Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode.

Meareg Amare,Senait Aklog

doi:10.1155/2017/3979068

Abstract

Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6 × 10−6 to 100 × 10−6 mol L−1 with determination coefficient and method detection limit (LoD = 3 s/slope) of 0.99925 and 8.37 × 10−7 mol L−1, respectively, supplemented by recovery results of 93.79–102.17% validated the developed method. An attempt was made to determine the caffeine content of aqueous coffee extracts of Ethiopian coffees grown in four coffee cultivating localities (Wonbera, Wolega, Finoteselam, and Zegie) and hence to evaluate the correlation between users preference and caffeine content. In agreement with reported works, caffeine contents (w/w%) of 0.164 in Wonbera coffee; 0.134 in Wolega coffee; 0.097 in Finoteselam coffee; and 0.089 in Zegie coffee were detected confirming the applicability of the developed method for determination of caffeine in a complex matrix environment. The result indicated that users' highest preference for Wonbera and least preference for Zegie cultivated coffees are in agreement with the caffeine content.

Highlights

Alkaloids are broad category of nitrogen containing organic metabolites produced by plants; the plants that produce these alkaloids make their leaves unattractive to eating by insects and higher animals [1]
Caffeine is a natural stimulant contained in many sources like coffee, tea, chocolate, soft drinks, and tablets for the treatment of many diseases such as asthma, nasal congestion, and headache and even for improving athletic endurance and facilitating weight loss [1]
Cyclic voltammetric and differential pulse voltammetric techniques were used to investigate the electrochemical behavior of caffeine and determine caffeine content in coffee samples, respectively

Summary

Introduction

Alkaloids are broad category of nitrogen containing organic metabolites produced by plants; the plants that produce these alkaloids make their leaves unattractive to eating by insects and higher animals [1]. High performance liquid chromatography [16, 17], capillary chromatography [18, 19], spectroscopy [20, 21], and electrochemical [22, 23] methods are among the reported methods for determination of caffeine in coffee, tea, and cola beverage samples. The electrochemical behavior of lignin at the surface of glassy carbon electrode has been reported [38], to the best of our knowledge, its application for electrochemical determination of caffeine in aqueous extracts of coffee samples has not been reported. This paper reports a simple, cheap, and environmentally friendly lignin based electrochemical method for determination of caffeine in aqueous extracts of coffee samples cultivated in different localities of Ethiopia, the origin of coffee

Experimental

Results and Discussion

Conclusion