Rodríguez-Díaz Rafael Carlos, Aguilar-Caballos Maria Paz, Gómez-Hens Agustina
Department of Analytical Chemistry, Marie Curie Building Annex, Campus of Rabanales, University of Córdoba, E-14071 Córdoba, Spain.
J Agric Food Chem. 2004 Dec 29;52(26):7777-81. doi: 10.1021/jf048826y.
Ytterbium(III) is used as reagent for the determination of sulfite by measuring the formation of the Yb(III)-sulfite complex through the variation of the light scattering intensity with time. The low solubility of this complex causes an efficient dispersion of the radiation at 490 nm, which is measured at 980 nm. Each kinetic datum is automatically obtained in only 0.5 s by stopped-flow mixing technique. The application of the initial rate method using a long emission wavelength minimizes the potential interference of fluorescent background signals from the sample matrix. The dynamic range of the calibration graph is 1-250 microg/mL, and the calculated detection limit is 0.35 microg/mL. The precision, expressed as relative standard deviation, is <6%. The method has been applied to the determination of total sulfites in white wine samples, which requires only the sample dilution and the use of two aliquots to improve selectivity. However, the matrix effect found for red wines precludes the application of the method to the direct analysis of these samples. Analytical recoveries ranged from 96.0 to 106.7%. The results obtained with the proposed method agreed with those provided by the p-rosaniline method. Unlike this method, in which toxic reagents are required, the use of ytterbium(III) as analytical reagent shows the advantage of its low acute toxic rating.
镱（III）用作测定亚硫酸盐的试剂，通过测量镱（III）-亚硫酸盐络合物的形成来实现，该络合物的形成通过光散射强度随时间的变化来测定。这种络合物的低溶解度导致在490 nm处的辐射有效散射，在980 nm处进行测量。每个动力学数据通过停流混合技术仅在0.5秒内自动获得。使用长发射波长的初始速率法的应用使来自样品基质的荧光背景信号的潜在干扰最小化。校准曲线的动态范围为1 - 250 μg/mL，计算出的检测限为0.35 μg/mL。以相对标准偏差表示的精密度<6%。该方法已应用于白葡萄酒样品中总亚硫酸盐的测定，该测定仅需要样品稀释并使用两份等分试样以提高选择性。然而，在红葡萄酒中发现的基质效应排除了该方法直接用于分析这些样品。分析回收率在96.0%至106.7%之间。用所提出的方法获得的结果与对氨基苯磺酸法提供的结果一致。与该方法不同，该方法需要使用有毒试剂，使用镱（III）作为分析试剂显示出其急性毒性等级低的优点。
