Department of Chemistry (Ch.)

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A Novel Sensor for Simultaneous Detection of Dihydroxybenzene Isomers
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2016-08) Tonu, Nusrat Tazeen; Yousuf, Prof. Dr. Mohammad Abu
A novel, facile and low-cost electrochemical technique for the detection of dihydroxybenzene isomers (DHBIs), catechol (CC), hydroquinone (HQ) and resorcinol (RS), in aqueous system was developed. An attempt was made for the analyses of HQ, CC and RS in the same aqueous system by UV-Vis spectroscopy. UV-Vis spectrum of CC, HQ and RS exhibited absorbance maxima in PBS supported aqueous solution at 275.4, 288.6 and 273.2 nm respectively. But in the possible binary and ternary mixture of CC, HQ and RS, UV-Vis spectra showed single absorption peak instead of two and three separate peaks respectively. So, simultaneous detection of DHBIs was impossible by UV-Vis spectroscopy. Three electrodes electrochemical system was employed which was controlled by computer supported auto potentiostat. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were adopted as detection techniques. 2B pencil collected from the local stationary shop was used for fabricating working electrode termed as pencil graphite electrode (PGE) in the experiment. PGE electrode was characterized by Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray Spectroscopy (EDX). From the SEM it was seen that surface morphology of PGE was not smooth as conventional glassy carbon electrode (GCE) instead contained huge grooves as well. It indicates that the graphite rod of the pencil was not pure crystalline. From EDX it was seen that PGE surface are impure as propped up by SEM. Results showed that it is composed of 79.39% carbon, 10.03% Si, 3.06% O2, 3.49% Al, 2.68% Fe and trace amount of Mg and Ca. So a lot of defects and few foreign materials were present in the surface of PGE confirmed by both SEM and EDX. PGE was first modified electrochemically by ionic liquid (IL), [1-Hexylpyridinium hexafluorophosphate (HIL) or 1-Butyl-3-Methylimidazolium hexafluorophosphate (BIL)] and then used in detection analyte by CV and DPV. Modified electrodes were termed as HIL-PGE and BIL-PGE in total working process. Modified electrodes showed excellent electroanalytical activity effect on the redox reaction of DHBIs. Total analyses and detection processes were performed in phosphate buffer solution (PBS) at pH 7.0 which was used as supporting electrolyte. The influences of scan rate and concentration on the redox behavior of HQ, CC and RS in both HIL-PGE and BIL-PGE were discussed. The anodic peak current versus the concentration of HQ, CC and RS showed a linear relationship. The variation of peak current was also plotted with Square root of scan rate. The electrochemical processes were diffusion controlled. Variation of peak potential separation was plotted with scan rate. The anodic peak potential shift was positive, which was due to IR drop. HIL-PGE showed splendid selectivity and strong anti-interference for detection of HQ, CC and RS simultaneously in aqueous media with excellent results. The limit of detection (LOD) was calculated by signal-to-noise ratio (S/N = 3). In simultaneous detection, the LOD for HQ, CC and RS at HIL-PGE were 6.38 μML-1, 4.56 μML-1 and 19.6 μML-1 respectively and those were 9.09 μML-1, 8.15 μML-1 and 26.78 μML-1 respectively at BIL-PGE. The sensitivity for HQ, CC and RS is 448.49 μA/mM/cm2, 627.35 μA/mM/cm2 and 146.10 μA/mM/cm2 respectively at HIL-PGE and 525.21 μA/mM/cm2, 585.68 μA/mM/cm2 and 178.0 μA/mM/cm2 respectively at BILPGE in simultaneous detection.
Adsorption Properties of Mahogani (Swietenia Mahogani) Leaf Powder: Removal of Acid Dyes from Aqueous Solution.
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh., 2014-04) Akther, Meghla; Badal, Dr. Md. Mizanur Rahman
The Mahogani (Su'itenic, Mahogani) leaf treated with used as an adsorbent for the sulphuric acid and !'formaldehyde were removal of Reactive yellow C8G and Reactive red MSB de from aqueous solution. The adsorption characteristics of reactive dyes on activated Mahogani leaf powder (MLP) were evaluated as a function of p1-I, adsorbent dose and initial concentration of adsorhate. The amount of dye adsorbed per unit weight of the adsorbent increased with the increase of concentration and contact time. The adsorption was favored by an acidic p1-I range for Reactive red but not significant change for reactive yellow dyes. The adsorption processes were best described by a second-order rate equation. Reactive Yellow and Reactive Red dyes adsorption on MLP agreed with both Langmuir and Freundlich isotherms. The isotherm plots showed that the Freundlich equation gave slightly better linearity than the l.angmuir equation (R 0.94 for Langmuir plots; R 0.99 for Freundlich plots) indicating the MLP surfoce to be heterogeneous in the long range, but having some amount of uniformity locally. Langmuir monolayer adsorption capacity ((1ni) decreased from 67.11 to 11 .93 mg/g br reactive vehlo\v and from 12.39 to 2.09 mg/g for reactive red. MLP amount varying from 0.5 to 1.0 g/L. Ihe adsorption equilibrium parameter, for reactive yellow. h. varied from 0.028 to 0.034 L!mg with the increase in MLP amount and similar trend observed for reactive red. 'l'he adsorption capacity, k fshowed a decrease from 143.52 to 19.76 L/g with increase in MLP amount Irom 0.5 to 1.0 g/L, Similar results found for reactive red dye. The adsorption affinity. 11. lies between 0.21 and 0.27 satisfying the condition a < I for favorable adsorption.
