A molecularly imprinted electrochemical sensor integrated with conversion factor T strategy for rapid and selective...

Establishing a comprehensive analytical method capable of accurately reflecting the composition of major lutein esters and enabling their rapid quantification is essential for the quality evaluation of marigold products. In this study, the major lutein esters present in marigolds were first identified by HPLC-MS, and a novel 'conversion factor T' strategy was established. Using lutein dipalmitate as the reference marker, the contents of other major lutein esters were calculated based on their relative conversion factors. To further simplify the analytical procedure, a molecularly imprinted electrochemical sensor based on conductive Ni₃(HITP)₂-MOF was developed for the rapid determination of lutein dipalmitate. The introduction of Ni₃(HITP)₂-MOF enhanced the electrode conductivity by approximately fourfold compared with the bare electrode. The sensor exhibited a wide linear range of 0.01-100 μM and a low detection limit of 8.20 nM toward lutein dipalmitate. Four major lutein esters, namely lutein dimyristate, lutein myristate-palmitate, lutein dipalmitate, and lutein palmitate-stearate, were quantified, and the corresponding conversion factors (T _d , T _m , and T _p ) were determined as 0.903, 0.964, and 1.035, respectively. The proposed strategy integrates rapid electrochemical sensing with conversion factor analysis, enabling indirect quantification of multiple lutein esters from a single target analyte. Furthermore, the method was successfully applied to the quality evaluation of marigold extracts and commercial eye care products, demonstrating its potential for rapid routine analysis and quality control.