Determination of fumaric acid in apple juice by on-line coupled capillary isotachophoresis–capillary zone electrophoresis with UV detection

An on-line coupled capillary isotachophoresis–capillary zone electrophoresis (cITP–CZE) method for the determination of the fumaric acid content in apple juice is presented. A clear separation of fumaric acid in real samples is achieved within 20 min. The leading, terminating and background electrolyte of the employed system consist of 10 mM HCl+β-alanine+5 mM β-cyclodextrin+0.05% hydroxypropylmethylcelullose (HPMC), pH 3, 10 mM citric acid and 20 mM citric acid+β-alanine+5 mM β-cyclodextrin+0.1% HPMC, pH 3.3, respectively. The linearity, recovery, repeatability and detection limit of the developed method are 25–1000 ng/ml, 1.07%, 95.4±3.5 (±s)% and 10 ng/ml, respectively. Low laboriousness (no sample pretreatment), sufficient sensitivity and low running cost are the important attributes of the cITP–CZE method which was successfully applied to analyses of real samples of apple juices.