Manganese Preconcentration and Speciation in Bioaccessible Fraction of Enteral Nutrition Formulas by Cloud Point Extraction (CPE) and Atomic Absorption Spectroscopy

The present study develops a new method for manganese (Mn) preconcentration and speciation in bioaccessible fraction (soluble and dialyzable fraction) of enteral nutrition formulas by cloud point extraction (CPE) and atomic absorption spectroscopy (AAS). For this purpose, a non-ionic surfactant (Triton X-100) and three chelating reagents [8-hydroxyquinoline (8-HQ); 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP); and ammonium pyrrolidine dithiocarbamate (APDC)] were used with different operating conditions. The results showed that an efficient extraction of ionic Mn could be achieved with the following conditions: pH = 10; chelating reagent concentrations of [8-HQ] = 0.36 M, [PMBP] = 0.09 M, and [APDC] = 0.09 M; surfactant Triton X-100 at 25% ( w / v ), and equilibration temperature-time of 85 °C and 30 min. Limits of detection and quantitation are 0.015 and 0.050 mg L −1 respectively. Furthermore, when analyzing the bioaccessible fraction of the enteral nutrition formulas, the proposed approach can be used to distinguish between ionic (free) Mn and Mn that has been previously bound to existing substances obtained from enzymatic digestion. These Mn speciation findings can be used to validate results obtained from the bioaccessibility assays.