Microchim. Acta 149, 109–116 (2005) DOI 10.1007/s00604-004-0294-3 Original Paper Determination of Iron(III), Cobalt(II) and Chromium(III) in Various Water Samples by Flame Atomic Absorption Spectrometry After Preconcentration by Means of Saccharomyces Carlsbergensis Immobilized on Amberlite XAD-4  Stk Baytak 1 and A. Rehber Tu ¨ rker 2; 1 Harran € Universitesi, Fen Edebiyat Fak€ ultesi, Kimya B€ ol€ um€ u, TR-63100 S ° anlurfa, Turkey 2 Gazi € Universitesi, Fen Edebiyat Fak€ ultesi, Kimya B€ ol€ um€ u, TR-06500 Ankara, Turkey Received April 8, 2004; accepted October 27, 2004; published online January 5, 2005 # Springer-Verlag 2005 Abstract. A method for the determination of Fe(III), Co(II) and Cr(III) by flame atomic absorption spectro- photometry (FAAS) after preconcentrating on a column containing S. carlsbergensis immobilized on Amberlite XAD-4 has been developed. The optimum values of pH, amount of adsorbent, elution solution and flow rate of the sample solution were determined for the quantitative recovery of the analytes. The effect of interfering ions on the recovery of the analytes was also investigated. Under the optimum conditions, recoveries of Fe(III), Co(II) and Cr(III) by S. carlsber- gensis immobilized on Amberlite XAD-4 were 99  2, 100  2 and 98  2% at 95% confidence level, respec- tively. The limit of detections for Fe(III), Co(II) and Cr(III) were 2.8, 3.9 and 7.4 ng mL 1 , respectively. The proposed method was applied to the determination of the analytes in various water samples. The validity of the method was checked with spiked water samples. Fe(III), Co(II) and Cr(III) was determined with a rela- tive error of less than 5%. Key words: Iron; cobalt; chromium; preconcentration; S. carls- bergensis; flame atomic absorption spectrometry. Water and soil contamination with metal ions has become a global environmental problem. The presence of trace metals in foods and water may result from various sources such as agricultural and industrial prac- tices. Metal ion contaminants may present a potential hazard for human health if exposure exceeds tolerable limits. Therefore, the accurate and precise determina- tion of trace metal ions is becoming increasingly important because of the increased interest in environ- mental samples including water, soil and plants, etc. To determine trace metals in water samples by instrumen- tal methods, separation and preconcentration tech- niques are frequently required because of the low concentration of trace metal ions and possible matrix interferences. Various preconcentration and separation techniques were employed prior to analysis [1–4]. Among the different separation and preconcentration techniques using adsorption, column and batch tech- niques in which analytes are sorbed on microorganisms immobilized on a water-insoluble substrate and eluted with a suitable eluent have been widely used [5–7]. Biological materials such as yeasts, fungi, bacteria and algae are capable of accumulating heavy metals  A part of this work was presented at the XVIth National Chemistry Congress, 4–7 September 2002, Konya, Turkey  Author for correspondence. E-mail: aturker@gazi.edu.tr