Determination of Zinc by Solid Surface Fluorescence in Natural Adaptogen Samples

Zinc is an essential element for living organisms which plays an important role in the metabolism of proteins and nucleic acids, participating in the activity of approximately 100 enzymes and collaborating in the proper functioning of the immune system. Deficiency of Zn(II) is associated with growth retardation, impaired immune response, premature birth, weight loss and anorexia. On the other hand, adaptogens are a unique group of herbal ingredients used to improve the health of the adrenal system, which is responsible for managing the body’s hormonal response to stress. Dietary supplements are often combined in clinical practice to achieve synergistic effects and consequently greater health benefits. The objective of this study was to develop a new method for monitoring Zn(II) in natural adaptogens and to demonstrate a potential magnifying effect on health benefits. It is proposed the Zn(II) determination based in the exaltation of the fluorescent signal of o-Phenanthroline (o-phen) and the dye eosin (eo), using filter paper as a solid supported (without pretreatment) by solid surface fluorescence at λ_em = 440 nm (emission), using λ_ext = 370 nm (excitation). A multivariate optimization strategy based on Design of Experiments (DoE) was employed. A full factorial design 2³ was first applied to screen the significant variables, followed by a Central Composite Design (CCD) to find the optimal conditions. Under optimal experimental conditions, selective and quantitative retention of the metal was achieved, with a detection limit of 0.12 ng L^?1 and a linearity range from 0.43 to 7.55 × 10⁵ ng L^?1. The methodology showed high sensitivity, good selectivity and adequate tolerance to possible interferents. It was applied to the determination of Zn(II) in a natural adaptogens samples with satisfactory results, representing a novel alternative to conventional methods for analysis of trace metals.Subject AreasAnalytical Chemistry