I have problem about Instrument 1 software.

[wiclef]

Morning everyone,

I have a problem related to the determination of ethanol in alcoholic beverages.
Normally I used the Agilent 6890 N GC with the packed column PORAPAQ and the FID as the detector
and I usually had a chromatogram showing a very large peak of ethanol at about 7 to 8 min.This last week, I tried to do this routine analysis and I obtained the chromatogram that you can see on this link: http://imgur.com/9yVwI.The problem is that I do not see the peak of the ethanol after I performed the 2 injections of the standard 3 (0.96 %).I noticed that the intensity of the signal is so low.How do you suggest me to do? I do not have any idea about this issue.

Regards,

[chromatographer1]

The link doesn't work.

Rod

[Don_Hilton]

With out being able to see the chromatogram, let me start with a question or two to check on common problems:

1) When did you last replace the septum? (Do you know how many injections have been made through the septum?) A septum that has seen too many injections will result in loss of the sample through the hole worn in the septum.

2) have you changed any instrument parameters or gas cylinders since the last time you ran the method. Incorrect flow adjustment to the FID can result in weak signals. Incorrect flow through the column can result in incorrect retention times.

[wiclef]

Dear Rod,

Thanks for that.May I send it to your email?Please give me your e- mail.
Mine is kagisha@yahoo.fr.

Regards,

[wiclef]

Dear Don_Hilton,

I have replace the septum before the last analysis and I did not not use it since on the 30 Nov 2011.
The last time I used the GC, the instrument was okay.If you give me your e - mail I can send you the chromatogram of the last analysis and this I performed yesterday and you can compare.
Please help me!!Do you have some literature on the Chemstation software?Cn you help me on these?

Kind regards,

Wiclef

[chromatographer1]

chromatographer1 at Yahoo

Rod

[Don_Hilton]

dchilton at mylink dot net

[chromatographer1]

Basically the only difference in the two chromatograms is the scaling (the presentation) of the printout. It is like having a microscope and looking at a slide with a 100X eyepiece and then looking at the slide with a 10x eyepiece. The water peak is about the same height in pA, just the scaling is different.

best wishes,

Rod

[wiclef]

Basically the only difference in the two chromatograms is the scaling (the presentation) of the printout. It is like having a microscope and looking at a slide with a 100X eyepiece and then looking at the slide with a 10x eyepiece. The water peak is about the same height in pA, just the scaling is different.

best wishes,

Rod

Dear Rod,

Thank you for your useful explanation.I am new about this software ( ChemStation Instrument 1).There are settings put by the analyst using the equipment before I use to.I think I change them unconsciously.The problem I have now is that I do not know how I can change the scaling.Could you guide me how I can resolve that?

Regards

Wiclef