2.7. Real Sample Measurements
The developed biosensor was used to analyze some different alcoholic beverages (beer, legen (a Javanese traditional fermented drink) and tape (fermented glutinous rice)). In all cases, a 1:10 dilution in phosphate buffer 0.1 M pH 7 was the only sample treatment needed. Then, the colour change was recorded upon dipping the biosensor into 1 mL of each sample solution.
2.8. Gas Chromatographic Measurements
For comparison purposes, real samples were also analyzed by gas chromatography with a HP6890 chromatograph composed of an injector, a 2 m long packed column and a flame ionization detector (FID). The alcoholic beverages were analyzed using an internal standard method. A calibration plot for ethanol in concentrations ranging between 0 and 10% (v/v) was constructed using 5% of propanol as internal standard. The samples were previously diluted to obtain an adequate ethanol concentration.