Recovery calculation in LC-MS-MS reg

[sivakumar]

Dear All,

Regarding the recovery calculation in Quantitative analysis of Drugs by LC-MS-MS, suppose our Drug is Ester and it is easily degrades to Acid in Plasma, in that case how can I calculate the recovery? I have to add both the areas of Ester and Acid or acid only? I would like to add that in the case of high concentration of Ester (drug) in plasma the degradation rate is less compared ot low concentration.

Kindly give your opinion regarding this problem

Thanks and Regards

B. Sivakumar

[Rolandas Plausinaitis]

Hi,

Unfortunately you can't add the areas (MS ionisation rate could be different).
If you measure only ester using your method ( I mean prepare calibration curve from ctandard etc.) you can't include other forms in recovery and other calculations.

Only way to include both forms would be to make calibration for acid and for ester and then add calculated amounts. However in your situation it is not realistic.

One solution would be to look for possibility to prevent transformation or minimise it.

Second solution is to transform all the drug to acid form and then measure it.

Good luck