Identification of an Interfering Substrate in Apple Juice and Improvement for Determination of Patulin with High-Performance Liquid Chromatography Analyses

An interfering substance that is not 5-hydroxymethylfurfural appears in some apple juices during high-performance liquid chromatography (HPLC) analysis of patulin based on the AOAC 995.10 method. Because this interfering substance could cause the overestimation of patulin in the apple juices, we tried to identify the substance and to develop an improved method of analyzing patulin free from the influence of this substance. We isolated the substance from the apple juice and identified it as adenosine based on its mass spectrometry, proton nuclear magnetic resonance, and photo diode array spectra. Because of the chemical properties of adenosine, changes in the extraction method under acidic conditions and the HPLC conditions (wavelength and analytical column) were effective for avoiding the influence of adenosine and more specifically for analyzing the patulin. The most effective and simple improvement of the official method was the use of column in-point carbon contents greater than 15.5%.