Techniques, hyphenated

It is a logical step to analyse the volatiles evolved during a TGA or STA experiment. The two techniques currently generating most interest are those of mass spectrometry (quadrupole resolution sufficient) and FTIR (one wave-number resolution sufficient). The volatiles are swept by an inert purge 

In recent years, the coupling of ion chromatography with element-specific detection methods has increasingly gained importance. Element-spedfic detection is carried out with atomic spectrometric techniques induding atomic absorption spectrometry (AAS), atomic emission spectrometry (ICP-OES) as well as the coupling between ICP and mass spectrometry (ICP-MS). 

The coupling of an atomic absorption spectrometer with an ion chromatograph is relatively straightforward. It only requires a capillary that connects the separator coluirm outlet with the nebulizer of the AAS instrument [87]. When 

The determination of the different forms (e. g. compounds or complexes) in which an element occurs (often referred to as the speciation of an element and speciation analysis, respectively [28]) is in most cases performed by hyphenated techniques. These are the combination of a high-performance separation technique such as gas or liquid chromatography, or electrophoresis, and an element- or compound-specific detector [29]. While the former provides the separation of the different elemental species prevalent in the sample, the latter brings selective and sensitive detection. In the case of AAS, only the hyphenation with gas and Hquid chromatography, respectively, has gained importance. The combination of atomic absorption spectrometry and electrophoresis has never proven successfiil, obviously due to the incompatibility of the extremely low flow rates of electrophoretic separations with the aspiration volumes of flame atomisers and the difficulties of interfacing the two techniques. 

Because SFE is a sample extraction-separation technique, it must precede other steps of the analytical process if the type and content of the species of interest in the extract are to be accurately determined. The analytical equipment required to develop the steps following extraction can either be coupled on-line to it or performed off-line. The way the extract should be treated with a view to identilying or quantifying the target analytes depends on its complexity and the type of information required. Thus, the analytes may require clean-up, individual separation or some other treatment prior to reaching the detector. 

The off-line mode is to be preferred when a deep knowledge of the features of the extraction process concerned is required as this will allow such experimental variables as pressure, temperature, SF polarity and flow-rate, extractor volume and dimensions, extraction time and sample size to be optimized. 

It should be noted that the dissolution of the samples of higher acrylic-acid content requires the addition of DMAc to chloroform. When running a conventional gradient from chloroform to DMAc, breakthrough peaks are observed, since the polar DMAc prevents adsorption of the polymer molecules onto the stationary phase. 

FIGURE 5.6 Coupling of separation methods with spectroscopic and spectrometric 

Comprehensive two-dimensional liquid chromatography—size-exclusion chromatography (LC x SEC) was refined considerably over the last 20 years. It allows characterizing by-products and impurities. 

Liquid Chromatography—Fourier-Transform Infrared Spectroscopy 

Hyphenation of Fourier-transform infrared spectroscopy (FTIR) with different modes of liquid chromatography is a useful approach to 

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Jinno, K., Hyphenated Techniques in Supercritical Fluid Chromatography and Extraction, Elsevier, Amsterdam, 1992. 

Silberring, J., Ekman, R., Desiderio, D.M., and Nibbering, N. M., Mass Spectrometry and Hyphenated Techniques in Neuropeptide Research, Wiley Interscience, New York, 2002. 

T. Provder, M. W. Urban, and H. G. Barth, eds.. Hyphenated Techniques in Polymer Characterisation Thermal-Spectroscopic and Other Methods, American Chemical Society, Washington, D.C., 1994. 

NMR MIXTURE ANALYSIS USING HYPHENATION TECHNIQUES AND SOFTWARE... 

Initial results prove the high potential of LA-based hyphenated techniques for depth profiling of coatings and multilayer samples. These techniques can be used as complementary methods to other surface-analysis techniques. Probably the most reasonable application of laser ablation for depth profiling would be the range from a few tens of nanometers to a few tens of microns, a range which is difficult to analyze by other techniques, e. g. SIMS, SNMS,TXRE, GD-OES-MS, etc. The lateral and depth resolution of LA can both be improved by use of femtosecond lasers. 

H. Casablanca, J.-B. Graff, P. Jame, C. Pemrcchietti and M. Chastr ette, Application of hyphenated techniques to the cl U omatogr aphic authentication of flavours in food products and perfumes , 7. High Resolut. Chromatogr. 18 279-285 (1995). 

In pharmaceutical analysis the detection of impurities under a chromatographic peak is a major issue. An important step forward in the assessment of peak purity was the introduction of hyphenated techniques. When selecting a method to perform a purity check, one has the choice between a global method which considers a whole peak cluster (from the start to the end of the peak), and evolutionary methods, which consider a window of the peak cluster, which is... 

Volume 17 Data Analysis for Hyphenated Techniques, by E.J. Karjalainen and U.P. Karjalainen... 

Separation and detection methods Very interesting hyphenated techniques have been developed for the separation and measurement of organic and inorganic lead spe-... 

Before the advent of modern hyphenated techniques (GC/HS, GC/FTIR), numerous qualitative physical and chemical tests were devised for the identification of peaks in a gas chromatograa [705]. For the most part these tests were simple to perform, inexpensive, required minimum instrument modification and, in a few instances, provided a simple and easy solution to an otherwise complex problem. They still have some value today as spectroscopic techniques do not solve.all problems. 

The spectrum of new analytical techniques includes superior separation techniques and sophisticated detection methods. Most of the novel instruments are hyphenated, where the separation and detection elements are combined, allowing efficient use of materials sometimes available only in minute quantities. The hyphenated techniques also significantly increase the information content of the analysis. Recent developments in separation sciences are directed towards micro-analytical techniques, including capillary gas chromatography, microbore high performance liquid chromatography, and capillary electrophoresis. 

F. Reche, M.C. Garrigos, M.L. Marin and A. Jimdnez, Abstracts 7th Inti. Symposium on Hyphenated Techniques in Chromatography and Hyphenated Chromatographic Analyzers (HTC-7), Bmges (2002), paper P132. 

Major advantages of LVI methods are higher sensitivity (compare the 100-1000 iL volume in LVI to the maximum injection volume of about 1 iL in conventional splitless or on-column injection), elimination of sample preparation steps (such as solvent evaporation) and use in hyphenated techniques (e.g. SPE-GC, LC-GC, GC-MS), which gives opportunities for greater automation, faster sample throughput, better data quality, improved quantitation, lower cost per analysis and fewer samples re-analysed. At-column is a very good reference technique for rapid LVI. Characteristics of LVI methods are summarised in Tables 4.19 and 4.20. Han-kemeier [100] has discussed automated sample preparation and LVI for GC with spectrometric detection. 

H.H. Hill and D.A. Atkinson, in Hyphenated Techniques in Supercritical Fluid Chromatography and Extraction (K. Jinno, ed.), Elsevier, Amsterdam (1992), pp. 1-8. 

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