温度控制对分光光度法测定pH的影响  

Study on the Effect of Temperature Control on pH Measurement by the Spectrophotometric Method

作　　者：刘玉[1] 司玉洁[1] 赵宇梅[1] 王宁[1] 

机构地区：[1]国家海洋技术中心,天津300112

出　　处：《海洋技术学报》2016年第3期94-97,共4页Journal of Ocean Technology

基　　金：国家自然科学基金资助项目(41206083);天津科技兴海项目资助(KJXH2013-21)

摘　　要：海洋中二氧化碳含量增加,使得海洋生态环境发生变化。海洋碳循环及海洋酸化的监测数据是评估生态环境变化的重要指标,p H作为一项碳循环监测重要指标,其测量的精度指标要求达到千分之五,传统意义上的敏感电极法测量海水中p H测量精度为±0.2,已不能满足海水碳循环监测的要求,分光光度法测定海水p H无需校正,精密度±0.005,该方法可用于碳循环船基监测和岸基监测。分光光度法测定海水p H,测量环境和样品恒温于25℃,一般商用分光光度计无恒温功能,本研究通过恒温水循环系统,对分光光度计舱内侧壁及比色皿架外壁进行恒温设计,准确控制温度。结果表明,标准缓冲溶液在24.0℃,24.5℃,25.0℃,25.5℃和26.0℃下,p H随温度呈线性变化、5组实测p H值与公式计算理论值差值无显著差异。在25.0℃测定5个不同海水样本p H,均得到了稳定数值。The increasing content of carbon oxide in seas and oceans has led to changes in marine ecological environment. The monitoring data of marine carbon cycle and ocean acidification are significant indicators used to evaluate the change of ecological environment in seas and oceans. As an important indicator, p H is to survey the carbon cycle, with its measuring accuracy being demanded to reach 5 ‰. So far, the accuracy of marine p H measured by the traditional sensitive electrode measurement method is ±0.2, not able to meet the requirement of seawater carbon cycle monitoring. However, the accuracy of the spectrophotometric method is ±0.005 and it needs not to be calibrated to measure marine p H. So the spectrophotometric method has been used in ship and shorebased monitoring on carbon cycle. In the Guide to best practices for ocean CO2 measurement, the temperature of the environment and samples to be measured is stipulated to be kept at 25 ℃ when the spectrophotometric method is adopted to measure the p H of seawater. However, the temperature can not be controlled using ordinary commercial spectrophotometers. Therefore, temperature control becomes the key factor restricting the development and application of the spectrophotometric method. In this study, the constant temperature system of water cycle is applied to design the chamber wall of the spectrophotometer and the outer wall of the cuvette holder to control the temperature. The results show that p H has linear change with changing temperature when the standard buffer solution is at the temperature of 24.0, 24.5, 25.0, 25.5 and 26.0 ℃. No significant difference is observed between the p H values of the five groups and the theoretical values calculated from the formula. Besides, the p H values of different seawater samples measured at 25.0 ℃ are all stable.

关 键 词：温度控制 分光光度法 PH测定 

分 类 号：X834[环境科学与工程—环境工程]