On-probe sample pretreatment for direct analysis of lipids in gram-positive bacterial cells by matrix-assisted laser desorption ionization mass spectrometry.

On-probe sample pretreatment using trifluoroacetic acid as an additional reagent enabled the direct detection of phospholipids in whole bacteria by means of matrix-assisted laser desorption ionization mass spectrometry for not only gram-negative organisms but also gram-positive ones with a thicker peptidoglycan layer.