Comprehensive two-dimensional liquid chromatography coupled to triple quadrupole mass spectrometry: application to a challenging food case-study

The high complexity of many food samples places a great demand in terms of both separation capabilities, and specificity of detection. Here we describe a novel system for comprehensive two-dimensional liquid chromatography (LC×LC), fully automated, in which on-line coupling of the two separation dimensions was achieved by means of two 6-port, two-position switching valves. High orthogonality was achieved by using a micro-bore cyano column (250 mm ×1.0 mm, 5 ???m d.p.) for the first dimension separation, interfaced to a secondary C18 column (30 mm × 4.6 mm, 2.7 um d.p.) packed with fused-core particles. The hyphenation to a triple quadrupole mass spectrometer generates a powerful analytical system, capable of extremely high resolving power as well as targeted and untargeted analysis. The so-called multiple reaction monitoring (MRM) mode in fact enhanced selectivity, reducing sample consumption and the need for tedious clean-up procedures, specifically for beta-carotene quantification in a red pepper extract.