Proposta de um novo método para avaliação rápida da vida útil de colunas para cromatografia líquida

Abstract

One of the principal problems related to the traditional stationary phases of high-performance liquid chromatography, the C18 chemically bonded silica phases, is their limited chemical stability in a pH range of 2-8. In the last ten years, the Research Laboratory in Separation Materials and Chromatography (CroMat) has been producing stationary phases by a simpler and lower cost method, based on the polymer immobilization in inorganic oxide particles. However, the stability of these materials is still unknown, since the conventional assessment of the stationary phase lifetime requires the consumption of a large volume of mobile phase and a long operating time of the chromatograph. Thus, in this work we sought to develop a method of rapid degradation of chromatographic columns, aiming to evaluate in a short period of time the stationary phase lifetime. Analysis conditions that lead to the stationary phase degradation were studied as mobile phase pH, type of buffer solution, additive concentration, and column temperature. Each effect of these conditions was evaluated using chromatographic parameters of compounds in a standard test mixture periodically separated by the same batch of commercial C18 phase. The conditions of these variables, which resulted in rapid degradation of the stationary phase, but capable of differentiating materials with close stability, were fixed defining the rapid degradation method. The method was used to evaluate the stability of stationary phases prepared by CroMat based on silica and aluminized silica. The Si(PEO) phase showed the greatest chemical stability among the silica-based phases evaluated, and the one that also had the most hydrophilic polymer layer of the analyzed materials. The stationary phases based on aluminized silica supports were not destroyed by the method within the 24 h, showing high stability due to the presence of alumina in the support material. Thus, it was concluded that it was possible to develop a method of rapid degradation of HPLC stationary phases, within 24 h, making it possible to analyze the stability of both lab-made and commercial phases. This method also allowed to define the lifetime of each stationary phase prepared in CroMat in the last ten years.