In situ analysis of copper speciation during in vitro digestion: Differences between copper in drinking water and food.

In recent years, the safety of copper in drinking water has increasingly been questioned. Copper speciation is an important factor that affects its bioavailability and toxicity; thus, it is critical to investigate the speciation of copper that is ingested from food and drinking water during in vitro digestion. After digestion, water- and food-derived copper formed 60 ± 4% 0.1-1 kDa and 49 ± 6% 10-1,000 kDa copper complexes, respectively. Under simulated fasting drinking water conditions, up to 90 ± 2% 0.1-1 kDa copper complexes formed. In addition, using ion selective electrode analysis, water-derived copper was detected that contained higher Cu concentrations after digestion than those of food-derived copper. These results indicate that water-derived copper forms smaller-sized species and exhibits higher Cu concentrations during digestion than those of food-derived copper, thereby highlighting the importance of reassessing the safety limit for copper in drinking water.