A rapid method for determination of total dissolved inorganic carbon in seawater with high accuracy and precision

Abstract

A rapid method for determination of total dissolved inorganic carbon ( C T) in seawater with high accuracy and precision has been developed. The method is based on continuous gas extraction of acidified seawater that is pumped through an extraction chamber at a constant flow rate. The purged carbon dioxide is determined with a NDIR gas analyser. A high accuracy was achieved by continually shifting between sample and a certified reference material in 2-min intervals. The method was compared with the current standard, the coulometric technique. Seawater samples having C T-concentrations between 1950 and 2160 μmol kg −1 were analysed and the results for the two methods showed good correlation (linear regression equalled C T coul=1.0011* C T NDIR−4.28, R 2=0.99994). Precision was comparable, with the method presented having a standard deviation of 0.05% and the coulometric having 0.08%. However the proposed method is faster than the coulometric method having a rate of about 12 samples per hour using a sample volume of less than 50 ml. Furthermore the hazardous chemicals associated with the coulometric technique are not needed.