Determination of Apremilast in Rat Plasma by UPLC–MS/MS in Esi-Negative Mode to Avoid Adduct Ions Formation

Abstract

Background: Quantification of target analyte by LC–MS/MS is sometimes hampering due to competitive adduct ions formation (sodium and/or ammonium) in positive ionization mode. A UPLC–MS/MS assay was developed for the determination of apremilast in rat plasma using ESI-negative mode to avoid adduct ions formation. Method & results: After extraction from plasma by ethyl acetate, analyte and IS were separated on Aquity BEH C₁₈ column using acetonitrile-10 mM ammonium acetate (85:15) as mobile phase. The calibration curve was linear between 3.04 and 1000 ng/ml with correlation coefficients (r²) of ≥0.995 and lower limit of quantification of 3.04 ng/ml. All validation parameter results were within the acceptable range. The assay was successfully employed in oral PK study with C_max of 584.29 ng/ml and AUC_0–20 of 6530 ng.h/ml after apremilast (2 mg/kg) administration. Conclusion: This result suggests that ESI in negative mode would be an alternative approach for LC–MS/MS quantification of analytes, which produce competitive adducts in positive mode.

Keywords::

• adduct ions
• apremilast
• negative ionization mode
• PK
• plasma
• rats
• UPLC–MS/MS

Financial & competing interests disclosure

The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding the work through the research group project no. RGP-VPP-203. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.