A simple solid-phase extraction method for the analysis of red cell phospholipids by liquid chromatography- tandem mass spectrometry.

Background: There has been increasing interest in the analysis of phospholipids in red blood cells as potential long-term biomarkers of different disease states. Here, we describe a simple method for the analysis of two phospholipids: 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanol (PE 16:0/18:1) and 1-Palmitoyl-2-linoleoyl-sn-glycero-3-phosphoethanol (PE 16:/0/18:2) in erythrocytes by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Methods: Whole blood samples were removed free of plasma and washed in isotonic saline. Red cells were lysed with ultrapure water. Lysate samples were processed using a hybrid solid-phase extraction (SPE) phospholipid cartridge (1 mL, 30 mg). Both PE 16:0/18:1 and PE 16:0/18:2 and their deuterated internal standards were separated on an ACE C4 (150 mm × 2.1 mm, 2.7 μm particle size) by gradient elution at a flow rate of 0.5 mL per minute using mobile phases consisting of 0.01 mol/L ammonium acetate in: water (A), methanol (B), and isopropanol (C). The phospholipid species were quantified by the following transitions: PE 16:0/18:1: 701.5→281.3 and PE 16:0/18:2: 699.5→279.3.

Results: Both PE species displayed linearity ranging from 10 to 500 μg/L. The coefficient of variation (CV%) of PE 16:0/18:1 concerning intraday and interday precision was between 1.9%-2.6% and 3.0%-4.3%, respectively. For PE 16:0/18:2, this was between 1.8%-3.4% and 3.7%-4.1%, respectively. Both phospholipid species had accuracy (PE 16:0/18:1: 91%-98% and PE 16:0/18:2: 94%-103%) and extraction recovery (PE 16:0/18:1: 95%-106% and PE 16:0/18:2: 92%-102%) exceeding 90% over the analytical range. The limit of detection was 5 μg/L.

Conclusion: Here we propose a simple SPE LC-MS/MS method for analyzing phospholipids in erythrocytes, which can be easily adopted.