Large Volume Injection of Aqueous Samples in Nano Liquid Chromatography Using Serially Coupled Columns

Abstract

One of the biggest challenges in the field of water analysis is the determination of trace concentrations of emerging contaminants. These contaminants must therefore be enriched, typically by either off-line or online solid phase extraction. An alternative method is the direct large volume injection onto the separation column. In liquid chromatography, the limitation of the injection volume depends on the column dimensions, the analyte hydrophobicity, the injection solvent and the nature of the stationary phase. Exceeding of the maximum injection volume is indicated by a deterioration of peak shapes and a loss in signal intensity. By serial coupling of two stationary phases with different hydrophobicities, the focusing can be improved and the maximum injection volume can be increased. A suitable combination could be the hyphenation of a carbon-based phase like Hypercarb and a C-18 phase. This paper describes how to implement this concept based on nano-LC and UV detection. To cover a wide range of polarity, a polar, semi-polar and non-polar compound were used as model analytes. The recommended injection volume of 25 nL for a nanobore column could be successfully increased to 3,000 nL, without deterioration of peak shapes.