Towards optoelectronic urea biosensors

Multipoint monitor of beer fermentation

This short communication is devoted to a fully-mechanized flow analysis system for the control of beer fermentation process. The developed system is based on microsolenoid flow controlling devices (valves and pumps) and a flow-through optoelectronic detector. All these components are powered and controlled by a Adruino-compatible microprocessor platform that creates an integrated, compact, and robust analytical tool. Multiplication of sample aspiration ports of the analytical system allows for simultaneous monitoring of several independently performed fermentation processes, as well as a single process at the different places of fermentation tank. To demonstrate its practical utility, the developed system has been applied for online and real-time monitoring of yeast propagation and distribution in beer worts in the course of various fermentation processes. Potentially, this flow analysis system can be easily expanded to the form of multianalyte monitor equipped with optoelectronic sensors and biosensors for the determination of other parameters and analytes.

Real scenario of metal ion sensor: is conjugated polymer helpful to detect hazardous metal ion

Metal ions from natural and anthropogenic sources cause pollution to society and the environment is major concern in the present scenario. The deposition and contamination of metal ions in soil and water affect the biogeochemical cycles. Thus, it threatens the everyday life of living and non-living organisms. Reviews on the detection of metal ions through several techniques (Analytical methods, electrochemical techniques, and sensors) and materials (Nanoparticles, carbon dots (quantum dots), polymers, chiral molecules, metal-organic framework, carbon nanotubes, etc.) are addressed separately in the present literature. This review reveals the advantages and disadvantages of the techniques and materials for metal ion sensing with crucial factors. Furthermore, it focus on the capability of conjugated polymers (CPs) as metal ion sensors able to detect/sense hazardous metal ions from environmental samples. Six different routes can synthesize this type of CPs to get specific properties and better metal ion detecting capability in vast research areas. The metal ion detection by CP is time-independent, simple, and low cost compared to other materials/techniques. This review outlines recent literature on the conjugated polymer for cation, anion, and dual ion sensors. Over the last half decades published articles on the conjugated polymer are discussed and compared.

LED PEDD Discharge Photometry: Effects of Software Driven Measurements for Sensing Applications

This work explores the effects of embedded software-driven measurements on a sensory target when using a LED as a photodetector. Water turbidity is used as the sensory target in this study to explore these effects using a practical and important water quality parameter. Impacts on turbidity measurements are examined by adopting the Paired Emitter Detector Diode (PEDD) capacitive discharge technique and comparing common embedded software/firmware implementations. The findings show that the chosen software method can (a) affect the detection performance by up to 67%, (b) result in a variable sampling frequency/period, and (c) lead to an disagreement of the photo capacitance by up to 23%. Optimized code is offered to correct for these issues and its effectiveness is shown through comparative analyses, with the disagreement reduced significantly from 23% to 0.18%. Overall, this work demonstrates that the embedded software is a key and critical factor for PEDD capacitive discharge measurements and must be considered carefully for future measurements in sensor related studies.

A mechanized urease activity assay

Two fully mechanized flow analysis systems for urease activity assays have been developed, characterized and compared. Both of them are based on almost the same compact system of solenoid micropumps and microvalves controlled and actuated by highly effective, low-power and economic Arduino microcontroller. For photometric detection of ammonia formed in the course of enzymatic hydrolysis of urea, the Berthelot method and the Nessler reaction have been examined. For both these detection schemes very simple dedicated optoelectronic flow-through detectors made of paired light emitting diodes have been developed. In both systems single enzyme assay lasting a few minutes allows determination of urease in activity range 0.02-5.3 U mL^-1 with detection limit 0.02 U mL^-1 and in 1.3-5.3 U mL^-1 range with 0.75 U mL^-1 detection limit for Nessler reaction and Berthelot method based systems, respectively. When compared with mechanized Berthelot method, the bioanalytical system based on Nessler reaction offers higher sensitivity, lower detection/determination limits, better selectivity and lower cost of the assay. It has been demonstrated that the developed bioanalytical flow systems could be useful for urease determination in complex biological matrix like plant extracts and media for microbial cultures as well as for inhibitive determination of heavy metals at sub-ppm levels.

Optoelectronic detectors for flow analysis systems manufactured by means of rapid prototyping technology

Universal, customizable design of 3D printed photometric, and fluorometric flow-through detectors have been presented. The developed designs were fabricated with the use of the most affordable 3D printing technique, namely Fused Filament Fabrication, and require neither hardware nor tools to assemble. Numerous variants of detector geometries have also been presented. The designed parameters varied both in aperture (i.e., the internal diameter of the flow channel in an optical path) and in thickness of an absorbing layer. As expected, the geometry of the channels resulted in changes in the internal volumes. Two concepts of fluorometric detectors have also been described. The utility of all developed flow-through detectors was proven with the use of mechanized calibrations of both photometric and fluorometric experiments. Analytical parameters were characterized with the use of two model dyes: bromothymol blue and fluorescein for photometric and fluorometric experiments, respectively. The repeatability of the 3D printed vessels was found at 3.5-8.0% of the mean relative standard deviation (RSD), depending on the construction of the vessel, which is comparable to rather expensive commercially available flow cells. The compatibility of used 3D printing materials was also examined. For both variants of detection light emitting diodes were applied as light emitters. As the light detectors, both CCD spectrophotometers and light-emitting diodes were used.

Recent advances in flow injection analysis

A dynamic development of methodologies of analytical flow injection measurements during four decades since their invention has reinforced the solid position of flow analysis in the arsenal of techniques and instrumentation of contemporary chemical analysis.