Fluorometric assay of iron(II) lactate hydrate and ammonium ferric citrate in food and medicine based on poly(sodium-p-styrenesulfonate)-enhanced Ag nanoclusters

Poly(sodium-p-styrenesulfonate)-enhanced and D-penicillamine stabilized Ag nanoclusters (PSS-DPA-AgNCs) were prepared using one-step ultraviolet irradiation combined with microwave heating method, and the effects of the AgNCs photo-luminescence performance based on different types of polyelectrolytes and energy suppliers were studied detailedly. The as-prepared AgNCs can be used as a viable fluorescent probe for monitoring indirectly iron(II) lactate hydrate (ILH) and ammonium ferric citrate (AFC), respectively. The fluorescence (FL) quenching of PSS-DPA-AgNCs by Fe³⁺ (it is obtained from oxidized ILH/ionized AFC) mainly derives from a dynamic quenching process. Excellent linear relationships exist between the FL quenching degree of the AgNCs and the concentrations of ILH/AFC in the range of 0.17-6.00/0.067-3.33 μmol·L^-1, and corresponding limit of detection (at 3σ/slope) is 12.4/6.04 nmol·L^-1. Moreover, the AgNCs probe was extended to the assays of ILH in tablets, solid beverage or ILH additive and AFC in two kinds of edible salts or syrup with satisfactory results compared with the standard 1, 10-phenanthroline method. In addition, the AgNCs probe reveals a good temperature sensing capability.