ISTD response/area not stabile

Hey.
I am doing GC MS analysis and I have a problem with the recovery of most heavy ISTD compounds (mainly perylene D12). The recovery is therefore too high and varies between different sample matrices/standards, even though the concentration of ISTD is the same. We have checked pipetting techniques and dosing, etc. For example, in the calibration series you can clearly see that the higher the concentration of calibration standart, the higher the ISTD area. Any suggestions as to what could be causing this?

0 kristen.sensabaugh 4 months ago

Hi SunFlower welcome to the Community!

I moved your question to the GC/MS Forum for better visibility.

Cheers,

Kristen
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0 paulsalverda 4 months ago

Which GC and MS, acquisition software version, and what is the configuration? What injection port, liner, column, and installed ion source? How long since the ion source was cleaned? How long since full inlet maintenance was performed? How long since the last preventive maintenance? What is your sample type? What sample preparation is performed? How much is being injected? Manual injection or by autosampler? What solvent is used? Are there any issues with lower molecular weight/lower boiling point compounds? When do you add the ISTD?

Would you please share the file acqmeth.txt (if a QQQ also acqmethtq.pdf) that are in Windows Explorer underneath your method's XXXX.D subdirectory along with the latest autotune report?
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