A do-it-yourself electrochemical cell based on pencil leads and transparency sheets: Application to the enzymatic...

The availability of more efficient analytical methods that answer the world's demands is a challenge and their development continues to be a difficult task. In this work the construction of an electrochemical cell, based on low-cost and accessible materials, that can be easily constructed and used for electroanalytical purposes, is described. Pencil leads were used as electrodes and a transparency sheet as the base. This cell was used as transducer for developing an amperometric biosensor for the quantification of histamine, which is the only biogenic amine regulated by law. The analysis was based on the use of diamine oxidase as biorecognition element, hexacyanoferrate(III) as electron-transfer mediator, and chronoamperometry, at +0.5 V during 100 s, to record the analytical signal. A linear relationship between histamine concentration and the analytical signal was established between 5.0 and 35 mg L^-1 and a low limit of detection (1.0 mg L^-1) was achieved. The analysis of different fish species (sardine and tuna) was performed, obtaining recovery values between 102% and 110%. The stability of the sensor is noteworthy: it maintained 95% of the initial analytical signal after 15 days.