application depends on the RMM range and polarities of the compounds in the mixture, as shown in
Figure 4.40.
The technology and value of HPLC-mass spectrometry has increased in parallel with developments in
mass spectrometry itself. Tandem mass spectrometry, MS/MS and (MS)n, systems to study additional
fragmentation inside the spectrometer and the possibility of analysing mixtures of analytes where
minimal or no HPLC separation is required, are two of the most significant. Very accurate RMM
measurements can now be made using a new generation of compact time-of-flight (TOF) spectrometers
whose performance is comparable to much larger and more expensive magnetic sector instruments.
Figure 4.40
Application range of different
coupling methods.Optimizing a Separation
Adequate resolution of the components of a mixture in the shortest possible time is nearly always a
principal goal. Establishing the optimum conditions by trial and error is inefficient and relies heavily on
the expertise of the analyst. The development of computer-controlled HPLC systems has enabled
systematic automated optimization techniques, based on statistical experimental design and
mathematical resolution functions, to be exploited. The basic choices of column (stationary phase) and
detector are made first followed by an investigation of the mobile phase composition and possibly other
parameters. This can be done manually but computer-controlled optimization has the advantage of
releasing the analyst for other