Quantitative determination of endogenous sorbitol and fructose in human erythrocytes by atmospheric-pressure chemical ionization LC tandem mass spectrometry

Evaluation of different extraction methods for quantification of endogenous sorbitol and fructose in human red blood cells (RBCs) and matrix effects in ESI and APCI showed that protein-precipitation followed by mixed-mode solid-phase extraction was more effective extraction method and APCI more effective ionization method. Then the LC/APCI-MS/MS method was fully validated and successfully applied to analysis of clinical RBC samples. The concentrations of endogenous sorbitol and fructose were determined using calibration curves employing sorbitiol-13C6 and fructose-13C6 as surrogate analytes. The method has provided excellent intra- and inter-assay precision and accuracy with a linear range of 50.0–10,000 ng/mL (correlation coefficient >0.999) for sorbitol-13C6 and 250–50000 ng/mL (correlation coefficient >0.999) for fructose-13C6 in human RBCs.