Determination of alkalinity and acidity of water by conductometric acid-base titration

Abstract

The alkalinity and acidity of water are parameters of great importance for studies of aquatic ecosystems. This paper describes the determination of total alkalinity by using acid-base titration with trichloroacetic acid solution as titrant. Total acidity is determined by titration with ammonium hydroxide solution. Both titrations are monitored conductometrically. Performance is evaluated and compared with performance of the potentiometric titration. Automated conductometric titration is simple, fast (30 s/titration), sensitive (detection limit 0.1 ppm CaCO3), and accurate. Relative error of the determination increased from about 1% at high levels to about 10% at 1 ppm CaCO3. The relative standard deviation of alkalinity measurements ranged from 1 to 5%; for acidity, these values ranged from 1.5 to 17%. Relative standard deviation reached 33% at lower detection limits. Samples containing noncarbonate contributory components of alkalinity (borate, silicate, phosphate, organic acids) can be reproducibly analyzed.