Dual parallel mass spectrometry for lipid and vitamin D analysis.

There are numerous options for mass spectrometric analysis of lipids, including different types of ionization, and a wide variety of experiments using different scan modes that can be conducted. Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) provide complementary types of information that are both desirable. However, the duty cycle of the mass spectrometer places limits on the number of experiments that can be performed, and instruments usually employ only one type of ionization at a time. This work describes the approaches we have used that employ two mass spectrometers in parallel or in a column-switching configuration that allows multiple ionization modes and types of experiments to be conducted simultaneously during a single chromatographic run. These data demonstrate how use of two systems can reduce or eliminate the need for repeat injections and repetitive experiments. Approaches are described that employ two mass spectrometers connected in parallel as detectors for a single chromatographic system (LC1/MS2) or that employ two liquid chromatographs and two mass spectrometers in a column-switching arrangement (LC2/MS2). Examples of LC1/MS2 analyses of triacylglycerols (TAGs), sphingolipids, and vitamin D are given, as well as an example of an LC2/MS2 experiment that is used to perform analysis of both polar and non-polar lipids in a total lipid extract.