离线二氧化碳发生原位再溶解-电感耦合等离子体原子发射光谱法测定水样中无机碳

ICP-AES Determination of Inorganic Carbon in Water Samples with Off-Line CO_2-Generation and in situ Re-dissolution

基于二氧化碳在水中具有较大的溶解度,提出了在电感耦合等离子体原子发射光谱法(ICP-AES)测定水样中无机碳含量时,用离线二氧化碳发生及原位再溶解作为样品溶液的制备方法。取一定量水样与4mL盐酸(1+9)溶液反应,使样品中碳酸盐及碳酸氢盐转化为二氧化碳,并在原溶液中原位再溶解。样品溶液的总体积为50mL,经过仪器上常规采用的单管进样装置导入于仪器中,经气液分离器在172.4kPa压力条件下,使试液中的二氧化碳分离析出,用ICP-AES测定其浓度。二氧化碳质量浓度在400mg·L-1以内与测定信号之间呈线性关系,方法的检出限(3s/k)为0.087mg·L-1。在20mg·L-1浓度水平做重复性试验,计算其相对标准偏差(n=10)为0.97%。应用此方法分析了4个水样,所得二氧化碳的测定值与滴定法测定值相一致。

Based on the relatively high solubility of CO2 in water, a method of off-line CO2-generation and in situ re-dissolution was proposed for sample preparation applied to the ICP-AES determination of inorganic carbon in water. Definite amount of water sample was reacted with 4 mL of HCI（＋9） to transform CO3^2- and HCO3- into CO2, which was redissolved in situ in the same sample solution （total volume 50 mL）. After separation of the CO2 from the solution by nebulizer at the pressure of 172.4 kPa, the gas was introduced into the instrument through the conventional single tube sample introduction, and the concentration of CO2 was determined by ICP-AES. Linearity was attained in the range up to 400 mg. L^-1. Detection limit （3s/k） of 0. 087 mg .L^-1 was found for the method. Testing for repeatability at the concentration level of 20 mg . L^-1 was performed, giving value of RSD （n= 10） 0. 97%. Four water samples were analyzed by this method, giving results of CO2 in consistency with those found by titrimetry.