Coupling of GC with

GC-AAS has found late acceptance because of the relatively low sensitivity of the flame graphite furnaces have also been proposed as detectors. The quartz tube atomiser (QTA) [186], in particular the version heated with a hydrogen-oxygen flame (QF), is particularly effective [187] and is used nowadays almost exclusively for GC-AAS. The major problem associated with coupling of GC with AAS is the limited volume of measurement solution that can be injected on to the column (about 100 xL). Virtually no GC-AAS applications have been reported. As for GC-plasma source techniques for element-selective detection, GC-ICP-MS and GC-MIP-AES dominate for organometallic analysis and are complementary to PDA, FTIR and MS analysis for structural elucidation of unknowns. Only a few industrial laboratories are active in this field for the purpose of polymer/additive analysis. GC-AES is generally the most helpful for the identification of additives on the basis of elemental detection, but applications are limited mainly to tin compounds as PVC stabilisers. 

Another emerging method is the coupling of GC with field-ionization MS (GG-FI-MS) [74]. Field-ionization MS yields essentially molecular ions for all hydrocarbons, except isoparaffins, with uniform sensitivities within each compound class [75]. This would gready simplify calibration since each class would require only one calibration compound. 

Krupp, E. M., P6cheyran, C., Brenner, I. B., Shaw, P., Nash, M., and Donard, O. F. X. (2003) Speciation analysis using a new commercial interface for the coupling of GC with ICP-MS. Oral presentation at Post Symposium CSIXXXIII, Almunecar, Spain. 

De Smaele, T., Moens, L., and Dams, R. (1997) Coupling of GC with ICP-MS for trace metal speciation. In Plasma Source Mass Spectrometry — Developments, Applications (eds G. Holland and S. D. Tanner), The Royal Society of Chemistry, Cambridge, pp. 109-23. 

From the very early stages of development of modem MS, the value of its combination with chromatography was quickly recognized. The coupling of GC with MS was a natural... 

Supercritical fluid extraction (SFE) has been extensively used for the extraction of volatile components such as essential oils, flavours and aromas from plant materials on an industrial as well as an analytical scale (61). The extract thus obtained is usually analysed by GC. Off-line SFE-GC is frequently employed, but on-line SEE-GC has also been used. The direct coupling of SEE with supercritical fluid chromatography (SEC) has also been successfully caried out. Coupling SEE with SEC provides several advantages for the separation and detection of organic substances low temperatures can be used for both SEE and SEC, so they are well suited for the analysis of natural materials that contain compounds which are temperature-sensitive, such as flavours and fragrances. 

H.-G. Schmarx, A. Mosandl and K. Grob, Stereoisomeric flavour compounds. XXXVIII dkect chir ospecific analysis of y-lactones using on-line coupled EC-GC with a chkal separation column , Chromatographia 29 125-130 (1990). 

Schafer C, Fu GC (2005) Catalytic asymmetric couplings of ketenes with aldehydes to generate enol esters. Angew Chem Int Ed 44 4606-4608... 

A recent extension of the scope of SPE-GC and SPE-GC-MS concerns the use of AED detection with its multielement detection capability and unusually high selectivity. Hankemeier [67] has described on-line SPE-GC-AED with an on-column interface to transfer 100 iL of desorbing solvent to the GC. The fully on-line set-up is characterised by detection limits of 5-20 ngL because of quantitative transfer of the analytes from the SPE to the GC module. On-line coupling of SPE with GC is more delicate than SPE-LC, because of the inherent incompatibility between the aqueous part of the SPE step and the dry part of the GC system. 

Principles and Characteristics Gas chromatogra-phy/infrared spectrometry systems couple the separation capability of GC with the selectivity for functional... 

The identification of GC peaks other than through retention data, which are sometimes ambiguous or inconclusive, can be facilitated by the direct interfacing of GC with infrared spectrometry (p. 378 et seq.) or mass spectrometry (p. 426 etseq.), so-called coupled or hyphenated techniques. The general instrumental arrangement is shown in Figure 4.29(a). 

Cyclization by amidomercuration has been reported (391). Reaction of N-methoxycarbonyl-6-aminohept-l-ene (211) with mercuric acetate gave the organomercurial (212). Reductive coupling of 212 with l-decen-3-one in the usual way gave the cis and trans isomers (213). Successive treatment of 213 with ethanedithiol, Raney nickel, and ethanolic hydrogen chloride afforded ( )-sole-nopsin A (Id, 2 parts) and its isomer (Ic, 3 parts), which were separable by preparative gas chromatography (GC) (Scheme 5) (391). 

A very exciting development in multidimensional separation involves the coupling of LC to GC or other techniques, such as capillary electrophoresis (CE). Online coupling of LC with multidimensional GC has allowed efficient determination of the stilbene hormones in corned beef (3), whereas LC-GC coupling permitted determination of levamisole residues in milk (4). With these hyphenated techniques, the potential of selective separation is becoming increasingly apparent. 

One of the first reported couplings of GC-ICP-MS was by Van Loon et al. [115], who used a coupled system for the speciation of organotin compounds. A Perkin-Elmer Sciex Elan quadrupole mass filter instrument was used as the detector with 1250 or 1500 W forward power. The GC system comprised a Chromasorb column with 8 ml min 1 Ar/2 ml min-1 02 carrier gas flow with an oven temperature of 250°C. The interface comprised a stainless-steel transfer line (0.8 m long) which connected from the GC column to the base of the ICP torch. The transfer line was heated to 250°C. Oxygen gas was injected at the midpoint of the transfer line to prevent carbon deposits in the ICP torch and on the sampler cone. Carbon deposits were found to contain tin and thus proved detrimental to analytical recoveries. Detection limits were in the range 6-16 ng Sn compared to 0.1 ng obtained by ETAAS, but the authors identified areas for future improvements in detection limits and scope of the coupled system. 

The use of LC also has increased in use in recent years, driven by greater sensitivities of the detectors. Traditional ultraviolet (UV) and photo diode-array detectors were frequently employed in triazine analysis, but advances in source designs have provided efficient coupling of MS with LC. The advantage of LC is the ability to analyze polar metabolites not amenable to analysis using GC. Recent progress in LC/MS/MS instrumentation has enabled the direct aqueous injection (DAI) of a water sample without prior cleanup. 

With the successful implementation of differentially-pumped external ion sources, FTMS is rapidly becoming a routine mass spectrometric technique. Medium-pressure interfaces for the coupling of GC, LC, FAB, and liquid SIMS into the external ionizer are currently under development, and should become available in the near future. 

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