锡(Ⅳ)的某些噻嗪染料络合吸附波研究和分析应用

Study on the Adsorptive Complex Wave of Tin (IV) With Some Thiazine Dyes and Analytical Application

研究表明噻嗪染料中新亚甲蓝(NMB)或甲苯胺蓝(TB)在硫酸-草酸介质中与Sn(Ⅳ)在-0.60 V(υs.SCE)处出现一高灵敏的络合吸附电流,比无上述染料时电流增高约 16倍.检出限0.8ng/mL(相当6.7×10～(-9)mol/L)Sn(Ⅳ).NMB和TB在酸性介质中被质子化,可用R～+表示,与Sn(Ⅳ)形成缔合物〔Sn(C_2O_4)_3〕～(2-)·R_2～(2+).其表观稳定常数(K)分别为5.2×10～(10)(-NMB)和4.9×10～(10)(-TB).研究了电极过程的可逆性、吸附特性及电极反应机制,求得一系列常数和参数.方法已用于饮用水和试剂中痕量锡的直接测定,结果满意.

Tin( Ⅳ ) in the medium of sulfuric acid-oxalic acid with some thiazine dyes, e. g. new methylene blue(NMB) or toluidine blue (TB) at -0. 60 V(vs,SCE) produced a high sensitive adsorptive complex wave. The sensitivity was increased about 16 time higher than that without such dyes in above medium. The detection limit was 0. 8 ng/mL (6. 7×10 9 mol/L) Sn( Ⅳ ). In the acidic medium NMB and TB were protonated with a positive charge, which could be expressed by R+. An associate complex CSn(C2O4)3]2- R22+ was formed, The apparent stability constant (K) was 5. 2×10-0(for -NMB) and 4. 9× 1010(for. - TB), respectively. The reversibility of electrode process, the character of adsorption and the mechanism of electrode reaction were investigated. A Series of constants and parameters were calculated. The proposed method has been applied to the determination of trace tin in drink water and reagent with satisfactory results.