Institute of Oceanographic Instrumentation, Qilu University of Technology (Shandong Academy of Sciences), Shandong Provincial Key Laboratory of Ocean Environmental Monitoring Techno1ogy, National Engineering and Technological Research Center of Marine Monitoring Equipment, Qingdao, 266061, China.
Key Laboratory of Global Change and Marine-Atmospheric Chemistry of Ministry of Natural Resources (MNR), Third Institute of Oceanography, MNR, Xiamen, 361005, China.
Talanta. 2021 Mar 1;224:121775. doi: 10.1016/j.talanta.2020.121775. Epub 2020 Nov 3.
Automated instrument for long-term measurement of seawater pH is important for documenting the changes of the marine carbonate system and the impacts of ocean acidification. An automated pH analyzer based on loop flow analysis (LFA-pH) was developed to achieve precise and accurate measurements of seawater pH. The circulating loop allows complete mixing of an indicator and seawater, constant mixing volume of two solutions, and correcting indicator perturbation for each measurement. During laboratory testing, the LFA-pH precision achieved 0.0004, and the accuracy was 0.0017 ± 0.0038 compared with the certified standard buffer at different temperatures. During the 59 day underway measurement across the mid and high latitudes, more than 2500 pH measurements were carried out. LFA-pH showed good stability with high temperature and salinity changes, and measurement results were consistent with the discrete surface seawater pH measurement data. In situ testing of two LFA-pHs was completed near the Zhongyuan pier in Qingdao. The average pH offset between the two LFA-pHs was 0.0010 ± 0.0032 (n = 788), with the accuracies of the two LFA-pHs of 0.0012 ± 0.0033 and 0.0005 ± 0.0035 compared to discrete measurements. For continuous measurement, the average power consumption is 3.6 W at a 10 min measurement frequency. Given its low power consumption, high precision, and accuracy, FLA-pH could be adapted for underway and in situ measurements of ocean acidification observations.
用于长期测量海水 pH 值的自动化仪器对于记录海洋碳酸盐系统的变化和海洋酸化的影响非常重要。本研究开发了一种基于环形流分析（LFA-pH）的自动化 pH 分析仪，以实现海水 pH 值的精确和准确测量。循环回路允许指示剂和海水完全混合，两种溶液的混合体积恒定，并为每次测量校正指示剂的扰动。在实验室测试中，LFA-pH 的精度达到 0.0004，在不同温度下与认证标准缓冲液相比，准确度为 0.0017±0.0038。在跨中高纬度的 59 天现场测量中，进行了 2500 多次 pH 值测量。LFA-pH 在高温和高盐度变化下表现出良好的稳定性，测量结果与离散的表层海水 pH 值测量数据一致。在青岛中原码头附近完成了两台 LFA-pH 的现场测试。两台 LFA-pH 的平均 pH 值偏差为 0.0010±0.0032（n=788），两台 LFA-pH 的准确度分别为 0.0012±0.0033 和 0.0005±0.0035，与离散测量相比。对于连续测量，在 10 分钟的测量频率下，平均功耗为 3.6 W。鉴于其低功耗、高精度和准确度，LFA-pH 可适应海洋酸化观测的现场和原位测量。
