Frequency-selective absorbance detection: Refractive index and turbidity compensation with dual-wavelength measurement

A frequency-selective absorbance detection approach and its applications are described. First, a digital signal processor-lock-in amplifier (DSP-LIA)-based absorbance detector was evaluated. Compared to a simple operational amplifier (TL082CP)-based detector, the DSP-LIA-based detector showed lower noise levels, but the relative advantage was reduced under very low photocurrent levels (down to few nA). A 7 cm pathlength flow cell with this commercial LIA-based detector exhibited excellent Beer's law linearity (r² = 0.9999) and a noise level of 7 micro absorbance units (μAU). The limit of detection (LOD, S/N = 3) for methyl orange (MO) was 7 nM with this detector. Finally, as a more affordable alternative to an LIA, a balanced demodulator integrated circuit chip was used to fabricate a dual wavelength-frequency-selective LED-based absorbance detector. This device successfully compensated refractive index (RI) effect and turbidity effect in test flow systems. The LOD for MO with this system was 8 nM.     

阻抑动力学光度法测定环境水样中苯胺

基于在乙酸-乙酸钠缓冲溶液介质中,痕量苯胺能灵敏地阻抑过氧化氢氧化溴甲酚绿褪色。研究了该阻抑褪色反应的最佳条件及动力学参数,建立了测定痕量苯胺的方法。该法的线性范围为0~45.0μg.L-1,检出限为4.30μg.L-1。用于环境水样中痕量苯胺的测定,结果的RSD值在2.35%~3.78%之间,回收率在95.8%~103.6%。     

差示火焰光度法测定硼酸盐中钾和钠

研究了火焰光度法测定硼酸盐中钾和钠含量的方法.分别在0～100 mg·L-1和0～200 mg·L-1的浓度范围内,采用差示测量法测定样品中钾和钠含量.考察了硼对钾、钠测定的影响以及钾、钠的相互影响.与四苯硼钠重量法(国家标准)相比,方法测定钾含量相对误差的绝对值≤3.91%,t检验和F检验也表明两种方法无显著性差异.与原子吸收光谱法相比,方法测定钾相对误差的绝对值≤3.63%.测定钠含量相对误差的绝对值≤3.76%,t检验和F检验表明两种方法无显著性差异.钾、钠的加标回收试验结果分别在97.5%～102.5%和97.1%～99.1%之间.     

流动注射微分光度法测定钛酸钡烧结物中微量钡

分析速度快、精密度好的流动注射分析技术(FIA),在光度法分析中得到了广泛应用和迅速发展[1-3]。就测试技术而言是在一个非平衡单光束动态检测完成的,而应用双光束检测器建立的分析方法报道很少[4,5]。本文自行研制两组流动比色装置,分别安置在检测器的样品池和参比池,实现了微