Chapter 10 - Extraction of Dissolved Inorganic Carbon (DIC) in Natural Waters for Isotopic Analyses

Abstract

This chapter provides a guide for selecting an appropriate technique for dissolved inorganic carbon (DIC) extraction for isotopic analysis. The main focus is on extraction techniques routinely used for DIC isotopic analyses. DIC consists of CO2(aq), H2CO3, HCO3−, and CO32−. Its concentration in natural waters is governed by the interaction of various carbon species. In terms of the extraction procedure, ease of sampling and reliability or reproducibility of the DIC extraction procedure is paramount. The vacutainer gas evolution technique is versatile, requires less technical sophistication and provides accurate DIC concentration. The precipitation and gas evolution techniques provide accurate determinations of the 13C of DIC. Accurate determinations of DIC concentration are possible with the precipitation and gas evolution technique. These techniques are less attractive due to the elaborate procedure and precautions needed to obtain accurate results. In addition, the large volumes of water sample used in current techniques make it less attractive for analyses involving smaller volumes of water extracted from sediment cores. The main advantage of the techniques is that sufficient CO2 can be produced for both conventional and AMS 14- C determinations.