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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.
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 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 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.
Investigation of the Electrochemical Behavior of Catechol in Presence of Glycine, Aspartic acid and Glutamic acid
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2016-07) Uddin, Md. Nazim; Motin, Prof. Dr. Md. Abdul
To monitor the electrochemical behavior of Catechol in presence of Glycine, L-Aspartic acid and L-Glutamic acid; cyclic voltammetry (CV), differential pulse voltammetry (DPV), controlled potential coulometry (CPC) and chronoamperometry (CA) techniques have been employed. A wide range of concentration (10mM to 150mM) of nucleophiles (Glycine, L-Aspartic acid and L-Glutamic acid), various pH media (5 to11), different electrodes ((Glassy carbon (GC), Gold (Au) and Platinum (P)) and successive scan rate (0.05 V/s to 0.5 V/s) have been used to find out the favorable condition. Catechol is an electroactive substance which shows a pair of redox peak whereas Glycine, L-Aspartic acid and L-Glutamic acid are electroinactive, hence it shows no anodic and cathodic peak in the potential range (-0.6 to 0.9 V) of investigation. By the addition of above nucleophiles in Catechol solution arises a new peak at lower potential, the corresponding redox peak shifts and peak current intensity of Catechol decreases with respect to the pure Catechol that indicates the participation of 1,4-Michael addition reaction of o-benzoquinone with mentioned nucleophiles. The formation of adducts from the reaction of Catechol with Glycine, L-Aspartic acid and L-Glutamic acid are assumed to be 2-((3,4-dihydroxyphenyl)amino)acetic acid, 2-((3,4-dihydroxy phenyl)amino)succinic acid and 2-((3,4-dihydroxyphenyl)amino)pentanedioic acid severally that go through electron transfer at more negative potentials than the Catechol. The influence of pH of Catechol in presence of Glycine, L-Aspartic acid and L-Glutamic acid has been studied by varying pH from 5 to 11. It is seen that at pH 3, 5, 9 and 11 no new anodic peak appears after repetitive cycling. In the neutral media (pH 7), the o-benzoquinone undergoes nucleophilic attack by the above nucleophiles that voltammetric new anodic peak A0 appears after repetitive cycling. The slopes of the peak potential was determined graphically from Ep vs pH plot as the anodic peaks of Catecholglycine adducts (27 mV/pH) proceeded via one step 2e−/2H+ process, Catechol-aspartic acid adducts (50 mV/pH) and Catechol-glutamic acid adducts (69 mV/pH) via two step 1e−/1H+ process. The reaction is strongly influenced by the different pH media as well as various compositions of nucleophiles. These reactions have been carried out wide range of concentration of nucleophiles. The optimum conditions for the formation of adducts such as Catechol-glycine (pH-7, Concentration 70 mM, GC electrode and Scan rate 0.1 V/s), Catechol-aspartic acid (pH-7, Concentration 70 mM, GC electrode and Scan rate 0.1 V/s) and Catechol-glutamic acid (pH-7, Concentration 30 mM, GC electrode and Scan rate 0.1 V/s) system are observed. The effect of scan rates has been investigated on cyclic voltammogram of Catechol in presence of above nucleophile. The anodic and cathodic peak current increases proportionally with increasing square root of scan rates. This linear relationship indicates the reaction is controlled by diffusion process. The current function, Ip/v1/2 decreases exponentially with increases scan rate which determine the reaction is controlled by ECE mechanism. The electro-synthesized adducts generated from the controlled potential coulometry of Catechol with Glycine, L-Aspartic acid and L-Glutamic acid was isolated and the generated adducts supported by FTIR spectra.
Low-Cost Rechargeable Battery Using Pencil Graphite as Ion Intercalation / De-Intercalation Electrode
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2018-06) Islam, Md. Jahidul; Jamal, Dr. A. B. M. Mamun
Remarkable improvement in utilizing renewable energy has pioneered to a critical demand for the large-scale energy storage system considering cost, safety and environmental aspect. Zn/Al-ion batteries are eco-friendly and advantageous over acid or alkali-based batteries as it is possible to utilize Zn metal as the negative electrode in aqueous medium. Here a Zn/Al-ion battery is developed using Pencil graphite, coated with graphene by cyclic voltammetry (CV), as the positive electrode and Zn metal as the negative electrode in an aqueous AlCl3/Zn(CH3COO)2 (0.5/0.5M) electrolyte. The Zn/Al-ion cell shows average discharge voltage plateaus around 1.0 V which offers a specific cathode capacity of ~54.1 mAh g−1 at a constant current density of 55 mA g−1 and exhibits capacity retention of more than ~95.8% over 100 cycles without any formation of dendrite at the negative electrode (Zn). Reversible Al3+ or [Al(H2O)6]3+ ion intercalation/de-intercalation storage process involving graphene coated pencil graphite (positive electrode) during charge-discharge cycling is proposed on the basis of CV, Electrochemical impedance spectroscopy (EIS), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX) analysis.
