The Open Split Interface

In addition, the open-split interface also offers an automatic peak dilution capability. Due to the transfer of the analyte gases in a helium stream more than one interface can be coupled in parallel for alternate use to an isotope ratio MS via separate needle valves. 

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Two principal GC-MS interfaces are available for open-tubular GC columns. The so-called direct interface provides the highest possible detector sensitivity, whereas the open-split interface offers the least possible interference with chromatographic separation. With the direct interface, the column exit is routed from the GC oven through a heated transfer line directly into the ionization chamber. As long as the vacuum-pumping system can remove the carrier gas and maintain a sufficiently low pressure, the MS detector will function. Also, little chance exists for adsorptive loses of solute because the analytes contact only the GC column. 

The open-split interface dilutes eluted analytes with additional makeup gas and then splits the mixture into two fractions. An inert, fused-silica restrictor routes a portion of the sample-carrier gas mixture from the interface into the MS ionization chamber, whereas the remainder is vented to atmosphere. An open-split interface can affect the shapes and areas of peaks because solutes make contact with several items including the interface liner, the outer surfaces of the fused-silica column, and the restrictor, which can adsorb trace-level analytes if they are not properly deactivated (21). 

The second issue is to interface two detectors to a single GC. Since both the MS and the matrix isolation interface are destructive detectors, the sample is split in a 1 1 effluent splitter and half the sample is routed to each detector via a specially-designed open split interface (18). 

Volatiles isolated by the purge-and-trap method were analyzed by GC-MS using a Varian 3400 gas chromatograph coupled to a Finnigan MAT 8230 high resolution mass spectrometer equipped with an open split interface. Mass spectra were obtained by electron ionization at 70 eV and an ion source temperature of 250°C. The filament emission current was 1 milliampere and spectra were recorded on a Finnigan MAT SS 300 Data system. 

Another option is an open split interface which sucks the helium out before the sample goes on to the ionisation chamber. These can concentrate the analytes which gives a sensitivity advantage. 

Ether extracts were analyzed via GC/MS. A Varian Model 3700 gas chromatograph was used with a 0.32 mm id x 15 m fused silica column coated with a 1 micron film of DB-5. The following oven conditions were employed 5 min at 60 C then 5 C/min to 230 C and a final hold of 10 min. The column effluent was passed through an open split interface into a Finnigan model 705 Ion Trap Mass spectrometer. Identifications were achieved by comparison of the generated spectra to those of the NBS Library Compilation or to published spectra. Relative concentrations of the products were determined using the Ion Trap quantitation program. 

H2, N2, and CO, are then separated via a 5 A packed GC molecular sieve column (or similar). The gases then enter the IRMS for analysis via an open split interface. Only a small portion of the analyte gases (e.g., 0.3%) enters the IRMS. Hydrogen and oxygen isotope values can be measured from a single analysis [1,9,32,33]. 

H2O. The analyte gases then pass to the IRMS via an open split interface [1]. 

The hyphenated techniques CGC - MS. CGC -FTIR, and CGC-AED are generally used as stand-alone units. Due to the nondestructive character of FTIR, CGC-FTIR-MS units (Fig. 39) are possible and have been commercialized. The software then allows simultaneous recording of the infrared and mass spectra of the eluting compounds. In principle. CGC-FTIR-MS-AED is also jxrssible if an open split interface is applied for the CGC- FTIR-MS combination and the split-line is directed into the AED detector. The fundamental aspects of CGC-MS, CGC-FTIR and CGC-AED are discussed in [58], [59], and [60]. 

Figure 2.208 Open split interface to IRMS, effected by moving the transfer capillary to IRMS from the column inlet to the He sample flow region. CThermo Fisher Scientific.)...

In this application the GC is coupled to the mass spectrometer by an open split interface. A restrictor limits the carrier gas flow. Open coupling was chosen because the sensitivity of the ion trap GC-MS makes the concentration of large quantities of air superfluous. Open coupling dilutes the moisture, which may be contained in the sample, to an acceptable level so that cryofocusing can be used without additional drying. 

Transferline Open split interface Ramp 1 Final temperature Temperature 8°C/min 200°C 250 °C SGE type GMCC/90, mounted in the transfer line to the MS restrictor capillary 0.05 mm ID, adjusted to 2.5% transmission... 

A gas chromatograph equipped with a methylsilicone WCOT column is interfaced to a fast scanning mass spectrometer which is suitable for capillary column GC/MS analyses. The sample is injected either through a capillary splitter port or a cool on column injector capable of introducing a small sample size without overloading the column. The capillary column is interfaced directly to the mass spectrometer or by way of an open split interface or other appropriate device. 

The composites described in this chapter present superior quality which is demonstrated by their surface properties and performance in comparison with the parent components, GO and MOF or other inorganic phases. The important aspect of these composite formations is taking advantage of the promising properties of both phases and the creation of the hybrid, which exhibits the surface features of both phases and, as a bonus, new unique properties created on the interface. Moreover, the specific behavior of the individual components when placed together can open the door for new applications, not foreseen in this concise chapter. One should see that the detailed characterization of these materials as adsorbents is only one example of their application, which we could explore in detail. Nevertheless, the zinc (hydr)oxide story, where the enhanced photoactivity and water splitting reactions were noticed while investigating the adsorption phenomena, is one more example of the open book of the usefulness of such new materials. 

The system used to obtain the mass spectra was a Finnigan MAT Series 8230 instrument interfaced to a Carlo Erba 5360 Mega Series gas chromatograph (open split coupling via a flexible transfer line). 

The behaviour of iron in CO-CO2 atmospheres was studied by Pettit and Wagner over the temperature range 700-1000 °C, where wustite is stable. They found that the kinetics were controlled by reactions at the scale-gas interface, but carbon pickup was not observed. In contrast, Surman oxidized iron in CO-CO2 mixtures in the temperature range 350-600 °C, where wustite was not stable and magnetite exists next to the iron. He observed breakaway oxidation whose onset, after an incubation period, coincided with the deposition of carbon within the scale. This was explained by Gibbs and Rowlands by the penetration of the scale by CO2 which achieved equilibrium in the scale, dissolved carbon in the metal substrate, and then deposited carbon within the scale, which split open the scale and left the system in a state of rapid breakaway oxidation. The incubation period observed corresponded to the time required to saturate the metal substrate with carbon. 

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