- Mass spectrometer detector: This is a universal detector that gives a mass spectrum of
the analyte and therefore gives both structural and quantitative data. Its detection
limit is less than 1 ng per scan. Analytes may be detected by atotal ion current(TIC)
(Section 9.4.1) trace that is non-selective, or byselected ion monitoring(SIM)
(Section 9.5.11) that can be specific for a selected analyte. In cases where authentic
samples of the test compounds are not available for calibration purposes or in cases
where the identity of the analytes is not known, a mass spectrometer is the best means
of detecting and identifying the analyte. Special separators are available for removing
the bulk of the carrier gas from the sample emerging from the column prior to its
introduction in the mass spectrometer (Section 9.3).
Modern GC systems are controlled by dedicated microcomputers capable of auto-
mating and optimising the experimental conditions, recording the calibration and test
retention data and carrying out statistical analysis of it and displaying the outputs in
colour graphics in real time. They are capable of carrying out both qualitative and
quantitative analysis on a similar basis to that of LC.
11.10 Suggestions for further reading
Niessen, W. M. A. (2007).Liquid Chromatography–Mass Spectrometry, 3rd edn. Boca Raton, FL:
CRC Press. (A definitive guide with particular emphasis on applications in proteomics, drug
discovery, food safety and environmental monitoring.)
Pyell, U. (ed.) (2006).Electrokinetic Chromatography: Theory, Instrumentation and Applications.
New York: John Wiley. (A comprehensive coverage of the techniques and its most recent
applications.)
Zachariou, M. (ed.) (2007).Affinity Chromatography: Methods and Protocols. Totowa, NJ:
Humana Press. (A detailed account of recent applications of this important method of protein
purification.)
476 Chromatographic techniques
