title: Determination of theophylline in rabbit plasma by triple quadrupole LC/MS.
abstract: OBJECTIVE
  A simple, sensitive and rapid method was developed for quantitation of theophylline in rabbit plasma utilizing Triple Quadrupole LC/MS.
  
  
  METHODS
  An aliquot of 0.1 mL of plasma sample was extracted with ethyl acetate using Heidolph Vortex. The chromatographic separation was performed by using HyPURITY ADVANCE™ C18 Column (3 × 50 mm) with a mobile phase of 80% methanol and 20% 2 mM ammonium acetate buffer followed by MS/MS detection. The analyte was quantitated in positive ionization mode. Multiple reaction monitoring (MRM) using the transition m/z 181.1→124.2 and m/z 180.2→110.1 was performed to quantify theophylline with internal standard (IS, Phenacetin), respectively. The method had a total chromatographic runtime of 3 min and linear calibration curves over the concentration range of 50.418-5062.063 ng/mL. The lower limit of quantification (LLOQ) was 50.418 ng/mL Sodium heparin (3.50%) used as an anticoagulant to prepare rabbit plasma and samples were maintained at 10°C in the auto sampler during the assay period. Inter and intraday batch precision and accuracy of the method were determined by using six quality control samples.
  
  
  RESULTS
  Average accuracies for the assay were 89 to 106%, inter and intra-day coefficients variation (CV) of <9% and the recovery is 39.30% for theophylline and 57.00% for Phenacetin.
  
  
  CONCLUSIONS
  Currently we are extensively using this method in our laboratory for quantitative analysis of theophylline in rabbit plasma samples and proved to be simple, accurate and precise.
authors.affiliation: Drug Discovery Research, Bioanalytical Division, G7 Synergon Private Limited, No. 537, 9 Cross, 5 Main, Tata Nagar, Sahakaranagar Post, Bangalore, India.
authors.forename: A R Suresh
authors.initials: AR
authors.lastname: Babu
authors.forename: B
authors.initials: B
authors.lastname: Thippeswamy
authors.forename: A B
authors.initials: AB
authors.lastname: Vinod
authors.forename: E G
authors.initials: EG
authors.lastname: Ramakishore
authors.forename: S
authors.initials: S
authors.lastname: Anand
authors.forename: Duraisamy
authors.initials: D
authors.lastname: Senthil
keywords: Phenacetin; rabbit plasma; sodium heparin; theophylline; triple quadrupole LCMS