Analysis of a Mixture of Several Dihalonicotinic Acids by Gas Chromatography and Gas Chromatography-Mass Spectrometry

摘要

Six, 2,5-and 5,6-dihalonicotinic acids I a mixture were concerted to their corresponding methyl esters and then analyzed by gas chromatography and gas chromatography-mass spectrometry. Four methods of conversion were compared for their GC sensitivity, efficiency and analysis time. In Method # 1, using HCl and methanol as the reagents, the displacement of the halo- gens by chlorine (from HCl) at 2-and 6-positions was a common occurrence, rendering the method inefficient. In Method #2 (BF_3/methanol), the displacement of halogens by methoxide was evident.