Preparation of glass capillary columns for routine gas chromatography analysis of nicotine and its main metabolites in extracts of urine and plasma

Quantitative analysis of trace amounts of nicotine and its metabolites requires capillary columns of very high inertness against basic compounds. Borosilicate glass contains high amounts of Bsub2Osub3 and Alsub2Osub3 which act as strong Lewis acids and therefore must be removed from the surface. This was accomplished by leaching with aqueous HCl. Subsequent high temperature silylation and coating with an apolar silicon gum phase like OV-1 or SE-52 yielded columns of very low adsorptivity for both basic and acidic compounds. Thus prepared columns were highly thermostable and long-lived unless water or large amounts of impurities were introduced into the capillary. To obtain sufficiently inert columns for routine analysis of such relatively impure extracts the acidic leaching was followed by forming of a BaCOsub3 intermediate layer. This pretreatment permits coating with polyglycol phases like carbowax 20 M or pluronic F 68. These columns exhibited besides satisfactory inertness a considerably higher durability in routine analysis of plasma and urine extracts. (Author)