Tandem analytical techniques

Tandem technique An alternative term for the combination of two or more analytical techniques. 

All previous discussion has focused on sample preparation, i.e., removal of the targeted analyte(s) from the sample matrix, isolation of the analyte(s) from other co-extracted, undesirable sample components, and transfer of the analytes into a solvent suitable for final analysis. Over the years, numerous types of analytical instruments have been employed for this final analysis step as noted in the preceding text and Tables 3 and 4. Overall, GC and LC are the most often used analytical techniques, and modern GC and LC instrumentation coupled with mass spectrometry (MS) and tandem mass spectrometry (MS/MS) detection systems are currently the analytical techniques of choice. Methods relying on spectrophotometric detection and thin-layer chromatography (TLC) are now rarely employed, except perhaps for qualitative purposes. 

Widespread interest has developed during the last few years in a new analytical technique which uses a tandem electrostatic acclerator as one element of a double mass spectrometer [1-19]1. With this technique, individual atoms of many nuclear species from most areas of the periodic table can be identified with good efficiency and in the presence of an almost zero background of unwanted atoms and molecular species of the same mass. 

At present, within modern analytical techniques, only GC and LC combined with MS and tandem MS, respectively, provide sufficient selectivity and inherent sensitivity in analysing surfactants in complex samples. 

The development of tandem MS techniques has undisputably contributed significantly to the basic understanding of fundamental aspects of nitro compounds. Further possible analytical applications have benefited from an advanced use of ion chemistry. In particular, the MS studies on nitroarenes (nitro-PAHs), which are known to be highly mutagenic, should be emphasized as fast and reliable analytical strategies. 

Natural products and natural-like compounds, generally coming from microbes, plants, sponges and animals [2, 3] may be fully identified and quantified by means of modem and advanced analytical techniques, such as high-performance liquid chromatography (HPLC) coupled to various detectors - from the most common UV/Vis to mass spectrometry and tandem mass spectrometry (HPLC-MS and HPLC-MS/MS). The role of MS is to provide quantitative and qualitative information about mixtures separated by liquid chromatography [4],... 

However, mass spectrometry itself offers two additional degrees of freedom . One can either resolve the complexity of a sample by going to high or even ultra-high mass resolution or one can employ tandem MS techniques to separate the fragmentation pattern of a single component from that of others in a mixture. [2,3] In practice, the coupling of separation techniques to mass spectrometry is often combined with advanced MS techniques to achieve the desired level of accuracy and reliability of analytical information. [1,7,24-27]... 

A major consequence of using regulatory limits based on degradant formation, rather than absolute change of the API level in the drug product, is that it necessitates the application and routine use of very sensitive analytical techniques [ 10]. In addition, the need to resolve both structurally similar, as well as structurally diverse degradants of the API, mandates the use of analytical separation techniques, for example, HPLC, CE, often coupled with highly sensitive detection modes, for example, ultraviolet (UV) spectroscopy, fluorescence (F) spectroscopy, electrochemical detection (EC), mass spectroscopy (MS), tandem mass spectroscopy (MS-MS) and so forth. 

They are highly efficient initiators since they are all converted to propagating species at the very early stage of the reaction. Theoretical treatments,198 and the use of advanced analytical techniques, for example, electrospray ionization tandem mass spectrometry199 have provided useful information about the nature and properties of intermediates involved in metathesis. 

Superior sensitivity, efficiency, and specificity have made high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS), the predominant analytical technique for characterization and quantitative analysis of metabolites (Kostiainen et al., 2003 Ma et al., 2006 Prakash et al., 2007). Ion trap, triple-quadrupole, and quadmpole time-of-flight (Q-TOF) mass spectrometers are routinely used to profile and characterize metabolites in plasma and excreta (Ma et al., 2006). The combination of scan types and features available on mass spectrometers of different design (product ion, MS", neutral loss, precursor ion scans, accurate mass measurements) allows identification and characterization of putative and unexpected metabolites with or without little prior knowledge of biotransformation pathways of a given dmg molecule. 

In recent years the rapid development of high-sensitivity analytical techniques such as mass spectrometry (MS) and liquid chromatography (LC) supported the investigation of the endocannabinoids as part of a complex lipid network. The identification of lipid components of the endocannabinoid system can be achieved in a single analytical step by state-of-the-art platforms such as tandem mass spectrometry (MS/MS), which provides the detailed structural information necessary for characterization of lipids and increases specificity in complex biological matrices. Furthermore, the implementation of ionization techniques such as electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) allow the coupling of LC to MS, and permits the separation and analysis of endocannabinoids with greater speed and accuracy. 

Moody, C.A., Kwan, W.C., Martin, J.W., Muir, D.C.G. and Mabury, S.A. (2001) Determination of perfluorinated surfactants in surface water samples by two independent analytical techniques liquid chromatography/tandem mass spectrometry and 19F NMR. Anal. Chem., 73, 2200. 

Tandem mass spectrometry (MS/MS) is a new analytical technique applied to problems in food and flavor analyses. Rapidity of analysis, a high discrimination against chemical noise, and the ability to analyze mixtures for functional groups are attributes of MS/MS that make it attractive for such problems. Sanple collection and pretreatment differ frcm methods used in GC/MS. Correct choice of an ionization method is paramount. Daughter ion MS/MS spectra are used for conpound identification via comparison with those of authentic compounds, and parent and neutral loss spectra are useful in functional group analysis. Applications to direct analysis of volatiles emitted from fruits and to spice analyses are considered. 

Background. As an analytical technique, tandem mass spectrometry is just entering its second decade of development. The variety of reported applications belies its relative youth. Tandem mass spectrometry (MS/MS) grew out of early work which used metastable ion transitions in order to establish ion structures and interrelationships. After extensive applications to ion structural studies, its usefulness in direct catplex mixture analysis became apparent with the early work of Cooks (1-3). Its successes in problem solving are summarized in a recent book edited by McLafferty (4). New, with several ccnmercial instruments available, MS/MS is being evaluated for application in several new areas, including biochemical analysis, forensic chemistry, and food and flavor analyses. The principles of MS/MS will be surmarized in the first part of this chapter. The second part of the chapter will deal with the reported applications of MS/MS to flavor analysis. 

Liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) is the analytical technique of choice for measurement of ionic PFCs in environmental samples. Recent reviews on the use of this technique for the analysis of PFCs have been published by de Voogt and Saez [111] and Villigrasa, Lopez de Alda and Barcelo [96]. 

Hyphenated technique The combination of two analytical techniques (see also Hybrid technique and Tandem technique). 

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