Determination of ortho-phenylphenol residues in lemon rind by high-performance liquid chromatography with electrochemical detection using a microbore column

A simple and highly sensitive method has been developed for determining ortho-phenylphenol (OPP) in lemon rind by high-performance liquid chromatography with electrochemical detection using a microbore column (microHPLC-ECD). Based on the voltammetric behavior of OPP, microHPLC-ECD was established using a CAPCELL PAK C-18 UG 120 microbore ODS column, 17 mM acetic acid-sodium acetate buffer (pH 4.0)/acetonitrile (60/40, v/v) as a mobile phase and an applied potential at +0.9 V vs. Ag/AgCl. The current peak height was found to be linearly related to the amount of OPP injected from 3.4 pg to 1.7 ng (r > 0.999). The detection limit (S/N = 3) was 3.4 pg (20 fmol), which was 100 times greater in terms of sensitivity when compared to conventional HPLC with UV detection. Standard OPP at 0.425 ng was detected with a relative standard deviation (RSD) of 1.9% (n = 10). The OPP contents in several lemon samples were determined by the present method. The recoveries of OPP from lemon rind exceeded 98% with an RSD (n = 5) of less than 3.01%.