An in vitro technique using simulated gastrointestinal (GI) fluids was applied to investigate the desorption of selected endocrine disrupting chemicals (EDCs), i.e. bisphenol A (BPA) and 17 α-ethinylestradiol (EE2), from the marine sediment in the digestive environment. The results show that the GI fluids suppressed chemical adsorption and greatly increased the desorption of BPA and EE2 from the sediment. Pepsin in the gastric fluid would compete for the adsorption sites with the adsorbates, and bile salts in the intestinal fluid had a solubilization effect on the chemicals. The amount of chemical release from the sediment in different fluids followed intestinal (fed)>intestinal (fasted)>gastric>saline water. During the dynamic desorption tests, 62% and 21% of sediment-bound BPA and EE2, respectively, could be released into the simulated GI fluids. The enhanced desorption of EDCs from sediment in the digestive system would make the pollutants more bioavailable in the ecosystem.

Adsorption/desorption and desorption hysteresis of methamphetamine (MMA) on carbon nanotubes (CNTs) as well as bioavailability of MMA were studied in simulated gastrointestinal fluids and background fluids. Adsorption of MMA in near-neutral (weak alkaline) intestinal fluid was enhanced, while adsorption of MMA on CNTs in acid gastric fluid was suppressed. Desorption of MMA is divided into fast and slow stages, and fast desorption conducting in the gastric fluid lasted shortly and slow desorption occurred in intestinal fluid; pepsin can enhance the release of MMA in gastrointestinal system. While, the acidic condition in gastric fluid is the main factor which causes the release of MMA. The amount of MMA released from CNTs in different fluids follows the order gastric > background (pH = 2.0) > intestinal (fed) > intestinal (fasted) > background (pH = 7.5). These findings in the simulated gastrointestinal system suggest that the release of MMA from CNTs could be promoted by biomacromolecules (such as pepsin and bile salts in digestive tract); thus, the bioavailability of MMA is enhanced.