EVALUATION OF TRANSITION-METAL COMPLEXES OF AMINOPROPYLSILYL-DITHIOOXAMIDE BONDED PHASES FOR GAS-CHROMATOGRAPHY

Copper(II) and cobalt(II) complexes of dithiooxamide chemisorbed on am inopropyl bonded silicas were prepared and evaluated for the separatio n of light hydrocarbons (C-4 and below) by microcolumn gas chromatogra phy (GC). All the columns appeared to be effective for the separation of C-1-C-4 saturates with reproducible retention times. In general, th e sample components were retained longer on the metal-containing packi ngs presumably due to specific solute-metal interactions. The cobalt(I I) complex of aminopropylsilyl-dithiooxamide bonded phase showed bette r selectivity for the test solutes, particularly the C-2 hydrocarbons. This result, which reflects the higher capability of cobalt(II) to fo rm pi-complexes with electron donor compounds than copper(II), showed a significant improvement in the separation of the C-2 hydrocarbons ov er molecular sieve 5A, alkyl bonded silicas and copper(II) complexes o f cyano- or mercaptopropyl bonded phase where ethane and ethylene elut ed as a single peak. Thermal stability test showed that the columns co uld be operated at temperatures up to 200 degrees C without any apprec iable change in retention properties.