Physico-Chemical Properties of Some Alcohols in SDS-Acetonitrile Containing Ternary Systems
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2016-11) Das, Biswajit Kumar; Motin, Prof. Dr. Md. Abdul
The critical micelle concentration (CMC) of sodium dodecyl sulfate (SDS) in 80% acetonitrile + 20% water was determined from the conductance and viscosity measurement. They shows a sharp break in their values where micelle starts to form. The estimated CMC of SDS was found to be 0.02 mol. L-1. Densities and viscosities of ternary mixtures of Ethanol + (80% acetonitrile + 20% water + 0.02M SDS), n-Propanol + (80% acetonitrile + 20% water + 0.02M SDS), iso-Propanol +(80% acetonitrile + 20% water + 0.02M SDS),n-Butanol + (80% acetonitrile + 20% water + 0.02M SDS), iso-Butanol + (80% acetonitrile + 20% water + 0.02M SDS), n-Pentanol + (80% acetonitrile + 20% water + 0.02M SDS) and iso-Pentanol + (80% acetonitrile + 20% water + 0.02M SDS) have been studied over the entire range of composition (0 ˂ X2 ˂ 1) at 98.15-323.15K with an interval of 5K. In pure state the density of alcohol has been found to be in the order of: n-Pentanol > Ethanol > n-Butanol > n-Propanol and iso-Pentanol > iso-Butanol > iso-Propanol The values of densities of Alkanols + (80% acetonitrile + 20% water + 0.02M SDS) at equimole fraction solvent systems has been found to be n-Pentanol + (80% acetonitrile + 20% water + 0.02M SDS) > Ethanol + (80% acetonitrile + 20% water + 0.02M SDS) > n-Butanol + (80% acetonitrile + 20% water + 0.02M SDS) > n-Propanol + (80% acetonitrile + 20% water + 0.02M SDS) and iso-Pentanol + (80% acetonitrile + 20% water + 0.02M SDS) > iso-Butanol + (80% acetonitrile + 20% water + 0.02M SDS) > iso-Propanol + (80% acetonitrile + 20% water + 0.02M SDS) The value of the density of alcohols in 80% acetonitrile + 20% water + 0.02M SDS increases with increasing of composition of the alcohols. The densities of all alcohols increase with carbon number which may be depend on the molecular weight of alcohols and structural formula. The densities decrease regularly with increasing of temperature. This is due to the thermal agitation and hence the dipole-dipole interaction or the dissociation of H-bonding are occurred. The excess molar volumes, VE were calculated from the densities of the mixtures at different temperatures. The values of VE for all the systems are negative over the entire range of composition, showing minima at ~ 0.5 mole fraction of Ethanol, ~ 0.8 mole fraction of n-Propanol, ~ 0.8 mole fraction of iso-Propanol, ~ 0.7-0.8 mole fraction of n- Butanol, ~ 0.8 mole fraction of iso-Butanol, ~ 0.7 mole fraction of n-Pentanol, ~ 0.7 mole fraction of iso-Pentanol. The increasing of VE with carbon chain length of alcohols may be related to increase of the size of alcohols. The values of VE for the studied alcohols increase with increase of temperature. The observed values of VE for the mixtures have been explained in terms of physical, chemical and geometrical contributions. The viscosity coefficients, ɳ of all the above mixtures at all the different temperatures have also been determined. The viscosities increase initially slowly up to ~ 0.8 mole fraction of Ethanol, n-Propanol, iso-Propanol, n-Butanol, iso-Butanol, n-Pentanol and iso-Pentanol in 80% acetonitrile + 20% Water + 0.02M SDS systems and later on, the viscosities increases sharply until the pure alcohol is reached specially at lower temperature. In the pure state the viscosity of the alcohols has been found to be in the order of n-Pentanol > n-Butanol > n-Propanol > Ethanol and iso-Pentanol > iso-Butanol > iso-Propanol and iso-Pentanol > n-Pentanol and iso-Butanol > n-Butanol and iso-Propanol > n-Propanol These are a marked decrease in the viscosity with the increase of temperature for all the studied alcohols. This ascribed that the alcohol solutions are less stable at higher temperature. The increasing of viscosity with carbon number of alcohols ascribed that the solution resistance increase with the increase of carbon chain length. The linear dependence of lnɳ against 1/T shows for the all studied alcohols. The branched chain isomers are less