C-trap

The contents of the trap are transferred to the glass vacuum line by vacuum distillation. The contents are condensed into a 150-mL stainless steel cylinder containing an excess of 20% aqueous sodium carbonate and allowed to react with occasional shaking for 24 h The products are fracbonated through 5, -78, -131, and -196 °C traps under active pumping (3 pm of Hg) The product (8.5 g) is collected in the -131 °C tiap. The remaining vacuum line traps were virtually empty. 

To determine whether the 8CB droplets condensed above 41°C (trapped in the isotropic phase) sit on a trilayer or on bare silicon, we used the ATM tip to mechanically spread the droplets and thus accelerate their conversion to a stable configuration. The SPFM images shown in Fignre 15 were obtained after such tip-induced spreading. A layered structure with 32-A-high steps typical of the smectic phase is obtained. The first, or bottom, layer is 41 A thick, while the layers above it are all 32 A thick. This indicates that the bottom layer of the film is a trilayer and that the remaining snbstrate is dry silicon, i.e.. 

Purge at 85°C, trap on Tenax sorbent trap, heat and desorb, backflush to GC... 

MS11 capabilities. However, ions may then subsequently be detected at unit resolution using an electron multiplier or, alternatively, focused in a C-Trap (Figure 5.2) and then transferred and detected at high resolution using the Orbitrap. In our experience with the LTQ-Orbitrap, ions may be measured with a resolution of approximately 60,000 with online LC/MS in the full scan mode. 

A -78°C trap to collect all volatile materials should be placed between the aspirator and the reaction vessel during this evaporative distillation. 

Chloryl fluoride is slightly less volatile than CIF3O2, and, therefore, most of it can be removed from CIF3O2 by fractional condensation in a —112°C trap. The remaining FClOg, however, has to be removed by complexing with BFg ... 

The injector was programmed to return to the split mode after 2 min from the beginning of a run. Split flow was set at 50 mL/min. The injector temperature was held constant at 270 °C. Trap temperatures, manifold temperatures, and transfer line temperatures were 250, 50, and 280 °C, respectively. 

The GC/MS-MS analyses were performed on a Varian 3800 gas chromatograph (Varian Chromatography Systems, Walnut Creek, CA) equipped with a 1079 split/splitless injector and a ion trap spectrometer (Varian Saturn 2000, Varian Chromatography Systems) with a waveboard for MS-MS analysis. The system was operated by Saturn GC/MS Workstation v5.4 software. The MS-MS detection method was adapted from elsewhere. PCBs were separated on a 25 m length X 0.32 mm i.d., CPSil-8 column coated with a 0.25 pm film. The GC oven temperature program was as follows 90 °C hold 2 min, rate 30 °C/min to 170 °C, hold for 10 min, rate 3 °C/min to 250 °C, rate 20 °C/min to a final temperature of 280 °C, and hold for 5 min. Helium was employed as a carrier gas, with a constant column flow of 1.0 mE/min. Injector was programmed to return to the split mode after 2 min from the beginning of a run. Split flow was set at 50 mL/min. Injector temperature was held constant at 270 °C. Trap temperatures, manifold temperatures, and transfer line temperatures were 250, 50, and 280 °C, respectively. 

Collect on Tenax-TA desorb thermally inject by cryotrap Collect on Tenax-GC desorb thermal 1y Purge from liquified fat at 115°C, trap on Tenax / silica gel, thermal desorpti on Macerate in water purge with inert gas trap on Tenax-GC desorb thermally Purge from water-serum mixture containing anti foam reagent at 115°... 

Catalysts Reagent Temperature (°C) Trapping reagent Products ... 

Azobis-(2-methylpropionitrile) (ABN) was recrystallized from methanol. Azobis-l-cyanocyclohexane (ABC) was furnished by D. E. Van Sickle, and di-ferf-butylperoxalate (DBPO) was prepared by a literature procedure (2). Oxygen (99.9% ) was passed through a — 80°C. trap to remove trace amounts of water. 

Figure 4.11 Transient current and voltage waveforms showing effect of trapping and detrapping, (a) No trapping, (b) Trapping, no detrapping, (c) Trapping and detrapping (from Ref. [13]).

The — 78 °C trap and molecular sieve trap are designed to remove CH3CN. Since traces of moisture are inevitably present, this means that HC1 is also likely to be produced the molecular sieve trap will also remove it. An alternate... 

