Glucose in der Photobox - eine neuartige Methode zur photometrischen Glucose-Bestimmung im Chemieunterricht durch Einsatz digitaler MedienGlucose in the photobox - a new method for photometric glucose determination in chemistry classes by using digital media

A new method for a quantitative analysis of glucose is presented. For this purpose, photometric recording of the oxidation of glucose in a weakly alkaline solution of iodine, potassium iodide and starch is used. The oxidation of D-glucose lowers the concentration of the blue polyiodide-amylose-complex, what can be detected photometrically. Using pseudo-first-order reaction conditions the reaction rate is found to be proportional to the absorption of the solution. The pseudo-first-order rate constant, k', is proportional to c(0)(glucose). Thus, an unknown glucose concentration can be determined by its rate constant k'. The analysis of the experimental data requires basic knowledge in reaction kinetics. The reactions that proceed within the solution can be used for exercises in chemical equilibria and redox reactions. Hence, the method can be introduced in upper secondary chemistry classes. It can be applied in order to analyze different soft drinks and juices. Furthermore, it is suited to implement digital media into chemistry lessons. The photometer can be replaced by a smartphone on which a suitable app is installed. The app allows a time-resolved measurement of the color-depth of the solution by recording RGB-data. The construction of a respective "photometer cell" is described. The results obtained with the smartphone are in very good accordance with those form the photometer.