Abstract
Cu(II) creates complexes with dipalmitoylphosphatidylcholine (lecithin), which are detectable using electrospray ionization mass spectrometry. Lecithin (L) as a relatively big ligand prevents Cu(II) reduction to Cu(I) during the electrospray process.
The detected complexes include (1) dications with a general formula: [Cu(L)n]2+, where n prevails from 2 to 5 (in the m/z range from 50 to 2,000); and (2) monocations originated from the metal salt precursor [CuCl(L)k]+ (k is 1 or 2). The Cu(II)/lecithin complexes are stable enough (appearance energy higher than 200 kJ mol-1) to utilize Cu(II) for stabilization of an artificial membrane.
The impermeability of an artificial phospholipid membrane for oxalic acid and its complexes with copper ions in slightly acidic pH 5 was confirmed voltammetrically. However, adsorption of copper-oxalate complexes on the membrane surface was proved using electrochemical impedance spectroscopy.