Interestingly, the µF/mnESI approach produced an enhanced ionization of around 20-fold, with striking improvements for particular lipid classes, such as sterol esters, glycosylated glycerolipids and oxidized TGs. A decreased variation in ionization efficiency between different lipids due to the employed spraying conditions is a possible explanation of this outcome. Such a phenomenon was earlier demonstrated for silicon chip devices by Hop, Chen and Yu in a mixture of 25 pharmaceutical compounds of six structurally different classes. The relative responses of the NSI analysis on a chip varied only 2.2-fold, whereas the AF approach resulted in 21-fold variation across all compounds . The higher electric field strength around the nozzles generates a large excess of charge in the smaller droplets, thus improving ionization of otherwise hardly ionizable analytes . We also observed an increase in the detection of low-abundant isomers in cell extracts. As an example, only one recognizable chromatographic peak of TG 49:3 is detected by the AF/ESI setup (Fig. ), whereas μF/mnESI approach revealed additional peaks of isomers with lower abundances (Fig. ). Given that ammonium ions are major charge carriers in ammonium acetate buffer conditions employed for the measurements, consistent detection of CEs typically ionized as NH4 + adducts 25 was unsurprising. Höring et al. reported that CE also increase their response both with increasing acyl chain length and number of double bonds . In accordance with their observations, only four CEs were detected by an analytical configuration, majority of those were with higher carbon and double bond counts (22:6, 22:5, 20:4, 18:2; all CVQC = 10 -15%). In turn, the µF/mnESI analysis delivered 38 CEs ranging from 14:0 to 26:5. Variation on pooled QC measurements for those species varied from 1.6 -32.7% with 22 of those displaying CVQC < 15%. Contributions from the additionally detected lipid subclasses may be rationalized in a similar fashion.