Department of Analytical Chemistry, Faculty of Chemistry, Dnipropetrovsk National University, Gagarina 72, Dnipropetrovsk 49050, Ukraine.
Talanta. 2010 Mar 15;80(5):1838-45. doi: 10.1016/j.talanta.2009.10.031. Epub 2009 Oct 24.
The guanidinium salt of the new heteropolymolybdate 11-molybdobismuthophosphate Gua(6)PBiMo(11)O(40) (11-MBP) was synthesized, characterized and used as a reagent for batch spectrophotometric (SP) and sequential injection determination of ascorbic acid (AsA). When compared to other Keggin's heteropolyanions, the reduction of 11-MBP with AsA is both fast and maximal within a pH range of 1.6-2.0. The stoichiometry of the reaction was determined using molar ratio and continuous variation methods and was shown to be 1:1. The molar absorptivity of the reduced form of 11-MBP was 6.0 x 10(3)L mol(-1)cm(-1) at 720 nm. The reaction is also specific for AsA. Only cysteine, hydroquinone and hydroxyacids were found to interfere with the reaction, while no interference was observed with the common reducing agents, including reducing sugars, catecholamines, nitrite, sulfite and iron(II) ions. Batch SP and sequential injection analysis (SIA) systems were developed for the determination of AsA, with calibration ranges of the SP methods at 2x10(-6)-8 x 10(-5)M for a 10mm cell and 5 x 10(-7)-3 x 10(-5)M for a 50mm cell and a limit of detection at 3 x 10(-7)M. The linear range of the SIA method was 6 x 10(-6)-5 x 10(-4)M, with a detection limit of 2 x 10(-6)M and a sample throughput of 15 h(-1). The proposed methods were successfully used for the determination of AsA in both pharmaceuticals and fruit juices, and the results were consistent with those provided by the 2,6-dichlorophenolindophenol method.
新的杂多钼酸盐 11-钼铋磷酸盐 Gua(6)PBiMo(11)O(40)（11-MBP）的胍盐被合成、表征，并用作批量分光光度法（SP）和顺序注射法测定抗坏血酸（AsA）的试剂。与其他 Keggin 杂多阴离子相比，11-MBP 与 AsA 的还原反应既快速又在 pH 值为 1.6-2.0 的范围内达到最大值。使用摩尔比和连续变化方法确定了反应的化学计量比，并表明为 1:1。还原形式 11-MBP 的摩尔吸光率在 720nm 处为 6.0 x 10(3)L mol(-1)cm(-1)。该反应也特异性地针对 AsA。仅发现半胱氨酸、对苯二酚和羟基酸会干扰反应，而常见的还原剂，包括还原糖、儿茶酚胺、亚硝酸盐、亚硫酸盐和铁（II）离子，则没有干扰。开发了用于测定 AsA 的批量 SP 和顺序注射分析（SIA）系统，SP 方法的校准范围为 10mm 池的 2x10(-6)-8 x 10(-5)M 和 50mm 池的 5 x 10(-7)-3 x 10(-5)M，检测限为 3 x 10(-7)M。SIA 方法的线性范围为 6 x 10(-6)-5 x 10(-4)M，检测限为 2 x 10(-6)M，样品通量为 15 h(-1)。该方法成功地用于测定药物和果汁中的 AsA，结果与 2,6-二氯苯酚靛酚法提供的结果一致。
