QUARTZ ROD COATED WITH MODIFIED SILICA-GEL AS A SOURCE OF CO AND CO2 FOR STANDARD GASEOUS-MIXTURES

Quartz rods coated with a thin layer of chemically modified silica gel have been used for the generation of a two-component gaseous standard mixture containing carbon monoxide and carbon dioxide. A new method b ased on thermal decomposition of immobilized compounds chemically bond ed to the surface of silica gel has been used in the generation proces s. The oxalic acid moiety bonded to the glycydoxypropylsilylated surfa ce of silica gel underwent decarbonylation and decarboxylation at 300 degrees C, yielding carbon monoxide and carbon dioxide, On-line connec tion of a thermal desorber with the GC/FID enabled calibration of the detector following the process of methanization of CO and CO2. The fol lowing amounts of CO and CO2 were generated per unit length of the rod : 15.1 x 10(-8) Mol cm(-1) (RSD = 5.71%) for CO and 34.2 x 10(-8) Mol cm(-1)(RSD = 5.16%) for CO2.