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Graphene Oxide Modified Pencil Graphite Electrode for the Detection of H2O2
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, June 2018.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 70-78).In this work, we propose a new, robust and reliable way to detect H2O2. Reduced graphene
oxide-supported tin oxide (SnO2-rGO) as electrochemical sensing material has been synthesized
and drop cased on pencil graphite electrode (PGE) for the detection of H2O2. Electrochemical
characterization has been done using cyclic voltammetry (CV) and amperometry. Hydrothermal
synthesis method was used for the fabrication of SnO2 nanoparticles and GO prepared by
modified Hummers method. For the detection of H2O2, the nanoparticles were mixed with
Nafion and chitosan before drop coating onto the PGE surface. In this work, we have found a
good catalytic activity of SnO2-rGO modified 3B PGE at pH 7.4. Electrochemical studies
showed that the sensing platform fabricated using SnO2-rGO possesses fast mass transport, good
electrical conductivity and high sensitivity and selectivity for the detection of H2O2. SnO2-
GO/PGE exhibited amperometric sensitivity of 53.4 μAmM−1cm-2 with a response time 2s, limit
of detection of 0.09μM (n=3), and linearity range of 1-7 mM. The electrode can be prepared
simply and at low cost, and present a promising tool for sensing H2O2.Joyanta Mistr
Development of Diethylamine Modified Electrode for the Determination of Paracetamol, Tramadol and Uric acid
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, March 2018.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 124-132).Paracetamol (PA) and Tramadol (TD) are very important drugs for the treatment of common diseases such as cold, fever, headache etc. They are co-exist in some tablets. Uric acid (UA) is the primary end product of purine metabolism. UA also exists in biological fluids such as blood and urine. A modified electrode has been developed using diethylamine (DEA) as a trifunctional electrochemical sensor for simultaneous detection of UA, PA and TD. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and UVVis. spectroscopy were used as detection techniques.
In this work, glassy carbon (GC), gold (Au) and platinum (Pt) electrodes were used as the working electrode. The electrodes were modified with DEA by applying continuous potential cycle for 15 scans at a range of -0.5 to 1.5 V. Then the electrodes were activated in phosphate buffer solution (PBS) (pH 7) by applying continuous potential cycle for 10 scans at a range of -0.5 V to 1.5 V. A ternary solution of UA, PA and TD was prepared and the CV and DPV were taken at the modified (GC, Au and Pt) electrodes. It is seen that the performance of modified GC electrode is better than the modified Au and Pt electrodes.
The influence of pH has been studied by varying pH from 3 to 9. The detection is mostly favorable at pH 7. The effect of different scan rates has been discussed and the variation of peak current plotted against square root of scan rate. The peak currents increase proportionally with increasing square root of scan rates indicates the electrochemical processes are controlled by diffusion process.
The effects of bare and modified GC electrode on single, binary and ternary solution of UA, PA and TD have been studied. CVs of the single solution of UA, PA and TD at bare GC electrode shows the oxidation peaks at 0.34V, 0.46V and 0.94V respectively. But at modified GC electrode it shows the oxidation peaks at 0.27V, 0.38V and 0.81V. At bare GC electrode, the ternary mixture of UA, PA and TD shows two oxidation peaks at 0.41V and 0.93V. But DEA modified GC electrode shows three separated and well defined oxidation peaks at 0.27V, 0.38V and 0.81V. The peak intensity of DEA modified electrodes are higher compared with the bare GC electrode. Similar behavior have been observed in the DPV technique.
Quantitative analysis of UA, PA and TD have been carried out by DPV using DEA modified GC electrode in a single, binary and ternary solution. In every case, the peak currents of UA, PA and TD increase linearly with increasing their concentrations over the range of 0.5-2.5 mM. The DEA modified GC electrode shows good selectivity and strong anti-interference activity for the determination of UA, PA and TD in binary and ternary mixture with excellent results. The limit of detection (LoD) has been calculated by signalto-noise (S/N=3) ratio. In simultaneous detection, the LoD for UA, PA and TD are 1.95 μmol L-1, 1.45 μmol L-1 and 1.26 μmol L-1 respectively at DEA modified GC electrode. The sensitivity of UA, PA and TD are 52.08 μA/mM/cm2, 62.25 μA/mM/cm2 and 33.67 μA/mM/cm2 respectively at DEA modified GC electrode.
