I did analysis of two compounds using LC-MS/MS. The calibration curve was established, The limit of detection obtained were 17.78 ppm and 18.65 ppm respectively and the limit of quantitation was 53.89 ppm and 56.52 ppm respectively. the values are too high, what could be the problem?
Anna Kibiki,
It is depend upon the selection of mobile phase because LOD & LOQ is very high considering the instrument used. I know this is not the complete solution but without knowing the details of chromatography parameters It is difficult to give solution. General suggestion is to check the detector response i.e make sure the vacuum and other tunning parameter should be set properly.
Selection of source should be appropriate.
Hopefully this general point will definitely help to resolve the issue.
Hi!
I have added the details on the experiment which I did.
I did analysis using LC-MS/MS ( LC- Agilent 1100) coupled with tandem MS from Waters company. I used Kinetex ®column um C18 100 A° (75X2.1 mm).
Mobile phase used was 0.1% FA water and solvent B 0.1% FA acetonitrile, gradient elution started with 30% of mobile phase B, at 0.3 ml/min flow rate.
The MS conditions : positive ESI mode was used, the desolvation temp was 400°C , source temp 120°C, cone voltage for dexamethasone was 17 kV and 16 kV for prednisolone.
The standard used were purified from tablets and percentage purity was checked using HPLC and I got 98% and 88% for dexamethasone and prednisolone.
The concentration used for calibration curves were 5, 20, 40, 60, 80, 100, and 120 ppm for both compounds.
The limit of detection obtained for dexamethasone and prednisolone were 17.78 ppm and 18.65 ppm respectively and the limit of quantitation for dexamethasone and prednisolone were 53.89 ppm and 56.52 ppm respectively.
But according to ICH guideline the LOQ is the lowest concentration which can be detected, I expected to get very small values. But values which I got are too high, what could be the problem?
I would appreciate to hear from you researchers.
Thank you.
Dear Anna Kibiki,
Sorry for late reply. I am working on your given details and will revert with appropriate solution by next week,
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