New differential pulse polarographic methods for the determination of boron, tin and arsenic species and application

It was found that sodiumborohydride (NaBH4) could be determined in an electrolyte containing both 0.05M phosphate buffer (pH=9) and 0.1 M KNO3 from its peak at ?0.06 V (the detection limit was 6 x10-7 M). No interference was observed from Fe(III), Cr(VI), Cd(II), Pb(II) and Zn(II) ion. Only copper(II) had an interference, which could be eliminated with EDTA.A catalytic method has been developed for the detection of nearly 10-14 M BH4- concentration.Trace tetraborate (B4O7=) determination could be accomplished indirectly by the use of the tetraborate complex of copper in 0.5 M KNO3. The detection limit was 8x10-7 M. The interference of Fe(III), Pb(II), Cd(II), Zn(II) and Ca(II) has been investigated. Borate has been determined in borax mineral, in waste water of borax factory and in tap water of Ankara.For the speciation of Sn(II) and Sn(IV) the medium of 0.1 M NaOH and 0.1 M KNO3 was found as the most suitable electrolyte. The detection limit was 5.5x10-7M. In a solution containing both of these ions first Sn(II) has been determined from its ?1.17 V peak, then total tin was determined after reduction of Sn(IV) . The interference of Fe, Cu, Pb, Cd and Zn ions has been investigated. Iron(III) and copper(II) ions will oxidize Sn(II) to Sn(IV) and thus interfere. It was shown that this interference could be eliminated with NaBH4 which was added for the reduction of Sn(IV) into Sn(II). Using this method Sn(IV) in tomato sauce was determined.For the determination of As(III) and As(V), effects of pH and several electrolytes have been investigated. The most suitable electrolyte was found as 0.1 M HCl for as As(III). Using the peak at ?0.82 V the detection limit was 6x 10-7 M. Since As(V) is not electroactive, it had to be reduced with KI into As(III) and then determined. The interference effect of Fe, Cu, Pb and Zn ions was investigated and it was found that only Fe oxidized As(III) to As(V). This interference could be eliminated with KI which was added for the reduction of As(V). This method was applied for the determination of As(III) in tap water of Ankara.