表面活性剂存在下借反应温差同时测定混合物中钯和铑

SIMULTANEOUS DETERMINATION OF PALLADIUM AND RHODIUM IN MIXTURES BASED ON THE DIFFERENCE IN REACTION TEMPERATURES IN THE PRESENCE OF SURFACTANT

研究了Ｐｄ（Ⅱ）、Ｒｈ（Ⅲ）在乙醇、各种表面活性剂分别存在下与２－（３，５－二溴－２－吡啶偶氮）－５－二乙氨基酚（３，５－ｄｉＢｒ－ＰＡＤＡＰ）的显色反应，发现溴化十六烷基吡啶（ＣＰＢ）存在下，于ｐＨ５．０～６．８ＨＡｃ－ＮａＡｃ缓冲介质中，Ｐｄ（Ⅱ）能于室温（ＲＴ）显色，其配合物经沸水浴加热（ＢＴ）后吸光度仅略有增加；而Ｒｈ（Ⅲ）必须在加热下才反应显色，，测Ｒｈ灵敏度高于已有文献值。测定了上述配合物组成，借此两显色反应所需温度差异，建立了同时测定Ｐｄ和Ｒｈ的速差动力学分析方法。该法简便灵敏，用于含Ｐｄ和Ｒｈ的合成混合物及催化剂分析，结果较满意。

A new differential kinetic method has been developed for simultaneous determination of palladium (Ⅱ) and rhodium (Ⅲ) based on the difference between temperatures required for their chromogenic reactions. At first, the color reactions of Pd(Ⅱ) and Rh(Ⅲ) with 2-(3, 5-dibromo-2-Pyridylazo)-5-diethyl aminophenol (3, 5-diBr-PADAP) in the presence of ethanol, cetyl pyridineium bromide (CPB), cetyltri-methyl ammonium bromide (CTMAB), Triton X-100 or polyethyleneglycol octylphenylether (emulsitier OP), respectively, have been investigated. In the presence of CPB and in a medium of PH 5.0-6.8 acetate buffer solution, the complex of Pd(Ⅱ) has a maximum absorption at 606urn with apparent molar absorptivity of 3.63×104 L.mol-1.cm-1 at room temperature, and its absorbance increases slightly after being heated in boiling water bath (4.25×104 L.mol-1.cm-1). The complex of Rh (Ⅲ) formed only after being heated maboiling water-bath has a maximum absorption at 606nm also, with apparent molar absorptivity of 1.24×105 L.mol-1. cm-1. The compositions of cited complexes are determined. Consequently, a new method of proportional equations has been developed based on the difference in reaction temperatures. The method is simple, rapid, sensitive, and has been applied to the analysis of several of synthetic mixtures and catalyst containing Pd and Rh with satisfactory results.