SPME MIB analysis issue
Posted: Tue Oct 13, 2015 2:28 pm
Hello forum people,
Any thoughts on how I can proceed troubleshooting MIB sensitivity issue I have been having lately?
I have a Thermo ISQ LT GCMS, run SPME for MIB and Geosmin. I just had the source (cartridge) cleaned and put back in. However, the issue with MIB has been happening before cleaning the source.
What I see is that Geosmin I can see at very low concentrations, 2 ppt the lowest point on my curve but MIB has slowly been deteriorating. I used to be able to see it at the 2ppt, but lately, its been very hard to get a good calibration curve and it is mainly the low points that are throwing it off.
I just installed a new column as well (conditioned etc...) same column specs are before I had issues.
The fibers are replaced routinely, as I see a decrease in Internal standard precision.
I use NaSo4 for the extraction process (in a 10 ml sample I add 1.5 grams salt). Extraction has always been in 65 C agitator, and for 30 minutes it extracts. Desorption is 2 min. in port.
Nothing has really changed in my methodology.
I have also tried out different lots of standard stock for MIB and Gesomin. I am currently running a MIB standard alone, without Geosmin in it (I usually use the combined standard).
I am really scratching my head since Geosmin seems to be looking fine.
Thoughts? Suggestions? Ideas? HELP??
Any thoughts on how I can proceed troubleshooting MIB sensitivity issue I have been having lately?
I have a Thermo ISQ LT GCMS, run SPME for MIB and Geosmin. I just had the source (cartridge) cleaned and put back in. However, the issue with MIB has been happening before cleaning the source.
What I see is that Geosmin I can see at very low concentrations, 2 ppt the lowest point on my curve but MIB has slowly been deteriorating. I used to be able to see it at the 2ppt, but lately, its been very hard to get a good calibration curve and it is mainly the low points that are throwing it off.
I just installed a new column as well (conditioned etc...) same column specs are before I had issues.
The fibers are replaced routinely, as I see a decrease in Internal standard precision.
I use NaSo4 for the extraction process (in a 10 ml sample I add 1.5 grams salt). Extraction has always been in 65 C agitator, and for 30 minutes it extracts. Desorption is 2 min. in port.
Nothing has really changed in my methodology.
I have also tried out different lots of standard stock for MIB and Gesomin. I am currently running a MIB standard alone, without Geosmin in it (I usually use the combined standard).
I am really scratching my head since Geosmin seems to be looking fine.
Thoughts? Suggestions? Ideas? HELP??
