Problem with GCMS 7890B-5977A

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

4 posts Page 1 of 1
Hello everyone'

I have some problems need to help.
Currently, i am using organochlorine pesticides 17 compounds standard and DB 5MS column. When i use Scan mode have peaks of all compound, but with SIM mode at level of concentrations ( 2, 5, 10, 50, 100ppb) peak of compounds: heptachlor, endrin and p,p DDT no see.
I have cleaned ion source, replaced liner, replaced septa. I also cut column but not result.
Please support me. Thank all of you.

Image Image Image Image
What level are you looking at in scan mode? Are you seeing the breakdown products enhanced, e.g. 4,4-DDE? Could you see them at higher concentrations?
I've only ever done these by ECD. However, you should share what you are using for SIM masses. You should pick a few for each compound. Start by using the 2-3 masses that the 8270 method suggests as the quant masses for those compounds. Also check the mass range around each peak. You may specify 81.0 AMU but the mass might actually be at 80.8 AMU and you miss it.
LALman wrote:
I've only ever done these by ECD. However, you should share what you are using for SIM masses. You should pick a few for each compound. Start by using the 2-3 masses that the 8270 method suggests as the quant masses for those compounds. Also check the mass range around each peak. You may specify 81.0 AMU but the mass might actually be at 80.8 AMU and you miss it.


Look in EPA Method 525.3, they list many of the Pesticides in both Scan and SIM mode with Masses to use. I run many of these every day this way down to ppb ranges on instrument (ppt or lower in original water before extraction).

My low calibration standard for Endrin is 0.01ug/ml and I use SIM for that one, the rest I can see in scan mode if above 0.05 ug/ml.

Oh and you won't see the peaks that low in the Total Chromatogram, only when looking at the extracted ion in the quantitation window.
The past is there to guide us into the future, not to dwell in.
4 posts Page 1 of 1

Who is online

In total there is 1 user online :: 0 registered, 0 hidden and 1 guest (based on users active over the past 5 minutes)
Most users ever online was 1117 on Mon Jan 31, 2022 2:50 pm

Users browsing this forum: No registered users and 1 guest

Latest Blog Posts from Separation Science

Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.

Subscribe to our eNewsletter with daily, weekly or monthly updates: Food & Beverage, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.

Liquid Chromatography

Gas Chromatography

Mass Spectrometry