GC-MS frequent source contamination

[mezek]

Dear all,

The GC-MS of our lab is Trace GC ultra-Trace DSQ single quadropole.
I have problems frequent MS contamination – I mean not only source
but also prefilter.
We analyze pesticide residues in plant matrixes. In previous we used
thorough sample cleanup but in order to speed up the process know we
use QuEChERS method which involve only dispersive SPE with PSA
sorbents. We perform concentration by factor of 4 or 2 and use a drop of
1-octanol as keeper during evaporation and the end solvent is
ethylacetate. After about 300 injections (of 1µL slitless) the source seems
dirty. Is it acceptable?
The previous time when the source and prefilter were dirty the air/water
spectrum was with poor sensitivity, now it is OK, but the 50-650m/z and
PFTBA is bad.
http://photo-zona.net/images/user60543/ ... titled.JPG
http://photo-zona.net/images/user60543/ ... 50_650.JPG
http://photo-zona.net/images/user60543/ ... _PFTBA.JPG

Is it clear indication that the source should be cleaned or there are some
options?
I will be grateful to read your opinion and suggestions what to do!?

Thank you in advance

P.S. we use single gooseneck liner without glass wool, we didn’t use
untreated pre-coloumn

[mauricio]

Do you Speak Spanish? Sorry but my English is not good .

I read your article . I implemented the quechers method by gs ms for analysis of pesticides in fruits.
Although I do not have the same instrument and I have not done so many samples, I would like to exchange information and experience with the analysis of pesticides by quechers method and gc ms.

If you are interested can contact emeve7@hotmail.com

Thanks

[pueblito]

Hola Mauricio.
Yo tambien analizo pesticidas, en un SHIMADZU QP 2010 pero cuadrupolo y tu?.
Saludos.

[mauricio]

Hola Pueblito uso un triple quadrupolo, si te interesa compartir experiencias me puedes contactar a mvaldi@vtr.net

Saludos

[astroguille]

Hi!
I speak Spanish too.
I have problems with contamination in the ion source too.
I analize fruits, vegetables, water and soil by finding pesticides, and last two matrixes are the devil.
I work at Agilent GC6890/MSD5973.
What method can I use to clean thats samples?
My e-mail is [b]vitulich@inti.gov.ar[/b]