAFILOV a, *, GORICA PAVLOVSKA a , IRINA KARADJOVA b and SONJA ARPADJAN b a Faculty of Science, Institute of Chemistry, St. Cyril and Methodius University, POB 162, 1001 Skopje, Macedonia; b Faculty of Chemistry, St. Kliment Ohridski University, Sofia, Bulgaria (Received 25 May 2003; In final form 3 July 2003) Nanotrace Cd determination in natural waters using two new flotation collectors, lead(II) heptyldithio- carbamate, Pb(HpDTC) 2 , and cobalt(III) heptyldithiocarbamate, Co(HpDTC) 3 , are presented. The optimiza- tion of the most important experimental parameters for flotation is given. Zeeman electrothermal atomic absorption spectrometry (ZETAAS) is used as an instrumental technique for Cd measurement. The results are compared with those obtained by other preconcentration procedures as independent methods. The limit of detection of ZETAAS using Pb(HpDTC) 2 as collector is 4.8 ng/L, while using Co(HpDTC) 3 it is 3.0 ng/L. Keywords: Cadmium; Preconcentration; Flotation; Zeeman ETAAS INTRODUCTION Cadmium is a toxic element and as a result of world-wide accumulation (electroplating, galvanizing, preparation of some low-melting alloys, cathode material for rechargeable batteries, colour pigment for paint and plastics, etc.), it presents a serious environ- mental hazard. In natural waters Cd concentrations often range from 5 to 100 ng/L. The detection power of mass spectrometry with inductively coupled plasma (ICP- MS) has the sensitivity to determine Cd in this concentration range. However, in natural waters with high hardness, this modern and very expensive instrumental technique suffers from problems with isobaric polyatomic interferences and signal suppression. Therefore, improvements, modifications, and the development of new methods for separation and preconcentration of this analyte are of practical value. Recently significant attention has been paid to colloid precipitate flotation as a method for heavy metal preconcentration prior to atomic absorption spectrometry (AAS) [1–5]. This bubble technique has advantages relative to other conventional *Corresponding author. Fax: þ389-2 226 865. E-mail: trajcest@iunona.pmf.ukim.edu.mk ISSN 0306-7319 print: ISSN 1029-0397 online ß 2003 Taylor & Francis Ltd DOI: 10.1080/03067310310001621051