A new fluorescence probe for simultaneous determination of Fe2+ and Fe3+ by orthogonal signal correction-principal component regression

• The proposed method determined the Fe 2+ and Fe 3+ simultaneously with acceptable accuracy. • Chemometrics method OSC-PCR was used for deconvolution of the fluorescence spectral data. • The complexation reaction was studied, and the stability constants were calculated. • Ligand DALD act as a turn-off fluorescence probe for iron ions. In this research, a newly reported fluorescence molecular probe [N, N’-bis(methylsalicylaldehyde)-4,4 bipyridinium] dichloride (DALD) was used for selective detection and determination of Fe 2+ and Fe 3+ in aqueous solutions. The complexation reaction between DALD and Fe 2+ and Fe 3+ is the basis of the variation in the emission intensity and their quantitative fluorescence determination. The stoichiometries and formation constants of DALD and both ions were obtained by appropriate chemical model and numerical refinement of spectrofluorometric-mole ratio titration data. The selectivity of the probe towards Fe 2+ and Fe 3+ was tested in the presence of M n+ ( n = 1, 2, 3) cations. None of the other ions show any observable fluorescence signal quenching at the excitation and emission wavelengths (345/456 nm). The emission profile of said iron species was in the range of 340–560 nm and has shown a high degree of overlap. The univariate calibration ranges and detection limits of Fe 2+ and Fe 3+ were 0.7–4.1 μM, 0.7–2.7 μM and 1.3 μM, and 0.69 μM, respectively. The orthogonal signal correction-principal component regression (OSC-PCR) as a factor-based and data compression method was used to determine both cations in aqueous solutions simultaneously. OSC-PCR correlates the fluorescence spectra to the concentration of metal ions very well, and the coefficients of determination were 0.9530 and 0.9919 for Fe 2+ and Fe 3+, respectively. The solution equilibria of interaction between the probe and metal ions were studied and the stability constants of complexes were 10.68 (± 0.05), 1:2 and 4.46 (± 0.12) 1:1 for Fe 2+ and Fe 3+ respectively. The factors that influenced sensitivity and selectivity were recognized and optimized.