What causes GC columns to bleed?

High bleed is one of the most common issues you’ll encounter when doing gas chromatography. Excessive bleed is often caused by something damaging the stationary phase of the column, things like oxygen from a leak or some aggressive component in the sample.

How is GC column prevented bleeding?

A thinner film column has lower column bleed due to the lower amount of stationary phase. The lower temperature of elution may avoid the high bleed region; the thinner stationary phase reduces the intensity of the baseline rise.

What is a GC column?

Capillary columns are gas chromatography (GC) columns that have the stationary phase coating their inner surfaces rather than being packed into the cavity. Capillary GC columns are used to analyze samples for the individual chemical compounds that they contain.

What is low bleed column?

Low Bleed = Better Signal-to-Noise Ratio = Lower Detection Limits. Signal refers to the response from an analyte passing through a detector. It is the peak you see when looking at a chromatogram. System noise refers to everything else, other than the analyte, producing a response in the detector.

How long does a GC column last?

Most columns, if run under reasonable conditions, will last at least a year. Those with very clean samples that run their columns at oven temperatures considerably below the columns’ maximum operational temperatures may get up to five years of operation.

What is temperature programming in gas chromatography?

Temperature programmed gas chromatography (TPGC) is the process of increasing the column temperature during a run. It is a very effective method for optimizing an analysis and is often used for screening new samples. Most methods in capillary GC are temperature programmed.

Which gas is used in GC?

Carrier gas is an inert gas used to carry samples. Helium (He), nitrogen (N2), hydrogen (H2), and argon (Ar) are often used. Helium and nitrogen are most commonly used and the use of helium is desirable when using a capillary column.

What is detector in GC?

A chromatography detector is a device used in gas chromatography (GC) or liquid chromatography (LC) to detect components of the mixture being eluted off the chromatography column. There are two general types of detectors: destructive and non-destructive.

What are theoretical plates used for?

Theoretical plate number (N) is an index that indicates column efficiency. It describes the number of plates as defined according to plate theory, and can be used to determine column efficiency based on calculation in which the larger the theoretical plate number the sharper the peaks.

What are the advantages of temperature programming in gas chromatography?

Temperature programming permits the higher resolution of lighter compounds and sharp peaks for heavier compounds, reducing the long run times generated by heavier compounds.

How do I know if my GC column is leaking?

There are 3 ways to check for gas leaks in a GC.

1. The 1st method of leak checking is called “looking for bubbles” or “snooping the fittings”.
2. The second method of leak check- ing is to use a leak detector.
3. The third method of leak checking is call the “pressure drop” test.

How do I know if my GC column is bad?

You can see the signs of : bleeding, peak broadening or skewing etc that the column can not separate well before replace with a new column. One of my experience is to cut off 1 or 2 meters at the inlet end of the bad column and it may help.

What is bleed in column chromatography?

Bleed is the loss of stationary phase. The column stationary phase is a long polymer chain of repeating groups. These polymers are also bonded to other polymer chains, this is called cross-linking, which helps to stabilize the phase and reduce the amount of bleed.

What is septum bleed in GC-MS?

Septum bleed happens when pieces of the septum that protects the injector port makes it all the way through the GC-MS system to the MS detector. Column bleed is characterized by a noticeably raised baseline that is called by the stationary phase (the inner column coating) coming off and making its way to the detector.

What happens when you bleed a column?

Note that bleed will occur over the entire length of the column and this results in a rise in baseline. If any peaks are observed, even if the ions are consistent with bleed, they are most likely coming from one specific source and being separated by the column.

Is your capillary GC column ready for use?

If you ‘do’ Gas Chromatography, then you will have undoubtedly conditioned a capillary GC column ready for use after a period of storage or before first use.