RESUMO
A laser plasma ion source was used to ionize volatile organic compounds in a gas sample. The plasma was generated on a metal target in the intermediate vacuum region of ~0.3 Torr using a pulsed Nd:YAG laser with a wavelength of 1 µm. The resulting ions mass spectra were acquired using orthogonal time-of-flight mass spectrometer (O-TOF MS). When using a copper target, the ions formed are simple complexes (CuM+ ) of copper ions with organic molecules. The possibility of online identification of trace amounts of alkanes in nitrogen and air, with a detection limit of ~10 ppb, was demonstrated. The ionization efficiency of volatile organic compounds through the formation of clusters with metal ions is 10-4 in terms of the quasimolecular complex ions. The rate constants of ion-molecular reactions of copper ions with octane and water molecules in nitrogen and air are estimated.
RESUMO
The goals of our study were to investigate abilities of two approaches to eliminate possible errors in electrospray mass spectrometry measurements of biomolecules. Passing of a relatively dense supersonic gas jet through ionization region followed by its hitting the spray of the analyzed solution in low vacuum may be effective to keep an initial biomolecule structure in solution. Provided that retention of charge carriers for some sites in the biomolecule cannot be changed noticeably in electrospray ion source, decomposition and separation of charge-state distributions of electrosprayed ions may give additional information about native structure of biomolecules in solution.