by
Rndirk » Tue Jul 04, 2017 9:40 am
I'm not experienced in the differences between the models you mention.
You could ask SCIEX but your information is not sufficient.
1) What kind of samples do you want to analyze? Are all the pesticides compatible with the LC-MS/MS conditions you're planning? Do you want to measure them in a single injection? Is it a screening or a quantification?
2) 10-20ppb are pesticide levels on sample basis (I assume): for example 10 µg/kg on a certain vegetable. This is not very relevant to compare different detectors.
It depends on your sample preparation and chromatographic conditions. If you want to compare different detectors, it's better to speak in terms of concentration of final extract or better, absolute amount of pesticides on-column.
For example (assuming 100% recovery in extraction):
- There is 10 ppb of pesticide X in vegetable Y (10 µg/kg).
- Your sample prep consist of 1g sample ending up in 10mL of solvent => this leads to 1 ppb in the vial you're going to inject (1 µg/L = 1 pg/µL)).
- You inject 10µL so there is 10pg on-column
The number of 1pg you have found in the paper you mention is most likely the amount on-column.
In the above example you see that you there is room for adjustments to develop the method for the limit your detector can handle. Adjusting the extraction or the injection volume can easily lead to 100 or 1 pg on column.
Be aware that a higher concentration/volume injected means more matrix (dirt) injected and a higher chance of interferences & more maintenance is needed, possible overloading of the column/detector,... This is the advantage of having of a more sensitive instrument.
-zwitterion+ wrote:
I have read somewhere else that the most current LC/MS/MS technology is barely achieving the levels mentioned above. And when I say current technology I am referring to Shimadzu's 8060 and Agilent 7000 series latest LC/MS/MS units.
This is wrong. Do you have a source?
Google application notes for pesticide analysis using LC-MS/MS: you will finds dozens.