On-line detection of hippuric acid by microextraction with a molecularly-imprinted polysulfone membrane sorbent and liquid chromatography–tandem mass spectrometry

• In the present study the surface of a polysulfone membrane was modified with molecularly imprinted polymer.
• The MIP membrane in combination with MEPS-LC–MSMS was applied for on-line extraction of hippuric acid in plasma and urine samples.
• The MIP membrane showed highly specific recognition for the hippuric acid.
• The membrane showed a long lifetime and could be used for more than 50 extractions.

Destruction of sorbents during consecutive extractions using the micro-extraction by packed sorbent (MEPS) technique is a serious problem. In MEPS the complex matrix such as plasma and blood can affect the sorbent physical properties and the sorbent can be deteriorated after handling of few samples. To overcome this problem, the surface of a polysulfone membrane (PSM) was modified by a molecularly imprinted sol–gel and utilized for online extraction of a lung cancer biomarker, hippuric acid (HA), in biological matrices. The molecularly imprinted polymer membrane provided fast, sensitive, selective and robust sample preparation method for HA in biological fluids. In addition, MIP membrane could be used for up to 50 extractions without a significant change in extraction recovery. To achieve the best results, the parameters that influenced the extraction efficiency were thoroughly investigated. Moreover, for evaluating the performance of the molecularly imprinted sol–gel membrane (MISM), a non-molecularly imprinted sol–gel membrane (NISM) as a blank was prepared. The limits of detection (LOD) and quantification (LOQ) for HA in both plasma and urine samples were 0.30 nmol L−1 and 1.0 nmol L−1, respectively. Standard calibration curves were obtained over the range of 1–1000 nmol L−1 for HA in plasma and urine samples. The coefficients of determination (R2) were ≥0.997. The extraction recoveries of HA from human plasma and urine samples were higher than 91%. The precision values for HA in plasma and urine samples were 2.2–4.8% and 1.1–6.7%, respectively.