Cost Effective Graphite Based Sensor for Simultaneous Detection of Phenolic Isomers
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2017-03) Khan, Md. Muzahedul Islam; Yousuf, Prof. Dr. Mohammad Abu
A facile and low-cost electrochemical technique for the detection of phenolic isomers (PIs), hydroquinone (HQ), catechol (CC), and resorcinol (RS), in aqueous system was developed. In this research, graphite based electrode (GBE) fabricated from a regular HB pencil (Brand: Faber Castell). HB pencil collected from the local stationary shop was used for fabricating working electrode termed as HB pencil electrode (HBPE) in the experiment. Then HBPE was also modified electrochemically by amino acid (AA), namely Glycine (GLY) and Aspartic Acid (ASA). Modified electrodes were termed as GLY-HB and ASA-HB in total working process. HBPE, GLY-HB and ASA-HB electrodes were used in detection of PIs by CV and DPV. The bare HBPE showed good electroanalytical activity effect on the redox reaction towards PIs. Both GLY-HB and ASA-HB electrodes showed catalytic activity on the redox reaction to PIs over HBPE. A series of pH dependent reactions were performed in phosphate buffer solution (PBS) and total analyses and detection processes were continued at pH 6.8 which was used as the supporting electrolyte. The influences of scan rate and concentration on the redox behavior of HQ, CC and RS in both GLY-HB and ASA-HB were discussed. The anodic peak current versus the concentration of HQ, CC and RS showed a linear relationship. The variation of peak current was also plotted with Square root of scan rate. The electrochemical processes were diffusion controlled in all cases. The constructed electrodes produced reproducible and stable results in all cases. The limit of detection (LOD) was calculated by signal-to-noise ratio (S/N) = 3. In simultaneous detection, the LOD for HQ, CC and RS at bare HBPE were 12.473 μML-1, 16.132 μML-1 and 25.25 μML-1, respectively. The sensitivity for HQ, CC and RS is 470.481 μA/mM/cm2, 363.781 μA/mM/cm2 and 232.416 μA/mM/cm2, respectively at bare HBPE. LOD for HQ, CC and RS at GLY-HB were 5.498 μML-1, 7.119 μML-1 and 14.794 μML-1, respectively and those were 22.459 μML-1, 25.478 μML-1 and 38.303 μML-1, respectively at ASA-HB in simultaneous detection. The sensitivity for HQ, CC and RS is 364.785 μA/mM/cm2, 282.712 μA/mM/cm2 and 135.560 μA/mM/cm2, respectively at GLY-HB and 374.483 μA/mM/cm2, 330.108 μA/mM/cm2 and 219.574 μA/mM/cm2, respectively at ASA-HB in simultaneous detection. Cost of one HBPE is about 5.00 BDT, one GLY-HB or ASA-HB electrode is about 7.00 BDT while one glassy carbon (GC) electrode is 14,000.00 BDT. So HBPE is at least 2800 times and that for GLY-HB or ASA-HB electrode is 2000 times cheaper than conventional commercial GC electrodes.
Development of Aspartic Acid Modified Waste Battery Electrode for Simultaneous Determination of Vitamin C, Paracetamol and Caffeine
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2018-07) Hasanuzzaman, Md.; Motin, Prof. Dr. Md. Abdul
Vitamin C (VC) is regarded as the most important water soluble antioxidant in human plasma. Paracetamol (PA) and Caffeine (CA) are important analgesic and antipyretic agents. The fixed combination of VC, PA and CA is widely used for the treatment of common diseases such as headache, cold, fever, muscle aches, arthritis, toothaches etc. A modified waste battery (WB) electrode sensor has been developed using Aspartic acid (APA) as a trifunctional electrochemical sensor for simultaneous detection of VC, PA and CA. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and UV-Vis spectroscopy were used as detection techniques. In this study, battery electrode and pencil graphite (PG) electrode were prepared from waste battery and pencil respectively. Then waste battery (WB), pencil graphite (PG), glassy carbon (GC), gold (Au) and platinum (Pt) electrodes were used as the working electrodes for the determination of VC, PA and CA. These electrodes were modified with APA by applying continuous potential cycle for 15 scans at a range of -0.3 to 1.8 V at 100 mVs-1. A ternary solution of VC, PA and CA was prepared and the CV and DPV were taken at the modified (WB, PG, GC, Au and Pt) electrodes. It is observed that the performances of modified WB and GC electrodes are better than that of the modified PG, Au, Pt electrodes. But the GC electrode is more costly than WB electrode. The influence of pH has been studied by varying pH from 3 to 9. The detection was mostly favorable at pH 7. The effect of different scan rates has been discussed and the variation of peak current was plotted with the square root of scan rate. The peak current increases with the increase of square root of scan rates. The nearly proportionality of the peak current suggests that the peak current of the reactant at each redox reaction is controlled by diffusion process with some chemical complications. The effects of bare and modified WB electrode on single, binary and ternary solution of VC, PA and CA have been studied carefully. CVs of the single solution of VC, PA and CA at bare WB electrode show the oxidation peaks at 0.27V, 0.51V and 1.44V respectively. But at modified WB electrode, they exhibit the oxidation peaks at 0.18V, 0.42V and 1.40V. At bare WB electrode, the ternary mixture of VC, PA and CA reveal two oxidation peaks at 0.49V and 1.44V. But the APA modified WB electrode shows three separated and well defined oxidation peaks at 0.18V, 0.42V and 1.40V. The peak intensity of APA modified electrode was higher than that of the bare WB electrode. Similar behavior has been observed in the DPV technique. Quantitative analysis of VC, PA and CA has been carried out by DPV using APA modified WB electrode in a single, binary and ternary solution. In every cases, the peak currents of VC, PA and CA increased linearly with the increasing of their concentrations over the range of 1.0 mM to 5.0 mM. The APA modified WB electrode showed good selectivity as well as strong anti-interference activity for the determination of VC, PA and CA in binary and ternary mixture with excellent result. The limit of detection (LoD) has been calculated by signal-to-noise (S/N=3) ratio. In simultaneous detection, the LoDs for VC, PA and CA are 0.20 μmol L-1, 0.16 μmol L-1 and 0.33 μmol L-1 respectively at APA modified WB electrode. The sensitivities of VC, PA and CA are 54.4 μA/mM/cm2, 99.9 μA/mM/cm2 and 151.7 μA/mM/cm2 respectively at APA modified WB electrode. APA modified WB electrode has been successfully used for the quantitative determination of VC, PA and CA in some commercial tablets of different pharmaceutical companies in Bangladesh. The results have been valided by UV-Vis spectroscopic method. The amount of VC, PA and CA in some well-established pharmaceutical (Square, ACI, Beximco, Glaxopharma, ACME, Opsonin, Aristopharma, Incepta etc) tablet samples have been found approximately same compared to the labeled value. But in some pharmaceutical companies (IBN Sina, Kemico, Shubatech, Novelta, Eskayef etc), the amount of VC, PA and CA have been found less compared to the labeled value in the tablets.
Development of Diethylamine Modified Electrode for the Determination of Paracetamol, Tramadol and Uric acid
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2018-03) Chowdhury, Bulbul; Motin, Prof. Dr. Md. Abdul
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.
