Hyphenation of supercritical fluid chromatography to high resolution Orbitrap mass spectrometry for the purpose of non-targeted small molecule analysis.

To cater for the rising need to identify current and emerging environmental contaminants, a hybrid chromatography-mass spectrometry interface was developed for supercritical fluid chromatography. Supercritical fluid chromatography was selected for normal phase and reverse phase selectivity and was hyphenated to an Orbitrap mass analyser for application to non-targeted methods and high-resolution mass spectrometry. This interface was achieved through ion source parameter optimisation and the use of make-up solvent flow delivered by a sheath pump. The method presented here was developed based on 23 reference standards of environmental contaminants, pharmaceuticals and polar compounds which have logD (pH 5.5) values between -2.50 and 4.96. Further non-targeted method evaluation was performed on treated wastewater effluent samples, where this non-targeted methodology allowed for the identification of 88 compounds across both positive and negative ion modes. Chromatography separation characteristics were assessed across both reference standard and WWTP sample runs. The major separation characteristic was polarisability represented by acidic and basic hydrogen bonding. Compounds with a pKa of <5 eluted earlier in the run and compounds with a pKa of 8-13 eluted later due to the acidity of the mobile phase and the capability of the Acquity Torus DIOL column for acidic hydrogen bonding. These separation characteristics demonstrate that this method has wide application to a large number of functional groups, with orthogonal separation capability for polar compounds to support reverse phase liquid chromatography methods.