RAPID ONLINE COMBUSTION SYSTEM FOR C-13 ANALYSIS OF NONVOLATILE COMPOUNDS

A novel on-line combustion system was designed and tested for dynamic C-13 analysis of minute quantities of previously isolated, nonvolatile organic compounds. The analyte was loaded onto a tungsten filament, s ealed in a helium/oxygen carrier gas stream, and heated to combustion by passing an electrical current through the filament. The accuracy of the filament system was 1-2 parts per thousand for natural abundance and highly enriched (-25 to 500 parts per thousand vs PDB) nonvolatile bioorganic compounds. The precision was 1-2 parts per thousand at nat ural abundance and 4 parts per thousand at high C-13 enrichments. Thes e precisions were obtained with similar to 500 ng of sample. Memory li mited the accuracy of the filament inlet when the envelope was not cha nged between samples. This on-line combustion system represents a new approach to isotope ratio analysis of nonvolatile organics. It has the potential for total carbon analysis of complex organic mixtures and h as sample requirements 100-fold lower than those of other systems desi gned for nonvolatile organics.