基于频谱细化算法的电泳光散射Zeta电位测量方法

Zeta Potential Measurement Method of Electrophoretic Light Scattering Based on Chirp Z-Transform

电泳光散射法测量Zeta电位时,散射光频移只有几百赫兹,在全频段求取散射光功率谱会降低频率分辨率。为此,提出先用傅里叶变换在全频段对散射光信号进行频谱估计,获取需要细化分析的频谱范围,然后用线性调频变换频谱细化算法在窄带范围内进行高分辨率的频谱细化分析,从而获得准确的散射光频移。设计了基于激光多普勒技术的散射光频移测量装置,使用该方法分别测量了3种标准聚苯乙烯乳胶微球的Zeta电位。实验结果表明,线性调频变换频谱细化算法可以有效地提高Zeta电位的测量精度,测量重复性小于5%。

When zeta potential is measured by the method of electrophoretic light scattering, the frequency shift of scattered light is typically no more than a few hundreds of hertz. If the power spectrum of the scattered light is calculated in the full-band, the frequency resolution will be reduced. To improve the frequency resolution, the full-band power spectrum is estimated first through the discrete Fourier transform, then the refined spectrum is analyzed in a narrow-band by a linear frequency modulating chirp Z-transform, and finally the frequency shift of the scattered light is obtained with good resolution. We have designed an instrument based on laser Doppler electrophoresis and have used it to measure the zeta potential of three types of polystyrene latex standard particles. The experimental data show that the chirp Z-transform improves the precision of zeta potential measurement and gives a measurement repeatability better than 5%.