title: Indirect voltammetric determination of caffeine content in coffee using 1,4-benzoquinone modified carbon paste electrode.
abstract: In this paper a simple and highly sensitive electroanalytical method for the determination of caffeine content using 1,4-benzoquinone modified carbon paste electrode is presented. The method is based on suppression of 1,4-benzoquinone peak current on addition of caffeine. Square-wave and cyclic voltammetric techniques were utilised for the investigation. The 1,4-benzoquinone modified electrode exhibited a well-defined peak with reproducible peak current values for repetitive measurements; and showed a decrease in peak current value with an increase in caffeine content. The result revealed two linear range regions between 0 mmol L(-1) and 0.5 mmol L(-1) and 0.5 mmol L(-1) and 8.0 mmol L(-1), with detection limits of 0.3 micromol L(-1) and 5.1 micromol L(-1), respectively. The method was then successfully applied to the determination of caffeine content in coffee samples. The effects of pH, electrode composition, step potential, pulse amplitude and square-wave frequency on the voltammetric responses were also investigated.
authors.affiliation: Chemistry Department, Addis Ababa University, PO Box 1176, Addis Ababa, Ethiopia.
authors.forename: Muluken
authors.initials: M
authors.lastname: Aklilu
authors.forename: Merid
authors.initials: M
authors.lastname: Tessema
authors.forename: Mesfin
authors.initials: M
authors.lastname: Redi-Abshiro
mesh_terms: D016227:Benzoquinones / Q000032:analysis / Q000737:chemistry*; D002110:Caffeine / Q000032:analysis*; D002244:Carbon / Q000737:chemistry*; D002623:Chemistry Techniques, Analytical / Q000379:methods; D003069:Coffee; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D004573:Electrolytes; D006863:Hydrogen-Ion Concentration; D015203:Reproducibility of Results
chemical_list: D016227:Benzoquinones; D003069:Coffee; D004573:Electrolytes; D002110:Caffeine; C004532:quinone; D002244:Carbon