Effects of the pre-column in automated on-column injection capillary gas chromatography

In this work, we investigated the effects of pre-columns and press-fit connectors on automated cold on-column injection capillary gas chromatography. Verapamil, a calcium channel blocking vasodilator used in the treatment of angina, arrhythmias and hypertension, and norverapamil, an active metabolite, were used as model compounds in these investigations. Wide-bore fused-silica tubing deactivated with OV-1701-vinyl was also studied with respect to its suitability as pre-column material. The detector response of verapamil versus an internal standard was consistent at micrograms/ml and ng/ml levels, while that of norverapamil decreased with the amount injected. However, the decrease in response of norverapamil appeared to be unrelated to the presence of a pre-column or press-fit connector in the chromatographic system.