Development of Glutamate Sensor Based on Nickel Oxide Nano Particle
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2016-08) Chakrabarty, Sumon; Jamal, Dr. A.B.M. Mamun
L-glutamic acid is one of the 20 standard amino acids used by all organisms. It plays an important role in clinical applications and in food processing and well known as a flavor enhancer commonly found in various foods. The excessive intake of this flavor enhancer can cause toxic effect to the human health. Therefore, development of sensors or biosensors for the determination of glutamate has been of great interest over the past two decades owing to its importance in food and biomedical industries. In this study nickel oxide nanocrystal and nickel oxide hollowsphere have synthesized by using sol-gel and hydrothermal methods. Morphological characterization of nickel oxide particle was carried out using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The crystallite size of nickel oxide prepared by sol-gel method has been found 60 nm. Nickel oxide nanocrystal shows higher selectivity towards glutamate detection compare to nickel oxide hollowsphere. The enzyme-free sensor has been fabricated through modification of glassy carbon using the mixture of nickel oxide nanocrystals and citosan (NiO/GCE). Cyclic voltammetry (CV) and amperometry were used to investigate the electrochemical behavior and catalytic properties of the assembled sensor for glutamate electro-oxidation in alkaline media. It has been found that NiO/GCE showed remarkably enhanced electrocatalytic activity towards glutamate and the electrochemical reaction is diffusion controlled. The sensitivity of NiO/ GCE has been found to be 11 μA/mM/cm2. Under optimal detection conditions, the sensor exhibited linear behavior for glutamate detection in the concentration up to 8 mM with a limit of detection of 272 μM. The interference study of NiO/GCE has been found a significant current response for glutamate compared to the uric acid and ascorbic acid. The stability of NiO/GCE has been studied over a period of one week and found to retain 65% of its original activity towards glutamate detection. Experimental results show that NiO/GCE has significant promise for fabricating cost effective, enzyme-less, sensitive, stable and selective sensor platform.
Development of Novel pH Sensor Based on Nanoparticle Modified Electrochemical Sensing Platform
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2017-04) Akhter, Irani; Jamal, Dr. A.B.M. Mamun
In biological and environmental applications, pH is an important parameter that needs to monitor in regular basis. Conventionally, the measurement processes take a considerable amount of time involving several calibration steps and handling of fragile electrodes. In this work, we propose a new, robust and reliable way of sensing pH. The sensor has been fabricated based on tungsten oxide nanoparticle modified glassy carbon electrode (WO3/GCE). WO3 is a promising material for pH sensor because of its availability, stability, good morphological and structural control of the synthesized nanostructures. In this work, hydrothermal synthesis method was used for the fabrication of WO3 nanoparticles. For the fabrication of the pH sensor, the nanoparticles were mixed with Nafion and chitosan before drop coating onto the GCE surface. Scanning electron microscopy (SEM), x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX) and Raman spectroscopy were used to characterize the nanoparticle. Cyclic voltammetry (CV), zero current potentiommetry (OCP) and square wave voltammetry (SWV) were used to monitor the potential shift based on different pH in the buffer solutions. This electrochemical pH sensor showed a sensitivity of 60 mVpH-1 and a potential drift of 2.4 – 5.0 % after three hours of continuous use. The sensor showed linearity range of pH 3 -11 and could retain 95% of its initial activity after 1 week of use. The electrode was found to respond both in the presence and absence of oxygen, further expanding the potential applications to include de-oxygenated environments. The WO3 based sensor showed good sensitivity and long term stability, which would be a potential platform to develop a low cost pH sensor for a wider range of applications.
Development of Sensor for Free Available Chlorine Estimation in Surface Water
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2016-08) Islam, Md. Juel; Jamal, Dr. A.B.M. Mamun
The development of portable sensors that can be used outside the lab is an active area of research in the electro analytical field. A major focus of such research is the development of low-cost electrodes for use in these sensors. Current electrodes, such as glassy carbon, platinum or gold electrodes, are costly and require time-consuming preparation. In this work an alternatives have been proposed, where pencil graphite electrodes (PGEs) has been used as sensing platform. Surface of pencil has been used to make it suitable for estimating free chlorine in water sample. Chlorine is a common disinfectant in the water industry, and the residual free chlorine concentration in water distributed to the consumers must be lower than the value set by the regulatory bodies. The pencil graphite-electrode shows high selectivity, low detection limit and linear response to free chlorine in the relevant concentration range at the applied potential of 1.5V and no response to commonly interfering ions such as NO3 -, SO4 2-, CO3 2-, Cl-, HCO3 - has been observed. Further investigation has been conducted on the storage stability and response time on FAC sensing. The sensitivity of free chlorine has been found to be 50μAmM-1cm-2. The pencil graphite electrodes were also used for detection of chlorine with a relatively wide concentrations ranging up to 8 mM, with a limit of detection of 46 μM. It exposes that the stability of PGEs 97.93% after 14 days of its initial activity. This sensor is being proposed as a low cost device for determining free chlorine in water samples with short response time of t90 less than 5 sec.
Development of Sulfolane Modified Electrode Sensor for the Determination of Vitamin-B6, Vitamin-C and Uric acid
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2017-05) Mitu, Shahin Ara; Motin, Prof. Dr. Md. Abdul
Vitamin-B6 (VB6) and Vitamin-C (VC) are important biomolecules and are widely used as food additives or antioxidants and for the treatment of anemia, depression, acute seizures, scurvy, cold problems etc. Uric acid (UA) is the primary end product of purine metabolism. UA also coexists with VB6 and VC in biological fluids such as blood and urine. In this study, a simple and sensitive modified electrode sensor has been developed using Sulfolane (SFL) as a trifunctional electrochemical sensor for the determination of VB6, VC and UA. Cyclic voltammetry (CV), Differential pulse voltammetry (DPV) and UV-Visible spectroscopy were performed 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 SFL by applying continuous potential cycle for 15 scans at a range of -1.0 to 2.0 V at 100 mV s-1. Then the electrodes were activated in phosphate buffer solution (PBS) (pH 7) by applying continuous potential cycle for 5 scans at a range of -0.5 V to 1.2 V. A ternary solution of VB6, VC and UA 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 was mostly favorable at pH 7. The effect of different scan rates has been discussed and the variation of peak current was plotted with square root of scan rate. The peak current increases with the increase of square root of scan rates. The nearly proportionality of the peak current suggests that the peak current of the reactant at each redox reaction is controlled by diffusion process with some chemical complications. The effect of bare and modified GC electrode on single, binary and ternary solution of VB6, VC and UA have been studied. CVs of the single solution of VC, UA and VB6 at bare GC electrode shows the oxidation peaks at 0.34 V, 0.35 V and 0.74 V respectively. But at modified GC electrode VC, UA and VB6 gives the oxidation peaks at 0.15 V, 0.33V and 0.72 V respectively. At bare GC electrode, the ternary mixture of VC, UA and VB6 shows two oxidation peaks at 0.5 V and 0.74 V. But SFL modified GC electrode shows three separated and well defined oxidation peaks at 0.18 V, 0.34 V and 0.79 V respectively. The peak intensity of SFL modified electrode was high compared with the bare GC electrode. Similar behavior have been seen in the DPV technique. Quantitative analysis of VB6, VC and UA have been carried out by DPV using SFL modified GC electrode in a single, binary and ternary solution. In every case, the peak currents of VB6, VC and UA increased linearly with increasing their concentrations over the range of 0.5-2.5mM. The SFL modified GC electrode showed good selectivity and strong anti-interference activity for the determination of VB6, VC and UA in binary and ternary mixture with excellent results. The limit of detection (LoD) has been calculated by signal-to-noise ratio (S/N=3). For the simultaneous concentration change, the LoD for VB6, VC and UA at SFL modified GC electrode are 0.8 μML-1, 1.0 μML-1 and 0.2 μML-1 respectively. The sensitivity of VB6, VC and UA are 41.84 μA/mM/cm2, 31.12 μA/mM/cm2 and 138.14 μA/mM/cm2 respectively at SFL modified GC electrode. The practical application of the SFL modified electrode sensor was demonstrated by the determination of VB6 and VC in pharmaceutical tablet samples and UA in blood sample. The results have been valided by UV-Vis spectroscopic method and pathological method. The amount of VB6 and VC in some well-established pharmaceutical (Beximco, ACI, Square, Aristopharma, Opsonin, ACME etc) tablet samples have been found approximately same with compared to the labeled value. The single determination of VB6, VC and UA in tablet and blood samples by SFL modified GC electrode is very consistent with the determination of VB6, VC and UA by UV-Vis spectroscopic method and pathological method in the same samples. Thus it is suggested that the SFL modified sensor may be used in the pharmaceutical industry and pathology for the determination of VB6, VC and UA.
