Redox titration on foldable paper-based analytical devices for the visual determination of alcohol content in whiskey samples

This report describes the development of foldable paper-based analytical devices (PADs) to perform redox titrations. Paper devices were designed to contain three spot tests, which were wax printed and folded to create a three-layer structured platform and to promote the sample transport based on ver...

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Bibliographic Details
Published in:Talanta (Oxford) 2019-03, Vol.194, p.363-369
Main Authors: Nogueira, Sandro A., Lemes, Adriano D., Chagas, Adriana C., Vieira, Maurício L., Talhavini, Márcio, Morais, Pedro A.O., Coltro, Wendell K.T.
Format: Article
Language:English
Subjects:
Alcoholic beverages
Crime scene
Food control
Forensic chemistry
Paper microfluidics
Point-of-need
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Summary:This report describes the development of foldable paper-based analytical devices (PADs) to perform redox titrations. Paper devices were designed to contain three spot tests, which were wax printed and folded to create a three-layer structured platform and to promote the sample transport based on vertical flow. The proposed devices were explored for the visual determination of the alcoholic content in whiskey samples. For this purpose, a classical permanganometry reaction was employed to allow the indirect determination of ethanol based on the required amount of oxalic acid to react with the excess of permanganate in acidic medium. The endpoint of the redox titrations performed in different alcoholic concentrations was measured and revealed a good linear behavior for the ethanol concentration range between 0% and 50% (R2 = 0.992), achieving a limit of detection equal to 2.1%. The alcoholic content was determined in a total of 44 whiskey samples seized by the Brazilian Federal Police. When compared to genuine samples and using an established cut-off limit, 73% of the seized samples were correctly classified as whiskeys containing adulterated alcoholic content. The proposed method was compared to a reference protocol and no difference was observed at the confidence level of 95%. The instrumental simplicity, the low cost, the sample volume requirement, the short analysis time and mainly the inherent portability make these devices quite attractive for on-site forensic applications. [Display omitted] •Foldable paper-based devices were developed to perform redox titrations.•The alcoholic content was determined in whiskey samples by permanganometry.•The back-titration provided inversely linear response to the alcohol concentration increase.•The proposed method requires only 1 μL of sample and provides response within 60 s.•Foldable platforms allowed to screen the authenticity of seized whiskey samples.
ISSN:0039-9140
1873-3573
DOI:10.1016/j.talanta.2018.10.036