ICP-AES Determination of Inorganic Carbon in Water Samples with Off-Line CO₂-Generation and in situ Re-dissolution

Based on the relatively high solubility of CO2 in water, a method of off-line CO2-generation and in situ re-dissolution was proposed for sample preparation applied to the ICP-AES determination of inorganic carbon in water. Definite amount of water sample was reacted with 4 mL of HCl(1+9) to transform CO32- and HCO3- into CO2, which was redissolved in situ in the same sample solution (total volume 50 mL). After separation of the CO2 from the solution by nebulizer at the pressure of 172.4 kPa, the gas was introduced into the instrument through the conventional single tube sample introduction, and the concentration of CO2 was determined by ICP-AES. Linearity was attained in the range up to 400 mg·L-1. Detection limit (3s/k) of 0.087 mg·L-1 was found for the method. Testing for repeatability at the concentration level of 20 mg·L-1 was performed, giving value of RSD (n=10) 0.97%. Four water samples were analyzed by this method, giving results of CO2 in consistency with those found by titrimetry.