Norita Mohamed

Sensitive voltammetric determination of paracetamol by poly (4-vinylpyridine)/multiwalled carbon nanotubes modified glassy carbon electrode

A novel glassy carbon electrode (GCE) modified with a composite film of poly (4-vinylpyridine) (P4VP) and multiwalled carbon nanotubes (P4VP/MWCNT GCE) was used for the voltammetric determination of paracetamol (PCT). This novel electrode displayed a combined effect of P4VP and MWCNT on the electro-oxidation of PCT in a solution of phosphate buffer at pH 7. Hence, conducting properties of P4VP along with the remarkable physical properties of MWCNTs might have combined effects in enhancing the kinetics of PCT oxidation. The P4VP/MWCNT GCE has also demonstrated excellent electrochemical activity toward PCT oxidation compared to that with bare GCE and MWCNT GCE. The anodic peak currents of PCT on the P4VP/MWCNT GCE were about 300 fold higher than that of the non-modified electrodes. By applying differential pulse voltammetry technique under optimized experimental conditions, a good linear ratio of oxidation peak currents and concentrations of PCT over the range of 0.02-450 μM with a limit of detection of 1.69 nM were achieved. This novel electrode was stable for more than 60 days and reproducible responses were obtained at 99% of the initial current of PCT without any influence of physiologically common interferences such as ascorbic acid and uric acid. The application of this electrode to determine PCT in tablets and urine samples was proposed.

Leaching of lead from local ceramic tableware

Abstract Ceramic tableware has long since been recognised as a source of lead poisoning. Locally available ceramic utensils (cups, bowls, sauce plates, cooking pots and spoons) were examined as possible sources of lead poisoning. The lead was leached out with 4% acetic acid stored in the samples at room temperature for 24 h. Overall, 54.7% of the sample items tested exceeded the US PDA maximum permitted lead release from earthenware. Of the sauce plates 83.7% exceeded the safety limit and released the highest levels of lead. The amount of lead leached out from the samples decreased with repetitive teachings and increased with temperature. Lead is also found to be leached into acidic foods such as thin soya sauce, tomato sauce and tamarind juice stored in samples of ceramic sauce plates for 24 h at room temperature.

Determination of oxolinic acid in feeds and cultured fish using capillary electrophoresis

Abstract A capillary electrophoretic method was developed for the determination of the antibiotic oxolinic acid. The electrolyte composed of a buffer solution (10 mM phosphate, pH 9.00) and methanol (9:1) was found to be the most suitable for this separation. The effect of type of buffer, its pH and concentration as well as injection times and applied voltage on the migration of oxolinic acid was also studied. Key analytical characteristics of the method are as follows: detection limit (signal-to-noise ratio 3), 0.08 μg ml −1 ; linear range, 0.5–40 μg ml −1 ; migration time, 5.3 min; relative standard deviation for within-day and day-to-day variation of 1.67 and 2.24%, respectively. The method, in conjunction with a solid phase extraction procedure, was successfully applied for the analysis of spiked oxolinic acid in fish feeds and fish muscles. The recoveries of oxolinic acid from spiked feeds and muscle tissues were 81.15 and 84.80%, respectively.

Effect of SiC on the corrosion resistance of electroless Cu-P-SiC composite coating

In this work, Cu–P–SiC composite coatings were deposited via electroless plating with the addition of sodium hypophoshite (NaH2PO2) as a reducing agent. The coating compositions deposited were determined by using energy dispersive X-ray spectroscopy (EDX). The surface morphology of the coatings that were analyzed using scanning electron microscopy (SEM) showed that SiC particles were uniformly distributed by virtue of surfactant addition and mechanical stirring. The anti-corrosion properties of Cu–P and Cu–P–SiC coatings in NaCl and HCl solutions were investigated by the weight loss and potentiodynamic polarization techniques. The results showed that the corrosion resistance of Cu–P–SiC coatings was superior to that of electroless Cu–P coatings and carbon steel substrates in various concentrations of NaCl and HCl solutions.

The effect of an individualized laboratory approach through microscale chemistry experimentation on students' understanding of chemistry concepts, motivation and attitudes

The main goal of this study was to investigate whether the use of an individualized approach through microscale chemistry experiments in secondary schools can increase students’ understanding of chemistry concepts, improve attitude towards chemistry practical work and motivation. Two comparable groups of Form Four students (16 years old) participated. The students in the experimental group (83) worked individually on ten microscale chemistry experiments, whereas the control group (87) worked in groups on traditional experiments both for a period of 8 weeks. Pre and post tests were conducted before and after the treatment for both groups. Teacher and student perceptions of microscale experimentation are also reported. Findings showed that the microscale approach can increase understanding of chemistry concepts, however, there was no significant difference in attitude and motivation among the students. Teachers and students both had a positive view of microscale experiments.

