Microfluidics for Environmental Applications

Microfluidic and lab-on-a-chip systems have become increasingly important tools across many research fields in recent years. As a result of their small size and precise flow control, as well as their ability to enable in situ process visualization, microfluidic systems are increasingly finding applications in environmental science and engineering. Broadly speaking, their main present applications within these fields include use as sensors for water contaminant analysis (e.g., heavy metals and organic pollutants), as tools for microorganism detection (e.g., virus and bacteria), and as platforms for the investigation of environment-related problems (e.g., bacteria electron transfer and biofilm formation). This chapter aims to review the applications of microfluidics in environmental science and engineering - with a particular focus on the foregoing topics. The advantages and limitations of microfluidics when compared to traditional methods are also surveyed, and several perspectives on the future of research and development into microfluidics for environmental applications are offered.

Total polyphenols content in white wines on a microfluidic flow injection analyzer with embedded optical fibers

Absorbance detection in food microdevices has not been thoroughly used due to low levels of sensitivity in measurements. Thus, it is necessary to develop microfluidic methods for improving photometric detection. For this purpose, a simple coupled-optical-fiber-polydimethylsiloxane (PDMS) microdevice was developed, to quantify polyphenols content in white wine employing the Folin-Ciocalteu reaction method. A 6V and 10W halogen lamp with an optical path length of 7mm between optical fibers, which were placed into the microchip, using guides at the outlet of the flow, increased the level of sensitivity during detection. The linear range was from 0.03mmol/L to 0.18mmol/L. Thus, the corresponding equation was: Abs=4.00(±0.16) [tannic acid]+0.17(±0.017). Intra-laboratory repeatability and reproducibility percentages were 2.95% and 6.84%, respectively. Such results were compared to those obtained from applying the conventional flow-injection analysis method, based on the same type of reaction. The relative error between methods was less than 13%.

Separation of natural antioxidants using PDMS electrophoresis microchips coupled with amperometric detection and reverse polarity

This report describes the use of PDMS ME coupled with amperometric detection for rapid separation of ascorbic, gallic , ferulic, p-coumaric acids using reverse polarity. ME devices were fabricated in PDMS by soft lithography and detection was accomplished using an integrated carbon fiber working electrode aligned in the end-channel configuration. Separation and detection parameters were investigated and the best conditions were obtained using a run buffer consisting of 5 mM phosphate buffer (pH 6.9) and a detection voltage of 1.0 V versus Ag/AgCl reference electrode. All compounds were separated within 70 s using gated injection mode with baseline resolution and separation efficiencies between 1200 and 9000 plates. Calibration curves exhibited good linearity and the LODs achieved ranged from 1.7 to 9.7 μM. The precision for migration time and peak height provided maximum values of 4% for the intrachip studies. Lastly, the analytical method was successfully applied for the analysis of ascorbic and gallic acids in commercial beverage samples. The results achieved using ME coupled with amperometric detection were in good agreement with the values provided by the supplier. Based on the data reported here, the proposed method shows suitability to be applied for the routine analysis of beverage samples.

Lights and shadows on food microfluidics

These insights attempt to share with the community the lights and shadows of one emerging and exciting topic, Food Microfluidics, defined as microfluidic technology for food analysis and diagnosis in important areas such as food safety and quality. The reader is invited to question non-easy interrogations such as why Food Microfluidics, what is the next step and what could we do with the available technology. This article invites food analysts to be seduced by this technology and then to take an interesting trip departing from the main gained achievements, having a look at the crossing bridges over Food Microfluidic challenges or having a look at available technology to start. Finally, this trip arrives at a privileged place to gaze the horizons. A wonderful landscape--full of inspiration--for Food Microfluidics is anticipated. These insights have also been written wishing to give improved conceptual and realistic solutions for food analysis, with the additional hope to attract the community with exciting technology, in order to get novel and unexpected achievements in this field.