Disposable and Low-cost Free Chlorine Sensor Based on Pencil Drawn Paper Electrode
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2017-04) Dutta, Apu Kumar; Jamal, Dr. A. B. M. Mamun
This is the first alternative analysis of pencil drawn paper electrode for free available chlorine (FAC) detection. It is one of the new technologies for fabricating simple, low lost, portable and disposable analytical device for many application areas including clinical diagnosis, food quality control and environmental monitoring. In this work a complete analysis of physical and electrochemical properties of pencil graphite electrode (POE) and pencil drawn paper electrode (PDPE) has been performed to detect FAC in surface water. Cyclic voltammetry (CV) and amperometry were used to study the electro-catalytic properties. Excellent catalytic activity has been obtained for free chlorine detection using both POE and PDPE with a sensitivity of 121 ± 5.38 .iAmMcm 2 and 36 ± 3.65 pAmM4cm 2 respectively and a linearity range up to 12 mM and 7 mM for both platforms respectively. Also limit of detection POE and PDPE has been found to be 59.5 and 88.9 p.M respectively. There is no response obtained for common interfering ions in surface water such as NO3 , SO 2 , C0 32 , Cl'and HCO3 . Both the sensors were evaluated for their storage stability and response time and thereby can be applied as a low-cost electrochemical sensor for determining FAC in surface water. The unique properties of this sensor allow the passive liquid transport and compatibility with chemical/biochemical are the main advantage of using this sensing platform. In addition, this sensor could better meet the current objectives of a viable low cost and portable device in addition to offering high sensitivity, selectivity and multiple analyte discrimination.
Drinking Water Quality Assessment in Khulna City Corporation Slum Area
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2017-03) Kundu, Abanti; Yousuf, Prof. Dr. Mohammad Abu
Drinking water is characterized as free from microorganisms, terribly toxic compounds and that have no adverse effects on health. Waterbome disease is a major concern of public health and it is important to know the microbial as well as the physico-chemical qualities of drinking water. This study was conducted to assess the quality and suitability of groundwater for drinking purposes in different slum area of Khulna City Corporation (KCC) and explored the variation of bacteriological status of water between sources (deep Tube-wells) and household stored water. The study was conducted from July 22, to August 28, 2016. A total of 100 samples; 50 from sources and other 50 samples from household storage vessels were collected for exploring physico-chemical and bacteriological status. The parameters that were investigated found to have variation in the range of pH 7.4 to 8.55 was slightly basic, electrical conductivity 544 tS/cm to 2.21 mS/cm; Hardness 50 to 650 as CaCO3 considered, hardness classification shows that maximum sample are hard type and very hard type. Total Dissolved Solid (TDS) 281 to 1176 mg/L, However, TDS classification of GW shows that maximum samples lie within good (300-600 mg/L), Chloride 31.68 to 721 mg/L, As
Effect of N-Acetylcysteine on Volumetric and Viscometric Properties of Chitosan in Aqueous Acidic Solution
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh., 2017-12-31) Kashem, Md. Abul; Yousuf, Prof. Dr. Mohammad Abu
Volumetric and viscometric studies of Chitosan-H20-CH3COOH and NAC (NAcetylcysteine)-Chitosan-[H20-CH3COOH] systems were investigated at 298.15 to 323.15 K at 5 K intervals. In a]l investigated systems concentrations of NAC were 0.10,0.50 & 1.00 mol.L' and concentrations of chitosan were 0.003, 0.006 & 0.012 mol.L* H20-CH3COOH mixed solvent was used for the experiment and H20 to CH3COOH ratios 9:1, 7:3 and 3:2 were maintained. Densities have been found to be increased with increasing concentration of both NAC and chitosan but decreased with increasing temperature. Densities were found to be increased with increasing the ratio of CH3COOH in Chitosan-H20-CH3COOH systems but this trend was not so significant is case of NAC-Chitosan-H20-CH3COOH systems. Density Values of NAC-Chitosan-[H20-CH3COOH] systems were remarkably higher than those Chitosan-H20-CH3COOH systems.The apparent molar volumes, φv of both Chitosan-H20-CH3COOH and NACChitosan-H20-CH3COOH systems were determined from the experimental density values data at 298.15 to 323.15 K at 5 intervals. The φv values were dependent upon concentration of NAC and chitosan in mixed solvents as well as the temperature. φv values have been found to be positive in all investigated systems. The φv values decreased throughout the whole concentration range for NAC and chitosan in their specific solvent systems. These results may be due to the solute—solvent, and solute—solute interaction through dipole-dipole interaction, ion-dipole interaction, hydrogen bond, hydrophilic or hydrophobic interaction among NAC, chitosan and aqueous acetic acid in the solutions. Besides, φv values were found to be increased with increasing temperature at any concentration of NAC and chitosan in solutions and this is may be due to increased thermal agitation at higher temperatures. Apparent molar volume at infinite dilution, φvo; apparent molar expansivity and Sv values were also determined. The φvo; values of chitosan-[H20-CH3COOH] systems decreased with increasing temperatures and increased with increasing the ratio of CH3COOH in H20-CH3COOH mixed solutions. At elevated temperatures cages in the investigated systems becomes less important hence the apparent molar volume at infinite dilution, φv3 decreased with increasing temperature. in addition, incorporation of more acetic acid ratio in Chitosan-H20-CH3COOH system hydrophobic-hydrophobic repulsion predominant over hydrogen bonding or dipole-dipoleinteraction. The apparent molar volume at infinite dilution gives an idea about the presence of solute—solvent interactions. The expansivity values are positive at all the investigated temperatures. Positive values indicate that, on heating some NAC and chitosan molecules may be released from the solvation layer of ion. It may also be conferred that the positive φEo;values may be originated from the hydrophobic character and steric effect of the NAC and chitosan in systems. As a whole there is a hydrophilic/hydrophobic balance among the solute and solvent molecules. S parameters contribute an idea about the prevailing solute—solute interactions in the mixtures. The negative and large in magnitude values of Sv in all investigated systems supports the weak solute-solute interaction present. Both Chitosan-H20-CHICOOH and NAC-Cli itosan-H20-CH3COOH systems showed rapid increase of viscosity values with the increase of chitosan and NAC concentrations but viscosities decreased with the increase of temperature. The increase of η values of with concentration of chitosan and NAC can be attributed to the increase in solute—solvent, and solute—solute interactions in solution. The small range of dissolution of chitosan and/or NAC in H2 0-Cl-13C00H might have intriguing aspects which may be the consequence of the great ability of H20 and Cl-13C00H to make hydrogen bond and dipole-dipole, ion-dipole