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Novel Coated Cellulose Carbamate Silica Based Phase to Enhance Selectivity of Compounds of Pharmaceutical Interest

Leslie Brown, Gregory K. Webster, Laila Kott, Nagaraja K.R. Rao, Trinh Anh Luu, Rekha Shah and Lorraine Henriques

Modern liquid chromatographic (LC) analyses of targets in complex matrices, even with mass spectroscopic (MS) detection, more commonly are also requiring an orthogonal method to ensure peak purity and resolution of all sample impurities. This is especially true when stereoisomer identity and separation are critical criteria. To help address this gap in orthogonality, a novel coated cellulose carbamate stationary phase was developed using a reoptimized coating density, a type B 500-angstrom silica as its base entity, and a secondary amine to facilitate the coating to the base silica. The chiral phase can be used in reverse phase chromatography but is designed to work with mixed polar eluents in both polar organic and normal phase chromatography. It is also selective for achiral applications as well. A critical difference is the stability of this cellulose carbamate stationary phase at higher alcohol concentrations and the prediction capability of the elution order of analytes. This stationary phase showed greater chromatographic selectivity by requiring less alcohol modifier for elution of chiral compounds, when compared to other cellulose carbamate columns and by the use of acetonitrile (ACN) as a modifier. The Cogent EE phase is also rugged and can easily switch between different pH's without loss of resolution or memory effects. Finally this phase was used to separate optical isomers of gossypol and tramadol, and worked well in a case study where diastereomers were isolated from a previously unknown impurity.