A new insight to the physical interpretation of activated carbon and iron doped carbon material: Sorption affinity towards organic dye

To enhance the potential of activated carbon (AC), iron incorporation into the AC surface was examined in the present investigations. Iron doped activated carbon (FeAC) material was synthesized and characterized by using surface area analysis, energy dispersive X-ray (EDX), temperature programmed reduction (TPR) and temperature programmed desorption (TPD). The surface area of FeAC (543 m(2)/g) was found to be lower than AC (1043 m(2)/g) as a result of the pores widening due to diffusion of iron particles into the porous AC. Iron uploading on AC surface was confirmed through EDX analysis, showing up to 13.75 wt.% iron on FeAC surface. TPR and TPD profiles revealed the presence of more active sites on FeAC surface. FeAC have shown up to 98% methylene blue (MB) removal from the aqueous media. Thermodynamic parameters indicated the spontaneous and exothermic nature of the sorption processes.

Iron Impregnated Activated Carbon as an Efficient Adsorbent for the Removal of Methylene Blue: Regeneration and Kinetics Studies

In this study, iron impregnated activated carbon (FeAC) was synthesized following an oxidation and iron impregnation of activated carbon (AC). Both the AC and FeAC were characterized by pHZPC and FTIR spectroscopy. The removal of Methylene Blue (MB) by AC and FeAC was examined under various experimental conditions. The FeAC showed up to 95% (higher than AC) MB removal in the pH range of 7–10. Although the reaction kinetics was pseudo–second order, the overall rate was controlled by a number of processes such as film diffusion, pore diffusion and intraparticle diffusion. The activation energy values for the MB uptake by AC and FeAC (21.79 and 14.82 kJ/mol, respectively) revealed a physisorption process. In the regeneration study, FeAC has shown consistently ≥ 90% MB removal even up to 10 repeated cycles. The reusable characteristic of the spent FeAC improved the practical use of activated carbon and can be a breakthrough for continuous flow system applications where it can work effectively without any significant reduction in its performance.

Electrooxidation of ethylene glycol using gold nanoparticles electrodeposited on pencil graphite in alkaline medium

The electrooxidation of ethylene glycol (EG) on the surface of gold nanoparticles (AuNPs) in alkaline medium was investigated. AuNPs were electrodeposited on pencil graphite (PG) by fast scan cyclic voltammetry. Different sizes of AuNPs deposited on the surface of PG (AuNPs/PG) were used for the electrooxidation process. AuNPs were electrodeposited on PG at various deposition times in the same potential range but with different scan rates and scan cycles. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to visualize and characterize the prepared AuNPs/PG electrodes. Cyclic voltammograms were also used to investigate the electrooxidation of EG. The effects of EG and supporting electrolyte concentrations, scan rate, particle size of AuNPs and final potential limit on the electrooxidation process have been investigated. Further studies showed that the electrooxidation of EG is affected by temperature of the medium. The prepared AuNPs showed stability after long-term use.

Electrooxidation of hydroquinone on simply prepared Au-Pt bimetallic nanoparticles

A facile method was used to prepare gold-platinum (Au-Pt) catalysts by direct electrodeposition via cyclic voltammetry in an acidic medium. Various parameters that affect the properties of electrodeposited catalysts were investigated such as initial applied potential, scan rate and deposition time. Initial applied potential plays a more important role in the preparation of bimetallic nanoparticles (AuPtNPs) since the kinetics of electrodeposition is in competition with the rate of hydrogen evolution. The AuPtNPs electrodeposited on pencil graphite (PG) were used to study the electrooxidation of hydroquinone. Various parameters such as pH, scan rate, concentration of hydroquinone and temperature were studied in the electrooxidation process. Apparent activation energy (Ea) for the electrooxidation of hydroquinone, calculated from the Arrhenius plot, shows that AuPtNPs catalysts (electrodeposited on the PG) offer less activation energy (ca. 9.500 kJ mol−1) than the bare PG (ca. 10.345 kJ mol−1). The AuPtNPs/PG shows better catalytic performance than the PG electrode due to the greater surface area it provides, thus resulting in more active sites available for adsorption of hydroquinone molecules on the surface of the catalyst.

Greening a Chemistry Teaching Methods Course at the School of Educational Studies, Universiti Sains Malaysia

Green chemistry is the design, development and implementation of chemical products and processes to reduce or eliminate the use of sub-stances hazardous to human health and the environment. This article reports on the integration of green chemistry and sustainable development concepts (SDCs) into an existing teaching methods course for chemistry pre-service teachers. Incorporation of SDCs with green chemistry enhances the interdisciplinary nature of green chemistry. It is in line with the course purpose of introducing instructional strategies for teaching chemistry at the secondary level. Through the experiences of hands-on activities, writing lesson plans and integration of SDC content into lectures and discussion, pre-service teachers learned how to integrate these elements into their own courses. The design of this course is an example of how to integrate green chemistry incorporated with SDCs into a teacher education curriculum.