RAPID, HIGH-PRECISION POTENTIOMETRIC TITRATION OF ALKALINITY IN OCEANAND SEDIMENT PORE WATERS

A system for rapid, high precision potentiometric determination of alk alinity in sea water and sediment pore water is presented. Two titrati on units were used: a 40 ml unit for seawater and a small volume unit for sediment pore water. Titration time was normally less than 10 minu tes per sample, including sample exchange. With a 40 ml sample volume, the relative standard deviation of the alkalinity obtained in the lab oratory was 0.05% and at sea 0.1%. The small-volume system (0.5-1.5 ml ) gave a precision of 0.07%. Five titration points, in two groups afte r the second equivalence point; were used to evaluate the equivalence volume. Results from equilibrium calculations and computer simulated a lkalinity titrations show that it was possible to use a non-modified G ran function [(V-0 + v)10((E/Z))] and still achieve good accuracy and precision. (C) 1998 Elsevier Science Ltd. All rights reserved.