Article Simultaneous determination of the quaternary ammonium pestic...
With all of the sample preparation step, you still have significant matrix effect and need standard addition or matrix-matched standard. Would it be quicker if you pass the 1:1 water:acidified methanol thru an Oasis HLB to trap fat (pass thru) and add internal standard to correct for suppression? The IS is not that expensive if you add into the sample at the end.
Please look at the following below links which may help you in your analysis:
http://quimica.udea.edu.co/~carlopez/cromatohplc/500_pesti_gc_hplc_ms_2006.pdf
https://www.sciencedirect.com/science/article/pii/S0021967318315954
https://link.springer.com/article/10.1007/s12161-018-1201-6
Thanks
If the matrix is plasma,
a) we can use phospholipid cartridges to reduce the matrix effect.
b) Sometimes change in solvent from methanol to acetonitrile also helps.
If the sensitivity if in ample amount with consistent effect of matrix and it is ok to have the observed matrix effect then deutrated or labeled ISTD can be used to correct for suppression or enhancement.
I agree, Narong, although I would think that you would want to add the IS prior to passing it through the HLB SPE column. The analytes should pass through unretained, so you should get rid of a lot of the matrix effects that they are seeing.
Matrix suppression is not predictable. No matter how you cleanup the sample, you will have it. Otherwise, if you have the ideal sample cleanup to eliminate the matrix, you would not need IS. My suggestion is to use a small amount of IS at the end just before injection to only fix the matrix effect, not to fix poor recovery due to bad protocol.
My point is many researchers are abusing the use of IS to correct for low recovery due to poor extraction, poor sample cleanup, and poor method transfer technique. If you choose a wrong solvent such as methylene chloride to extract moderate polar compounds from a sample and get on 5% out of the sample, you will get 5% of IS as well (if you add IS just before extraction). Your "apparent" recovery will be 100% even if you drop half of the sample extract on the floor. You would not need sample cleanup to fix matrix effect because whatever may happen to the native standard, it will happen to the IS (particularly the deuterated one). I prefer to use IS just to fix the matrix effect at the end. Again, you don't need to agree with me my suggestion.
There are at least two ways to minimize matrix effect in order to get accurate quanttification of the method (by LCMS or GCMS). First clean the sample until the matrix disappear without losing the analyte. This is hard because we don’t exactly what they are. Secondly, use matrix-mateched standard to compensate the effect. However, we may not be able to get blankmatrix that has the exact match. If you are lucky to have IS that is similar to the analyte (same RT and structure) be available and affordable, then you can have std in solvent with IS to quantify the analyte in any samples in the set with minimum matrix effect. It is scientifically sound to develop an extraction/cleanup method to eliminate sample matrix as much as possible to minimize coelution, improve peak shape, keep the insturment/column clean and still have good recovery. However, if you are looking for analytes with different polarity, it is a bit harder. One easy way is to use the very sensitive instrument and inject the small amount iof sample (dilution/small injection volume).
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