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Dear all,
I have been tuning Tizanidine for quantitative purpose and obtained Q1/
Q3 as 254.0/44.1 at Unit resolution in 50% Methanol using FIP.
Considering that all the dissolved fattyacids of plasma appear at such
masses (during the processing step) I thought that I cannot further
with the above combination of MRM.
Interestingly an article "Rapid Commun. Mass Spectrom. 2006; 20:
2286-2292" also has chosen the above ions and validated their method
for a pharmacokinetic study.
My question is :
1. If the mass calibration range of mass spectrometer between at 59
-2200 amu then, will the above MRM using 44.1 be valid for regulatory
submission, and if it is valid how can one substantiate the impact.
2. The proposed fragments seems to be highly unstable and therefore
there is no alternative than chosing that fragment of 44.1 amu. How
ever has anyone worked using a derivatization of imidazolines (class
to which Tizanidine belongs) for quantitation in LC-MS/MS???
opinions are welcome.
Regards,
Santosh Tata
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Dear Santosh,
I would suggest you to pass the molecular ion without fragmenting and
quantitate only Q1 mass i.e. 254. (Keep collision energy very low).
The fragment 44.1 is as such a very low and will certainly give non
reproducible results. Moreover the fragmented mass (44.1) is below the
calibration range and would certainly attract inspectors attention.
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Dear Santosh
I hope you can calibrate your Mass spectrometer below m/z 59 also,
contact your service engineer or go through literature in this regard
Devender
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