**3.1 Electrochemical techniques: principles, advantages, and sensing mechanisms**

As an analytical approach, electroanalysis offers many advantages including but not limited to simplicity, sensitivity, specificity, and applicability in various matrices and cost-effectiveness. These advantages are of specific importance when it comes to detection of drugs and pharmaceuticals, especially in food and water samples as well as in quality control (QC) and quality assurance (QA) laboratories. According to the signal being measured (voltage/potential, current, conductance, impedance), electroanalytical techniques can be categorized into potentiometric, amperometric, conductometric, and impedimetric techniques. Subcategories for each technique also exist, and coupling with other technologies has been investigated.

Sensors, and in particular those based on the classical potentiometric technique, or the new polyion, galvanostatic, or voltammetric sensing mechanisms, now possess the foothold in analytical chemistry. Offering irresistible advantages, on the in vitro scale, such as operation simplicity, sturdiness, and remarkable sensitivity hitting nine orders of magnitude, selectivity, and functionality over wide range of matrices, suitability for on-line or real-time analyses, and most prominently their liability for miniaturization, make the use of sensors indispensable [50–53].

**Figure 1** shows an illustration of ISE (ion-selective electrode) potentiometric sensor and generation of potential across the different phase boundaries.

The sensing mechanism especially if the target analyte is a biomolecule depends on tailoring the surface of the sensor with a bio-receptor that can selectively bind to the target bio-analyte. Following the adsorption of the bio-analyte from the solution on the surface of the probe, a change in the electrochemical signal can be observed and measured. Such a change is correspondingly dependent on the bioanalyte concentration.

**Figure 2** shows a schematic illustration of the sensing mechanism in plastic microfluidic channels. The left panel shows the generation of streaming potential,

*Schematic illustration of ISE cell assembly and the generation of EMF across different phase boundaries.*

**143**

**Figure 2.**

**4. EIS in drug analysis**

*Electrochemical Impedance Spectroscopy (EIS) in Food, Water, and Drug Analyses: Recent…*

ΔE, as a result of pressure-driven flow and surface charge at the electric double layer (EDL). The right panel shows a sensogram with signal inversion upon adsorption of the analyte. The bottom graph shows the pulsed streaming potentials as a

*Schematic illustration of the generation of streaming potential as a result of pressure-driven flow and surface charge at the electric double layer (EDL)—left upper panel. The right panel shows a sensogram with signal inversion upon adsorption of the analyte. The bottom graph shows the pulsed streaming potentials as a function of heparin with immobilized protamine on a surface of a cyclo-olefin copolymer (COC) microchannel. Data points were fitted using Langmuir isotherm. Graphs are replicated from the authors' own work with permission* 

EIS as an electrochemical technique entails measurement of the change in the charge transfer resistance (Rct) following the interactions between the analyte and the receptor and the consequent change in the interfacial electron transfer kinetics. The following sections will be dealing with the application for EIS for sensing

The effects of presence of the PhAMs either in waste and drinking water or even in wastewater treatment plants (WWTPs) are still inarticulate. However,

function of heparin with immobilized protamine.

*from Copyrights@ American Chemical Society (ACS) [45].*

different target analytes in different matrices [53, 54].

*DOI: http://dx.doi.org/10.5772/intechopen.92333*

*Electrochemical Impedance Spectroscopy (EIS) in Food, Water, and Drug Analyses: Recent… DOI: http://dx.doi.org/10.5772/intechopen.92333*

#### **Figure 2.**

*Electrochemical Impedance Spectroscopy*

in water and food samples.

**mechanisms**

investigated.

analyte concentration.

on the electrochemical approaches and EIS in specific in detection of contaminants

As an analytical approach, electroanalysis offers many advantages including but not limited to simplicity, sensitivity, specificity, and applicability in various matrices and cost-effectiveness. These advantages are of specific importance when it comes to detection of drugs and pharmaceuticals, especially in food and water samples as well as in quality control (QC) and quality assurance (QA) laboratories. According to the signal being measured (voltage/potential, current, conductance, impedance), electroanalytical techniques can be categorized into potentiometric, amperometric, conductometric, and impedimetric techniques. Subcategories for each technique also exist, and coupling with other technologies has been

Sensors, and in particular those based on the classical potentiometric technique,

**Figure 1** shows an illustration of ISE (ion-selective electrode) potentiometric

**Figure 2** shows a schematic illustration of the sensing mechanism in plastic microfluidic channels. The left panel shows the generation of streaming potential,

*Schematic illustration of ISE cell assembly and the generation of EMF across different phase boundaries.*

The sensing mechanism especially if the target analyte is a biomolecule depends on tailoring the surface of the sensor with a bio-receptor that can selectively bind to the target bio-analyte. Following the adsorption of the bio-analyte from the solution on the surface of the probe, a change in the electrochemical signal can be observed and measured. Such a change is correspondingly dependent on the bio-

sensor and generation of potential across the different phase boundaries.

or the new polyion, galvanostatic, or voltammetric sensing mechanisms, now possess the foothold in analytical chemistry. Offering irresistible advantages, on the in vitro scale, such as operation simplicity, sturdiness, and remarkable sensitivity hitting nine orders of magnitude, selectivity, and functionality over wide range of matrices, suitability for on-line or real-time analyses, and most prominently their liability for miniaturization, make the use of sensors indispensable [50–53].

**3.1 Electrochemical techniques: principles, advantages, and sensing** 

**142**

**Figure 1.**

*Schematic illustration of the generation of streaming potential as a result of pressure-driven flow and surface charge at the electric double layer (EDL)—left upper panel. The right panel shows a sensogram with signal inversion upon adsorption of the analyte. The bottom graph shows the pulsed streaming potentials as a function of heparin with immobilized protamine on a surface of a cyclo-olefin copolymer (COC) microchannel. Data points were fitted using Langmuir isotherm. Graphs are replicated from the authors' own work with permission from Copyrights@ American Chemical Society (ACS) [45].*

ΔE, as a result of pressure-driven flow and surface charge at the electric double layer (EDL). The right panel shows a sensogram with signal inversion upon adsorption of the analyte. The bottom graph shows the pulsed streaming potentials as a function of heparin with immobilized protamine.

EIS as an electrochemical technique entails measurement of the change in the charge transfer resistance (Rct) following the interactions between the analyte and the receptor and the consequent change in the interfacial electron transfer kinetics. The following sections will be dealing with the application for EIS for sensing different target analytes in different matrices [53, 54].
