On-line pervaporation-capillary electrophoresis for the determination of volatile analytes in food slurries

Pervaporation has been coupled on-line to capillary electrophoresis (CE) by a flow injection manifold and the replenishment system of the CE instrument. The approach allows volatile analytes to be removed, derivatisated and injected into the capillary meanwhile the sample matrix remains in the pervaporator. Acetone and four aldehydes (namely: formaldehyde, acetaldehyde, hexenal, 2-trans-hexenal) have been simultaneously determined in slurries samples by this approach. The detection limits (LOD) ranged between 0.1 and 0.6 μg/ml, the quantification limits between 0.5 and 2.0 μg/ml and the linear dynamic ranges between the limit of quantitation and 150 μg/ml. The precision, expressed as relative standard deviation (RSD), ranged between 0.76 and 4.21% for repeatability and between 1.12 and 4.78% for within laboratory intermediary precision. The errors involved in the analysis of the target analytes – expressed as RSD for all compounds – ranged between 0.13 and 4.87%. The optimal pervaporation time and that necessary for the individual separation/detection of the target analytes are 15 and 10 min, respectively. The analysis frequency is 4 h−1. The accuracy of the method and potential matrix effects were established by analysing spiked samples. Recoveries between 96.12 and 105.67% were obtained. The proposed method was applied to 10 samples with different solid contents (namely, such yoghurt, juice and yoghurt–juice mixtures).