Mass spectrometry as a detector

Explain and give at least two reasons why using UV-Vis or mass spectrometry as a detector for chromatography might be beneficial. 

Tomlinson, M.J., Lin, L. and Caruso, J.A. (1995) Plasma mass spectrometry as a detector for chemical speciation studies. Analyst, 120, 583-589. 

The use of mass spectrometry as a detector in g.l.c. has the advantage that isomeric materials with the same retention times may still be distinguished, e.g. a phosphate and phosphonate. Mono-, di-, and tri-butyl phosphates may be separated by g.l.c. after conversion of the acidic components into their silyl esters. A dual flame photometric detector has been described for the simultaneous determination of phosphorus-, sulphur-, and chlorine-containing compounds. The method is based on the measurement of the... 

Numerous papers have relied on only UV-visible spectra for their identification of phenolics, but for positive identification purposes, HPLC-mass spectrometry (MS) is another detection mode that can provide detection of all phenolic compounds in foods. This technique involves a hyphenated instrument that uses a mass spectrometer as a detector for HPLC or uses HPLC as cleanup step for mass spectrometry. After preparative HPLC, the MS technique has frequently been employed for structural identification of phenolics in many foods and essential oils because of its sensitivity and selectivity and its ability to provide structural information. 

The use of mass spectrometry as a tool for the structural analysis of flavonoids has constituted a fundamental step forward, particularly after the development of emerging techniques that allow work to be con-ductedat atmospheric pressure without the need for compound deriv-atization before analyzing for volatilization and ionization. On the other hand, coupling these mass detectors to separation systems, particularly HPLC, has permitted the screening and characterization of flavonoids in complex matrices, and a tentative structural identification of complex... 

Detection by Mass Spectrometry The use of a mass spectrometer as a detector (HPLC-MS) can provide much information concerning the structures of the compounds being separated. Interfaces are available (see under Mass Spectrometry, p. 253). 

Also, Steady enhancements, especially the adaptation of other detection techniques, continuously add to its flexibility. The advent of mass spectrometry as a powerful detector significantly improves the applicability of modem HPLC, and NMR is on its way to become just another HPLC detector. 

In modem mass spectrometry, ion collectors (detectors) are generally based on the electron multiplier and can be separated into two classes those that detect the arrival of all ions sequentially at a point (a single-point ion collector) and those that detect the arrival of all ions simultaneously (an array or multipoint collector). This chapter compares the uses of single- and multipoint ion collectors. For more detailed discussions of their construction and operation, see Chapter 28, Point Ion Collectors (Detectors), and Chapter 29, Array Collectors (Detectors). In some forms of mass spectrometry, other methods of ion detection can be used, as with ion cyclotron instmments, but these are not considered here. 

ICPMS can be considered a high-sensitivity extension of mass spectrometry, as well as an increased-sensitivity detector replacing optical ICP (ICP-OES) analysis. In fret, both viewpoints are accurate, and the wide application of ICPMS analysis... 

VL medium, pH 6 4, with or without cells was incubated in sealed tubes for 10 hrs at 37 C NDMA was determined by gas chromatography with the Thermal Energy Analyzer as a detector (Thermo Electron Corp, Waltham, MA). The identity of NDMA was confirmed by 6C mass spectrometry. 

In the past decade, as systems have become simpler to operate, mass spectrometry (MS) has become increasingly popular as a detector for GC. Of all detectors for GC, mass spectrometry, often termed mass selective detector (MSD) in bench-top systems, offers the most versatile combination of sensitivity and selectivity. The fundamentals of MS are discussed elsewhere in this text. Quadrupole (and ion trap, which is a variant of quadrupole) mass analyzers, with electron impact ionization are by far (over 95%) the most commonly used with GC. They offer the benefits of simplicity, small size, rapid scanning of the entire mass range and sensitivity that make an ideal detector for GC. 

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