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

A rapid method for determination of total dissolved inorganic carbon (CT) 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 CT-concentrations between 1950 and 2160 μmol kg−1 were analysed and the results for the two methods showed good correlation (linear regression equalled CTcoul=1.0011*CTNDIR−4.28, R2=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.