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Supported liquid extraction offers improved sample preparation for aldosterone analysis by liquid chromatography tandem mass spectrometry
  1. Jessica Grace Van Der Gugten1,
  2. Matthew Crawford2,
  3. Russell P Grant2,
  4. Daniel T Holmes1
  1. 1Department of Pathology and Laboratory Medicine, St Paul's Hospital, Vancouver, British Columbia, Canada
  2. 2Laboratory Corporation of America, Burlington, North Carolina, USA
  1. Correspondence to Dr Daniel T Holmes, Department of Pathology and Laboratory Medicine, St Paul's Hospital, 1081 Burrard Street, Vancouver, BC, Canada V5J 4B7; dtholmes{at}mail.ubc.ca

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 (R2=0.985) and SLE=0.96×LLE-0.44 pmol/l (R2=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.

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