IRMS

FTICR. Fourier-transform ion cyclotron resonance GC/IRMS. gas chromatography isotope ratio mass spectrometry... 

GD/IRMS. glow discharge isotope ratio mass spectrometry HPLC. high-pressure liquid chromatography... 

IKES. ion kinetic energy spectroscopy IRMS. isotope ratio mass spectrometry ISDMS. isotope dilution mass spectrometry ITMS. ion trap mass spectrometry LA. laser ablation... 

Nittile mbber is much like SBR in its physical properties. It can be compounded for physical strength and abrasion resistance using traditional fillers such as carbon black, siUca, and reinforcing clays. The primary benefit of the polymer is its oil and solvent resistance. At a medium ACN content of 34% the swell in IRM 903 oil at 70°C is typically 25—30%. Nitrile mbber processes on conventional mbber equipment and can be compression, transfer, or injection molded. It can also be extmded easily. 

The C4H7+ cation shown as the first entry in Scheme 5.5 is a particularly interesting example. It is a bridged ion which can be reached from isomeric cyclopropylmethyl and cyclobutyl irms. 

Fig. 13. Load vs. stiffness response for diamond hemisphere (R = 5.3 irm) vs. silicone polymer. Solid line is JKR Hi.

S. Nitz, B. Weinreich and F. Draweit, Multidimensional gas cliromatography-isotope ratio mass spectrometry (MDGC-IRMS). Part A system description and technical requirements , 7. High Resolut. Chromatogr. 15 387-391 (1992). 

Figure 10.4 Schematic representation of the multidimensional GC-IRMS system developed by Nitz et al. (27) PRl and PR2, pressure regulators SV1-SV4, solenoid valves NV— and NV-I-, needle valves FID1-FID3, flame-ionization detectors. Reprinted from Journal of High Resolution Chromatography, 15, S. Nitz et al, Multidimensional gas cliro-matography-isotope ratio mass specti ometiy, (MDGC-IRMS). Pait A system description and teclinical requirements , pp. 387-391, 1992, with permission from Wiley-VCFI.

Conventional IRMS requires relatively large sample volumes in a purified gaseous form. Recently, an on-line GC-IRMS system has been developed which combines the high purification effect of GC with the utmost precision of IRMS. Sometimes this system may not be Sufficient to determine characteristic minor components from complex matrices, and therefore MDGC-IRMS systems have been developed for the analysis of complex plant extracts and flavour components (25-27). 

Figure 10.4 shows a schematic representation of the multidimensional GC-IRMS System developed by Nitz et al. (27). The performance of this system is demonstrated with an application from the field of flavour analysis. A Siemens SiChromat 2-8 double-oven gas chromatograph equipped with two FIDs, a live-T switching device and two capillary columns was coupled on-line with a triple-collector (masses 44,45 and 46) isotope ratio mass spectrometer via a high efficiency combustion furnace. The column eluate could be directed either to FID3 or to the MS by means of a modified Deans switching system . 

In 1998, another application of MDGC-IRMS analysis was developed (25). A Siemens SiChromat 2-8 MDGC system, connected to a Finnigan MAT Delta S... 

The authors demonstrated the importance that correct use of the MDGC-IRMS System is essential for the achievement of precise and accurate measurements. Table 10.4 reports the GC-IRMS measurements of some standard reference materials, obtained with different cut conditions. As can be seen from this table, premature cuts result in 8 C values which are significantly higher than the true values, while delayed cuts give lower 8 C values. This fact indicates that the beginning of the peak is enriched in C, while the end is depleted. 

Table 10.4 GC-IRMS measurements of standard reference materials obtained under different cut conditions (25)...

Reprinted from Journal of High Resolution Chromatography, 21, D. Juchelka et al., Multidimensional gas chromatography coupled on-line with isotype ratio mass specti ometry (MDGC-IRMS) progress in the analytical authentication of genuine flavor components , pp. 145-151, 1998, with peraiission from Wiley-VCH. 

Forderung, /. furthering, etc. (see fordern). Fbrderungsnuttel, n. Ph/irm.) adjuvant. Forder-werk, n. conveyer elevator, lift. 

Sharp, Z.D. and Cerling, T.E. 1995 A laser GC-IRMS method for in-situ carbon and oxygen isotope analyses of carbonates and phosphates. Geological Society of America, Abstracts Program 27 A255. 

Fig. 25—Diagram of friction versus load of monolayer Cjo-Pst polymer molecules L-B film (point B, scan range 1 /irm).

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