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 (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 mu mol 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. (c) 2004 Elsevier B.V. All rights reserved.