Polytetrafluoroethylene column

Some authors have suggested the use of fluorene polymers for this kind of chromatography. Fluorinated polymers have attracted attention due to their unique adsorption properties. Polytetrafluoroethylene (PTFE) is antiadhesive, thus adsorption of hydrophobic as well as hydrophilic molecules is low. Such adsorbents possess extremely low adsorption activity and nonspecific sorption towards many compounds [109 111]. Fluorene polymers as sorbents were first suggested by Hjerten [112] in 1978 and were tested by desalting and concentration of tRN A [113]. Recently Williams et al. [114] presented a new fluorocarbon sorbent (Poly F Column, Du Pont, USA) for reversed-phase HPLC of peptides and proteins. The sorbent has 20 pm in diameter particles (pore size 30 nm, specific surface area 5 m2/g) and withstands pressure of eluent up to 135 bar. There is no limitation of pH range, however, low specific area and capacity (1.1 mg tRNA/g) and relatively low limits of working pressure do not allow the use of this sorbent for preparative chromatography. 

TTie manifolds described for preconcentration by Bysouth et al. [26] involve a column included within the sample loop of an injection valve. This enables timed sample loading onto the column without the matrix components passing to the spectrometer. Elution is achieved by switching the valve to place the column into the carrier stream which contains eluent. Four manifolds were used and these are shown in Fig. 5.10. Polytetrafluoroethylene (PTFE) tubing was used throughout the experiment. Manifolds 1— 3 were used for preconcentration studies and were based on a commercially available... 

Urine (5 ml) urine spiked with 0.2% (v/v) isopropylamine is placed in a screw-capped 15-ml vial [28]. Pelleted potassium hydroxide (3 g) is added before sealing the vial with an airtight polytetrafluoroethylene-lined septum cap. Potassium hydroxide raises the pH of the sample to ensure that the amines are present as volatile bases. The vial is heated in an aluminium block at 90 C for 20 min. While still in this block, 2 ml head-space gas is withdrawn through the septum with a disposable syringe and injected immediately on the gas chromatography column. The operating temperatures of the column, injector port and detector unit are 70 C isothermal, 150 C and 200 C, respectively, with nitrogen carrier gas at 60 ml/min. This allows quantification of TMA and other amines. TMA N-oxide is measured after quantitative reduction into TMA. For this, titanous chloride (30%, w/v 0.2 ml) is added to 2 ml urine in a screw-capped vial and incubated for 30 min at room temperature. The sample is then diluted ten-fold with distilled water and analysed as described above. The result represents the sum of TMA and TMA N-oxide present in the sample. 

Bio-Rex membranes (AG1, AG50), which are crosslinked anion- and cation-exchange resins enmeshed in polytetrafluoroethylene, are an alternative to ion-exchange resins. These membranes achieve the same effectiveness as open ion-exchange columns, but analysis times are shorter (51). 

All samples were filtered with a 0.45pm polytetrafluoroethylene (PTFE) membrane filter before injection into the column. 

The C1F3 molecule has a planar distorted T-shaped structure with one short (0.1598 nm) and two long (0.1698 nm) Cl—F bonds. The angle between the two different kinds of Cl—F bonds is 87.48° [86,87]. The infrared and Raman spectra [88] and NMR [89] were measured. Gas chromatography was applied and data were obtained using a polytetrafluoroethylene-packed stainless steel column [90-92]. 

This technique permits the detection of volatile substances in a liquid sample and minimises contamination of the column. A snudl volume (0.2 to 0.5 ml) of the smnple is placed in a small Adseeded with a septum sk which is faced with polytetrafluoroethylene, elevated temperature for about toi minutes. A sour is r oved with a syringe, hddng cother solvents in blood lex household preparations such as polishes, which contain volatile substances. 

The equipment used in HPIEC is different from that used in CIEC. The columns, valves, and pipes are exposed to high pressures. This requires them to be not only corrosion resistant to acids, bases, and other chemical agents, but they also need to be pressure resistant. Because of this, the materials used in their construction are required to be of higher quality than the material used to construct the CIEC devices. The devices, e.g., the column, valves, pipes, sieves, pressure vessels, and pressure gauges used by the authors, were primarily made of special stainless steel. Some junctions were made of polytetrafluoroethylene plastic. Usually the last column of a system of columns was made of glass so as to permit observation of the separation affected. 

The separation column was prepared using a pair of eccentric coil assemblies, which were made by winding a 1 mm-ID PTFE (polytetrafluoroethylene) tubing onto... 

HSCCC-thermospray (TSP) MS was initiated using an analytical HSCCC apparatus of a 5-cm revolution radius, equipped with a 0.85-mm-inner diameter (i.d.) polytetrafluoroethylene (PTFE) column at 2000 rpm [6-8]. Directly interfacing HSCCC to the MS produced, however, a problem in that the high back-pressure generated by the TSP vaporizer often damaged the HSCCC column. To overcome this problem, an additional high-performance liquid chromatography... 

Cai, Y., Jiang, G., and Liu, J., Solid-phase extraction of several phthalate esters from environmental water samples on a column packed with polytetrafluoroethylene turnings. Anal. Sci., 19, 1491-1494,... 

Fig. 4.6.8. (Right) Example of the fixed column end fitting for glass columns, suitable for water and organic solvents (after Ref. 18). 1, inlet capillary 2, thrust screw 3, seal made of soft polytetrafluoroeth-ylene 4, end fitting body made of plastics or metal 5, polyamide or polytetrafluoroethylene filter 6, cap nut 7, seal ring made of polytetrafluoroethylene powder or powdered mixture of graphite and polytetrafluoroethylene 8, rubber rings 9, column.

Tests have shown that the polymers polytetrafluoroethylene and polypropylene arc suitable packing materials for columns using concentrated sulphuric acid or acid water as liquids [143]. 

The separation column was prepared using a pair of eccentric cod assembhes, which were made by winding a 1 mm l.D. polytetrafluoroethylene (PTFE) tubing onto 7.6 cm long, 5 mm O.D. nylon pipes forming a series of tight left-handed cods. A set of these cod units was symmetrically arranged around the holder hub of 7.6 cm diameter in such a way that the axis of each cod unit is parallel to the axis of the holder. A pair of eccentric coil assemblies was mounted on the rotary frame, one on each side, and seriaUy connected with a flow tube. 

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