interaction. In all cases with the increase of temperature internal energy of the systems increased as a result solute-solute or solute-solvent interaction may be depleted and viscosity values decreased. The viscosity data were employed to determine A and B-coefficients; change of free energy, ∆G*; change of enthalpy. ∆H* and change of entropy,∆*. From these thermodynamic parameters state of the spontaneity of the investigated systems were known. Besides, negative A and positive B co-efficient suggesting that weak solute solute but strong solute-solvent interaction present. The change of free energy values for viscous flow,∆G* were found to be positive indicate that work has to be done to overcome the energy barrier for the flow process. The positive AH values indicate that work has to be done for all the investigated systems. The ∆S* values are negative for all the systems studied. This means that Chitosan-[H20-GH3COOH] and NACChitosan-[H20-CH3COOH]systems are regular than those of the pure one. Here one point may be remarked that as ∆S < 0 and ∆H> 0, so the processes are never spontaneous but the reverse process is always spontaneous.
Effect of Surfactant on Formation of Hydroxyapatite under Reverse Micelle Condition
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2018-12-23) Yeasmin, Fargana; Yousuf, Prof. Dr. Mohammad Abu
Hydroxyapatite, (HAp), Ca10(PO4)6(OH)2, is a naturally occurring material found in the inorganic component of human bone and enamel. The constituent elements of HAp are primarily calcium and phosphorous, with a stoichiometric calcium to phosphorous ratio is 1.667 capable of promoting intimate bone growth onto femoral implants. The performance, lifespan and quality of the resultant biological coating in vivo is largely dependent on the coating morphology, phase composition, particle size and crystallinity of the powders pre-coating application. The present study focused on preparing Hydroxyapatite nanoparticles (HAp-NPs) through chemical precipitation technique using mixed micelle core as a nanoreactor. Mixed micelle core was used to control morphology such as crystallinity, particle size, particle shape, particle size. Anionic (sodium dodecyl sulphate (SOS)) and cationic (Cetyl trimethyl ammonium bromide (CTAB)) surfactants were used to prepare the mixed micellar core. 18 : 2 ratio of propanol-1 : water system experimentally selected for the formation of reverse micelle for the afore mentioned surfactants. Compositions of both surfactants were varied to control the morphology of HAp-NPs under the same experimental condition. Several techniques such as FTIR, XRD, TOA and SEM were used to characterize the prepared HAp-NPs. Appearance of peaks at various position of the FTIR spectrum shows the PO vibrations of PO;- which are characteristics of hydroxyapatite. In addition, the diffraction pattern of the prepared HAp-NPs are in well agreement with the standard published by the International Centre for Diffraction Data. However, the diffractogram indicates the presence of crystalline as well as amorphous phase. No significant weight loss was observed for the prepared HAp-NPs. SEM result reveals significant morphological variation of the prepared HAp-NPs by changing the amount of two surfactants. Variation of the ratio of surfactants SOS and CT AB allow the variation in the morphology of the prepared particles.
Effect of tri-Potassium citrate on the Structure of Sucrose and Maltose in Solutions at Different Temperatures: Volumetric and Ultrasonic Studies
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2018-09) Sarkar, Subhas Chandra; Motin, Prof. Dr. Md. Abdul
A volumetric and sound velocity method was used for the analysis of effect of tri- Potassium citrate (TPC) on the structure of sucrose and maltose. Densities and sound velocities of sucrose and maltose in water and in aqueous 0.05 mol.kg-1, 0.20 mol.kg-1, 0.35 mol.kg-1 and 0.5 mol.kg-1 (TPC) solutions have been studied at 293.15K to 313.15K with an interval of 5K. From density values, various parameters such as apparent molar volume (φv), limiting apparent molar volume (φv 0), limiting apparent molar volume transfer (Δtrφv 0), apparent molar expansibilities (δφv 0/δT)p and Hepler’s constant have been calculated. The acoustic properties such as adiabatic compressibility (βs), apparent molar adiabatic compressibility (k), limiting apparent molar adiabatic compressibility (φk 0), apparent molar adiabatic compressibility of transfer (Δtrφk 0), acoustic impedance (Z) and hydration number (nH) have been calculated by densities sound velocities data. The densities increase with the increase of concentration of sucrose and maltose. Densities of sucrose and maltose in aqueous TPC solutions are higher than that of sucrose and maltose in pure water solution. The apparent molar volume varies upon the disaccharides (sucrose and maltose) concentration as well as on the temperature. The smaller values of experimental slope (Sv) as compared to limiting apparent molar volume (φv 0) values suggest the dominance of solute-solvent interaction over the solute-solute interaction. The true volume (φv 0) of disaccharides are found to be order of: maltose > sucrose. The limiting apparent molar volume transfer (Δtrφv 0) values of sucrose and maltose are positive which suggest the dominance of ion-hydrophilic and hydrophilic-hydrophilic interactions over the hydrophobic-hydrophobic and ion-hydrophobic interactions. The Δtrφv 0 values increase with an increase in concentration of the TPC which indicates the presence of strong ion-hydrophilic interactions in the mixtures. The values of limiting apparent molar volume expansion (δφv 0/δT)p are positive. Hepler’s constant values are positive or small negative for all studied disaccharides in binary and ternary system suggest the studied systems act as structure maker. The values of partial molar volumes (V2) increase with increasing of concentration of sucrose and maltose for the studied systems. The sound velocity increases with the increase of concentration of sucrose and maltose. Sound velocities of disaccharides in aqueous TPC solutions are higher than that of disaccharides in pure water solution. This indicate that the increase of compactness of the medium with the increase in disaccharides and TPC concentration. The adiabatic compressibility (βs) decreases with the increase of concentration of disaccharides. This indicates the water molecules around the disaccharides are less compressible than the water molecules in the bulk solution. The negative k values indicate the greater loss of structural compressibility of water. The positive Δtrφk 0 values for all the saccharides indicate the presence of ionic-hydrophilic and hydrophilic-hydrophilic interactions. The small Sk values also indicates the dominating of solute- solvent interactions over solutesolute interaction. The acoustic impedance, Z increases with the increase of concentration of disaccharides indicates the presence of effective solute-solvent interactions. The hydration number (nH) decrease with the increase of concentration and temperature for both binary and ternary systems. The positive hydration number (nH) values indicate an appreciable solvation of solutes. Hydration capacity of maltose is higher than sucrose in water and in aqueous TPC solution.
