Gas chromatography (GC) with flame ionization detection (FID) is still an important relatively inexpensive problem solving analytical method despite the maturity of this technique. Although the FID is a sensitive and rugged detector, it does not provide qualitative identification of the separated components. We have initiated a dynamic GC stationary phase modification research program to permit on-column reaction chemistry which can identify certain classes of organic compounds. In particular, we have adopted the Leukhart reaction to identify the presence of carbonyl compounds. This reaction between formamide and an aldehyde or ketone will generate the N-formyl derivative at elevated temperature, preferentially greater than 165 ^oC. Standard one microliter injections with an autosampler of the ketone 2-nonanone or the aldehyde benzaldehyde on a 30 m x 0.53 mm ID (0.5 micron film thickness) 65% dimethyl/35% diphenyl polysiloxane capillary column gave the expected single peaks retained around 8-9 min. The temperature program was an initial 40 ^oC hold for 5 min before a 30^o/min ramp to 260 ^oC and then a 5 min hold. Then a five microliter injection of a moderate percentage of formamide in ethanol solution was made and the column conditioned isothermally at a low temperature for a set time. Upon reinjection of the ketone or aldehyde, a second small peak was definitely distinguished with about a 30 second earlier retention time from the starting compound using the same temperature program. No such second peak was noted upon injection of either decane or ethylbenzene on the formamide treated column using the same temperature program. Some baseline drift is noted as the nonvolatile formamide gradually comes off the column but the response is minimal because formamide, with only a single C-H bond, has a weak FID response. Optimization of the formamide column coating procedure and versatility of the response for other carbonyl compounds are being ascertained. In particular, the reaction of aldehydes with acetamide to form the corresponding diacetamide derivatives is being explored. Formylation of amines is also under consideration.

Andrew Freeman

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