Publicado em 17/12/2015
Renewable Energy, em 12/2015.
Microemulsification-based method (MEC) was recently proposed by these authors like a powerful way for the development of point-of-use technologies; simple, low-cost, fast, and portable methods for quantitative chemical analyses. Microemulsification relies on effect of the analyte on thermodynamic formation of microemulsions (ME). Its experimental protocol is similar to conventional chemical titration. ‘Titrant volume’ in microemulsification is the minimum volume of amphiphile required to stabilize water-oil mixtures (on right) and, then, cloudy emulsions (on middle) generating transparent microemulsions (Erlenmeyer flask on left shown in photo below). Such a cloudy-to-transparent transition acts like a ‘turning point’. As a consequence, the signal in microemulsification (volume of amphiphile in cloudy-to-transparent transition) can be precisely detected with naked eyes ensuring not only screening analyses as the most of colorimetry-based rapid testing approaches, but also precise determinations. In practice, the method was performed in low-cost glass bottles (like in photo) or Eppendorf® tubes with the aid of micropipette. Plastic syringes can be used also in screening analyses or experiments that do not need high precision.
Microemulsification was so far applied in quality control of renewable energy fuels by monitoring different contaminants, namely: water in ethanol (Analytical Chemistry, 86, 9082, 2014 and Journal of Analytical and Bioanalytical Techniques, 6: 261 doi:10.4172/2155-9872.1000261, 2015), ethanol in fermentation broths of sugar cane (Analytical Methods, 7, 10061, 2015; article highlighted in back cover), and monoethylene glycol (MEG) in complex samples of liquefied natural gas processing (Analytical Chemistry, 86, 9082, 2014 and this paper). MEG is used in processing of natural gas by Petrobras (Brazilian multinational energy corporation) to avoid the clogging of pipes because the formation of hydrates. Conversely, this dialcohol is regenerated from gas exploration system as it produces piping corrosion, catalyst poisoning, reduction in quality of the final product, and environment contamination. Accordingly, it is important to monitor the concentrations of microemulsification for evaluating the effectiveness of this regeneration. Natural gas processing samples exhibited color, particulate material, high ionic strength, and diverse compounds as metals, carboxylic acids, and anions. Despite these downsides, the method allowed accurate measures bypassing steps such as extraction and preconcentration of the samples. In addition, the method showed to be robust as regards to deviations in volumetric preparation of the dispersions and changes in temperature and ionic strength. Lastly, in edited theory considerations on analytical response of microemulsification were outlined in such an article.
Figure: showcasing the research into a relationship between microemulsification-based method and the experimental protocol of conventional chemical titrations. Credit: Karen Mayumi Higa.