Talanta 52 (2000) 539–544 Extraction spectrophotometric determination of vanadium in natural waters and aluminium alloys using pyridyl azo resorcinol (PAR) and iodo-nitro-tetrazolium chloride (INT) K. Gavazov *, Zh. Simeonova, A. Alexandrov Department of General and Inorganic Chemistry, Plodi Uniersity, 24 Tsar Assen, 4000 Plodi, Bulgaria Received 21 September 1999; received in revised form 21 March 2000; accepted 3 April 2000 Abstract Extraction-spectrophotometric methods are developed for the determination of vanadium content in natural waters and aluminium alloys. They are based on the formation and subsequent extraction into chloroform of the ternary ion association complex of V(V) with PAR and INT in the presence of CDTA and NH 4 F as masking agents. Optimum pH range of the reaction is 5.5–7.5. Maximum absorbance of the extracted complex is at 560 nm. The method for determination of V(V) in drinking waters can be successfully applied at a concentration level of 3 ppb and higher without additional pre-concentration. Among studied more than 30 foreign ions potentially present in natural waters only Ca(II) can interfere. It is removed by precipitation as CaF 2 and filtration. A 40-fold excess of V(IV) does not interfere with determination of V(V) and can also be determined indirectly (after oxidation to V(V)). The proposed method is applied to analysis of model mixtures as well as to the analysis of tap and mineral waters. Beer’s law is obeyed for up to 15 g of V(V) in 40 ml aqueous phase. The accuracy and precision are reasonable. The RSD is in the range 6.5 – 23.2% for determination of 6.3 ppb V(V). The procedure for analysis of aluminium alloys differs from the procedure for analysis of waters by the order of introduction of the reagents. The macrocomponent does not interfere and is not separated. Mg, Mn, Cu, Zn, Fe, Cr, Ti and Zr do not interfere. A 25-fold excess of Ni interferes. The method is tested in the analysis of reference standards containing 0.005 and 0.007% V, respectively. The RSD is 1.4%. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Vanadium-PAR complex; Extraction-spectrophotometry; Water analysis; Aluminium base alloys analysis www.elsevier.com/locate/talanta 1. Introduction Vanadium is of importance for living organ- isms. Its role in physiological systems includes an insulin like effect, inhibitory effect on some en- zymes and cholesterol synthesis, catalytic effect in oxidation of various amines [1,2]. Vanadium af- fects favourably the diuretic kidney function, the cardiac muscle and cell growth. Antidiabetic func- tion of vanadium is a subject of intense studies [2]. It has been established that drink water contain- * Corresponding author. Tel.: +395-32-261420. E-mail address: kgavazov@ulcc.pu.acad.bg (K. Gavazov) 0039-9140/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII:S0039-9140(00)00405-7