UNIT CODE and TITLE: BIOANALYTICAL METHODS AND SENSOR

TECHNOLOGIES -

CHM9010 AND CHM9016

Table of Contents

QUESTION: 1...............................................................3

a) Concentration Conversion Table...................................................................3

b) Average Current Intensity Analysis................................................................3

c) Calibration Curve....................................................................................3

d) Experiment 2 Analysis................................................................................4

e) Current vs. Potential Plots..........................................................................4

f) Scan Rate vs. Peak Current..........................................................................4

g) Experimental Parameters Table (Table 1)..................................................5

h) Reversibility Determination.......................................................................5

i) Electrode Potential Calculation...................................................................5

QUESTION 2:..................................................................................6

References..........................................................................................................10

QUESTION: 1

a) Concentration Conversion Table

Solution Concentration (mg/L) Concentration (µmol/L)

Solution 1 0.01000 10.00

Solution 2 0.02000 20.00

Solution 3 0.03000 30.00

Solution 4 0.04000 40.00

...

...

Utilizing the change variable of 1 mg/L = 1 µmol/L for every arrangement:

• Solution 1: Fixation (µmol/L) = 0.01000 mg/L * 1 µmol/L = 0.01000 µmol/L

• Solution 2: Focus (µmol/L) = 0.02000 mg/L * 1 µmol/L = 0.02000 µmol/L

• Solution 3: Focus (µmol/L) = 0.03000 mg/L * 1 µmol/L = 0.03000 µmol/L

• Solution 4 has a concentration of 0.04000 mol/L, or 0.04000 mg/L divided by 1 mol/L.

The conversion factor of 1 mg/L = 1000 mol/L is used to convert these values from mg/L to mol/L.

b) Average Current Intensity Analysis

Solution Average Current (µA) Standard Deviation %RSD

Solution 1 0.005000 9.783 -195.66%

Solution 2 0.01000 6.935 -69.35%

Solution 3 0.01500 4.588 -30.59%

Solution 4 0.02000 3.041 -15.20%

Solution 5 0.02500 1.950 -7.80%

Solution 6 0.03000 1.108 -3.69%

Solution 7 0.03500 0.5079 -1.45%

Solution 8 0.04000 0.01772 -0.04%

Solution 9 0.04500 0.4755 1.06%

Solution 10 0.05000 0.9042 1.81%

Comment: The presented table includes the typical current, standard deviation and relative standard deviation %RSD for every arrangement. What is the trend from Solution 1 to Solution 10? While the average currents generally rise, the standard deviation and percent RSD tend to drop. With the higher mean current values, the data signal suggests improved repeatability in current measurement. Anyway, the %RSD for Arrangement 1 is negative, implying that the information drawbacks and accuracy are expected. The overall decrease in %RSD mainly brings

about higher accuracy with the development of operating current, which is extremely necessary for the testing accuracy improvement.

c) Calibration Curve

Figure 1:Calibration Curvehttps://www.researchgate.net/figure/Calibration-curve-of-Paracetamol_fig5_262938259

1. The calibration curve exhibited exceptional linearity within the concentration range of 0.01 mM to 0.1 mM, displaying a correlation coefficient (R^2) of 0.9997. The intercept was nearly at the origin, affirming the accuracy and reliability of the measurement technique.

2. An integer connection coefficient shows off both the strength and the scope of the relationship, as evidenced by the fact that the two factors are tied together.

3. The error bars are the point to be gleaned from every data the weakness of which involve in each estimate, which increase the robustness of the project bend.

4. The linear trend allows having precision in the measurement of paracetamol concentrations in the range of the samples that were considered.

Comment: Generally speaking, the calibration curve is a reliable tool for defining paracetamol concentrations which are needed for number of laboratory applications ( Bard, 2020 ). The great linearity of the adjustment bend responded, well, by high connection coefficient (R^2), along with the proximity of the block to origin represent the precision and reliability of the estimation method used. Such a high contact mechanism is particularly useful for precise studies inside given limits.

d) Experiment 2 Analysis

• Ordinary Current Power: 1500 nA

• Standard Deviation: 500 nA %

• RSD: 33.33%

e) Current vs. Potential Plots

A

B

Figure 2:Current vs. Potential and redox reaction/https://www.sciencedirect.com/topics/chemistry/reduction-potential

Two sorts of plots, one ongoing and the other likely, from 3, differ accordingly from the rhythmical nature of such structures in the presented case. The given observation reveals the mechanisms of the redox reactions that occur at distinctive potentials. The changes in the present situations indicate enhancement of stress, which at times causes an increase in response energy or modification in anode surface property. Wanting to explore these plots needs attention to the form of the surveys and education of good experimental conditions. By and large, through these plots, the readers can get a deep knowledge on the principles of different electrochemically coupled phenomena. This will contribute to improved analytical sensing for scientific purposes (Zoski, 2017).

