锑-溴酸钾-偶氮胭脂红B催化动力学光度法测定痕量锑

锑及其化合物是全球性污染物,易造成环境污染。但是,锑的催化效果差,测定锑的动力学光度法相对较少。在磷酸介质中,痕量锑(Ⅲ)对溴酸钾氧化偶氮胭脂红B褪色反应有催化作用,据此,建立了动力学光度法测定锑的新方法。在两只比色管中分别加入适量的锑(Ⅲ)样品溶液(催化反应,吸光度A)和同量的水(非催化反应,吸光度A0),再分别加入0.7mL4.0×10-3 mol/L溴酸钾溶液、1.8mL 1.0mol/L磷酸和2.2mL 0.5g/L偶氮胭脂红B溶液,然后在90℃水浴中加热15min,在波长515nm处测定体系的吸光度A和A0。实验结果表明,表观活化能Ea=33.6kJ/mol,锑的质量浓度在0.02～0.26μg/mL范围内与lg(A0/A)呈良好的线性关系,检出限为8.79×10^-9 g/mL。对复杂样品河泥的测定,先采用萃取的方法,规避了共存离子的干扰,再采用实验方法测定锑,结果的相对标准偏差(RSD,n=6)为3.3%～3.5%;加标回收率为96%～98%;并与原子荧光光谱法测定结果相吻合。

Determination of trace antimony by catalytic kinetic spectrophotometrywith antimony-potassium bromate-azocarmine B

Antimony and its compounds can easily cause environmental pollution and belong to global priority pollutants. However, the catalytic activity of antimony is poor and there are few reports on the catalytic kinetic spectrophotometric determination of antimony. It was found that trace antimony (III) had catalytic effect on the fading reaction of azocarmine B oxidized by potassium bromate in phosphoric acid medium. Thus a novel determination method of antimony by kinetic spectrophotometry was established. Appropriate amount of antimony (III) sample solution (catalytic reaction, absorbance A) and same amount of water (non-catalytic reaction, absorbance A₀) was added into colorimetric tube, respectively. Then, 0.7mL of 4.0×10^-3 mol/L potassium bromated solution, 1.8mL of 1.0mol/L phosphoric acid and 2.2mL of 0.5g/L azocarmine B solution were added in sequence. After heating in water bath at 90℃ for 15min, the absorbance (A and A₀) of two systems was measured at wavelength of 515nm. The experimental results indicated that the apparent activation energy was Ea=33.6kJ/mol. lg(A₀/A) exhibited good linearity to the mass concentration of antimony in range of 0.02-0.26μg/mL and the limit of detection was 8.79×10^-9 g/mL. For the measurement of complex sample (i.e., river mud), the extraction method was firstly used to avoid the interference of coexisting ions. Then the content of antimony was determined according to the experimental method. The relative standard deviations (RSD, n=6) of results were between 3.3% and 3.5%. The spiked recoveries were between 96% and 98%. The measured results were consistent with those obtained by atomic fluorescence spectrometry.