碱性二苯基萘基甲烷染料褪色分光光度法测定藻酸钠

Spectrophotometric Determination of Sodium Alginate by Decoloration of Some Basic Dyes

在B-R缓冲溶液中，藻酸钠与维多利亚蓝4R、维多利亚蓝B、夜蓝等碱性二苯基萘基甲烷染料发生反应，形成结合产物，染料发生明显的褪色。对于不同染料，最大褪色波长分别位于612nm（维多利亚蓝4R体系）、616nm（维多利亚蓝B体系）、614nm（夜蓝体系）。体系吸光度的降低与藻酸钠的质量浓度成正比。藻酸钠的质量浓度在5．0mg·L^-1（维多利亚蓝4R体系）、3．0mg·L^-1（维多利亚蓝B体系）、3．0mg·L^-1（夜蓝体系）以内符合比耳定律，摩尔吸光率根据染料的不同在4．8×10^6～9．5×10^6L·mol^-1·cm^-1之间，其中以维多利亚蓝4R体系最为灵敏，对藻酸钠的检出限为21μg·L^-1。以维多利亚蓝4R体系为例研究共存物质的影响，表明方法选择性好。此法用于面条样品中藻酸钠的分析测定，结果满意。

In a BR-buffer of pH 3. 0, association compounds were formed between large anion of sodium alginate （NaAGN） and cation R^＋ of some basic dyes, e.g. victoria blue 4R （VB4R）, victoria blue B （VBB） and night blue （NB）, leading to color-fading of the dye reagents. Linear relationships between the magnitude of colorfading intensity （△A） and concentration of NaAGN were obtained in the ranges within 5. 0 mg·L^-1 （for VB4R system） and 3. 0 mg·L^-1 （for either VBB or NB system）. Absorbance were measured at the absorption maxima 612 nm, 616 nm and 614 nm for VB4R, VBB and NB respectively. Values of molar absorptivity for the 3 dyes were found in the range 4. 8 × 10^6 -9. 5 × 10^6L · mol^-1·cm^-1, among which the value of VB4R was the highest. Detection limit of this method with VB4R as reactant was 21 μg· L^-1. Selectivity was tested giving satisfactory results for determination of NaAGN. In applying the method to analysis of noodle sample, average values of RSD （n=7） and recovery obtained were 2% and 105% respectively.