title: Supported liquid extraction offers improved sample preparation for aldosterone analysis by liquid chromatography tandem mass spectrometry.
abstract: BACKGROUND
  To evaluate the accuracy and precision of a method for serum aldosterone using supported liquid extraction (SLE) for sample preparation instead of the more conventional liquid-liquid extraction (LLE) approach.
  
  
  METHODS
  Two independently developed SLE-based LC-MS/MS methods for serum aldosterone (sample volumes 250 μl and 300 μl respectively) were compared to a modification of a previously reported LLE approach (sample volume 500 μl) in two method comparisons (n=75 and n=97). SLE analyses were performed at two separate centres. Precision was evaluated at a single site using human pools in head-to-head comparison between SLE and LLE. All analyses were performed on the ABSCIEX API-5000 LC-MS/MS system.
  
  
  RESULTS
  At four increasing pool concentrations spanning 67-1060 pmol/l, total precision for SLE ranged from 6.8-4.1% compared with 11.1-4.3% for LLE. Differences did not reach statistical significance except at the lowest concentration where SLE was superior. Pasing Bablok regression comparisons were SLE=0.96×LLE-5.8 pmol/l (R(2)=0.985) and SLE=0.96×LLE-0.44 pmol/l (R(2)=0.969).
  
  
  CONCLUSIONS
  For analysis of serum aldosterone on the ABSCIEX API-5000, SLE affords a smaller sample volume while maintaining the accuracy and precision performance of LLE. By avoiding specimen vortexing, SLE also allows for greater automation in the sample preparation.
authors.affiliation: Department of Pathology and Laboratory Medicine, St Paul's Hospital, Vancouver, British Columbia, Canada.
authors.forename: Jessica Grace
authors.initials: JG
authors.lastname: Van Der Gugten
authors.forename: Matthew
authors.initials: M
authors.lastname: Crawford
authors.forename: Russell P
authors.initials: RP
authors.lastname: Grant
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Holmes
mesh_terms: D000450:Aldosterone / Q000097:blood*; D001774:Blood Chemical Analysis / Q000379:methods*; D005591:Chemical Fractionation / Q000379:methods; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D059625:Liquid-Liquid Extraction / Q000379:methods*; D015203:Reproducibility of Results; D013048:Specimen Handling; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000450:Aldosterone