A flow injection low-pressure chromatographic system exploiting fused-core columns

Abstract

Chromatography with ultra-short monolithic columns, although attractive in view of its operation at low pressure without the need for expensive pumps, presents limited selectivity due to the low availability of stationary phases. In this work, fused-core columns are for the first time exploited in flow injection systems aimed at low-pressure chromatography. The proposed approach expands selectivity of flow injection low-pressure chromatography by considering the range of different stationary phases available for fused-core columns. Separation of methyl, ethyl and propylparabens was selected as an application and a critical comparison of chromatographic efficiencies of four columns (C18, RP-amide, F5 and phenyl-hexyl) is presented. An acetonitrile/phosphoric acid pH 2.5 solution was selected as the mobile phase, with specific ratios for each column. RP-amide provided the best chromatographic efficiency, performing quantitative separation of the three analytes in 8.0 min, with resolutions > 1.72, peak symmetry < 1.66, LODs between 0.12 and 0.39 mg L⁻¹, linear response ranges up to 5.0 mg L⁻¹ (r > 0.996) and coefficients of variation of peak heights < 3.5% (n = 10). The procedure was applied to the determination of parabens in personal care products, and the results agreed with the HPLC reference procedure at the 95% confidence level.