Liquid chromatography—mass coupling principles

See also Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Inductively Coupled Plasma. Cosmetics and Toiletries. Derivatization of Analytes. Electrophoresis Is-otachophoresls. Environmental Analysis. Enzymes Overview. Extraction Supercritical Fluid Extraction Solid-Phase Extraction Solid-Phase Microextraction. Ion Exchange Ion Chromatography Applications. Liquid Chromatography Reversed Phase Liquid Chromatography-Mass Spectrometry. Nuclear Magnetic Resonance Spectroscopy - Applicable Elements Carbon-13 Phosphorus-31. Perfumes. 

This article begins with a brief history. It then explains the principles of operation of this mass spectrometer. The idealized view of its operation has to be tempered by consideration of some real-world situations that influence performance, such as the finite length of the field, the inevitability of fringing fields and field imperfections. Observations of performance and its limitations are illustrated. The applications section deals with residual gas analysis, gas chromatography and liquid chromatography mass spectrometry (GC-MS and LC-MS), collision induced dissociation using triple quadrupoles (MS/MS) and inductively coupled plasma mass spectrometry (ICP-MS) used for elemental analysis. 

In principle, all powerful element-specific methods that are able to monitor continuously the effluents of separation processes commonly in the range of a few mimin-1 and in element concentrations of some Klpg liter-1. A well-suited method is based on modern element-specific quadrupole mass spectrometry (MS) with an inductively coupled plasma (ICP) interface to the separation unit [e.g., liquid chromatography (LC) or field-flow fractionation (FFF)].Tlie ICP-MS detection can also be used for continuously characterizing the effluent of any kind of packed column (Metreveli and Frimmel, 2007). By this, the transport and elution properties of... 

Figure 4.5 Principle of high performance liquid chromatography (HPLC) linked to inductively coupled plasma mass spectrometry (ICP-MS). (Adapted from Fairman Walhen 2001.)...

There are two types of GC gas-solid (adsorption) chromatography and gas-liquid (partition) chromatography. The more important of the two is gas-liquid chromatography (GLC), used in the form of a capillary column. In this chapter, we describe the principles of operation of gas chromatography, the types of GC columns, and GC detectors. The principles of mass spectrometry (MS) are described, along with coupling of the gas chromatograph with a mass spectrometer (GC-MS). 

Earlier methods used to determine mercury in biological tissue and fluids were mainly colorimetric, using dithizone as the com-plexing agent. However, during the past two to three decades, AAS methods - predominantly the cold vapor principle with atomic absorption or atomic fluorescence detection - have become widely used due to their simplicity, sensitivity, and relatively low price. Neutron activation analysis (NAA), either in the instrumental or radiochemical mode, is still frequently used where nuclear reactors are available. Inductively coupled plasma mass spectrometry (ICP-MS) has become a valuable tool in mercury speciation. Gas and liquid chromatography, coupled with various detectors have also gained much importance for separa-tion/detection of mercury compounds (Table 17.1). 

See also Atomic Absorption Spectrometry Principles and Instrumentation Interferences and Background Correction. Atomic Mass Spectrometry Inductively Coupled Plasma Laser Microprobe. Liquid Chromatography Column Technology. 

See also Chromatography Overview Principles. Gas Chromatography Overview Principles Multidimensional Techniques Online Coupled LC-GC Mass Spectrometry. Liquid Chromatography Multidimensional. 

In the past 15 years, electrospray ionization has become one of the most important ionization methods in mass spectrometry. It is the method of choice in the coupling of liquid chromatography (LC) and mass spectrometry (MS). By estimation, it is used in over 90% of all LC-MS applications. It is especially useful in the analysis of highly polar, ionic, and macromolecular analytes. In addition, electrospray ionization plays an important role in the characterization of biomacromolecules, especially peptides and proteins. History, principle, instrumentation, practical aspects, and application of electrospray ionization are discussed in this article. 

See also Atomic Absorption Spectrometry Interferences and Background Correction. Atomic Emission Spectrometry Principles and Instrumentation Interferences and Background Correction Flame Photometry Inductively Coupled Plasma Microwave-Induced Plasma. Atomic Mass Spectrometry Inductively Coupled Plasma Laser Microprobe. Countercurrent Chromatography Solvent Extraction with a Helical Column. Derivatization of Analytes. Elemental Speciation Overview Practicalities and Instrumentation. Extraction Solvent Extraction Principles Solvent Extraction Multistage Countercurrent Distribution Microwave-Assisted Solvent Extraction Pressurized Fluid Extraction Solid-Phase Extraction Solid-Phase Microextraction. Gas Chromatography Ovenriew. Isotope Dilution Analysis. Liquid Chromatography Ovenriew. 

Apart from the mentioned technological advances, the separation power and selectivity of HPLC have been drastically improved over the last years. In this context, ultra-high-performance liquid chromatography coupled with mass spectrometry (UHPLC-MS) represents a relatively new category of analytical coupled techniques that respects the principles of the classic HPLC-MS while bringing some improvements in chromatographic resolution, speed, and sensitivity. 

Ion-exchange chromatography inductively coupled plasma—mass spectrometry (IC-ICP-MS) uses anion or cation ion-exchange resins or other solid phases with ion-exchange properties to separate ionic species prior to their sequential introduction into the ICP. Ions are separated according to their ionic affinity to the resin, rather than their differences in solubihty, which is the principle used in liquid chromatography. Separations are also highly dependent on the properties of the mobile phase. The mobile phase is usually composed of an aqueous-salt solution, which competes for the weakly electrostatically bonded analyte species. 

A very recent volume edited by Berthed (2002) is on countercurrent chromatography - the support-free liquid stationary phase. Ebdon et al. (1987) review directly coupled liquid chromatogramphy-atomic spectroscopy. The review by Uden (1995) on element-specific chromatographic detection by atomic absorption, plasma atomic emission and plasma mass spectrometry covers the principles and applications of contemporary methods of element selective chromatographic detection utilizing AA, AES and MS. Flame and furnace are considered for GC and HPLC, while MIP emission is considered for GC and ICPAES for HPLC. Combinations of GC and HPLC with both MIPAES and ICPAES are covered and supercritical fluid chromatographic (SFC) and field flow fractionation (FFF) are also considered. 

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