基于AgI_2^-缔合微粒共振散射效应测定阳离子表面活性剂

A new Spectral Method for the Determination of Cationic Surfactant Based on the Resonance Scattering Effect of AgI^-_2 Association Particles

在pH 3.5 NaAc-HCl介质中,Ag+与过量的I-形成可溶性AgI2-;当十六烷基三甲基溴化铵(CT-MAB)与AgI2-共存时形成粒径为700 nm的(CTMA-AgI2)n缔合微粒,在360 nm处产生一个共振散射峰,在470 nm处产生一同步散射峰。CTMAB浓度cCTMAB在2.0~50.0×10-7mol.L-1范围内与散射光强度I360 nm呈线性关系,回归方程为I360 nm=2.03×107cCTMAB+0.48,相关系数r为0.998 5,检出限为8.0×10-8mol.L-1。据此建立了一个测定阳离子表面活性剂含量的共振散射光谱法,用于水样分析,结果满意。共振散射光谱和激光散射研究表明,CTMAB+与AgI2-可通过静电力形成疏水性的CTMA-AgI2缔合物分子,该缔合物分子自动聚集形成稳定的(CTMA-AgI2)n缔合微粒。由于该缔合微粒仅在360 nm处产生共振散射效应,故体系呈乳白色。

In pH 3.5 NaAc-HCl medium, there is a maximum resonance scattering （RS） peak at 360 nm and a synchronous scattering peak at 470 nm for the association particle system of （CTMAB-AgI2）, in white color, with a diameter of 700 nm. The CTMAB concentration CCTMAB in the range of 2.0-50.0×10^-7 4mol·L^-1 is linear to the I360nm value. Its regression equation is I360nm=2.03×10^7CCTMAB＋0.48, and regression coefficient is 0. 9985. The detection limit is 8.0×10^-8 mol·L^-1. A new RS method has been proposed for the determination of cationic surfactant in samples with satisfactory results. The laser scattering and RS spectra show that CTMAB^＋ and AgI2^- combine to CTMA-AgI2^- association molecule by means of attractive forces. The association molecules automatically aggregate to （CTMA-AgI2^）n association particles, so that the particles exhibit a resonance scattering peak at 360nm, and the system is in white color.