Evaluation of trace elements released by edible clays in physicochemically simulated physiological media.
Physicochemical simulation (pH, electrolytes and temperature) of three physiological media was carried out in order to follow the release of trace elements contained in seven edible clays (mainly kaolinite, illite, muscovite and quartz) collected from the West African countries of Côte d'Ivoire, Guinée and Sénégal. These clays are ingested by pregnant women for diverse reasons that are related to their condition. Simulated oral (6.5<pH<7), stomach (pH approximately 1.8) and intestinal (pH approximately 8.3) media were prepared separately in order to compare the quantities of the trace elements released. Samples were analyzed by inductively coupled plasma emission spectrometry and spectrophotometry for the evaluation of copper, iron ((Fe(II) and Fe(III)), lead, manganese, nickel and zinc, since some of these elements can palliate deficiency problems and others can induce toxic effects. The quantities of the chemical elements released were pH dependent. The lower the pH, the higher the quantities of copper, Fe(III) and zinc. The quantities of Fe(II) were similar at both lower (stomach) and higher (intestinal) pH values. However, the quantities of manganese, nickel and lead were lower than quantification limits. Heating (110 °C) of the clays increased the quantities of trace elements released and could also participate in the microbiological 'decontamination' of raw materials. Microbiological analysis shows that all samples tested were in compliance with the recommendations of the European Pharmacopoeia. To verify the existence of possible beneficial and hazardous effects on human health, the quantities of copper, iron and zinc were compared with the recommended allowances for trace elements in France. In addition, the quantities of manganese, nickel and lead were compared with the maximum admissible concentrations in drinking water.