Electrospray ionisation time of flight mass spectrometry (ESI-TOF-MS) is applicable to many fields including the analysis of proteins, natural extracts, synthetic mixtures, medical drugs and human or animal body fluids (urine and plasma).
In mass spectrometer the mass of an unknown molecule will be determined by m/z-value (mass-charging-ratio) by time of flight from ion to a detector (TOF). In contrast to classical mass spectrometers (for example quadropol- and sector-field instruments) TOF measurement allows simultaneously detection of all ions contained in the sample so that a complete mass spectrum is obtained at each time point. This "scan" occurs several thousand times per second.
The computer based calculation of possible empirical formulae of molecules on the basis of these mass spectra requires a determination of ion masses with an accuracy of 6-7 decimal places. The mass spectrometer used in our lab produces high-resolution mass-spectra with this accuracy which corresponds to a deviation of measured to effective mass of less than 5 ppm. For the calculation of possible empirical formulae a comparison of the measured value with appropriate empirical formulae of the expected isotope pattern distribution can be performed.
Determination of mass spectra from pure substances can be made directly from the substance in solution. By linking the mass spectrometer with a HPLC device a mass spectroscopic investigation of single components is possible. Furthermore by simultaneously measuring the ultra violet (UV)-spectra with diode array detection (DAD) further structural characterisation is possible.
Application of mass spectrometer in LC-SPE-NMR/MS allows a complete structure determination of single components in complex mixtures.