Reagentless Acid-Base Titration for Alkalinity Detection in Seawater

被引:13
|
作者
Wiorek, Alexander [1 ]
Hussain, Ghulam [1 ]
Molina-Osorio, Andres F. [1 ]
Cuartero, Maria [1 ]
Crespo, Gaston A. [1 ]
机构
[1] KTH Royal Inst Technol, Dept Chem, Sch Engn Sci Chem Biochem & Hlth, SE-10044 Stockholm, Sweden
基金
瑞典研究理事会;
关键词
IN-SITU MEASUREMENTS; CONFORMATIONAL RELAXATION; CYCLIC VOLTAMMETRY; POLYANILINE; ACIDIFICATION; SENSOR; ELECTRODES; TRANSPORT; OXIDATION; SYSTEMS;
D O I
10.1021/acs.analchem.1c02545
中图分类号
O65 [分析化学];
学科分类号
070302 ; 081704 ;
摘要
Herein, we report on a reagentless electroanalytical methodology for automatized acid-base titrations of water samples that are confined into very thin spatial domains. The concept is based on the recent discovery from our group (Wiorek, A. et al. Anal. Chem. 2019, 91, 14951-14959), in which polyaniline (PANI) films were found to be an excellent material to release a massive charge of protons in a short time, achieving hence the efficient (and controlled) acidification of a sample. We now demonstrate and validate the analytical usefulness of this approach with samples collected from the Baltic Sea: the titration protocol indeed acts as an alkalinity sensor via the calculation of the proton charge needed to reach pH 4.0 in the sample, as per the formal definition of the alkalinity parameter. In essence, the alkalinity sensor is based on the linear relationship found between the released charge from the PANI film and the bicarbonate concentration in the sample (i.e., the way to express alkalinity measurements). The observed alkalinity in the samples presented a good agreement with the values obtained by manual (classical) acid-base titrations (discrepancies <10%). Some crucial advantages of the new methodology are that titrations are completed in less than 1 min (end point), the PANI film can be reused at least 74 times over a 2 week period (<5% of decrease in the released charge), and the utility of the PANI film to even more decrease the final pH of the sample (pH similar to 2) toward applications different from alkalinity detection. Furthermore, the acidification can be accomplished in a discrete or continuous mode depending on the application demands. The new methodology is expected to impact the future digitalization of in situ acid-base titrations to obtain high-resolution data on alkalinity in water resources.
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页码:14130 / 14137
页数:8
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