A continuous-flow dialysis system with inductively coupled plasma optical emission spectrometry for in vitro estimation of bioavailability

A continuous-flow dialysis (CFD) method with on-line inductively coupled plasma optical emission spectrometric (ICP-OES) simultaneous multielement measurement for the study of in vitro mineral bioavailability was developed. The method was based on a simulated gastric digestion in a batch system followed by a continuous-flow intestinal digestion. The simulated intestinal digestion was performed in a dialysis bag placed inside a channel in a flowing stream of dialyzing solution (NaHCO₃). The mineral concentrations in the dialysate were determined by ICP-OES using Y and Sc as internal standards. The pH of the dialysate was also monitored on-line to ensure pH changes similar to the situation in the gastrointestinal tract. The developed system was applied to determining the dialysability of five essential elements (Ca, Mg, P, Fe, Zn) for various kinds of foods, i.e., milk-based infant formula reference material (NIST SRM 1846), milk powder, kale, mungbean, chicken meat, jasmine rice, and Acacia pennata. The dialysis profiles of elements and pH change profiles can be useful in understanding the dialysis change and factors affecting dialysability. All studied elements were rapidly dialysed in the first 30 min of simulated intestinal digestion. It is expected that this system will be useful for estimation of dialysability and for studying the mutual effects of components in food.