LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY AND RELATED TECHNIQUES VIA ATMOSPHERIC-PRESSURE IONIZATION

Mass spectrometry may be the ultimate detector for the separation sciences. It combines sensitivity with excellent specificity, so the analyst can obtain definitive information regarding components separated in a mixture. Thus, mass spectrometric detection not only provides evidence of a "peak", but it also provides important clues including molecular weight and structural information that can help to identify the components. The coupling of an atmospheric pressure ionization (API) mass spectrometer to most of the separation science techniques offers a simpler alternative from earlier nonroutine, less sensitive systems where the vacuum systems struggled to handle the liquid effluent from these systems. Today's sensitive and analytically rugged API systems can be operated unattended for extended periods of time, thus reducing the cost per sample to a reasonable value, especially given the wealth of information provided. Although the mass spectrometer is more complicated than conventional spectroscopic detectors, today's API systems effectively decouple the liquid phase separation inlet from the high-vacuum system where mass analysis occurs. The ability to form gas-phase ions at atmospheric pressure and sample primarily the analyte ions into the mass spectrometer promises a bright future for combined on-line separation-mass spectrometry with modern separation science techniques.