PharmPK Discussion - Docetaxel HPLC method

• On 8 Feb 2013 at 02:51:05, Rafid Salim (rafidewadh.-at-.yahoo.com) sent the message
  

  
  Dear all PK-PD forum members.
  
  I am trying to build up a calibration curve for docetaxel (at nano molar
  level) in HPLC using the following conditions (Andersen et al., 2006).
  The docetaxel is dissolved in 40% acetonitrile, mobile phase is composed
  of ACN:Potassium phosphate buffer (pH=3) at (42.5/57.5) using merck
  column (12.5X3X3) at 55 degree celesius.
  The problem is that the peak areas are not proportional to the
  concentration of the docetaxel standard especially at the nano molar
  level.
  Please I would like to ask your help and advice to solve this problem.
  
  Rafid Salim
  
  

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• On 11 Feb 2013 at 10:30:59, Muhammed Ayub (mayub.-a-.ttpharma.com) sent the message
  

  
  Dear Rafid Salim,
  
  Are you using an internal standard?  Did you evaluate non-specific
  binding for this compound?
  
  Thanks,
  Muhammed
  
  

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• On 11 Feb 2013 at 16:32:21, (R.ter.Heine.at.meandermc.nl) sent the message
  

  
  The following message was posted to: PharmPK
  
  Dear Rafid,
  
  the method described by Andersen et al is a UV-based method. So, it
  seems that your problem is either at the detection level (is your UV
  detector still OK?) or there is an interference which does not become
  apparent until  docetaxel concentrations become very low. Have you
  thoroughly checked the selectivity and sensitivity of your assay yet?
  
  Cheers,
  Rob
  
  

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• On 11 Feb 2013 at 12:53:36, "Edward O'Connor" (efoconnor.at.gmail.com) sent the message
  

  
  Are you using an ISTD?
            How similar is it
            Does it interfere
  
  Where is the relationship falling off?
  
  Have you tried
                1/y 1/y2 weighting?
                 Other algorithim
  
  Increasing the LLOQ?
  
  How does your detection cell volume compare with the one in the paper you cited?
  

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• On 12 Feb 2013 at 01:08:09, Eltayeb (chemisteltayeb.-at-.yahoo.com) sent the message
  

  
  The following message was posted to: PharmPK
  
  Dear Dr Rafid
  Where you build your calibration curve ? I mean in  biological fluids
  or
  directly. Because the propotionality of areas/ heights to conc. of the analyte
  depends upon the recovery of it from the desired matrics ........
  
  Dr.ELTAYEB E.M.EID PhD
  Assistant Professor
  Dept. of Pharmaceutics
  College of Pharmacy
  Qassim University
  Saudi Arabia
  

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