Abstract

The determination of glucose in beverages is demonstrated using newly developed fluoride selective optical sensing polymeric film that contains aluminum (III) octaethylporphyrin (Al[OEP]) ionophore and the chromoionophore ETH7075 cast at the bottom of wells of a 96-well polypropylene microtiter plate. The method uses a dual enzymatic reaction involving glucose oxidase enzyme (GOD) and horseradish peroxidase (HRP), along with an organofluoro-substrate (4-fluorophenol) as the source of fluoride ions. The concentration of fluoride ions after enzymatic reaction is directly proportional to the glucose level in the sample. The method has a detection limit of 0.8 mmol L −1, a linear range of 0.9–40 mmol L −1 and a sensitivity of 0.125 absorbance/decade of glucose concentration. Glucose levels in several beverage samples determined using the proposed method correlate well with a reference spectrophotometric enzyme method based on detection of hydrogen peroxide using bromopyrogallol red dye (BPR). The new method can also be used to determine H 2O 2 concentrations in the 0.1–50 mmol L −1 range using a single enzymatic reaction involving H 2O 2 oxidation of 4-fluorophenol catalyzed by HRP. The methodology could potentially be used to detect a wide range of substrates for which selective oxidase enzymes exist (to generate H 2O 2), with the high throughput of simple microtiter plate detection scheme.

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