Electro-oxidation of 1,2-dihydroxybenzene in Presence of Alanine, Phenylalanine and Leucine at Different pH Media
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2016-08) Dhar, Palash Kumar; Motin, Prof. Dr. Md. Abdul
The electro-oxidation of 1,2-dihydroxybenzene generates o-benzoquinone (Michael acceptor) and its reaction in presence of different concentration of L-Alanine, LPhenylalanine and L-Leucine (nucleophiles) has been investigated. The overall study has been carried out in buffer solution of different pH (5, 7, 9 and 11) by using Cyclic Voltammetry (CV), Controlled Potential Coulometry (CPC) and Differential Pulse Voltammetry (DPV) techniques at different electrodes (GC, Pt and Au) and scan rates (0.05-0.5 V/s). Cyclic voltammogram of electro-active 1,2-dihydroxybenzene in pure buffer solution (5-11) shows one anodic and corresponding cathodic peak within a quasireversible process. Pure L-Alanine, L-Phenylalanine and L-Leucine are electro-inactive having no peak in the potential range of investigation (-0.6 to 0.9V). Addition of different composition of L-Alanine (10-150 mM), L-Phenylalanine (2-100 mM) and L-Leucine (30-200 mM) in fixed 2 mM of 1,2-dihydroxybenzene solution, in the second scan of potential a new anodic peak (A0) arises at the more negative potential with respect to the pure 1,2-dihydroxybenzene. The anodic (A1) and cathodic peak (C1) current intensity of 1,2-dihydroxybenzene also decreases significantly. This indicates the participation of 1,4-Michael addition reaction of o-benzoquinone with L-Alanine, LPhenylalanine and L-Leucine to produce 2-((3,4-dihy droxyphenyl)amino)propanoic acid, 2-((3,4-dihydroxyphenyl)amino)-3-phenylpropanoic acid and 2-((3,4-dihydroxyphenyl) amino)-4-methyl-pentanoic acid adducts. The 1,4-Michael addition reaction of 1,2-dihydroxybenzene is strongly influenced by the concentration of nucleophiles. The electrooxidation of 2 mM 1,2-dihydroxybenzene is mostly favorable in 50 mM of L-Alaline, 20 mM of L-Phenylalanine and 100 mM of L-Leucine respectively. The effect of pH on 1,2-dihydroxybenzene in presence of different nucleophiles has been studied by varying pH ranging from 5 to 11. In acidic pH media (pH <7), no new anodic peak arises after repetitive cycling due to protonation of amine group. But in the neutral (pH=7) and basic media (pH >7), o-benzoquinone undergoes nucleophilic attack by the amine part of amino acids and the maximum peak current is observed at pH 7. The slope value of 1,2-dihydroxybenzene-Alanine, 1,2-dihydroxybenzene-Phenylalanine and 1,2-dihydroxybenzene-Leucine adducts have been calculated (70.5 mV/pH for first anodic peak A1), (59 mV/pH for first anodic peak A1) and (68.5 mV/pH for first anodic peak A1) at 0.1 V/s respectively. These values indicate that the nucleophilic substitution reactions are preceded via 1e−/1H+ process. It is also suggested that during the course of reaction, electron and proton are released simultaneously from the 1,2-dihydroxybenzene-Amino acid adducts. The nature of voltammogram, peak position and current intensity for the studied systems are different for different electrodes and the voltammetric response of GC electrode is better than Au and Pt electrodes. The effect scan rates on cyclic voltammogram of 1,2-dihydroxybenzene in presence of LAlanine, L-Phenylalanine and L-Leucine have also been studied. The peak current of both the anodic and the corresponding cathodic peaks increases with the increase of scan rate. The nearly proportionality of the anodic and corresponding cathodic peak suggests that the peak current of the reactant at each redox reaction is controlled by diffusion process with some chemical complications. The current function, Ip/v1/2 vs scan rates (v) of 1,2-dihydroxybenzene-Amino acid adducts are found to be decreased exponentially with increasing scan rate which suggests that the behavior of reaction mechanism is Electron transfer-Chemical reaction-Electron transfer (ECE) type for all the studied system. The products obtained by bulk electrolysis have also been analyzed by FTIR spectra.
