This paper describes the preparation of and experimentation undertaken by heterogeneous chitosan membrane as ion selective electrode for glutamate ion. The linearity response was obtained in the range of 1.0x10(-5) to 1.0x10(-1)M with a detection limit of 1.0x10(-6)M. The performance of the electrode was found in the pH range of 4.0-8.0 at temperature 25+/-3 degrees C. The response time was at 5-35s and was useful for a period of more than 4 months. The selectivity values towards some anions indicates good selectivity over a number of interfering anions. No significant improvement of membrane performance over additional of plasticizers such as 2-NPOE, BEHA and DOPP. The electrodes gave sufficient Nernstian responses with the exception of membrane with 2-NPOE.
A new cobalt(II) ion selective electrode based on palladium(II) dichloro acetylthiophene fenchone azine(I) has been developed. The best membrane composition is found to be 10:60:10:21.1 (I)/PVC/NaTPB/DOP (w/w). The electrode exhibits a Nerstian response in the range of 1.0 × 10(-1)-1.0 × 10(-6)M with a detection limit and slope of 8.0 × 10(-7)M and 29.6 ± 0.2 mV per decade respectively. The response time is within the range of 20-25s and can be used for a period of up to 4 months. The electrode developed reveals good selectivity for cobalt(II) and could be used in pH range of 3-7. The electrode has been successfully used in the determination of cobalt(II) in water samples.
This paper presents the fabrication of a highly sensitive and selective glucose sensor based on cuprous oxide/graphene nanocomposites-modified glassy carbon electrode (Cu2O/graphene/GCE). The Cu2O/graphene nanocomposites were synthesized based on a simple and straightforward chemical reduction process in alkaline aqueous solution using sodium carbonate as reductant. The size and shape of Cu2O nanoparticles on graphene sheets can be controlled by changing the amount of graphene oxide added during reaction. The electrochemical properties of Cu2O/graphene/GCE in 0.1M phosphate buffer solution were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. It was found that the pH, concentration of supporting electrolyte, and scan rate had very crucial effect on the sensitivity of prepared sensor towards glucose oxidation. At an applied potential of +0.50V, the Cu2O/graphene/GCE presented a high sensitivity of 1330.05μAmM(-1)cm(-2) and fast response (within 3s). The amperometric non-enzymatic glucose sensor developed had a linear relationship from 0.01mM to 3.0mM glucose and detection limit of 0.36μM. In the presence of ascorbic acid, uric acid, dopamine, chloride and citrate ion and other carbohydrates, the interferences were negligible. The proposed sensor was successfully applied for the determination of glucose concentration in real human blood samples.
Immobilisation of heavy metals in a 30-year old active scrap metal yard soil using three waste materials, namely coconut tree sawdust (CTS), sugarcane bagasse (SB) and eggshell (ES) was investigated. The contaminated soil was amended with amendments at application rates of 0 %, 1 % and 3 % (w/w). The effects of amendments on metal accumulation in water spinach (Ipomoea aquatica) and soil metal bioavailability were studied in a pot experiment. All amendments increased biomass yield and reduced metal accumulation in the plant shoots. The bioconcentration factor and translocation factor values of the metals were in the order of Zn > Cu > Pb. The addition of ES, an alternative source of calcium carbonate (CaCO3), has significantly increased soil pH and resulted in marked reduction in soil metal bioavailability. Therefore, CTS, SB and ES are promising low-cost immobilising agents to restore metal contaminated land.
The objective of this study is to investigate Napa soil's potential as an alternative additive in producing Portland composite cement. The Napa soil of Tanah Datar district, West Sumatra, Indonesia is a natural material which contains SiO2 and Al2O3 as its major components. The parameters used were the fineness of the cement particles, the amount left on a 45 μm sieve, the setting time, normal consistency, loss on ignition, insoluble parts, compressive strength and chemical composition. The composition of Napa soils (% w/w) used as variables include 4, 8, 12 and 16%. Furthermore, 8% pozzolan was used as a control in this research. The results showed that the compressive strength of Napa soil cement which contained 4% Napa soil was much better compared to that of the control on the 7th and 20th day. Furthermore, all the analyzed Napa soil cements met the standard of cement as stipulated in Indonesian National Standard, SNI 7064, 2016.
Residues of oxytetracycline (OTC), a veterinary antibiotic and growth promoter, can be present in animal-derived foods; their consumption is harmful to human health and their presence must therefore be detected and regulated. However, the maximum residue limit is low, and consequently highly sensitive and accurate detectors are required to detect the residues. In this study, a novel highly sensitive electrochemical sensor for the detection of OTC was developed using a screen-printed electrode modified with fluorine-doped activated carbon (F-AC/SPE) combined with a novel deep eutectic solvent (DES). The modification of activated carbon by doping with fluorine atoms (F-AC) enhanced the adsorption and electrical activity of the activated carbon. The novel hydrophobic DES was prepared from tetrabutylammonium bromide (TBABr) and a fatty acid (malonic acid) using a green synthesis method. The addition of the DES increased the electrochemical response of F-AC for OTC detection; furthermore, it induced preconcentration of OTC, which increased its detectability. The electrostatic interactions between DES and OTC as well as the adsorption of OTC on the surface of the modified electrode through H-bonding and π-π interactions helped in OTC detection, which was quantified based on the decrease in the anodic peak potential (E pa = 0.3 V) of AC. The electrochemical behavior of the modified electrode was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Under optimum conditions, the calibration plot of OTC exhibited a linear response in the range 5-1500 μg L-1, with a detection limit of 1.74 μg L-1. The fabricated electrochemical sensor was successfully applied to determine the OTC in shrimp pond and shrimp samples with recoveries of 83.8-100.5% and 93.3-104.5%, respectively. In addition to the high sensitivity of OTC detection, the proposed electrochemical sensor is simple, cost-effective, and environmentally friendly.
The fabrication of a zinc hydroxide nitrate-sodium dodecylsulfate bispyribac modified with multi-walled carbon nanotube (ZHN-SDS-BP/MWCNT) paste electrode for uric acid and bisphenol A detection was presented in this study. Electrochemical impedance spectroscopy, chronocoulometry, square-wave voltammetry, and cyclic voltammetry were all used to examine the electrocatalytic activities of modified paste electrodes. The modified electrode's sensitivity and selectivity have been considered in terms of the composition of the modifier in percentages, the types of supporting electrolytes used, the pH of the electrolyte, and square-wave voltammetry parameters like frequency, pulse size, and step increment. Square-wave voltammetry is performed by applying a small amplitude square-wave voltage to a scanning potential from -0.3 V to +1.0 V, demonstrating a quick response time and high sensitivity. The ZHN-SDS-BP/MWCNT sensor demonstrated a linear range for uric acid and bisphenol A from 5.0 µM to 0.7 mM, with a limit of detection of 0.4 µM and 0.8 µM, respectively, with good reproducibility, repeatability, and stability as well. The modified paste electrode was successfully used in the determination of uric acid and bisphenol A in samples of human urine and lake water.
We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3' and/or 5' end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5' differences and in support of this we report that a 5' isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5' isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes.