Metal capillary columns

Figure 6.22. Ideal configuration for metal capillary columns (500-foot coil).

Dynamic Solid Phase Extraction The technique of dynamic solid phase extraction (SPDE) can be regarded as similar to NTD, where the rimer wall of the needle is coated with polymer. Lipinski introduced such a concept and attached a short section of metal capillary column coated with typical PDMS polymer to a gas-tight syringe [87]. The SPDE system is presented in Fig. 14.7 [88]. 

Metal capillary columns need to be cleaned to remove traces of extrusion lubricants by washing them with methylene dichloride, methanol, and then water. They should also be washed with dilute acid to remove any metal oxides or corrosion products that remain adhering to the walls. The acid is removed with water and the tubing is again washed with methanol and methylene dichloride and dried in a stream of hot nitrogen. 

The dissemination of GC-MS after 1965 strongly accelerated the development of Py-GC. til 1966, Simon and co-workers reported the first directly coupled Py-GC/MS system using a Curie-point pyrolyzer, a metal capillary column GC, and a rapid scanning MS." In 1968, huddemage and Hummel introduced field ionization MS(FI-MS) to simplify the mass spectra resulting from Py-MS. This technique dramatically improved the effectiveness of direct Py-MS, because of the simpler fragmentation in FI-MS. 

Partial pyrogram of the tetramer region for various PMMA samples, from Ref. 18. P)frolysis temp 500°C. Column metal capillary column (Frontier Lab Ultra AUoy-1,0.25 mm I. D. x 50 m, 0.15 iJm of immobilized PDMS) and programmed from 50 to 340°C at 4°C/min. Sample size ca. 0.4 mg. Detector FID. 

The preparation of capillary columns with porous polymers was first described by Hollis [21] in 1973. The styrene-divinylbenzene polymers were synthesized in situ inside the capillary. An example of the gas chromatographic separation possible on such columns is shown in Fig. 1-6 [21]. These columns were usable for hydrocarbon separations (note the separation by carbon number) but polar molecules such as alcohols have the tailing peaks characteristic of adsorption. In Hollis opinion, this is probably due to the same forces as are seen with a metal capillary column using apolar squalane without a tailing reducer [21]. 

De Zeeuw, J., Luong, J. The Design and Optimization of a Bench Top Fixed Gas Analyzer using Metal Capillary Column Technology. Ibid. 413p. 

The first column materials employed in the developmental stage of the technique were fabricated from plastic materials (Tygon and nylon) and metal (aluminum, nickel, copper, stainless steel, and gold). Plastic capillaries, which are thermoplastic in nature, had temperature limitations, whereas metallic capillary columns had the disadvantage of catalytic activity. Rugged, flexible stainless-steel columns rapidly became state-of-the-art, and were widely used for many applications, mainly for petroleum analyses. The reactive metallic surface proved to be unfavorable in the analysis of polar and catalytically sensitive species. In addition. 

For capillary columns fused siHca is the material of choice for the column container. It has virtually no impurities (<1 ppm metal oxides) and tends to be quite inert. In addition, fused siHca is relatively easily processed and manufacture of columns from this material is reproducible. In trace analysis, inertness of tubing is an important consideration to prevent all of the tiny amounts of sample from becoming lost through interaction with the wall during an analysis. 

Miniaturised SEC uses small fused-silica packed-capillary columns (0.32-1 mm i.d., 30-200cm) instead of relatively large metal columns. Miniaturisation puts stringent requirements on the quality of SEC columns. Advantages of ptSEC are (i) much smaller amounts of (toxic, expensive) solvents (ii) smaller samples (iii) better and easier temperature control (iv) increased detector compatibility (e.g. MS) and (v) greatly reduced... 

Metal-modified silicas were exposed to excess BuOOH vapor in order to generate the supported feri-butylperoxide complexes, followed by evacuation to remove PrOH and unreacted BuOOH. Reaction kinetics were monitored as the uptake of cyclohexene from the gas phase, using a ThermoNicolet Nexus FTIR spectrometer to measure the intensity of the o(C=C) mode. In situ spectra were recorded in custom-made glass reactors under vacuum. Formation of cyclohexene oxide was confirmed by GC/MS on an HP 6890 equipped with a DBI capillary column (J W Scientific). 

Electrospray ionization (ESI) is ideally suited as a detection technique for the online interfacing of liquid-phase separations (HPLC and CE) to MS, because it facilitates the transfer of analytes from the liquid phase of the HPLC or CE column to the gas phase of the MS. Also, it allows the detection of high molecular weight species, such as peptides. Three interface designs have been developed in the past 18 years for coupling CE with MS. The first CE-MS interface, coaxial sheath flow, was introduced by Smith and his group in 1987 (Olivares et al., 1987) and was improved upon in later work (Smith et al., 1988). Coaxial sheath flow is formed using two concentric metal capillaries, whereby the CE terminus and the makeup flow line are inserted into the... 

HPLC on a Cosmosil 5 Cis column, using a perchloric acid-acetonitrile eluent (pH 7.6), followed by CLD in the presence of hydrogen peroxide and bis(2,4,6-trichlorophenyl) oxalate (42), was applied to the determination of 1-aminopyrene (43a) and various diaminopyrenes (43b-d). Ascorbic acid was added to avoid oxidative degradation of the aminopyrenes in the presence of metals LOD in the sub-fmol range (SNR 3)147. A fast (less than 10 min) HPLC-ELCD method was proposed for determination of dopamine (19b) and its metabolites in microdialysates, using packed fused silica capillary columns LOD 0.05 Xg/L of dopamine in a 2 XL sample, RSD 3% (n = 10)148. 

Carrier-gas is transferred from the column through a heated metal capillary, which minimizes the dead volume at the end of the column and prevents condensation of the column effluent prior to its entry into the scrubbing unit. The tube carrying the liquid stream is joined to the gas stream tube, at a T-junction that is joined to the mixing coil by a glass-to-metal seal. Furfural is transferred from the gas stream into the liquid stream and the colour develops the two phases are then separated by the debubbling unit and the liquid stream is re-sampled through the flow cell of the colorimeter. A Technicon peristaltic... 

One of the most sophisticated methods is the use of chiral gas chromatographic capillary columns for the direct separation of volatile enantiomers. Complexation gas chromatography with enantioselec-tive transition metal fl-ketoenolates permits the stereochemical analysis of volatile oxygenated compounds in the nanogram range with high 44,45... 

Elemental composition Mo 36.34%, C 27.30%, 0 36.36%. A benzene solution of the hexacarbonyl may be analyzed by GC/MS. Molybdenum metal digested in nitric acid solution may be analyzed by various instrumental techniques. Also, the compound may be thermally dissociated and the liberated CO may be identified by GC using a TCD or by GC/MS using an appropriate capillary column. 

---