Chromatography Forum

My apologies for the newb question, but Ive been tearing my hair out the last two weeks trying to figure this out!

I run a HP6890-FID and recently switched from peaksimple over to chemstation version A.10.01. I injected my standards for my six compounds of analysis and was able to get some okay calibration curves. My trouble lies in calibrating the internal standard and generating a report with useful results.

Here is my sample prep:
Approximately 50mg of sample is dissolved into 40ml of Internal standard solution. My internal standard solution is ~1g of methyl stearate in 1 gallon of acetone. I am manually injecting right now, so I than inject 1.0uL of the sample solution into the GC for analysis.

Here is my calibration table:
https://drive.google.com/file/d/1Qsl2OB ... sp=sharing

Here is the sample input parameters:
https://drive.google.com/file/d/11sJbZu ... sp=sharing

Here is an example of the output report:
https://drive.google.com/file/d/1Eh81sB ... sp=sharing


Please let me know if any additional info would help, thank you in advance!

When you generate your report do you use the INSTD or EXTSTD report format? The EXSTD format will ignore the internal standard as it is for External Standard Calibration and it is normally the default format the system wants to use.

Ive been using the ISTD% option, I suspect that my problems lie in the sample input parameters, but I am also unsure if I somehow calibrated the internal standard wrong. Since its an internal standard, do I just enter an arbitrary amount in the amount column? Same for Area? Or do I need to go through and calibrate the internal standard with five different samples? (the amounts would all theoretically be the same, but I'd imagine the area would be slightly different for each one due to variance in manual injection)

Since everything on my chemstation is in ng/uL, I am assuming that the sample amount is the amount of sample injected in ng? I am also unsure how to tell the software I am using 40ml, does that involve changing the dilution or multiplier?

If you looking to make the internal standard calculation simple and it will always be added at the same concentration, set the concentration at 1.0. That way it will be easy to tell the recovery.
How you convert ng/uL to ug/L is up to you and your reporting system.

We used Chemstation with internal standard to assay ethanol levels in finished products, worked fine. Before I retired, I could've helped you in 10 minutes, now it's a little fuzzy.

I will try to look into this further for you when I have time this afternoon.

I've also got past experience with GC and Chemstation internal standard automated calculations. We used Chemstation A.07 and A.09 but doubt anything changed for A.10.

I can send captures of set up of calibration table and sample table for this if you post your E-mail address here. Like abc at 123 dot com instead of abc@123.com

I was actually able to get Chip Lewis from Agilent on the phone just now and he told me that all I need to do is adjust the dilution factor for each sample.
Apparently the sample amount box does nothing except display your sample amount on the report. He wasn't sure how to calculate the dilution though. Since I have ~50mg in 40ml of solvent, anyone know what that dilution would be? I am confused since its mass and volume instead of volume/volume or mass/mass.

Since I have ~50mg in 40ml of solvent, anyone know what that dilution would be? I am confused since its mass and volume instead of volume/volume or mass/mass.[/quote]

Acetone is 0.79 grams/ml at room temperature.

So 40 ml of acetone or internal standard solution would be like 31.6 grams. So 0.050 grams in 31.6 grams, keeping grams/grams.

This is helpful
https://www.google.com/url?sa=t&rct=j&q ... zJLlKEVZO1