DEA modified GC electrode has been successfully used for the quantitative determination of UA, PA and TD in some commercial tablets of different pharmaceutical companies of Bangladesh and biological fluids. The results have been valided by UV-Vis spectroscopic method and pathological report. The amount of PA and TD in some well-established pharmaceutical (Beximco, ACI, Square, Incepta, ACME etc) tablet samples have been found approximately same with compared to the labeled value. But the amount of PA, TD have been found less with compared to the labeled value in the tablets of some pharmaceutical companies (Opsonin, Renata, General, etc). Simultaneous detection of UA, PA and TD is not possible by UV-Vis spectroscopic method due to their very close absorbance maxima. The single determination of PA, TD and UA in tablet and blood samples by DEA modified GC electrode is very consistent with the determination of PA, TD and UA by UV-Vis spectroscopic method and pathological method in the same samples. Thus it is suggested that the DEA modified sensor may be used in the pharmaceutical industry and pathology for the determination of PA, TD and UA.Bulbul ChowdhuryMaster of Science in Chemistr
Volumetric and Sound Velocity Studies of L-Serine, L-Asparagine and L-Glutamine in Aqueous Vitamin B6 Solution at Different Temperatures
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, March 2018.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 177-184).In this study, a simple volumetric and sound velocity method was used for the analysis of
effect of vitamin B6 (pyridoxine) on the structure of amino acids (L-serine, L-asparagine
and L-glutamine). Densities and sound velocities of L-serine, L-asparagine and
L-glutamine in aqueous and in aqueous 0.05 mol.kg-1, 0.20 mol.kg-1, 0.35 mol.kg-1 and
0.50 mol.kg-1 vitamin B6 solutions have been studied at 293.15K to 318.15K with an
interval of 5K. The density data have been used to calculate apparent molar volume (φv),
limiting apparent molar volume (φv0), limiting apparent molar volume transfer (Δtrφv0),
apparent molar expansibilities (Eφ0) and Helper’s constant (δEφ0/δT)p. The ultrasonic
properties such as adiabatic compressibility (βs), apparent molar adiabatic compressibility
(φk0), limiting apparent molar adiabatic compressibility (φk0), apparent molar adiabatic
compressibility of transfer (Δtrφk0), acoustic impedance (Z) and hydration number (nH)
have been calculated by densities and sound velocities data.
The densities increase with the increase of concentration of amino acids. Densities of
amino acids in aqueous vitamin B6 solutions are higher than that of amino acids in
aqueous solution. The limiting apparent molar volumes (φv0) are positive at the studied
temperatures for the binary and ternary mixtures indicate the presence of solute-solvent
interactions. The smaller values of experimental slope (Sv) as compared to φv0 values
suggest the dominance of solute-solvent interaction over the solute-solute interaction.
The limiting apparent molar volume transfer (Δtrφv0) values of L-glutamine and
L-asparagine in aqueous 0.2 mol.kg-1, 0.35 mol.kg-1 and 0.5 mol.kg-1 vitamin B6 solution
are negative which suggest the dominance of ion-hydrophobic and hydrophobichydrophobic
interactions. But Δtrφv0 values of L-serine in aqueous 0.05 mol.kg-1, 0.20
mol.kg-1, 0.35 mol.kg-1 and 0.50 mol.kg-1 vitamin B6 solutions positive which suggest the
dominance of ion-hydrophilic and hydrophilic-hydrophilic interactions. The values of
limiting apparent molar expansion (Eφ0) are positive. The Hepler’s constant (δEφ0/δT)p
values of binary system are small negative for all studied amino acids. In ternary systems,
the Hepler’s constant values are mainly positive. This suggest that amino acids in ternary
solution are more structural than binary solution. The values of partial molar volumes (V2)
increase with increasing of concentration of L-serine, L-asparagine and L-glutamine for
the studied systems.
The sound velocity increases with the increase of concentration of amino acids (L-serine,
L-asparagine and L-glutamine). Sound velocities of amino acids in aqueous vitamin B6
solutions are higher than that of amino acids in aqueous solution. This indicate that the
increase of compactness of the medium with the increase in amino acids and vitamin B6
concentration.
The adiabatic compressibility (βs) decreases with the increase of concentration of amino
acids. This indicates the water molecules around the amino acids are less compressible
than the water molecules in the bulk solution. The negative apparent molar adiabatic
compressibility (φk) values indicate the greater loss of structural compressibility of water.
The values of limiting apparent molar adiabatic compressibility (φk0) are negative. The
values of apparent molar adiabatic compressibility transfer (Δtrφk
0) are mainly negative.
