Chromatography Forum

Hello

I study amoxicillin/clavulanic acid in plasma. I tried many extraction and HPLC methods. However till now the recovery is low and there is interference near the peak of clavulanic acid. Could you help me in finding a better extraction and HPLC method. If you like I can send you the methods I tried till now. I'm looking forward for your kind helps.

Development of a Solid Phase Extraction-Liquid Chromatographic Method for the Determination of Amoxicillin in Plasma
N. Lindegårdh, T. Singtoroj, A. Annerberg, N. Day
Therapeutic Drug Monitoring, 27 (2005) 503-508


Let me know if you like to get a personal copy of this paper.

/Einar

Hello Einar

Thank you your answer. I don`t have a problem with amoxicillin but there is interference near the peak of clavulanic acid. My extraction method ;

To a tube ,500 ul plasma sample ,1500 ul ( 0.1 M HCI/ Acetonitrile; 1/9) were added. The mixture was vortex-mixed on a vortex mixer for 30 seconds.The mixture was then centrifuged at 5000 g 15 min. After centrifuged the supernatant was transferred a new tube. After evaporation to dryness at 350 C under a stream of nitrogen, the dried extracts werw resolved in 200 ul in water.
Mobile phase 0.01 M potassium dihiydrogen phosphate buffer adjusted to a pH 2.5 with orto phosphoric acid and acetonitrile ( 98/2)
Column Ace C8 ( 150 mm x 4.6mm x 5um) , room temperature .
I tried with SPE( C18) to separated interferences from clavulanic acid . but not separeted.

I don`t know, what can I do ???

The clavulanic acid looks quite hydrophilic so maybe it could be a good idea to test a ZIC®-HILIC SPE as they did in the paper I mentioned above.

Hello Einar

I visit your web site but I don`t received you said paper.If you can send it to me , I will try again.
My email serap.guven@ege.edu.tr

Thank you…

In such cases, we have been successful with changes in solvent (methanol to acetonitrile) or changes in pH (high/low). This moves interferences and analyte around at random, and you may end up in a better spot.

However, a well executed SPE method can remove interferences much more effectively than the type of changes in LC that I pointed out above.

Either way is some work...

After evaporation to dryness at 350 C under a stream of nitrogen,

Good morning! I think this temperature is much to high...... Could it be you have degradation products?

Regards Bert

You are right Bert..

I have a mistake .It is only 35 degress centigrade... Thank you