Evaluation of transition metal complexes of aminopropylsilyl-dithiooxamide bonded phases for gas chromatography

Copper(II) and cobalt(II) complexes of dithiooxamide chemisorbed on aminopropyl bonded silicas were prepared and evaluated for the separation of light hydrocarbons (C4 and below) by microcolumn gas chromatography (GC). All the columns appeared to be effective for the separation of C1–C4 saturates with reproducible retention times. In general, the sample components were retained longer on the metal-containing packings presumably due to specific solute-metal interactions. The cobalt(II) complex of aminopropylsilyl-dithiooxamide bonded phase showed better selectivity for the test solutes, particularly the C2 hydrocarbons. This result, which reflects the higher capability of cobalt(II) to form pi-complexes with electron donor compounds than copper(II), showed a significant improvement in the separation of the C2 hydrocarbons over molecular sieve 5A, alkyl bonded silicas and copper(II) complexes of cyano- or mercaptopropyl bonded phase where ethane and ethylene eluted as a single peak. Thermal stability test showed that the columns could be operated at temperatures up to 200 °C without any appreciable change in retention properties.