吖啶红共振散射光谱法测定痕量铁(Ⅲ)

摘要

In hydrochloric acid solution of pH =3.2, ferrum ( III ) can oxidize I - into the form of I3- and acridine red( AR) can react with I3- to form of AR-I3 ion association complexes( the composition stoichiometry was defined as n ( I3- ) : n ( AR) =1:1). The association complexes automatically aggregate to ( AR-I3 ) n association particles. In this case, the resonance light scattering( RLS) intensities are enhanced greatly. The maximum RLS wavelength locates at 468 nm. The optimum conditions of the reaction, influence factors and the effect of coexisting substances were investigated. In addition, the reaction mechanism of the ion-association complex was discussed. The resonance scattering intensity ( ΔI46g nm ) was linearly related to the concentration of ferrum ( III ) in the range of 0. 08 ~0. 56 mg/L with a detection limit of 5. 76 × 10 -7 g/L. The assay was applied to the detection of trace ferrum( III) in realistic samples, with a RSD of 3. 3% and the recovery range of 96. 0% ~ 102. 4% , and the results were in a good agreement with that of atomic absorption spectrometryassay.%在pH =3.2的HC1介质中,Fe(Ⅲ)氧化Ⅰ-产生Ⅰ2,Ⅰ2与过量Ⅰ-形成Ⅰ-3,Ⅰ-3与吖啶红(AR)通过静电引力缔合形成AR-Ⅰ3离子缔合物(结合比为n(Ⅰ-3)∶n(AR) =1∶1),AR-Ⅰ3分子自动聚集形成(AR-Ⅰ3)n缔合物微粒,从而引起共振散射光谱显著增强,其最大散射峰位于468 nm.实验研究了介质条件、共振探针用量等因素对散射体系的影响,考察了该散射反应稳定性及共存物质的影响,并对反应机理和散射光谱增强的原因进行了探讨.结果表明,Fe(Ⅲ)与共振光散射强度增强值△I468nm在0.08 ～0.56 mg/L范围内呈现良好线性关系,检测限为5.76×10-7g/L.该方法有较好的选择性,可用于水样中痕量Fe(Ⅲ)的测定,结果与原子吸收法一致,回收率为96.0％ ～ 102.4％,相对标准偏差小于3.3％.