GC045 Capillary columns

Capillary columns are columns that are not filled with packing material. Instead, they are internally covered by a thin film of a liquid phase. They are formally called “wall-coated open tubular” or open tubular (WCOT or OT columns). Their resistance to flow is very low, and long lengths are possible, up to 100m, which also permits efficient separation of very complex sample mixtures. Fused silica columns are the more inert.

Comments

Post a Comment

Popular posts from this blog

GC011 Advantages of gas chromatography - Part 1

  Fast analysis, in the order of minutes High resolution and efficient High sensitivity, can detect ppm and ppb. Is a nondestructive technique, can be coupled to a mass spectrometer Quantitative analysis is very accurate with RSDs in the order of 1-5%. Only small samples are needed (microliters) Reliable and relatively simple technique Inexpensive
Read more

GC036 Flow Measurement

There are two ways of measuring the flows independently. The first one is an inexpensive soap-bubble flowmeter which consists of a calibrated tube (usually a modified pipet or buret) through which the carrier gas flows. With a rubber bulb we can create a bubble, which is raised into the path of the gas. After that, the ascension of a particular bubble to a defined volume is measured with a stopwatch. The carrier gas in mL/min is easily obtained from this measurement. There are also available electronic soap film flowmeters at a cost around $50. The second alternative is the use of a sophisticated device, composed of a solid-state sensor and a microprocessor to accurately flow measurements without using soap bubbles. Silicone-on-ceramic sensor can be used to measure flow rates of 0.1-500 mL/min for air, nitrogen, oxygen, helium, hydrogen and 5% argon in methane. The cost for this device is around $700. Very small flow rates, like the ones found in tubular columns, cannot be measured rel...
Read more

GC013 Advantages of gas chromatography - Part 3

  Efficiency is a measure of how well the separations can be performed and is expressed in plate numbers. Capillary columns are known to possess several hundred thousand plate numbers. The efficiency of a column increases with column length. In theory, having very long columns can make analysis very efficient, however and unlimited increase in length is not practical and nowadays complex separations are performed by using comprehensive two-dimensional GC.
Read more