Calibration not succes

[JUNIPRA]

Greeting recognize.
I am new comer and wish to ask as for GC
At the time of calibration with standard which consist of Hydrogen sulfide, mercaptan methyl, sulfide dimethyl, disulfide dimethyl. Of four of component this emerging only three component. Is there any friends which can assist ?

thank you
Juni Pranata[/b]

[dcav]

Hi!
I'm not an expert, but i think that two compounds have a very similar retention time in the conditions you are using, so the GC can't separe them.
It could be also possible that you do not elute one of them, because you don't reach in your run an adeguate temp.If i was in you i would start injecting them one by one, then make your conclusion

Best wishes

Dario

[yuri]

Hi,

what kind of column and detector do you use?
If the column is 100 % PDMS (for example DB-1) the separation between the four compounds must be good.

Yuri

[JUNIPRA]

Hi, Yuri

I use FPD detector and coulumn type of SPB-1, 30 M x 0.32 mm. and carrier gas Helium at 3.0 psi.




best regard,
junipra

[chromatographer1]

have you spoken with their technical service department?

800-359-3041

or

techservice@sial.com

[arie2044]

Hi
First you must check that you don't stop the run too early, so you loose the last peak.
Second check the GC temp & gas flows - i think that 3psi is too low flow so you don't ellute the last peak. increase the pressure on inlet.

[Ron]

These compounds are know to be reactive, and easily lost if the sample introduction system is not inert. For this standard I am assuming that you are introducing a gas standard using a gas sampling valve. If you are using standard stainless steel tubing and sampling valve you may be losing the compounds before they ever reasch the column. Silcosteel or Sulfinert tubing and an inert sampling valve is usually used for these analytes.

[misty]

I agree with dcav... I think that two compounds have a very similar retention time and the best place to start would be to injet one at a time and note the retention times. You may have to change your temperature ramp settings to separate these out.

[arie2044]

Hi Junipra
The best think for your application is to consult the Agilent Chromatography & Spectroscopy Supplies Reference Guide for the year 2002-2003 ,on page 432 they present the application you need. try to follow the GC conditions they describe, and thene you will know what do you receive, is the problem in GC conditions, unsuficient detector sensitivity, or what else.

Good luck