title: Sensitive determination of a drug candidate in dried blood spots using a TLC-MS interface integrated into a column-switching LC-MS/MS system.
abstract: BACKGROUND
  A thin-layer chromatography-mass spectrometry interface was previously reported to extract compounds from dried blood spots online. Here, we integrated this interface into a column-switching LC-MS/MS system for online solid-phase extraction and addressed internal standard addition.
  
  
  RESULTS
  A drug was analyzed in dried blood spots with a lower limit of quantitation of 50 pg/ml. The internal standard was added via an autosampler to the extraction solvent. The method featured online aqueous dilution of the dried blood spots extract with subsequent trapping and gradient analytical separation. Good precision, accuracy and recovery were obtained.
  
  
  CONCLUSIONS
  The thin-layer chromatography-mass spectrometry interface provided high reproducibility and good extraction efficiency. Although manually operated, it significantly reduced sample preparation efforts. The combination with online solid-phase extraction allowed enrichment of larger sample/extract volumes and efficient clean-up.
authors.affiliation: F. Hoffmann-La Roche Ltd., Pharma Research, Nonclinical Safety, Bioanalytical Section, CH-4070 Basel, Switzerland. katja.heinig@roche.com
authors.forename: Katja
authors.initials: K
authors.lastname: Heinig
authors.forename: Thomas
authors.initials: T
authors.lastname: Wirz
authors.forename: Almudena
authors.initials: A
authors.lastname: Gajate-Perez
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards; D001800:Blood Specimen Collection / Q000379:methods*; D002855:Chromatography, Thin Layer / Q000379:methods*; D003890:Desiccation; D006801:Humans; D004364:Pharmaceutical Preparations / Q000097:blood* / Q000302:isolation & purification; D012015:Reference Standards; D012680:Sensitivity and Specificity; D052616:Solid Phase Extraction; D018511:Systems Integration; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D004364:Pharmaceutical Preparations