SCOT column

Excellent open tubular columns may now be purchased, providing a number of stationary phases of differing polarity on WCOT and SCOT columns, and whose efficiency, greatly improved sample detectability, and thermal stability surpass those exhibited by packed columns their chief disadvantage is that they have a lower sample capacity than packed columns.65,66... 

Five types of columns are routinely used in gas chromatography classical packed columns with internal diameters greater than 2 mm containing particles in the range 100 to 250 micrometers micropacked columns having diameters less than 1 mm with a packing density similar to classical packed columns (dp/d less than 0.3, where dp is the particle diameter and d the column diameter) packed capillary lumns have a column diameter less than 0.5 mm and a packing density less than classical packed columns (dp/d 0.2-0.3) SCOT columns (support-coated open... 

Porous-Layer Open Tubular (PLOT) and Support-Coated Open Tabular (SCOT) Columns... 

Porous-layer- open tubular (PLOT) and support-coated open tubular (SCOT) columns are prepared by extending the inner surface area of the capillary tube. A layer of particles can be deposited on the surface or the column wall can be chemically treated to create a porous adsorbent layer. Obviously some of the wall-modified open tubular columns discussed in section 2.3.3 could be... 

Figura 2.9 Dse of th Grob test Mixture to compare tbe activity of various glass surfaces coated with ov-ioi. Surface types A > Untreated pyrex glass, B pyrex glass deactivated by thermal degradation of Ceurbowax 20M, C < SCOT column, prepared with Silanox 101, D pyrex glass column coated with a layer of barium carbonate and deactivated as in (B), and E - untreated fused silica. Components are identified in Table 2.7 with ac - 2-ethylhexanoic acid. (Reproduced with permission from ref. 152. Copyright Elsevier Scientific Publishing Co.)...

Analysis Techniques. The contents of the major breakdown products of xetralin (naphthalene and 1-methyl indan) present in the distillate were determined by gas-liquid chromatography using a Hewlett Packard Series 5750 Research Chromatograph with a 62m x 0.5mm diameter glass capillary SCOT column coated with nonpolar SE 30 liquid phase (see Reference (4 ) for details). 

Rasmussen [82] describes a gas chromatographic analysis and a method for data interpretation that he has successfully used to identify crude oil and bunker fuel spills. Samples were analysed using a Dexsil-300 support coated open tube (SCOT) column and a flame ionisation detector. The high-resolution chromatogram was mathematically treated to give GC patterns that were a characteristic of the oil and were relatively unaffected by moderate weathering. He compiled the GC patterns of 20 crude oils. Rasmussen [82] uses metal and sulfur determinations and infrared spectroscopy to complement the capillary gas chromatographic technique. 

Support coated open tubular (SCOT) columns, 4 615 6 379 Supported liquid membranes, 16 28 Support material, in fluidized-bed encapsulation, 11 540 affinity chromatography, 6 392-393 chromatography, 6 375 gas chromatography, 6 375 Supported metals... 

It is usual to convert fatty acids to their methyl ester derivatives before separation by GLC, although it may be possible to analyse those with short chain lengths (two to eight carbon atoms) as the free fatty acids. Polar or non-polar stationary phases can be used and capillary (open-tubular) or SCOT columns will separate positional and geometric isomers. The cis isomers have shorter retention times than the corresponding trans isomers on a non-polar phase and visa versa on a polar phase. 

PLOT Columns. Porous-layer open tubular columns wherein the internal wall is coated with a layer of adsorbent support. If the support is then coated with a liquid phase it is referred to as a SCOT Column (i.e., support-coated open tubular column). 

The inside diameter of these columns is usually -l mm. The SCOT columns contain a larger amount of stationary phase (liquid coating) per column segment, thus sample capacity is higher than the standard open tubular column (WCOT). 

Since open tubular columns have low sample capacity this necessitates smaller sample sizes which in turn requires the use of sensitive detectors. The PLOT or SCOT columns, however, have a larger sample capacity than the WCOT columns, thus permitting larger sample sizes. These columns (PLOT, SCOT) can be operated without splitters and therefore, less sensitive detectors. One potential use for the SCOT columns is in the area of trace analysis. 

One type of column is the wall-coated open tubular column (WCOT) in which the stationary phase is applied and bound directly to the walls of the column. Porous-layer open tubular columns (PLOT) are columns in which the stationary phase is deposited on fine particles of absorbent, absorbed on the walls of the column, increasing the available surface area of the column wall. Support-coated open tubular (SCOT) columns are those... 

