PharmPK Discussion - Drug concentrations in Alginate beads

• On 22 Mar 2011 at 23:30:25, vijay sripuram (sripuramvijay.-a-.gmail.com) sent the message
  

  
  Dear all,
  
  We are using drug entrapped calcium alginate beads for dosing in our  studies. In order to
  assess the concentrations in beads, they are been  treated with sodium citrate and
  extracted by using DCM treatment  followed by it's evaporation. But there is no expected
  pattern observed  after LC-MS analysis.
  
  Still we suspect on extraction process. Can any body give me the basic  idea for LLE
  process (science in selection of buffer for neutralisation  of the analyte in matrix) for
  molecules with different chemical  nature.And can the same extraction method be used for
  diffent  matrices(tissue particularly).
  
  Regards
   VIJAY
  
  

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• On 24 Mar 2011 at 12:10:58, Larger Patrice (Patrice.Larger.-a-.rottapharm.com) sent the message
  

  
  The following message was posted to: PharmPK
  
  Dear Vijay,
  
  In LLE you use the partition of your analyte into the immiscible organic  phase to extract
  it from the aqueous solution (if it actually does  partition preferentially into the
  organic phase). The buffer used should  therefore ensure it is under the neutral form,
  which will have highest  partition coefficient; that is well below pKa for acids, well
  above pKa  for bases.
  Did you try to adapt the extraction from beads upon existing extraction  from other sample
  types? It may anyway be useful to test extraction from  simple aqueous solution before to
  test on beads to check the LLE  extraction method works fine (to test the pH used is
  correct but also  that DCM is the best solvent for your compound). You are doing a double
  extraction: are you sure the citrate buffer is  actually extracting the compound from the
  bead material? Check pH in  this extract.
  Another confounding factor may be stability of the compound during  extraction and drying.
  
  Good luck
  
  Patrice Larger
  Translational Sciences & Pharmacokinetics Dpt
  ROTTAPHARM | MADAUS
  
  

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• On 25 Mar 2011 at 23:25:24, vijay sripuram (sripuramvijay.aaa.gmail.com) sent the message
  

  
  Dear Patrice,
  
   Thanks for your reply. Here the usage of sodium citrate is mainly to  digest the calcium
  alginate beads and it is coincidence that sodium  citrate is acting as a neutralising
  buffer. I have not checked with  other sample types. But it is essential to measure the
  loaded drug  concentrations in beads in order check the entrapment efficiency. Can  you
  give references for the buffer selection depending on the drug  chemistry?
  
   Regards
  
  VijayKumar Sripuram
  Senior Research Associate
  Institute Of Life Sciences
  Hyderabad Central University
  India
  
  

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• On 30 Mar 2011 at 12:27:07, Larger Patrice (Patrice.Larger.-at-.rottapharm.com) sent the message
  

  
  The following message was posted to: PharmPK
  
  Dear Vijay,
  
  The buffer for extraction in LLE should be such as to favor partition of  your drug into the organic phase (i.e. keep it in neutral species), any  aqueous buffer offering the right pH could be tried. I suggested to test  with simpler solutions to check you have complete recovery from a  relevant simple buffer system (essentially that your drug actually  partition favorably in the DCM phase and is stable), to confirm any  difference from your digested beads sample would be due to interference  from the alginate (effect on pH, interfering with partition into the  organic phase ...).
  
  Patrice
  Pharmacokinetics, Metabolism & Dynamics
  Translational Sciences & Pharmacokinetics Dpt
  ROTTAPHARM | MADAUS
  
  

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