Peroxidase mimic feroxyhyte (FeOOH) nanoparticles enabled highly specific colorimetric detection of arsenate in water and fish

Arsenic poses a serious health risk to humans. Hence, a simple and robust analytical approach for monitoring arsenic levels in water and food matrixes is required. We present a simple and rapid approach for quantifying arsenate in water and fish using feroxyhyte (FeOOH) nanoparticles as a sensor probe. The FeOOH nanoparticles showed peroxidase mimetic activity oxidizing 3,5,3′5′-tetramethylbenzidine (TMB) to a blue product (oxTMB, λ_max 650 nm) in the presence of H₂O₂. However, arsenate’s presence inhibits the peroxidase activity of FeOOH nanoparticles through binding on the catalytic active sites. Based on this principle, the presently developed method obtained a good linear response (R², 0.99) over the range of 0.005 to 5.000 mg L⁻¹ arsenate with 0.006 mg L⁻¹ as the detection limit which is less than the prescribed limit (0.010 mg L⁻¹) by WHO for drinking water. The average recoveries at different fortification levels ranged from 89.51 to 115.61 % in water and 101.11 to 106.99 % in fish muscle. The present analytical technique showed good selectivity due to pronounced peroxidase inhibition alibility (60.53–103.78 %) by arsenate than other non-target ions like PO₄³⁻, NO³⁻, Cr₂O₇²⁻, etc. The FeOOH nanoparticles showed a promising application prospect for colorimetric detection of arsenate with a wide detection range in water and fish samples.