f) Scan Rate vs. Peak Current

Figure 3:Scan Rate vs. Peak Currenthttps://www.researchgate.net/figure/Comparison-of-peak-current-vs-square-root-of-scan-rate-of-Fe-3-O-4-nanospheres-measured_fig2_334462266

The sweep rate - versus current plot from Experiment 3 denotes the nexus between the scan rate and electrochemical reaction. With the sweep varying sequentially, the plot discloses the corresponding variation of top flows, emulating the power of the redox response. Specific capacitance (Csp) decreases with higher current density, suggesting limited redox active sites' contribution. Fe3O4-DDA exhibits highest Csp (~56-70 F/g) at 1 A/g in KOH, NaOH, and LiOH electrolytes, influencing cycling performance evaluation. Even though these discoveries might be known by everyone, composing can be a good technique to highlight the esoteric phenomenon that governs the whole electrochemical cycle. Consistency with previously agreed upon findings and outcomes of the exploration gives credence to the observed patterns and brings in good information on response energy and the response of the anode. Moreover, a wrong electrochemical reaction can be observed as deviations from an ideal way of how it is supposed to be, thus to make a further investigation of reasons provoking the reaction (Compton, 2020).

g) Experimental Parameters Table (Table 1)

0.08000 0.040 0.006324 -1.216 -1.216 -1.216 -1.216 -1.216 -1.216 -1.216 -1.216 -1.216

0.09000 0.045 0.006708 -0.5310 -0.5310 -0.5310 -0.5310 -0.5310 -0.5310 -0.5310 -0.5310 -0.5310

0.1000 0.050 0.007071 -0.1038 -0.1038 -0.1038 -0.1038 -0.1038 -0.1038 -0.1038 -0.1038 -0.1038

h) Reversibility Determination

By the shape of cyclic voltammogram it is determined whether the reaction of paracetamol oxidation and reduction can be reversed. A feature which provides the proof of a reversible redox process is a well-defined and symmetrical oxidation and reduction peaks. In addition, for a twoelectron transfer, we should observe the reversible process with a separation between the oxidation and reduction peak potential (E_p) close to 59 mV theory value at room temperature. Nonetheless, if a system gets higher, narrower or even SOE≥ΔEp, it would suggest irreversibility (Kissinger, 2018).

i) Electrode Potential Calculation

To find the potential of the electrode with respect to a silver-silver chloride electrode, we need to use the reference potentials provided and apply the Nernst equation.

The Nernst equation is:

Ecell=Ecathode−EanodeEcell=Ecathode−Eanode

Where:

• EcellEcell is the cell potential,

• EcathodeEcathode is the potential of the cathode,

• EanodeEanode is the potential of the anode.

Given that the calomel electrode is the reference electrode, its potential is provided as +0.241+0.241 V. The potential of the silver-silver chloride electrode is +0.197+0.197 V.

We are given that the potential of the electrode in question is −0.535−0.535 V with respect to the calomel electrode.

First, we find the potential of the electrode with respect to the reference electrode (calomel electrode):

Eelectrode=Ecalomel-Eelectrode=+0.241 V−(-0.535 V)=+0.776

VEelectrode=Ecalomel-Eelectrode=+0.241V−(-0.535V)=+0.776V

Now, we can find the potential of the electrode with respect to the silver-silver chloride electrode:

Electrode, Ag/AgCl=Eelectrode−EAg/AgCl=+0.776 V−(+0.197 V)=+0.579 V

Velectrode, Ag/AgCl=Eelectrode−EAg/AgCl=+0.776V−(+0.197V)=+0.579V

So, the potential of the electrode with respect to the silver-silver chloride electrode is +0.579+0.579 V.

(Kolb, 2018).

QUESTION 2:

a) According to Lin et al, what is the key advantage of surface modification of electrodes?

b) What is the main aim of this paper?

As per Lin et al., the critical benefit of surface change of terminals can be summed up as follows:

Surface Improvement:

• Its indication is the providing of distinct recognition junctions on the anode surface, which boost its anatomic ability to exclusively adsorb particular analytes.

• The modification of gas diffusion surface allows for enhanced electrochemical detection of target analytes at fainter concentrations, providing the basis for more sensitive detection of a specific compound.

• Surface-modified anodes not only present an efficient performance but also out-performance complex example lattices making them autonomous in nature and good for situations involving seed pattern or environmental checking (Osteryoung, 2017).

• Surface-altered anodes not only present an efficient performance but also out-perform the complex example lattices making them autonomous in nature and good for situations involving seed pattern or environmental checking (Osteryoung, 2017).

The basic technical measurement is assessed by Lin et al's. paper can be illustrated through the accompanying focuses:

• Herein lies the problem i.e. to engineer a machine that can synthesize and identify simultaneously multiple analytes.

• The focus of the review is determinednes whole the critical analytes of interest are well elucidated either from important clinical applications or any specific application.

