Quality control of the final product requires a large and varied number of chemi­cal analyses to evaluate the physical and chemical parameters in comparison with quality standards, usually established by regulatory legislation. Table 7 shows the specifications and analytical methods for the quality control of ethanol, an impor­tant Brazilian biofuel.

These data highlight the large number of techniques required to ensure ethanol quality, from classical techniques (volumetry, gravimetry, and direct potentiometry) to instrumental techniques (ion chromatography, GC-flame ionization detector, and AAS). The method for each analytical technique needs to be rigorously and systematically applied in order to enable accurate comparison between samples and to accurately assess the quality of the sample.

Figure 8 shows a flowchart for the use of AAS for quality control of ethanol. AAS is a rapid technique for the determination of the presence and concentration of several metals and some nonmetals. Nevertheless, preparation steps require attention because this step will release the analyte into the solution to be meas­ured. If not all of the species is released into the solution, inaccurate results will be obtained. The analytical result could be obtained as a concentration (mg kg-1 or mg L-1) or as a mass percentage in a certain volume (% m/v), depending on the individual’s interest or standard regulation.