Complexation properties of glyoxaldithiosemi-carbazone in N, N-dimethylforrnamide and 60 % (v/v)-N, N-dimethylformamide-water mixture and its application to the spectrophotometric

Abstract

Glyoxaldithiosemicarbazone (GDS, H2L) had the ab-sorption maximum at 347 nm (ε=5.0 ×104) in 60% (v/v)-N, N-dimethylformamide-(DMF)-water mixture and effectively no absorption band above 400 nm. GDS formed stable 1 : 1 complexes with Pd(II) (molar absor-ptivity, ε, was 1.3 ×104 at 385 nm and 2.5 ×103 at 600 nm), with Ni(II) (ε=1.2 ×104 at 405 nm), with Cu(II)(ε=6.7×103 at 485 nm), with Zn (II) (ε = 1.3×104 at 433 nm) and with Cd(II) (ε=1.3 ×104 at 427 nm), respectively, over pH ranges of 1.0~9.5, 3.5~11, 3.0~10, 9.0~11 and 9.0~11 in 60% (v/v) DMF-water mixture. Masking reactions of EDTA for GDS-metal ion systems were investigated; only Pd(II) ion did selectively form the blue GDS complex in the presence of EDTA(2 × 10-3 M). Based on these results, selective method for the spectrophotometric determination of Pd(II) was proposed; Take 10 ml of sample solution containing 051 gg of Pd(II), add 0.5 ml of 0.1 M EDTA aq. solution and stand for 10 min. Then, add 10 ml of 5 × 10-5M GDS-DMF solution, 4 ml of DMF, adjust the pH to 2.0~4.0 with 0.5 ml of 5 M acetic acid aq. solution and dilute to 25 ml with water. After 20 min, measure the absorbance at 600 nm against the blank solution prepared by above procedure except that 10 ml of DMF was added instead of 10 ml of GDS-DMF solution. Beer's law was confirmed over a range of 0~51 μg/25 ml and sensitivity for 0.001 absorbance unit was 0.042μg Pd2+/cm2. The determination of 25.5μg/25 ml of Pb(II) was not interfered in the presece of 500 μg/25 ml of Ag(I) and Hg(II), and 1000 μg/25 ml of Pt(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Pb(II), Sn(II), Ga(III), Sn(IV) and Mo(IV), respectively. © 1977, The Japan Society for Analytical Chemistry. All rights reserved.