GC—MS jet separator

Interfacing micro-LC and MS via a capillary inlet interface coimected to a GC-MS jet separator was described in 1978 by Takeuchi et al. [55]. In the period until 1982, this system was subsequently developed towards a vacuum nebuhzer, in which the column effluent is pneumatically nebulized into a modified jet-separator type of device [56-57]. The instrumental developments of the vacuum nebulizer interfaces are discussed in Ch. 4.3. Pneumatic nebulization of column effluents directly into the Cl somce was described by a number of groups [58-61]. A so-called helium interface for the introduction of organic solvents was described by Apffel et al. [59]. It was primarily applied to the analysis of pesticides in aqueous samples. Although the system was commercially available, it did not find wide application. 

MS has more analytical flexibility than FTIR, but interfacing a thermal analyzer is more difficult because of the low operating pressure required for MS. MS instruments typically operate at approximately 10" torr, while thermal analyzers are usually at atmospheric pressure. One approach is to evacuate the thermal analyzer, but the common method used is a differential pumping system such as that used for GC-MS. This reduces the pressure from the thermal analyzer in several stages prior to allowing the gas flow into the mass analyzer. A commercial interface for a thermal analyzer-MS system, shown in Figure 16.31, uses a supersonic jet to skim analyte molecules into the MS, in a manner similar to the jet separators used in GC-MS. Jet separator operation is discussed in the chapter on GC (Chapter 12) under hyphenated techniques. 

Separator GC/MS interface. An interface in which the effluent from the gas chromatograph is enriched in the ratio of sample to carrier gas. Separator, molecular separator, and enricher are synonymous terms. A separator should generally be defined as an effusion separator, a jet separator, or a membrane separator. 

GC/MS Hewlett Packard HP5890 connected to HP5971 mass detector with a jet separator... 

Wall-jet cell (LC) 589 Watson-Biemann separator (GC/MS) 963 WCOT... 

A gas chromatograph (GC) can be used for the chromatographic separation of volatile analytes in complex mixtures prior to mass spectrometric analysis. This becomes especially advantageous if the GC elutes directly ( online ) into the ion source of a mass spectrometer, so-called GC-MS coupling. [63-65] Packed GC columns with a high flow can be connected via a jet-separator, but these are almost out of use at present. [66] Capillary columns provide flow rates in the order of a few milliliters per minute, therefore their back end can be connected directly at the entrance of the ion volume. 

In early GC-MS with paeked GC columns eluting several tens of milliliters per minute most of the flow had to be separated before entering the ion source to prevent the vacuum system from breakdown. [4,29,34] This was either effected by a simple split to divide the effluent in front of the inlet system by a faetor of about 1 100 or by means of a more elaborate separator, the jet separator being the best... 

Useful interface which Is applicable to a wide range of molecules. The volatile solvent molecules are stripped from the sample and lost in a process similar to that used in the early jet separators used in GC-MS. The heavier sample molecules enter the MS and can be ionised by the standard methods of El, PICI or NICI. Gives spectra with El fragmentation which can be referred for identification to El spectral libraries built up over many years. No solvent background thus sensitive to the 1(h g level. Solvent flow rate up to 1 ml/min, mass range up to 1000 amu... 

This method uses purge and trap with GC-MS (with a wide-bore capillary column, a jet separator interface, and a quadrupole mass spectrometer). 

Methods exist for detection of benzene in other environmental media such as cigarette smoke, gasoline, and jet fuel and its fumes (Brunnemann et al. 1989 Byrd et al. 1990 Ludwig and Eksteen 1988 Poole et al. 1988). HPLC/UV, GC/FID, and GC/MS separation and detection techniques have been used for these analyses. Sensitivity and reliability of these methods cannot be compared because of the lack of data. 

Further chromatographic peak identification also was carried out by interfaced GC-mass spectrometry (MS) using a Hitachi-Perkin Elmer RMU6L mass spectrometer interfaced through a jet separator (Scientific Glass Engineering Pty., Melbourne, Australia). 

In a vacuum nebulizer the column effluent is nebulized into an evacuated chamber that is connected to the ion source by means of a heated tube. The design of these interfaces is based on jet separator interfaces used in packed column GC-MS. The development of these interfaces took place in the Japanese research group of... 

Analyte-enrichment interfaces for LC-MS show similarities with the interfaces used in packed colunm GC-MS, such as the jet separator, the Watson-Biemann fritted-glass, or the membrane interface. Various analyte-enrichment interfaces have been developed for LC-MS application, as discussed in Ch. 3.3.2. In API, gas-phase analyte-emichment is performed by means of a molecular-beam system. The vaporized column effluent is sampled from an atmospheric-pressure spray chamber via a differentially pumped expansion chamber system [3]. 

GC-MS Analysis and Identification. A portion of the acidic fractions were quantitatively converted to methyl esters using a BF3-methanol reagent. The procedure used was that of Metcalfe and Schmitz (8). The esterified acidic fractions were analyzed using a coupled gas chromatograph-mass spectrometer (GC-MS) system consisting of a Varian Moduline 2700 gas chromatograph equipped with a flame ionization detector interfaced by a jet separator to a Du Pont Instruments Model 21-490 mass spectrometer. A 10 ft x 1/8 in o d stainless steel column packed with 10% stabilized DEGS on 80/ 100 mesh Chromosorb W AW DWCS was used. The He flow rate was 30 ml/min. The column temperature was held 5 minutes at 30°C, then... 

Figure 7.7 GC-MS interfaces, (a) Direct injection from capillary columns, (b) Open slit interface. (c) Molecular jet separator, (d) Effusion separator, (e) Diffusion separator.

Figure 9.4. A jet separator for GC-MS with high-flow rate columns.

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