stability of minocycline in extracted samples from plasma

[anilray1155]

friends, i am trying a develop method of assay determination of minocycline in human plasma using LC-MS/MS.
Extraction procedure :SPE
and acidic mobile phase .but here the problem is that the drug response is not stable while the sample were prepare from same sample.it may be any stability issue or unsuitable extrastion procedure.plz... suggest me.
thanks.

[Bruce Hamilton]

From a simple Pubmed search I found several apparently-relevant articles.. The choice of Internal Standard and handling conditions are important,and others have achieved acceptable results.

Perhaps if you carefully reviewed the following articles you might obtain some helpful information.

Determination of minocycline in human plasma by high-performance liquid chromatography coupled to tandem mass spectrometry: application to bioequivalence study.
Araujo MV, Ifa DR, Ribeiro W, Moraes ME, Moraes MO, de Nucci G.
J Chromatogr B Biomed Sci Appl. 2001 May 5;755(1-2):1-7.

High-performance liquid chromatographic assay for minocycline in human plasma and parotid saliva.
Orti V, Audran M, Gibert P, Bougard G, Bressolle F.
J Chromatogr B Biomed Sci Appl. 2000 Feb 11;738(2):357-65.
" In the two matrices studied at 20 and 4 degrees C, rapid degradation of the drug occurred. Frozen at -30 degrees C, this drug was stable for at least 2 months, the percent recovery averaged 90%. "

Liquid chromatographic determination of minocycline in brain-to-plasma distribution studies in the rat.
Colovic M, Caccia S.
J Chromatogr B Analyt Technol Biomed Life Sci. 2003 Jul 5;791(1-2):337-43.

Bruce Hamilton

[Brooke]

We had huge problems with an SPE method from literature that included a derivatisation step, eliminating that step gave us great results. Different class of analyte, but I guess the lesson is to experiment a bit.