Characterisation and quantification of liposome-type nanoparticles in a beverage matrix using hydrodynamic chromatography and MALDI–TOF mass spectrometry

This paper describes the characterisation of liposome-type nanoparticles (NPs) dispersed in a beverage matrix. Characterisation is based on a two-step procedure: first, liposomes are separated on the basis of size in the nanometre range by use of hydrodynamic chromatography (HDC); second, chemical characterisation is performed by use of MALDI–TOF mass spectrometry (MS). Characterisation of three types of Coatsome liposome, a commercially available type of empty liposome, was investigated. All three liposome types, Coatsome A¿=¿anionic, N¿=¿neutral, and C¿=¿cationic, gave single peaks in HDC, reflecting diameters of 153, 187, and 205 nm, respectively. Subsequent MALDI–TOF MS in positive mode furnished major signals at m/z¿=¿734.5 ([M¿+¿H]+ adduct) and m/z¿=¿756.6 ([M¿+¿Na]+ adduct) of l-(a)-dipalmitoylphosphatidylcholine (DPPC) monomer and dimeric adducts at m/z¿=¿1468.1 and m/z¿=¿1490.1, respectively. MALDI–TOF MS in negative mode gave a signal at m/z¿=¿721.3 ([M¿-¿H]- adduct) of l-(a)-dipalmitoylphosphatidylglycerol (DPPG), except for Coatsome C which lacks this phospholipid. After HDC separation of Coatsome A NPs the major DPPC and DPPG signals can be detected in the expected fractions by use of MALDI–TOF MS in positive and negative modes, respectively. Validation of the analytical strategy revealed linearity (R2¿>¿0.99), repeatability (relative standard deviation