Journal of Chromatography A Analytical Chemistry By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.
Advanced search. Skip to main content. Subscribe Search My Account Login. Abstract SINCE their invention by Golay 1 , the use of open tubular columns with liquid phase coating on the inside wall became one of the most important techniques of gas chromatography. Rent or Buy article Get time limited or full article access on ReadCube. References 1 Golay, M. Google Scholar 2 Halasz, I.
Rights and permissions Reprints and Permissions. McEwen Analytical Chemistry Comments By submitting a comment you agree to abide by our Terms and Community Guidelines.
Getting new data
Nature menu. Nature Research menu. Compared with state-of-the-art-type PLOT columns, new-generation PLOT columns demonstrate constant flow behavior permeability and have significantly improved mechanical stability, resulting in easier operation, better chromatography, reproducible retention times, and longer lifetimes. One of the biggest challenges with PLOT columns is that the layer is built by particles. Any change in gas velocity, pressure, surface stress, or vibration can result in a release of particles or even complete segments of the adsorption layer.
When a particle reaches the detector, the detector produces a spike.
Gas Chromatographic Analysis of C 1 –C 4 Hydrocarbons with open Tubular Columns | Nature
The release of many particles results in serious flow restriction of the column and contamination of the detection system. Particle traps consist of a 1—2 m section of a polydimethyl siloxane PDMS -coated capillary, and a 0. The particle trap is usually made of the same i. The siloxane coating acts as a glue that immobilizes the adsorption particle.
Particle traps can be connected to all ordinary capillary connectors. Even with this type of particle trap, by emitting many particles, column flow restriction can build up. Sometimes this also happens inside the connector. As a result, most commercial PLOT columns suffer from nonreproducible and nonpredictable flow behavior, because restrictions can be formed randomly. This is an important issue when flow switching techniques are used i.
It is preferable to stabilize PLOT columns so that particle traps are no longer required. By making concentric coatings and in situ bonding of particles, the adsorption layers of molecular sieve, porous polymers, and alumina have been stabilized, and as a result, the columns have become much more reproducible on flow resistance—from column to column and also when the column is used in practical applications, where pressure changes occur via injection or flow switching.
These thick layers are difficult to deposit as a homogeneous layer.
Typically, there are areas in which the layer is thicker or thinner see Figure 1. As a result, the positions in which the layer is thicker act as a flow restriction for the whole column. Depending on the number and intensity of these flow restrictions, PLOT columns will show more variation on flow resistance than WCOT capillary columns. PLOT columns with the same dimensions can differ in flow by a factor of 4—6 while operated at the same nominal pressure.
- Open Tubular Columns in Gas Chromatography - Leslie S. Ettre - Google книги.
- Whisker-walled open-tubular glass columns in gas chromatography.
- The Breath of Rapture.
- ESSAYS ON PHILOSOPHICAL SUBJECTS (Glasgow Edition of the Works and Correspondence of Adam Smith );
- Advances in Porous Layer Open Tubular Columns.
For applications in which flow predictability is essential, like Deans switching, reproducible flow behavior is preferred. In order to have a value for reproducibility of flow resistance, a new factor, the flow resistance factor F , was introduced. This factor can be calculated according to Eq. The retention time of an unretained component is used as a measurement.
Open Tubular Columns in Gas Chromatography
For a fixed column dimension and stationary phase coating, the ratio of retention time relative to the uncoated tubing is a measure of the flow resistance. From this can be calculated the percent flow restriction, according to Eq. The values for F will always be less than 1, since the coated column always has more flow restriction than the uncoated column.
For instance, with molecular sieves in a 0.