Negative values of Δtrφk0 indicate that increase in hydrophobic-hydrophobic and
hydrophilic-hydrophobic group interactions. The small Sk values also indicates the
dominating of solute-solvent interaction over solute-solute interaction.
The increase of acoustic impedance, Z with the increase of concentration of amino acids
indicates the presence of effective solute-solvent interactions. The positive hydration
number (nH) indicate the appreciable solvation of solutes.Musharat IslamMaster of Science in Chemistr
Studies on Volumetric and Ultrasonic Properties of L-Lysine, L-Ornithine and Glycine in Aqueous Fructose Solution at Different Temperatures
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, March 2018.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 196-205).In this study, the interaction of amino acids (glycine, L-ornithine and L-lysine) in water and aqueous fructose solution has been determined by using volumetric and sound velocity method. Interactions of glycine, L-ornithine and L-lysine in aqueous fructose solution play an important role to understand biochemical process in living cells. Densities and sound velocities of glycine, L-ornithine and L-lysine in water and in aqueous 0.05 mol.kg , 0.20 mol.kg -1 , 0.35 mol.kg -1 and 0.50 mol.kg -1 fructose solutions have been studied at 293.15K to 318.15K with an interval of 5K. The density data have been used to calculate apparent molar volume (φ v ), limiting apparent molar volume (φ v 0 ), limiting apparent molar volume transfer (Δ tr φ v 0 ), apparent molar expansibilities (δφ v 0 /δT) and Hepler’s constant (δ2φv0/δT2)p. The acoustic properties such as adiabatic compressibility (βp), apparent molaradiabatic compressibility (ks), limiting apparent molar adiabatic compressibility (φ),apparent molar adiabatic compressibility of transfer (Δtrφk0), acoustic impedance (Z),relative association (RA) and hydration number (n) have been calculated by densities and sound velocities data.
The densities increase with the increase of concentration of amino acids (glycine,L-ornithine and L-lysine). Densities of glycine, L-ornithine and L-lysine in aqueous fructose solutions are higher than that of glycine, L-ornithine and L-lysine in aqueous solution. The smaller values of experimental slope (S
) as compared to limiting apparent molar volume (φ v 0v) values suggest the dominance of solute-solvent interaction over the solute-solute interaction. The true volume (φ v0) of amino acids are found to be order of L-lysine > L-ornithine > glycine.
The limiting apparent molar volume transfer (Δtrφv0) values of glycine, L-ornithine and L-lysine are positive which suggest the dominance of ion-hydrophilic and hydrophilichydrophilic interactions over the hydrophobic-hydrophobic and ion-hydrophobic interaction. The values of limiting apparent molar expansion (δφ v0/δT) are positive.
Hepler’s constant (δ2φv0/δT2) values are small negative for all studied amino acids in binary and ternary system suggest the studied systems act as structure maker. The values of partial molar volumes (p2p) increase with increasing of concentration of glycine,-1k0L-ornithine and L-lysine for the studied systems. This trend of indicates solute-solvent interactions increase with increasing concentration of amino acids. vi 2 The sound velocity increases with the increase of concentration of L-lysine, L-ornithine and glycine. This may be attributed to the increase of compactness of the medium with the increase in amino acids concentration. Sound velocities of L-lysine, L-ornithine and glycine in aqueous fructose solutions are higher than that of L-lysine, L-ornithine and glycine in aqueous solution. The adiabatic compressibility (β ) decreases with the increase of concentration of L-lysine, L-ornithine and glycine. This indicates the water molecules around the amino acids are less compressible than the water molecules in the bulk solution.
The negative apparent molar adiabatic compressibility (ks) values indicate the greater loss of structural compressibility of water. The values of limiting apparent molar adiabatic compressibility (φk0) are negative. The values of apparent molar adiabatic compressibility transfer (Δtrφk0) are positive which suggest the existence of strong solute-solvent interaction. At lower concentration, negative values of Δtrφk0 indicate that increase in hydrophobic-hydrophobic group interactions. The small S values also indicates the dominating of solute-solvent interactions over solute-solute interaction. The acoustic impedance, Z increases with the increase of concentration of amino acids. The relative association, RAk decreases linearly with increasing the concentration of solute. The positive hydration number (n ) values indicate an appreciable solvation of solutes.
Therefore, the water molecules around amino acids are less compressible than water molecules in the bulk solution. The compressibility of ternary solution is lower than binary solution. This result suggests that the proteins or peptides generated from the studied amino acids will be denatured in ternary fructose solution.Md. TariquzzamanMaster of Science in Chemistr