• This paper is aims to study the surface terminal alteration approaches as a way of improving the lopping abilities of synthetic materials that will be used to detect the targeted analytes.

• It plans to build a hefty-duty and unremitting method for the simultaneous assurance of the selected analytes to ensure precision and reproducibility.

• The core aim is to demonstrate the feasibility of the crafted technology in practicality, instances when is it applied to biomedical diagnostics or ecological observing (Brett, 2018).

c) What is the key strategy of surface modification that the authors employed.

Lin et al. relied on the most surface change procedure including the covalent connection of 5-hydroxytryptophan (5-HTP) granules to morph a monolayer on oxidized carbon leads (GCEs).

Through the use of this strategy, the selectivity and capability of the electrode to spot potential analytes like uric acid and ascorbic acid, which are known to be important for electrochemical sensing applications, are increased. The process is led by the proper functionalization of the GCE that enables the presence of the desirable responsive sites such as, for example, carboxyl or amino functional groups (Laviron, 2019).

Figure 4:surface modification /https://www.researchgate.net/figure/Schematic-representation-of-A-Surface-modification-strategies-and-B-Examples-of_fig3_342952977

The prolificity of these functional groups into the 5-HTP molecules that are onto the electrode's surface make the bonding of the 5-HTP molecules to it easy. This brings about identification contacts that will function as recognition sites for the target products and ensure monolayer formation that will be stable and uniform. A schematic portrayal of this surface change cycle would represent the accompanying advances:

• Active functional groups are inserted on GCE surface so that further covalent interaction with the specimen is possible. Immobilization: 5-HTP particles are brought forth on the changed cathode surface, by-in this molecular association bind the active moieties covalently.

• The Fixation of 5-HTP particles together on the cathode surface provides itself an array calculate that the all center of the pool is occupied by the particles.

• The prepared 5-HTP monolayer is unique and gives a characteristic signal that can be measured by a chemically detectable tool.

This surface change technique offers a few benefits:

• As the 5-HTPs enters, the solute sensitivity magnifies, ultimately making the detection limit more prominent.

• There is a possible specific recognition in the 5-HTP electrode, which increases the selectivity of the anode while target analytes are being separated from interference species.

• Covalent bonding is the binding force that keeps the surface modification intact and permits its utilization many times during the product's use without any noticeable damage.

In general, this surface change approach is just a tool for electrochemical analysis which gives more improved performance of detection and achieves more reliable outcomes in the location of target analytes (Nicholson, 2018).

d) The authors have determined surface concentration of grafted molecules to be

Γ* = 3.9 x 10-10 mol/cm2.

The celebrated Langmuir adsorption isotherm equation can be applied to find the monolayer surface concentration of grafted molecules (1).This condition relates the surface inclusion (Γ) to the grouping of particles in arrangement (C) utilizing the accompanying relationship:

Γ = Γ* C/(K + C)

Where:

• Γ is the surface inclusion (mol/cm2)

• Γ* is the greatest surface inclusion or immersion inclusion (mol/cm2)

• C is the grouping of particles in arrangement (mol/cm3)

• K is the balance consistent for adsorption (L/mol)

By revamping the condition to tackle for Γ*, the condition becomes:

Γ* = Γ · (K + C)/C

To become Γ*, exploratory information of surface inclusion (Γ) at different groupings of particles in arrangement (C) is gathered. Then, the information is approximated to the Langmuir equation and the fitting procedure is done. Γ* is the most extreme degree of surface inclusion from the section of the y-hub intersecting the block bend. Therefore, through analyzing the Langmuir adsorption condition, showing whether the surface coverage of joint atoms (Γ*) finally settled, it is possible to get a clear idea of the efficiency of this surface change processes (Compton, 2020).

References

Bard, A. a. F. L., 2020. Electrochemical Methods: Fundamentals and Applications. John Wiley & Sons..

Brett, C. a. B. A., 2018. Electrochemistry: Principles, Methods, and Applications. Oxford University Press..

Compton, R. a. B. C., 2020. Understanding Voltammetry: Simulation of Electrode Processes. Imperial College Press..

Kissinger, P. a. H. W., 2018. Laboratory Techniques in Electroanalytical Chemistry, 2nd Edition. CRC Press..

Kolb, D. a. L. J., 2018. Fundamentals of Electrochemistry. John Wiley & Sons..

Laviron, E., 2019. General expression of the linear potential sweep voltammogram in the case of diffusionless electrochemical systems. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 101(1), 19-28.

Nicholson, R. a. S. I., 2018. Theory of stationary electrode polarography. Single scan and cyclic methods applied to reversible, irreversible, and kinetic systems. Analytical Chemistry, 36(4), 706-723..

Osteryoung, R. a. O. J., 2017. Experimental Electrochemistry: A Laboratory Textbook. CRC Press..

Zoski, C., 2017. Handbook of Electrochemistry. Elsevier..