Electrochemical Characterization Of Biologically Important Electroactive Metal Ligand Complexes With Multi-electron Transfer Reactio
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh., 2014-07) Rahman, Md. Matiar; Motin, Prof. Dr. Md. Abdul
The redox behavior of Cu (II) only and Cu (II) with aspartic acid (Apa), L-phenl alanine (Phe), 3-nitrobenzene sulfnate (NBS) ; Zn(II) only and Zn(ll) with Apa, Phe, NBS and Catechol ((ate) has been studied Cyclic voltammetry (CV), Differential pulse voltammetry (DPV) and Chronamperometry (CA) techniques. The voltammetri technique demonstrates the interaction of biologically important metals (Cu, Zn) with the ligands (Apa, Phe, NBS, Cate) that is formed of metal-ligand complexes. The interaction studies have been carried out in variation of metal ion concentration, ligand concentration, Buffer solution of different pH and scan rate. In all the studies of Cu(II) and Zn(II) complexes, with some exception, Cu(II )-ligand systems and Zn(II)-ligand systems have been found to undergo quasireversible electrode reaction with EC mechanism. For all the ligands, Apa and Phe are electroinactive ligands whereas Cate and NBS are electroactive ligands. Both the anodic and cathodic voltamnietric peaks were shifted and sometimes developed new peaks with the addition of Apa, Phe, NBS, Cate in Cu(II) and Zn(II) solutions. On the addition of Apa, Phe and NBS in Cu(II) solution, the peak positions of the voltammogram of Cu(II)-Apa, Cu(II)-Phe and Cu(II)-NBS, first anodic peak was shifted positively but the second oxidation peak was shifted negatively with respect to that of only Cu ( II). The peak current decreases significantly compared with that for free Cu(II) in the same experimental conditions, This behavior confirms the interaction and complexation between Cu(II) and Apa, Phe. The effect of pH of Cu(II)-Apa, Cu(II)-Phe and Cu(II)-NBS were studied by varying pH from 3.5 to 7.0. The peak current of Cu(II)-Apa, Cu (II)-Phe and Cu(II)-NBS increases with the decrease of pH indicating that at lower pH the Cu(II)-Apa, Cu(II)-Phe and Cu(II)-NBS is highly electroactive. The maximum peak current was obtained at pH 3.5. This shows that the electrochemical oxidation of Cu(II)-Apa, Cu(II)-Phe and Cu(II)-NBS is aicilitated in acid media and hence the rate of electron transfer is faster.The average diffusion coefficient, D of Cu(II)- Apa or Cu(II)-Phe is found to he 4.5 x l0-6cm2s-1. The cyclic voltammogram of Zn(II) only and Zn(II) with Apa, Phe, NBS and Cate in aqueous and in buffer solution of different pH were taken at different scan rates. The CV of Zn (II) shows at pH (1 .5, 3 and 4.5) one well defined anodic and cathodic peak at different scan rate hut in aqueous solution only Zn(II) showed very weak anodic peak. Upon the addition of Apa, Phe, NBS, Cate with Zn(II) the first anodic peak shifted positively and the cathodic peak is shifted negatively which indicates the formation of Zn (II)-Apa or Zn ( II)- Phe complex. The intensity of the anodic and cathodic peak current decreases with the increasing of Apa or Phe or NBS or Cate suggesting that is formed of more Zn( 11 )-Apa or Zn(II)- Phe or n(ll)- NBS complex. The effect of pH of Zn(II)-Apa, Zn(II)-Phe, Zn(II)-N BS and Zn(II)-Cate were studied by varying pH from 1.5 to 11. The peak current decreases with the increase of pH .The maximum peak current was obtained at pH 3-4.5.At higher pH(7-11), the anodic peak disappeared. This shos that the electrochemical oxidation of Zn(II) complexes is hindered in basic media. For the comparison CV of Zn(II) only and Zn( II) —Asp, Zn(II)-Phe, Zn( II)- Cate, Zn( II)-NBS at similar condition (pH 3, scan rate 0.1 V/s). it is seen that the anodic peak current of Zn(II)-Asp and Zn(II)-Phe are lower than that of Zn(II) only hereas the anodic peak current of Zn(II) - Cate and Zn(II)-NBS is higher than that of Zn(II) only. When Cate and NBS are coordinated with Zn(II) both metal and ligands are electroactive, So constructive interference of peak appeared whereas Asp and Phe are coordinated with Zn(II), here ligands are eleciroinactive so the overall peak currents are lower than Zn(II) only. The slopes of the plots of Ep against pH of all studied metal ligand complexes ere determined graphically as anodic peak 25- 35 mV/pH at 0.1 V/s, which is close to the theoretical value of 30 mV for a two-electron, two-proton transfer process which indicates that the oxidation of all metal-ligand complexes proceeded via the 2e-2H+ processes. This suggests that during the reaction not only electron but also protons are released from the metal-ligand complexes. For all the studied system, with the increasing of metal: ligand composition from 1:1 to 1:5 (metal fixed), the current decreases linearly but after more addition of ligands, the current intensity change is constant. This indicates that the availability of metal is limited for the formation of the metal-ligand complex at saturation point. When the composition of metal increases with the fixed of the composition of ligands from 1:1 to 5:1. after certain concentration, the voltammogram pattern reflected into the only metal, because of the deficiency, of ligands in solution. The relation between metal - ligand concentration and cyclic voltammetric anodic and cathodic peak current (Ipaand Ipc) is linear. The proportionality of the anodic and cathodic peak currents with square root of scan rate of all the studied metal ligand complexes with few exceptions suggests that the peak current of the difièrent complexes at each redox reaction is controlled by diffusion process. From the studied of all systems it is seen that current functions (1/v-1/2) decreased with the increasing of' scan rate except Zn(II)- Cate. So the behavior of electrode reaction of all Cu(II)- ligands and Zn(II)- ligands are of ECE mechanism except Zn(II)- Cate is of CE mechanism.
Electrochemical Characterization of Some Electroactive Nucleophilic Substitution Reactions
(Khulna University of Engineering & Technology (KUET), 2016-07) Islam, Md. Rabiul; Motin, Dr. Md. Abdul
The substitution reaction of Catechol in presence of Imidazole, L-Arginine and L-Serine have been studied by cyclic voltammetry, controlled potential coulometry and differential pulse voltammetry techniques using Glassy carbon (GC), Gold (Au) and Platinum (Pt) electrodes. The voltammetric studies have been carried out by varying the composition of Catechol, Imidazole, L-Arginine and L-Serine in the buffer solution of different pH, different electrodes and scan rate. Pure Imidazole, L-Arginine and L-Serine are electro-inactive whereas pure Catechol is electro-active. In the second scan of potential, a new anodic peak appears at the lower potential and the oxidation and reduction peak shifted with respect of pure catechol after addition of Imidazole, L- Arginine and L-Serine in catechol solution. At the same time the anodic and cathodic peak current decreases significantly compared with the pure catechol that indicates the participation of reaction of o-benzoquinone with Imidazole, L-Arginine and L-Serine. The reaction products generated from the reaction of catechol in presence of Imidazole, L-Arginine and L-Serine are assumed to be 4-(1H-imidazol-1-yl)cyclohexa- 3,5-diene-1,2-dione- 2-amino-4-(1-(3,4-dioxocyclo hexa-1,5-dien-1-yl)guanidino)-4- oxobutanoic acid and 3-hydroxy-2-((3-hydroxy-4-oxocyclohexa-2,5-dien-1- ylidene)amine)propanoic acid respectively that undergo electron transfer at more negative potentials than the Catechol. The electro –synthesized products generated from Catechol with Imidazole, L-Arginine and L-Serine were isolated. The formation of Catechol-nucleophile adducts are also confirmed by FTIR spectra. The pH effect of catechol in presence of Imidazole, L-Arginine and L-Serine has been investigated in different pH from 3 to 11. From the experiment it has been observed that almost no new anodic peak appeared after repetitive cycling at pH 3-5 (acidic media) and pH 9-11 (basic media). At pH 7, the o-benzoquinone undergoes nucleophilic attack by the amines that is reflected from voltammetric new anodic peak, A0 appeared after repetitive cycling. The slopes of the peak potential, Ep vs pH plot has determined graphically as the anodic peaks of Catechol-Imidazole (60 mV/pH), Catechol-Arginine (56mV/pH) and Catechol-Serine (61.5 mV/pH) at 0.1V/s.