Rasmussen [495] has described gas chromatography methods for the identification of hydrocarbon oil spills. The spill samples are analysed on a 30.5m Dexsil-300 support coated open tube (SCOT) column to obtain maximum resolution. 

The column which gives the most effective separation of the mixtures of accelerants generally encountered is a Support-Coated, Open Tubular (SCOT) column commercially available from Perkin-Elmer Corporation. The stainless steel column is 0.020 inch inner diameter coated with DC 550 on an inert support and consists of two fifty-foot sections joined with a zero dead... 

For a period of time, OT columns that had characteristics intermediate between those of WCOT and packed columns were popular. There were two types, but they were similar. Support coated open tubular (SCOT) columns had a thin layer of solid support coated on the inside wall of a capillary tube of larger diameter than that used for WCOT columns. This layer was coated with stationary liquid similar to packed columns. Porous layer open tubular (PLOT) columns were similar but made differently for example, the solid support was added while the capillary tube was being drawn. With a few exceptions, SCOT and PLOT columns are no longer popular because wide diameter WCOT fused silica columns are as good, more stable (no layer to flake off), and easier to use. Subsequent discussion will be restricted to WCOT columns. 

Fatty acids are usually measured as their methylesters by gas liquid chromatography on packed, capillary or surface-coated open tubular (SCOT), columns with flame ionization detection (Christie, 1982a). HPLC can also be used to separate fatty acid esters with measurement by UV-absorption or fluorescence detection (Christie, 1987). 

It is usually necessary to modify the inside surface to assist wetting, e.g. by etching. If the glass surface itself is coated the column is referred to as a wall-coated open tubular (WCOT) column, whereas support-coated open tubular (SCOT) columns have a support bonded on to the glass walls, e.g. microcrystals of sodium or barium chloride. 

Scopolamine methylnitrate, 675 Scopolia, 674 Scopos, 674 SCOT columns, 182 Screening, for diuretics, 32 for drugs of abuse, 27 for laxatives, 32 for solvent abuse, 31 tests on blood, 6 tests on stomach contents, 5 tests on urine, 4 Scuroforme, 419 S-Diazine, 982 S-Dimidine, 984 SDMO, 991 SE-30, 180 Sea-legs, 724 Sebizon, 981 Secadrex, 309, 663 Secbutobarbital, 967 Secbutobarbitone, 967 Secbutobarbitone sodium, 968 Seclodin, 677 Secobarbital, 951 Secobarbital sodium, 951... 

A range of open tubular GC columns were used. A 150 ft X 0.01 in. i.d. stainless steel wall-coated open tubular (WCOT) column (Perkin Elmer Corp., Norwalk, CT), a 50 ft X 0.02 in. i.d. support coated open tubular (SCOT) column (Perkin Elmer), and 33 ft and 100 ft X 0.03 in. i.d. porous layer open tubular (PLOT) columns. The latter were pre-... 

The analysis was carried out on a Perkin-Elmer 3920B gas chromatograph interfaced to a modified Bendix model 12 time-of-flight mass spectrometer with a variable split between a flame ionization detector and the source of the mass spectrometer. The separation was made on a 15.2 m x 0.51 mm SCOT column coated with OV 17 and temperature programmed from 100°-250°C at 4°C min. ... 

The split/splitless detector has been designed for use with open-tubular columns or solid-coated open-tubular (SCOT) columns. Due to the small dimensions of such columns, they have very limited sample load capacity and, thus, for their effective use, require sample sizes that are practically impossible to inject directly. The split injector allows a relatively large sample (a sample size that is practical to inject with modern injection syringes) to be volatilized, and by means of a split-flow arrangement, a proportion of the sample is passed to the column while the remainder is passed to waste. A diagram of a split/splitless injector is shown in Fig. 1. 

Support-coated open tubular (SCOT) columns Capillary gas chromatography columns whose interior walls are lined with a solid support. 

A small volume TCD still requires a reference flow to be well matched with the sample flow. For most wide bore WCOT columns, make-up gas is required to obtain the available resolution of the system For SCOT columns this can be neglected without serious loss In efficiency. Regulation and balancing of the reference and sample flows are relatively easy when only Isothermal operation is employed, but become very difficult when temperature programming is necessary. 

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