Application of hollow fibre based microextraction for voltammetric determination of vanillylmandelic acid in human urine

Abstract

A new hollow-fibre microextraction method has been developed for the determination of a clinical biomarker vanillylmandelic acid (VMA) in human urine. The extraction was used in combination with differential pulse voltammetry (DPV) on cathodically pre-treated boron doped diamond electrode (BDDE). Butyl benzoate was found to be the optimum solvent for creation of supported liquid membrane. Optimum donor and acceptor phases were 0.1 mol L−1 HCl and 0.1 mol L−1 NaOH, respectively, optimum extraction time was 30 min. Linear range was from 0.5 to 100 μmol L−1 (r = 0.9989), with good repeatability (RSD 7.9% for 50 μmol L−1 VMA aqueous sample (n = 7)). The limit of detection (LOD) was 0.5 μmol L−1. The method was successfully applied for the determination of VMA in real human urine sample using a standard addition method, obtained RSD being 8.1% (n = 5). The method is sufficiently selective and sensitive for its intended use as a screening tool for elevated concentration of VMA.