新型光声光谱法测定总无机碳酸盐含量

采用新型富氏变换红外光谱气体分析仪测定固体及水体样品中总无机碳酸盐含量,原理是CO₂对红外线的主动式光声吸收.反应器浸没在恒温水浴中,经氮气吹洗后,在连续搅动条件下,向样品中加入一定量高氯酸.酸解生成的CO₂对特定波段的红外吸收造成温度和压力的波动,从而产生频率取决于吸收波长的光声信号,再由微型麦克风加以记录.实验对固体和液体标准样品的线性检测范围分别为120 mg的CaCO₃和36.4 mmol/L的NaHCO₃,灵敏度分别为0.02 mg和3 mmol/L.因总无机碳酸盐的酸性缓冲容量对黏土矿物的表面酸碱性质影响显著,故选择不同来源天然伊利石作为模型样品进行测定,并探讨一些影响因素和改进方案.

A novel approach for determination of total inorganic carbonate by photoacoustic spectroscopy

A new FT-IR spectrometer gas analyzer was employed to determine the total inorganic carbonate content in solid and waters based on active photoacoustic absorption of infrared light by CO2. The reactor, immersed in a water-bath at constant temperature, was purged with N2, then certain amount of HClO4 was added into the samples under continuous agitation. The specific absorption of infrared radiation by the released CO2 invoked corresponding fluctuations oftemperature and pressure. Consequently, photoacoustic signals, with frequencies dependent on the absorbed wavelengths, were generated and recorded by the microphones. In this study, for solid standard samples, the method exhibited a linear response up to 120 mg CaCO3 with sensitity of 0.02 mg; and in the case of water samples, these indices were 36.4 mmol/L NaHCO3 with 3 mmol/L. Since proton consumption by total inorganci carbonate in clay minerals may obviously influence the surface acid-base properties, natural illites from different origins were selected as model samples to determine thecarbonates. In addition, some affecting factors and improvement of this method were discussed.