Comparison of electrospray ionization, atmospheric pressure chemical ionization and atmospheric pressure photoionization for a lipidomic analysis of Leishmania donovani

A comparison of electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) for the analysis of a wide range of lipids has been performed on standard mixtures and extracts of Leishmania donovani promastigotes resistant to Amphotericin B (AmB). Calibration model, precision, limits of detection and quantification (LOD and LOQ) were assessed for each source. APPI provided the highest signal, signal-to-noise (S/N), and sensitivity for non-polar and low-polarity lipids, while ESI and APCI gave better results for the most polar ones. The linear model was valid for all lipids, except for one class with APPI, six classes with ESI, and eleven classes with APCI. LODs ranged from 0.2 to 20 μg mL−1 for ESI, from 0.1 to 10 μg mL−1 for APCI, and from 0.02 to 9.5 μg mL−1 for APPI. LOQs ranged from 0.2 to 61 μg mL−1 for ESI, from 0.4 to 31 μg mL−1 for APCI, and from 0.1 to 29 μg mL−1 for APPI. Each source provided similar lipid composition and variations in a comparison of three different L. donovani samples: miltefosine-treated, miltefosine-resistant and treated miltefosine-resistant parasites. A treated miltefosine-resistant sample was finally analyzed with each ion source in order to verify that the same lipid molecular species are detected.

► We coupled a normal-phase chromatographic separation of lipids to a mass spectrometer.
► We compared the performance of the three atmospheric pressure ion sources.
► Atmospheric pressure photoionization is interesting for non-polar and low polarity lipids.
► Polar lipids are better analyzed through electrospray ionization.