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Integrated Electrochemical Analysis System with Microfluidic and Sensing Functions

View Article: PubMed Central - PubMed

ABSTRACT

An integrated device that carries out the timely transport of solutions and conducts electroanalysis was constructed. The transport of solutions was based on capillary action in overall hydrophilic flow channels and control by valves that operate on the basis of electrowetting. Electrochemical sensors including glucose, lactate, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), pH, ammonia, urea, and creatinine were integrated. An air gap structure was used for the ammonia, urea, and creatinine sensors to realize a rapid response. To enhance the transport of ammonia that existed or was produced by the enzymatic reactions, the pH of the solution was elevated by mixing it with a NaOH solution using a valve based on electrowetting. The sensors for GOT and GPT used a freeze-dried substrate matrix to realize rapid mixing. The sample solution was transported to required sensing sites at desired times. The integrated sensors showed distinct responses when a sample solution reached the respective sensing sites. Linear relationships were observed between the output signals and the concentration or the logarithm of the concentration of the analytes. An interferent, L-ascorbic acid, could be eliminated electrochemically in the sample injection port.

No MeSH data available.


Calibration plots for the pH (a), ammonia (b), urea (c, □), and creatinine (c, △; sensors. The insets are typical response curves to the analytes of the corresponding concentrations.
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f10-sensors-08-01111: Calibration plots for the pH (a), ammonia (b), urea (c, □), and creatinine (c, △; sensors. The insets are typical response curves to the analytes of the corresponding concentrations.

Mentions: Figure 10 (a) shows the calibration plot for the pH sensor. When a sample solution arrived at the pH indicator electrode, the potential settled at a level corresponding to the solution pH. A linear relationship was observed between the potential of the pH-indicator electrode and the pH of the solution. In a potentiometric sensor, both the indicator electrode and the reference electrode play a critical role. The small scattering of the data points suggests that the liquid-junction reference electrode produced a stable potential. After a sample solution containing ammonium ions and the NaOH solution were mixed, gaseous ammonia was produced. When the diffused ammonia dissolved into the electrolyte solution, the potential of the pH-indicator electrode of the ammonia sensor changed immediately and stabilized at a level. Figure 10 (b) shows the dependence of the potential of the ammonia sensor on the concentration of ammonia. A linear relationship was observed between the indicator electrode potential and the logarithm of the ammonia concentration. The lower detection limit was 1 μM. For the determination of urea and creatinine, the enzymatic reactions were allowed to proceed, and the same procedure was followed. Linear relationships were observed in the calibration plot for both cases [Figure 10 (c)].


Integrated Electrochemical Analysis System with Microfluidic and Sensing Functions
Calibration plots for the pH (a), ammonia (b), urea (c, □), and creatinine (c, △; sensors. The insets are typical response curves to the analytes of the corresponding concentrations.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3927525&req=5

f10-sensors-08-01111: Calibration plots for the pH (a), ammonia (b), urea (c, □), and creatinine (c, △; sensors. The insets are typical response curves to the analytes of the corresponding concentrations.
Mentions: Figure 10 (a) shows the calibration plot for the pH sensor. When a sample solution arrived at the pH indicator electrode, the potential settled at a level corresponding to the solution pH. A linear relationship was observed between the potential of the pH-indicator electrode and the pH of the solution. In a potentiometric sensor, both the indicator electrode and the reference electrode play a critical role. The small scattering of the data points suggests that the liquid-junction reference electrode produced a stable potential. After a sample solution containing ammonium ions and the NaOH solution were mixed, gaseous ammonia was produced. When the diffused ammonia dissolved into the electrolyte solution, the potential of the pH-indicator electrode of the ammonia sensor changed immediately and stabilized at a level. Figure 10 (b) shows the dependence of the potential of the ammonia sensor on the concentration of ammonia. A linear relationship was observed between the indicator electrode potential and the logarithm of the ammonia concentration. The lower detection limit was 1 μM. For the determination of urea and creatinine, the enzymatic reactions were allowed to proceed, and the same procedure was followed. Linear relationships were observed in the calibration plot for both cases [Figure 10 (c)].

View Article: PubMed Central - PubMed

ABSTRACT

An integrated device that carries out the timely transport of solutions and conducts electroanalysis was constructed. The transport of solutions was based on capillary action in overall hydrophilic flow channels and control by valves that operate on the basis of electrowetting. Electrochemical sensors including glucose, lactate, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), pH, ammonia, urea, and creatinine were integrated. An air gap structure was used for the ammonia, urea, and creatinine sensors to realize a rapid response. To enhance the transport of ammonia that existed or was produced by the enzymatic reactions, the pH of the solution was elevated by mixing it with a NaOH solution using a valve based on electrowetting. The sensors for GOT and GPT used a freeze-dried substrate matrix to realize rapid mixing. The sample solution was transported to required sensing sites at desired times. The integrated sensors showed distinct responses when a sample solution reached the respective sensing sites. Linear relationships were observed between the output signals and the concentration or the logarithm of the concentration of the analytes. An interferent, L-ascorbic acid, could be eliminated electrochemically in the sample injection port.

No MeSH data available.