Chemometrics is a subfield of chemistry that emerged from advances in analytical instrumentation and computing. When seeking to solve chemical problems that depend on many concomitants experimental variables, chemometrics can be employed in order to extract as much information as possible in the least possible number of experiments. In addition, it is possible to evaluate the important effects and interactions among the variables to understand the processes being monitored in each system. In this sense, this article aimed to develop a didactic experiment of caffeine extraction using an espresso machine, applying the 25-1 fractional factorial design. The variables studied were temperature (75 and 78 °C), pressure (2 and 15 bar), granulation (bean and ground), type of coffee (special and traditional) and period of the day (morning and afternoon) to obtain maximum extraction of caffeine. The coffee extracts obtained were analyzed using UV-Vis molecular absorption spectrophotometry. The developed experiment showed the potential to spread the application of chemometrics in the academic environment and to facilitate the teaching of fractional factorial design.

Volatile Organic Compounds (VOCs) are air pollutants emitted from different sources, mainly by industries and motor vehicles. The evaluation of the emission of these compounds into the atmosphere should be done systematically and with a varied class of compounds. The large number of data generated during the monitoring of these VOCs requires the use of multivariate data tools to interpret the results. In this sense, this work aimed to monitor 10 aromatic VOCs present in the atmosphere of the largest cities in the Norte Fluminense (Campos dos Goytacazes) and Noroeste Fluminense (Itaperuna) regions. The VOCs were actively sampled and analyzed by gas chromatography with mass spectrometry detection after thermal desorption. After treatment of analytical results, it was observed that in both cities there is influence of vehicular emissions. In the city of Itaperuna, due to the relief and lower dispersion of contaminants, there is a higher occurrence of photochemical reactions. The exploratory analysis of the data allowed identifying the variables that were more significant and correlating these variables with the main sources of emission of the compounds. This is the first study of VOCs evaluation in Campos dos Goytacazes and Itaperuna, demonstrating the relevance of this research for understanding the behavior of VOCs in these cities, which have different reliefs and high traffic of cars and trucks in the studied sites.