FALSE POSITIVES AND THE DETECTION OF CYCLODEXTRIN INCLUSION COMPLEXESBY ELECTROSPRAY MASS-SPECTROMETRY

The results of previous works that have claimed to detect cyclodextrin inclusion complexes via the ''soft'' ionization technique of electros pray ionization mass spectrometry are revisited. A more extensive stud y of cyclodextrin mixtures with amino acids and small peptides demonst rates that amino acid and peptide ''complexes'' are detected by electr ospray mass spectrometry regardless of the presence (or not) of an aro matic moiety on the side chain. Amino acids that may be least likely t o form hydrophobic inclusion complexes with cyclodextrin in solution g enerally show the most intense complex ions. The data suggest that the se ''complexes'' are, in all likelihood, electrostatic adducts formed during the electrospray process. Systematic controls are suggested to ensure that ''false positives'' do not negate many of the claims conce rning the detection of solution-derived noncovalent compounds.