Simultaneously speciation and determination of manganese (II) and (VII) ions in water, food, and vegetable samples based on immobilization of N-acetylcysteine on multi-walled carbon nanotubes

•Simultaneously speciation and determination of manganese (II) and (VII) ions in water samples by MWCNTs@NAC adsorbent.•Determination of total manganese in food and vegetable samples based on MWCNTs@NAC after microwave digestion process.•Determination manganese in different matrixes by USA-DILT-μ-SPE coupled to AT-FAAS. A novel method based on the immobilization of N-acetylcysteine on chloro-functionalized multi-walled carbon nanotubes (MWCNTs@NAC) was used for the speciation of manganese ions [Mn (II) and Mn(VII)] in water samples. Also, the total manganese (TMn) in vegetables and food samples was determined by the AT-FAAS. By ultrasound-assisted-dispersive ionic liquid trap micro solid-phase extraction (UA-DILT-μ-SPE), the Mn (II)/Mn(VII) ions were extracted in the presence of MWCNTs@NAC for 50 mL of water samples at a pH of 6.5 and 3.0, respectively. The adsorption capacity of MWCNTs@NAC for Mn(II) and Mn(VII) ions was obtained at 146.7 mg g−1 and 138.8 mg g−1, respectively. Under the optimized conditions, the detection limits (LOD), linear range (LR), and enrichment factor (EF) for Mn(II) and Mn(VII) ions were obtained (0.12 μg L−1; 0.14 μg L−1), (0.48–36 μg L−1; 0.55–38.1 μg L−1) and (100.2; 94.5), respectively. The proposed methodology was successfully validated by the CRM samples.