Derivatization reaction-based multi-spectroscopic techniques for ultrasensitive and rapid detection of phosphate in food using Nile blue A as probe

Abstract

Herein, a multi-spectroscopic assay based on a derivatization reaction was proposed for phosphate detection. In this assay, the phosphate with weak spectral signals was transformed to a large ion-association complex via a derivatization reaction. The operation procedure of the assay was easily performed by physically mixing sulfuric acid, derivatization reagent, phosphate (or sample solution), and dye probe (Nile blue A) for 10 min. Considerable changes in three types of spectral signals, i.e., resonance Rayleigh scattering (RRS), fluorescence, and ultraviolet-visible absorption, could be achieved. Under certain conditions, good linear relationship was obtained between each of the three signal variations and the phosphate concentration. The assay shows good selectivity and high sensitivity with limits of detection (LOD) of 4.8, 4.9 and 5.2 ng/mL for the RRS method, fluorophotometry and spectrophotometry, respectively. The multi-spectroscopic assay was applied to detect phosphate in real food samples, achieving recoveries of 93.3 %–109.6 % and relative standard divisions of 1.8 %–7.1 %. Owing to its speediness, easy operation, high sensitivity, good selectivity, self-comparison function, the multi-spectroscopic assay exhibits great potential for determination of phosphate in complex samples and provides an instructive strategy for detecting analytes with no or weak spectral signal.