Applicability of Reversed-Phase Base-Deactivated Columns for Systematic Toxicological Analysis

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Abstract
The chromatographic properties of seven reversed-phase columns from different manufacturers, specially prepared for analysis of basic drugs, were investigated. Three test mixtures were used: Neutral (1-nitroalkanes), acidic (salicylamide and four barbiturates) and basic (diphenhydramine, imipramine, amitriptyline, fluphenazine and thioridazine). The mixtures were eluted with three mobile phases, consisting of acetonitrile-water, acetoni-trile-phosphate buffer and acetonitrile-triethylammonium phosphate buffer. The concentration of acetonitrile, pH and molarity of buffers were identical. The neutral and acidic drugs were separated in all mobile phases. The addition of buffer or amine to the mobile phase exerted virtually no influence on the chromatographic behavior of these compounds. The results indicate, that the investigated base-deactivated columns - with one exception - may be used for general toxicological screening. The silanol effects were negligible, but present in all examined columns. Therefore, although it is possible to separate basic compounds on these column in mobile phase consisting of acetonitrile and acidic buffer, the use of amine modifier is still advisable. Basic drugs were not eluted in acetonitrile-water mixture. These drugs were eluted and separated fairly well in acetonitrile-phosphate buffer; the application of triethylammonium phosphate buffer was associated with faster elution of basic drugs and narrower peaks on all examined columns.

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