Electrochemical Study Of Catechol In Presence Of Sulfanilic Acid And Diethytamine At Different Ph
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2015-12) Uddin, Md. AIim; Motin, Prof. Dr. Md. Abdul.
The electrochemical behavior of catechol in presence of diethylamide and sulfanilic acid & catechol in presence of sulfanilic acid + diethylamide have been studied by cyclic voltammetry, controlled potential coulometry, differential pulse voltammetry and chronoamperometry techniques using Glassy carbon (GC), Gold (Au) and Platinum (Pt) electrodes. The voltammetry studies have been carried out in variation of catechol, diethylamine and sulfanilic acid concentration, buffer solution of different pH, different electrodes and scan rate. Upon addition of diethyl amine and sulfanilic acid in catechol solution at the second scan of potential a new anodic peak appeared at the negative potential and the reduction peak shifted with respect of pure catechol. Also the anodic and cathodic peak current decreases significantly compared with the pure catechol that indicates the participation of reaction of o-benzoquinone with diethylamine, sulfanilic acid and their mixtures. The products generated from the reaction of catechol with diethylamine and sulfanilic acid are assumed to be 4-(diethylamino)-benzene- I ,2-diol, and 4-(bis(3,4-dihydroxyphenyl)amino) benzenesulfonic acid, respectively that undergo electron transfer at more negative potentials than the catechol. The electro-synthesized products originated from catechol with diethylamine and sulfanilic acid were isolated. The formation of new products was also confirmed by FTIR spectra. The effect of pH of catechol in presence of diethylamine and sulfanilic acid were studied by varying pH from 3 to II except sulfanilic acid 2-9. For diethylamine, it is seen that at pH 3-5, no new anodic peak appeared after repetitive cycling. In the pH 7-1 1, the o- benzoquinone undergoes nucleophilic attack by the amines that voltammetric new anodic peak A0 appeared after repetitive cycling. In contrast, for sulfanilic acid at pH 9 no new anodic peak appeared after repetitive cycling. Whereas in pH 7, the voltammogram shows a small peak. For diethylamine, the maximum peak current is obtained at pH 7 but the maximum peak current of sulfanilic acid is obtained at pH 3. The slopes of the peak potential, E vs pH plot was determined graphically as the anodic peaks of catecholdiethylamine (69 mV/pH for first anodic peak A1mV/pH for appeared peak Ao) and catechol-sulfanilic acid (36 mV/pH for first anodic peak A1 or 38 mV/pH for appeared peak Ao) at 0.1 V/s. This indicates that the oxidation reaction of catechol-diethylamine adduct proceeded via the 1e71H process whereas catechol-sulfanilic acid adduct proceeded via the 2ei2H processes. This also suggests that during the reaction not only electron but also proton are released from the catechol-amine adduct. The reaction was strongly influenced by the pH as well as concentration of diethylamine and sulfanilic acid. The reaction was mostly favorable in 250 mM of diethylamine with fixed 2 mM of catechol at pH 7. The reaction of catechol in presence of sulfanilic acid was favorable in 2 mM sulfanilic acid, 2 mM catechol at pH 3. The electro-oxidation of catechol-diethylamine adduct are facilitated in neutral media whereas catechol-sulfanilic acid in acid media. The scan rate effect on cyclic voltammogram of catechol in presence of diethylamine and sulfanilic acid were also studied. The peak current of both the anodic and the corresponding cathodic peaks increases with the increase of scan rate. The nearly proportionality of the anodic and corresponding cathodic peak suggests that the peak current of the reactant at each redox reaction is controlled by diffusion process. The current function for anodic peak A0, (I/v) of catechol-diethylamine derivative was found to be decreased exponentially with increasing scan rate. Catechol-diethylamine derivatives have been found to undergo electrochemical reaction with ECE (electron transferchemical reaction- electron transfer) type mechanism. But, the current function for the anodic peak A0, (I1,/v) of catechol-sulfanilic acid derivative was found to be decreased with increasing scan rate and such a behavior is adopted as indicative of an ECECE type mechanism.
Fabrication of a pH Sensor Based on Metal Oxide Nanoparticle and Ion Exchanging Surfaces
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2018-02) Toma, Sanzida Mohosina; Jamal, Dr. A. B. M. Mamun
The nanostructures of metal oxides are attractive and important for nanosensor research in the broad range of applications in various fields of biological, environmental and analytical chemistry. Due to their potential applications and special properties metal oxides nanoparticle have concerned considerable attention which are strongly related with their size, structure and morphology. Among the metal oxide, cupric oxide (CuO) is found to be one of the most popular oxide. Owing to its exceptional electrochemical activity and the possibility of promoting electron transfer at a low potential, availability, stability, good morphological and structural control of the synthesized nanostructures, CuO is a good candidate for pH sensing application. In this paper, an electrochemical pH sensor that has been fabricated using copper oxide modified glassy carbon electrode (CuO/GCE). The difference in peak potential shift while using CuO/GCE as pH sensor was measured using square wave voltammetry (SWV); and was found to be linear over the range of pH 3-9, with a sensitivity of 60 mVpl-f'. The sensor shows a potential drift of 1.97 —3.33 % after three hours of continuous use; and could retain 95% of its initial sensitivity after 1 week of use. The electrode was found to respond both in the presence and absence of oxygen, further expanding the potential applications to include it into de-oxygenated environments. This prototype has been tested in real samples and verified by using commercial pH meter. The CuO based sensor showed good sensitivity and long term stability that may show the way to develop a low cost solid state pH sensor for a wider range of applications.
Graphene Oxide Modified Pencil Graphite Electrode for the Detection of H2O2
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2018-06) Mistry, Joyanta; Jamal, Dr. A. B. M. Mamun
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.