Hyphenated separation techniques

Liquid chromatography Liquid chromatography-mass spectrometry (LC/MS) 174, 175 

Thin layer Thin layer chromatography-mass spectrometry (TLC/MS) 192, 193 

Superaitical fluid Supercritical fluid extraction-capillary gas chromatography- 196 

Fundamentals of Contemporary Mass Spectrometry, by Chhabif Dass Copyright 2007 John Wiley Sons, Inc. 

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Instrumental developments (e.g., of sector field instruments with multiple ion collection, introduced in 1992, or the insertion of collision and reaction cells in order to reduce disturbing isobaric interferences), the progress in applications for ultratrace analysis, also in combination with on line hyphenated separation techniques (HPLC, CE), especially routine capability as well as decreasing price and user friendly maintenance mean that sales are increasing by 10 % every year. To improve the analytical performance of ICP mass spectrometers for precise isotope ratio measurements (e.g., for geochronology or for the study of fine isotope variation in nature) powerful instrumentation with high mass dispersion and multiple ion collector systems instead of single ion collection are commercially available on the analytical market. 

Both CE-NMR and CEC-NMR have been established as powerful hyphenated separation techniques. The NMR sensitivity should be improved further in order for CE-NMR and CEC-NMR to become more widely applied techniques. One... 

Table 2.2 Summary of hyphenated separation techniques used in pharmaceutical analysis...

Today, the use of sophisticated and large capacity computers with faster and more wide ranging ADCs and DACs allows con tlete conttol of all the mass spectrometers functions, acquisition of data in several forms, and powerful post acquisition processing to automatically search the enormous data files for relevant information. A high degree of automation is possible including conttol of any hyphenated separation technique. The mass spectrometer operator can load the samples and then process the information at a comfortable work station away from the noisy laboratory as the instrument carries out the analyses. The scope of the computer s abilities will be exenplified by the exanples given as apphcations. 

For convenience, the book is organized into three parts and 15 chapters. Part I has five chapters that provide a detailed description of the instrumentation aspects of mass spectrometry. Topics in this section include modes of ionization (Chapter 2), mass analysis and ion detection (Chapter 3), tandem mass spectrometry (Chapter 4), and hyphenated separation techniques (Chapter 5). Mass... 

Recently, there is a strong shift from the isolation of compounds present in an extract to the search for bioactive natural compounds using rapid hyphenated separation techniques. Most of today s isolation protocols comprise in vitro assays, frequently coupled online to LC-MS isolation of natural products is still mainly carried out using multi-step isolation procedures. This review covers the methods for the extraction... 

However, most of the time, due to the complexity of the food samples and the need to minimize the sample treatment, that is, the chemical separation of the interferences from the compounds of interest, more powerful instrumental measurements, such as 2D spectroscopies, for example EEM fluorescence spectra, or hyphenated separation techniques, for example gas chromatogra-phy/MS (GC/MS), HPLC/DAD or HPLC/MS, are used. As mentioned in previous sections, obtaining a data table per sample is a much more natural scenario for the application of MCR techniques. In these instances, the typical strategy is to perform the simultaneous analysis of data tables related to standards of known concentration together with tables from unknown samples, in which the concentration(s) of the analyte(s) are determined. Either using multiset analysis or multiway analysis, these determinations benefit from the so-called second-order advantage, which means that analytes can be determined in the presence of interferences, even if those are absent from the calibration samples [48]. The reason why this second-order advantage exists is that MCR techniques describe the information of the compounds in separate concentration profiles and spectra, that is, they make a mathematicar separation of the information related to aU compounds in the analysed sample, analytes and interferences. Afterwards, only the information of the profiles related to the analytes is used for quantitation purposes. 

Erom a chemometric point of view, the EEM measurements hold the trilin-ear property, that is, the shape of the excitation and emissirm spectrum of a particular compound is invariant in all the samples analysed and, therefore, adapt optimally to the underlying PARAFAC model. The same cannot be said of the data coming from hyphenated separation techniques, where the elution... 

MCR techniques are also adaptable to handle responses of varying complexity, from single spectra to data tables coming from EEM measurements or hyphenated separation techniques. When either the problem to solve or the measurement to handle becomes very complex, multiset and multiway strategies can be applied that can work simultaneously with many data tables coming from different samples or experiments. Although many examples of... 

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