drift in base line

[famahyari]

Hi
what are the sources of drift in base line?(in high sensitivity)
thanks

[skunked_once]

Column bleed! The bleed could be normal bleed from the column and this is dependant on the type of column (brand, polarity, etc.), how new the column is, how well conditioned the column is, and whether the column has been loaded with lots of dirty samples. Contamination on the column could come from impure carrier gas, a dirty injection liner, or too many dirty samples.

[famahyari]

1-the column is moderately polar(CBP10=SE-30), FUSED SILICA, bonded phase.I just injected standards,...
but I don't sure that carrier gas is pure, does it cause a high drift in base line?
2-what is meaning of normal bleed and has a new column bleed?
3- what happen when I change the WIDTH in recorder?
thank you

[skunked_once]

1-The column you are using should give minimul drift assuming that you have conditioned it according to the manufacturer's directions. If your carrier gas is impure, the impurities will build up on the column then bleed off during the temperature program. It's a good idea to use gas purifiers.
2-Keep in mind that all columns will have some baseline rise when doing a temperature program. If you are operating at maximum sensitivity, the rise will be more obvious.
3-I assume that you are using a recording integrator. The width parameter is set according to the sharpness of the peaks. It will not have an influence on the baseline drift.

[pochengjean]

1. Above normal signal or signal to noise ration on the baseline through out the entire injection...could be your carrier gas or dirty detector.
2. There is a upward drift in the middle of the injection, but somehow stay at that level till the end of the injection, could be your inlet or septums.
3. There is a upward drift in the baseline, and continuing drifting upward till the end of the injection, column bleed.

change your recorder might not be a good idea since you might run into compatibility problems with the new recorder.

[famahyari]

thank you
There is a upward drift in the baseline, without any injection and temprature keep at 100 C (isothermal)!!!is there bleeding in the low temprature?

[chromatographer1]

Sounds like dirty gas, dirty lines, dirthy injection liner, or septum bleed

Something that burns in coming off the column in larger and larger amounts. Find out where and eliminated it.

Good luck.

[JI2002]

What kind of detector you are using? Sounds like a detector problem.

[pochengjean]

what i usually did is trying to isolate the possible causes.

get a different column, see if newly installed column performs as well as before (not a very smart move cause you are risking another column, but time saving). If it shows the same weird upward drift as you described, then the column you had is OK. However, your detector/injector might not.

and you go on to find the possible causes in the detector/injector to see where the sources are from.

[famahyari]

What kind of detector you are using? Sounds like a detector problem.

Dear JI2002
my detector is FID.
now I change The carreir gas (helium instead of nitrogen) and base line at high sensitivity is better but upward drift changes to up and down drift.
thanks

[JI2002]

What are the flow rates of carrier gas, make-up gas, hydrogen and air? Make sure to set up the flow rates properly.

[famahyari]

What are the flow rates of carrier gas, make-up gas, hydrogen and air? Make sure to set up the flow rates properly.

carreir gas 1 ml/min, make-up gas 30 ml/min, hydrogen 30ml/min, air 300ml/ min.

[CIL-BAHA]

(removed)

[oscarBAL]

for me sounds like something wrong with the amplifier detector, But I think that you should with other column as pochengjean wrote.
CIL-BAHA says that could be a broken column, I relly would like to know why?

[famahyari]

Easy! Sounds like a broken column.

Hi
I don't think. this problem apears with a new column.