Needle-based sampling coupled with colorimetric reaction catalyzed by layered double hydroxide peroxidase mimic for rapid detection of the change of d-glucose levels with time in bananas

Abstract

For analyte detection in raw fruits, the conventional sample pretreatment method usually involves mashing (blending or homogenization), extraction, and dilution. This process is time-consuming, solvent-intensive and laborious. Usually, there is also a lot wastage with multiple fruits being combined into composite samples. In this work, a new micro-sampling approach based on a syringe needle is developed; it was coupled with micro liquid-phase extraction to determine and quantify d-glucose in bananas. This sampling and extraction approach was quick, easy and required only minimal use of solvent. The d-glucose in the extracted banana flesh was first oxidized enzymatically with glucose oxidase. The resulting peroxide was then detected colorimetrically via oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of a catalyst. The latter, consisting of an iron (III)-nickel (II) layered double hydroxide (LDH[Ni^II-Fe^III]) was synthesized in this work for the purpose. The results of this new detection method for d-glucose in fruits provided low limits of detection (0.025 μg/mL), wide linear range (0.1-3000 μg/mL) and good linearity (r² = 0.9998). Quantification of d-glucose using this approach was applied to banana samples over a period of 10 days. The results showed that the d-glucose levels in bananas increased as the fruits ripened, as expected. This work demonstrated a new and interesting approach for easy and efficient detection of analytes in raw fruit samples.

Keywords: Banana; Layered double hydroxide; Needle-based sampling; d-glucose.