title: IS addition in bioanalysis of DBS: results from the EBF DBS-microsampling consortium.
abstract: BACKGROUND
  In the framework of wider exploration of the application of dried blood spots (DBS) in bioanalysis, by the DBS consortium of the European Bioanalytical Forum, one team of five laboratories investigated the merits of the various ways of IS addition prior to LC-MS/MS analysis. A set of 22 pharmaceutical compounds with log P in the range of 0-10 was selected for this purpose. Assessments were made of precision, recovery, and of the effects of prolonged storage.
  
  
  RESULTS
  Assay precision was not significantly different for 3 month-aged samples as compared with 'fresh' samples stored for 7-22 days. Extraction recovery from 3 month-aged spots decreased for some of the analytes; the most widely employed addition of IS in the extraction solvent does not compensate for recovery in such cases.
  
  
  CONCLUSIONS
  From the overall results, it is clear that there is no 'one size fits all' approach to IS addition in DBS bioanalysis.
authors.affiliation: QPS Netherlands B.V., Petrus Campersingel 123, 9713 AG Groningen, The Netherlands. ben.van.baar@qps.com
authors.forename: Ben L M
authors.initials: BL
authors.lastname: van Baar
authors.forename: Tom
authors.initials: T
authors.lastname: Verhaeghe
authors.forename: Olivier
authors.initials: O
authors.lastname: Heudi
authors.forename: Morten
authors.initials: M
authors.lastname: Rohde
authors.forename: Simon
authors.initials: S
authors.lastname: Wood
authors.forename: Jaap
authors.initials: J
authors.lastname: Wieling
authors.forename: Ronald
authors.initials: R
authors.lastname: de Vries
authors.forename: Steve
authors.initials: S
authors.lastname: White
authors.forename: Zoe
authors.initials: Z
authors.lastname: Cobb
authors.forename: Philip
authors.initials: P
authors.lastname: Timmerman
mesh_terms: D000818:Animals; D059788:Dried Blood Spot Testing / Q000592:standards*; D005060:Europe; D006801:Humans; D007193:Independent Practice Associations; D000432:Methanol; D051381:Rats; D015203:Reproducibility of Results; D052617:Solid Phase Microextraction; D012997:Solvents; D013048:Specimen Handling / Q000592:standards*; D053719:Tandem Mass Spectrometry; D013997:Time Factors
chemical_list: D012997:Solvents; D000432:Methanol