Dear Dr.
thanks for your answers, I really appreciate your professionalism!
Concerning C18, I also thought that it had a limited use but we were suprised. Indeed C18 traps neophytadiens and phytol (e.g. major peaks from spinach), late GC-eluting compounds (vitamin E, sterols etc.) but also has a major impact on chlorophyls, this is why it may for green vegetables relieve PSA. I put you in the attached document a picture showing the C18 trapping chlorophyll (uper layer). In this case, if your final extract is not too coloured, you can imagine bypassing the GCB clean-up and thus avoiding having lower recoveries for some planar pesticides.
Until now, the only pesticides we evaluated that was trapped by PSA is flubenzimine (we are not analysing acidic pesticides by GC). I attached a poster + abstract we presented in Berlin (July 2008). The goal is still to have all GC-pesticides monitored with optimised cleanup for each compementary extracts. In fact we are now trying to replace the home-made columns with your SPE cartridges assembled together, and pushing the extract and elution solvent with a syringe. I am also compiling contentd of acids and fatty acids in different food matrices to try to have matrix adapted clean-up. Next step will be the use of your cartridge in ~ september coupled to an automated apparatus.
We really appreciate your effort in trying to solve problems. We also already recommended you to collegues and will clearly mentionned in a publication that I am now writing that we used your sorbents based on previous study (I also did a price comparison, you are also more attractive than concurrent in Europa.
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Dear Dr.
Marie performed the same trials with the new cartridges. The chromatograms are much cleaner than the old ones and much more comparable with the other supplier.
Only few "small" peaks were observed, however not identified but with ions that seems typical for silane. I send you the chromatograms, but it is difficult to compare them to the previous ones as we changed the column and perform MS maintenance (so baseline is much lower now).
Thank you again a lot for your reactivity and help!
Best regards and a good WE
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Dear Frank,
Marie performed the same trials with the new cartridges. The chromatograms are much cleaner than the old ones and much more comparable with the other supplier.
Only few 、 "small" peaks were observed, however not identified but with ions that seems typical for silane. I send you the chromatograms, but it is difficult to compare them to the previous ones as we changed the column and perform MS maintenance (so baseline is much lower now).
Thank you again a lot for your reactivity and help!
Best regards and a good WE
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Dear Dr
Thank you for this information. As I am working mainly with GC, the way PSA cleans the extract is very important. In this sense I prefer a better clean-up with losses of flubenzimin run on GC-MS/EI, and to inject an extract without PSA on GC-MS/NCI. In this last case the selectivity of the detector compensates for the dirtier extract.
However as soon as my GC-MS is working again I will try your elution with 1% acetic acid on let say a cereal to see the impact of chromato cleanliness.
In any case we are now using only your PSA and will use it also for the validation of our clean-up
Best regards
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