stable than linear chain isomers at higher temperature. The excess viscosities, ηE values are found to be negative, indicating that the (80% acetonitrile + 20% water + 0.02M SDS) solutions of alcohols are non-ideal. Excess viscosities are negative at all the temperature over the entire range of composition for all the systems with minima occurring between 0.7-0.8 mole fraction of Ethanol, n-Propanol, iso-Propanol, n-Butanol, iso-Butanol, n-Pentanol and iso-Pentanol. The negative excess viscosities, ηE of the systems indicate that the dissociation of component through dispersion force or steric hindrance. The position of minima virtually does not change remarkably with the variation of temperature. The negative VE, negative ηE and negative  for the systems indicate the segmental inclusion of Acetonitrile in the interstices of polymolecular alkanols aggregate; these will be fewer surfaces available for friction that may results in a reduction of viscosity. For long chain or branched chain alkanols, maximum geometrical for the steric hindrance are occurred. The thermodynamic parameters such as free energy (ΔG#), enthalpy (ΔH#) and entropy (ΔS#) change of activation for the viscous flow for these systems were examined for the entire range of composition. The free energy (ΔG#) were found to be positive in magnitude indicating that the kinetic species involved in forming cavities or holes in the liquid medium is giving by the work required in forming the hole against surface tension of the solution. The excess properties (VE, ηE, ΔG#E) data have been fitted by the least square method to the four parameter Redlich-kister equation and the values of the parameter ai and standard deviation have been reported.
Studies on Arsenic and Lead contamination in Crops and Vegetables of Harischandrapur Village of Jessore District in Bangladesh
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2017-02) Sultana, Nusrat; Morshed, Prof. Dr. Mohammad Hasan
Various fruits and vegetables such as Mango (Mangifera indica L.), Jackfruit (Artocarpus heterophyllus L.), Guava (Psidiun guajava L.), Pummelo (Citrus grandis L.), Lime (Citrus aurantifollia), Papaya (Carica papaya L.), Coconut (Cocos nucifera L.), Sapodilla (Manilkara zapota),Yard long bean (Vigna sesquipedalis), Okra(Abelmoschus esculentus), Ribbed gourd (Luffa acutangula), Plantain (Musa paradisiacal), Cucumber (Cucumis sativus), Green hot chili (Capsicum frutescens), Stem Amaranth leaf (Amaranthus lividus), Red Amaranth (Amaranthus gangeticus), Indian Spinach (Basella rubra), Brinjal (Solanum melongena), Pumpkin (Cucurbita moschata), Pea seed (Pisum sativum), Rice (Oryza sativa L), Leaf of Taro (Colocasia esculenta) and Corm of elephant yam (Amorphophallus paeoniifolius) were collected from Harischandrapur village of Jessore district of Bangladesh and screened for arsenic, lead, iron, manganese, copper and zinc by Atomic Absorption Spectrophotometer (AAS). The average moisture contents in soil, fruits, fruity vegetables, root-stem vegetables, leafy vegetables and seed vegetables were found 19.91%, 82.25%, 87.67%, 88.65%, 83.36% and 45.00% respectively. The mean concentrations of arsenic, iron and manganese in irrigation water were 0.11 mg/L, 4.28 mg/L and 0.48 mg/L respectively which are higher than Bangladesh drinking water standard. The average concentration of arsenic in irrigation water is higher than FAO standard (<0.100 mg/L for irrigation water). The average concentrations of arsenic, iron, manganese, copper and zinc were found 8.63 mg/Kg, 12162.78 mg/Kg, 256.07 mg/Kg, 21.91 mg/Kg and 57.40 mg/Kg respectively in soils which are lower than FAO, USEPA & EU standard for agricultural soil. The average concentrations of arsenic in fruits, fruity vegetables, root-stem vegetables, leafy vegetables and seed vegetables were detected 0.17 mg/Kg, 0.14 mg/Kg, 0.23 mg/Kg, 0.51 mg/Kg and 0.15 mg/Kg respectively which are lower than that of standard value recommended by WHO and FAO (<1.00 mg/Kg) for food. The average concentrations of iron in fruits, fruity vegetables, leafy vegetables and seed vegetables were monitored 31.13 mg/Kg, 60.38 mg/Kg, 338.68 mg/Kg and 