Following the reaction, the borazine collected in the liquid-nitrogen traps (I) is further purified by a single vacuum fractionation,9 as shown in Figure 2, through a U-trap series cooled at — 45°C (A), — 78°C (B), and — 196°C (C). In the — 78°C trap (B), 13.1 g (0.16 mol, 60% yield based on starting BH4) of borazine is condensed. No other products are detected in the IR, nB NMR, H NMR (see below), or GC/MS spectra of the product, and its vapor pressure (85 Torr at 0°C) matches the literature value,10 indicating that the borazine is obtained in excellent purity. 

Difluoroethene (0.19 g. 3 mmol) was dissolved in CF3C1 (2 mL) at — 95 C. The alkcnc was ozonized to 100% completion using flow rates of 0.10-0.15 mL of 03 min" . Immediately after the completion of ozonolysis. the volatile material in the reactor was allowed to w arm and was lrap-to-trap distilled through - 140 and — 196 C traps. The contents of the — 196 C trap were examined by gas-phase IR spectroscopy and contained only CF3C1 and a small amount of unreacled o/one. SiF4 and HCOF. 

The contents of the — 140 C trap were purified further by another trap-to-lrap distillation through traps cooled to —95. — 116, and — 196 C. The contents of the — 95 C trap were found to be m-2,3-difluorooxirane(n.v-44), ci.s- and ow -3.5-difluoro-1,2,4-trioxolane(43), and small amountsofrK,m-l,2,3-trifluorocyclopropane and HC02H. As previously mentioned the ci.v.fM-cyclopropane is formed only on ozonolysis of the Z-alkene. The — 116 C trap contained Pw v-2.3-difluorooxirane (lrans-44), m.trcms-1,2,3-trifiuorocyclopropane. and small amounts of the cw-epoxide. The — 196 C trap contained mostly HCOF and small amounts of SiF4. The contents of each trap were further purified by preparative GC (17 ft x 0.25 in. Teflon column packed with 10% Halocarbon oil on 40 60 mesh Chromosorb T at 22 C). 

One of the key developments in the development of thermal desorption devices was the possibility for cryofocusing systems that have the advantage of injection-like samples. A short section of capillary tubing at liquid nitrogen temperatures (i.e., -160°C) traps the volatiles. When capillary columns replaced packed columns as the standard, complete flow from the desorption trap (5 ml/min minimum) to the capillary columns ( 1 ml/min) was possible through the use of cryofocusing. The split injection interface was another development that splits the flow so that only a part of the desorbed volatiles entered the column. While this allowed the need for cryofocusing to be circumvented, sensitivity was lost due to the split. 

The nitrogen flow is stopped, and the two liquid-nitrogen traps are isolated. The phosphine is purified by evacuating the traps (still at —196°C.) and distilling into a vacuum line through a —131°C. trap (rc-CsH12 slush) into a —196°C. trap. Typical yields by this method are 75-77%. 

This operation ensures the transfer of the bulk of the perchloryl fluoride from the reaction vessel and associated lines. Concurrently, some anhydrous hydrogen fluoride from the — 40 C. traps will tend to transfer also (vapor pressure of hydrogen fluoride at -40°C. = ca. 50 mm.) but will be absorbed in the sodium fluoride scrubber. 

The concurrent method allowed aqueous beef slurries to be irradiated (in the presence of oxygen) and at almost the same time volatile components were removed at pressures of about 25 mm. of Hg and at a temperature around 32°-36°C. When irradiation was carried out before distillation, the cans of irradiated beef were opened immediately or after G-months storage at ambient temperature. The beef was then slurried, and distillation was carried out in the usual manner 15,16). Nonirradiated beef slurries were distilled in exactly the same way as were periodic blank distillations of distilled water, to allow detection of contaminants or artifacts contributed by the distillation apparatus. In all cases, one condensate was collected at 0°C. (distillate) and another at — 78°C. (traps). 

Fig. 2 Representation of binding sites heterogeneity high affinity site in macropore (A) and micropore (F), and lower affinity sites (B) in macropore, (C) trapped template, (E) embedded site, (D) highest affinity site with shape selectivity from polymer. Reproduced from [12] with permission of The royal Society of Chemistry...

Due to its radically different design, the latest hybrid linear ion trap FTMS instrument, the LTQ-Orbitrap (Fig. 5.6), does not suffer from the time-of-flight effect. In this instrument, the superconducting magnet and the ICR cell are replaced by an electrostatic trap (C-trap) and so distances traveled by the ions from one MS device to the other are much smaller in addition a radically different ion transfer mechanism virtually eliminates any possibility for a time-of-flight effect (Makarov,... 

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