Automated High-Performance, High-Temperature Combustion Total Organic Carbon Analyzer

Abstract

A high-temperature combustion (HTC) total organic carbon analyzer, which has significant design improvements over existing systems, was developed. The new injection system directly connects a loop-type autoinjector to the head of the HTC column. This connection facilitates the coupling of an autosampler to the injection system. The entire injection process is closed to the atmosphere, thereby improving the precision and eliminating potential contamination during injection. Injections can be made every 3−5 min, depending on the injection and inorganic carbon sparging modes used. The HTC column was designed without a “cold” zone or dead space at the top. These improvements eliminated the memory (or carry-over) effect, which is a potential problem in some HTC column designs. The HTC column is packed with pure quartz beads instead of a relatively expensive Pt-based catalyst, without loss in the oxidation efficiency, as indicated by 100% recovery for various compounds with different refractory properties and by intercomparison with Pt-based HTC systems. The precision for seawater is ∼±0.6% (RSD) at the 80 μM C level. Typically, greater than 5000 injections of seawater can be made without significant deterioration of column performance. The effects of column temperature and carrier gas flow rate on the oxidation efficiency, sensitivity, and reproducibility are reported. Finally, evidence is presented that suggests that there is a relationship between the refractory nature of pure compounds and the peak width. This potential relationship may be a useful tool for quantifying the refractory nature of organic carbon in natural waters.