42.83 mg/Kg respectively that are lower than WHO/FAO standard (<1.00mg/Kg) for food. The mean concentrations of manganese in fruits, fruity vegetables, leafy vegetables and seed vegetables were detected 2.86 mg/Kg, 12.90 mg/Kg, 24.26 mg/Kg and 8.48 mg/Kg respectively which are lower than EU standard (<500mg/Kg). The mean concentrations of copper were found 3.40 mg/Kg, 9.36 mg/Kg, 4.76 mg/Kg, 9.70 mg/Kg respectively in fruits, fruity vegetables, leafy vegetables and seed vegetables which are lower than EU standard (<20.00 mg/Kg) for food. The average concentrations of zinc in fruits, fruity vegetables, leafy vegetables and seed vegetables were detected 14.72 mg/Kg, 28.48 mg/Kg, 23.37 mg/Kg and 27.15 mg/Kg respectively which are lower than EU standard (<50.00 mg/Kg). The concentration of lead in all selected soil, water, fruits and vegetables were lower than detection level. Maximum average concentration of arsenic, iron and manganese was found in leafy vegetables. On the other hand maximum mean concentration of copper and zinc were measured in fruity and seed vegetables. In our research, 40 peoples were monitored for calculating the consuming of arsenic, iron, manganese, copper and zinc through daily intake of food (fruits and vegetables), water and their health risk factors were also analyzed. In this study area, the people’s average age, body weight and daily intake of water, rice, vegetables and fruits were 28.48 years, 46.60Kg, 2.80L, 0.39Kg, 0.12Kg and 0.14Kg respectively. The order of daily intake and health risk index of metals from food and water was Iron>Manganese>Arsenic>Zinc>Copper. The fruits and vegetables of the study area are safe for human health according to WHO oral dose reference data (Rfd) for metals and health risk index.
Studies on Heavy Metals in Fruits of Samta Village of Jessore in Bangladesh
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2015-12) Rahim, Md. Abdur; Morshed, Prof. Dr. Mohammad Hasan
Various fruits such as Mango (Mangifera indica L.), Jackfruit (Artocarpus heterophyllus L.), Guava (Psidiun guajava L.), Hog plum (Spondias dulcis L.), Carambola (Averrhoa carambola L.), Pomelo (Citrus grandis L.), Lemon (Citrus limon), Wax apple (Syzygium samarangense), Papaya (Carica papaya L.), Coconut (Cocos nucifera L.) and Sapodilla (Manilkara zapota) were collected from Samta village of Jessore district of Bangladesh, and screened for arsenic, manganese, lead, cadmium and chromium by Atomic Absorption Spectrophotometer (AAS). The average moisture contents in soil and fruits were found 11.90±0.19% and 80.10±12.92% respectively. The mean concentration of arsenic in irrigation water, soil and fruits were 0.51±0.17mg/L, 8.40±1.73mg/Kg and 0.206±0.14mg/Kg respectively. Maximum concentration of arsenic in irrigation water, soil and fruits were monitored 0.78mg/L, 11.31mg/Kg and 0.53mg/Kg respectively. Minimum concentration of arsenic in fruits was 0.10mg/Kg. In case of irrigation water, arsenic concentration was higher than that of standard (0.100mg/L) value of Bangladesh. The concentrations of arsenic in soil and fruits were observed somewhat less than that of standard value recommended by WHO. The average concentrations of manganese in irrigation water, soil and fruits were found 0.10±0.03mg/L, 269.14±20.71mg/Kg and 4.96±4.28mg/Kg respectively. The maximum concentration of manganese in soil and fruits were 296.82mg/Kg and 12.83mg/Kg respectively which were lower than that of standard value recommended by WHO, EU and BADC. The presence of lead, cadmium and chromium was not found in water, soil and fruits in this study area. In our research, 120 people were monitored for calculating the consuming of arsenic and manganese through daily intake of fruits and their health risk factor was analyzed. The average age, body weight and daily intake of fruits per person per day were 35.04±14.55 year, 60.77±8.62Kg and 263.20±166.73g respectively. Average 0.0018mg of arsenic and 0.055mg of manganese was consumed in each person (61Kg body weight) per day which was lower than WHO standard for arsenic (0.002mg/Kg body weight) and manganese (0.033mg/Kg body weight) intake for human body.