5-(5-氰基-2-吡啶偶氮)-2,4-二氨基甲苯分光光度法测定微量钌(Ⅱ)

Spectrophotometric determination of micro ruthenium (Ⅱ) with 5-(5-cyano-2-pyridylazo)-2,4-diaminotoluene

研究了钌(Ⅱ)与5-(5-氰基-2-吡啶偶氮)-2,4-二氨基甲苯(5-CN-PADAT)的反应,并将方法应用于钌炭催化、钌分子筛中微量钌的测定。实验表明,盐酸羟胺存在时,在pH 4.0～5.5HAc-NaAc缓冲溶液中,钌(Ⅱ)与试剂形成稳定的深红色络合物,最大吸收波长位于520nm处;使用0.3mol/L HCl酸化后,络合物转变为另一种具有较高吸收特性的双质子化型体,并呈现两个吸收峰,分别位于538nm和611nm。在优化的实验条件下,钌(Ⅱ)质量浓度在0.1～0.9μg/mL范围内与其在538nm和611nm处的吸光度加和呈线性关系,相关系数为0.999 7。表观摩尔吸光系数为1.08×105 L·mol^(-1)·cm^(-1)。方法应用于钌炭催化剂、钌分子筛中微量钌的测定,结果与参考值相符,结果的相对标准偏差(RSD,n=6)为1.3%～3.4%,加标回收率为96.5%～101.0%。

The coloring reaction between ruthenium (Ⅱ) and 5-(5-cyano-2-pyridylazo)-2, 4-diaminotoluene (5-CN-PADAT) was studied, which was then applied for the determination of micro ruthenium in ruthenium catalysts on activated carbon and molecular sieve. The experimental results showed that ruthenium (Ⅱ) could react with 5-CN-PADAT in HAc-NaAc buffer solution at pH 4.0-5.5 in presence of hydroxylamine hydrochloride to form a stable wine-colored complex which had maximum absorption wavelength at 520 nm. After acidification with 0.3 mol/L HCl, the complex was converted to another kind of doubly protonated type with higher absorption features. It presented two absorption peaks located at 538 nm and 611 nm, respectively. Under the optimal experimental conditions, the mass concentration of ruthenium (Ⅱ) in range of 0.1-0.9 μg/mL was linear to the sum of absorbance at 538 nm and 611 nm. The correlation coefficient was 0.999 7. The apparent molar absorptivity was 1.08×10^5 L·mol^-1 ·cm^-1 . The proposed method was applied for the determination of micro ruthenium in ruthenium catalysts on activated carbon and molecular sieve. The found results were consistent with the reference values. The relative standard deviations (RSD, n =6) were in range of 1.3%-3.4%. The spiked recoveries were between 96.5% and 101.0%.