Sugaring-out assisted liquid/liquid extraction with acetonitrile for bioanalysis using liquid chromatography–mass spectrometry

Abstract

Recent research demonstrated that sugar at a high concentration can induce the mixture of acetonitrile and water to form phase separation. As a result of phase separation, more acetonitrile and low polarity solutes tend to go to the upper layer and more water and high polarity components tend to stay at the bottom. This sugaring-out assisted liquid/liquid extraction (SULLE) has been successfully demonstrated in the determination of eight compounds in human plasma. SULLE for lopinavir and ritonavir from human plasma has been validated with reference to good laboratory practice guidance, and cross-validated against a previously reported method. Achieved method performance of SULLE–LC–MS/MS is similar to that of the reported method using salting-out assisted liquid/liquid extraction (SALLE). SULLE can be used to enrich low polarity analyte by varying the volume ratios of acetonitrile, aqueous phase and sugar concentration. SULLE extract is compatible with reversed phase liquid chromatography and can be directly injected into an LC–MS/MS system with an optional dilution with water when needed. All liquid transfers can be handled easily with multichannel pipettes and the high throughput extraction can be achieved without difficulty in most bioanalytical laboratories.