Mohamed Rozali Othman

Surfactants in the sea-surface microlayer and their contribution to atmospheric aerosols around coastal areas of the Malaysian peninsula.

A study was done to determine the concentrations of surfactants on the sea-surface microlayer and in atmospheric aerosols in several coastal areas around the Malaysian peninsula. The concentrations of surfactants from the sea-surface microlayer (collected using rotation drum) and from aerosols (collected using HVS) were analyzed as methylene blue active substances and disulphine blue active substances through the colorimetric method using a UV-vis spectrophotometer. The results of this study showed that the average concentrations of surfactants in the sea-surface microlayer ranged between undetected and 0.36+/-0.34 micromol L(-1) for MBAS and between 0.11+/-0.02 and 0.21+/-0.13 micromol L(-1) for DBAS. The contribution of surfactants from the sea-surface microlayer to the composition of surfactants in atmospheric aerosols appears to be very minimal and more dominant in fine mode aerosols.

Multi-residue analytical methodology-based liquid chromatography-time-of-flight-mass spectrometry for the analysis of pharmaceutical residues in surface water and effluents from sewage treatment plants and hospitals.

An analytical method that facilitated the analysis of 11 pharmaceuticals residue (caffeine, prazosin, enalapril, carbamazepine, nifedipine, levonorgestrel, simvastatin, hydrochlorothiazide, gliclazide, diclofenac-Na, and mefenamic acid) with a single pre-treatment protocol was developed. The proposed method included an isolation and concentration procedure using solid phase extraction (Oasis HLB), a separation step using high-performance liquid chromatography, and a detection procedure that applies time-of-flight mass spectrometry. The method was validated for drinking water (DW), surface water (SW), sewage treatment plant (STP) influent and effluent, and hospital (HSP) influent and effluent. The limits of quantification were as low as 0.4, 1.6, 5, 3, 2.2 and 11 ng/L in DW, SW, HSP influent and effluent, STP effluent, and STP influent, respectively. On average, good recoveries higher than 75% were obtained for most of the target analytes in all matrices. Matrix effect was evaluated for all samples matrices. The proposed method successfully determined and quantified the target compounds in raw and treated wastewater of four STPs and three hospitals in Malaysia, as well as in two SW sites. The results showed that a number of the studied compounds pose moderate to high persistency in sewage treatment effluents as well as in the recipient rivers, namely; caffeine, simvastatin, and hydrochlorothiazide. Ten out of 11 compounds were detected and quantified in 13 sampling points. Caffeine was detected with the highest level, with concentrations reaching up to 9099 ng/L in STP influent.

Composition of Household Dust in Semi-urban Areas in Malaysia

A study of household dust composition was conducted in a semi-urban area around Kajang and Bandar Baru Bangi Selangor, Malaysia. Samples of household dust were collected from 31 randomly selected houses using a vacuum cleaner equipped with a changeable dust bag. Parameters analysed were anions (Cl , SO 4 , and NO3 ), cations (K þ, Ca2þ, and Mg2þ), and heavy metals (Cd, Fe, Ni, and Pb) to deduce the possible sources and evaluate the toxicity of indoor dust. The concentration of each parameter was compared to the concentration of street dust collected outside the houses. The results showed that the composition of anions was dominated by Cl followed by SO 4 and NO3-; cations concentration by the sequence of Ca2þ4Kþ4Mg2þ and for heavy metals concentration, Pb was present in the highest concentration followed by Ni 4 Fe 4Cd 4Zn. The study also showed that the concentration of most parameters analyzed were higher in household dust than street dust, suggesting that the composition of household dust is more closely related to indoor activities and theA study of household dust composition was conducted in a semi-urban area around Kajang and Bandar Baru Bangi Selangor, Malaysia. Samples of household dust were collected from 31 randomly selected houses using a vacuum cleaner equipped with a changeable dust bag. Parameters analysed were anions (Cl � , SO 2� 4 , and NO3� ), cations (K þ ,C a 2þ , and Mg 2þ ), and heavy metals (Cd, Fe, Ni, and Pb) to deduce the possible sources and evaluate the toxicity of indoor dust. The concentration of each parameter was compared to the concentration of street dust collected outside the houses. The results showed that the composition

Electrochemical Oxidation of Landfill Leachate: Investigation of Operational Parameters and Kinetics Using Graphite-PVC Composite Electrode as Anode

The preparation of a new carbon composite electrode constructed from graphite-polyvinyl chloride (graphite-PVC) compressed mixtures was used for the first time to treat landfill leachate in Malaysia under electrochemical oxidation. The electrochemical oxidation of landfill leachate was studied on graphite-PVC and Pt electrodes as anode and cathode, respectively, with the presence of NaCl electrolyte in a batch electrochemical reactor. The highest chemical oxygen demand (COD) and color removals of 87% and 97%, respectively, were achieved at pH 3, 0.58% (m/v) + 2078 mg L-1 electrolyte concentration, 15 V applied voltage, and 105 min electrolysis time. To confirm electrochemical oxidation, a field emission scanning electron microscopy (FESEM) was used to evaluate the surface of graphite-PVC electrode before and after treatment. The constant rate in terms of pseudo-first-order kinetics increased from 0.0015 min-1 to 0.0186 min-1 at 5 and 20 V applied voltage. The graphite-PVC composite exhibits favorable qualities as an electrode material because of its mechanical resistance, low cost, simple preparation, and easy renewal of the electrode surface.

Removal of caffeine from aqueous solution by indirect electrochemical oxidation using a graphite-PVC composite electrode: A role of hypochlorite ion as an oxidising agent

The electrochemical oxidation of caffeine, a widely over-the-counter stimulant drug, has been investigated in effluent wastewater and deionized water (DIW) using graphite-poly vinyl chloride (PVC) composite electrode as anode. Effects of initial concentration of caffeine, chloride ion (Cl(-)) loading, presence of hydrogen peroxide (H2O2), sample volume, type of sample and applied voltage were determined to test and to validate a kinetic model for the oxidation of caffeine by the electrochemical oxidation process. The results revealed that the electrochemical oxidation rates of caffeine followed pseudo first-order kinetics, with rate constant values ranged from 0.006 to 0.23 min(-1) depending on the operating parameters. The removal efficiency of caffeine increases with applied voltage very significantly, suggesting a very important role of mediated oxidation process. However, the consumption energy was considered during electrochemical oxidation process. In chloride media, removal of caffeine is faster and more efficiently, although occurrence of more intermediates takes place. The study found that the adding H2O2 to the NaCl solution will inhibit slightly the electrochemical oxidation rate in comparison with only NaCl in solution. Liquid chromatography-time of flight-mass spectrometry (LC-TOF-MS) technique was applied to the identification of the by-products generated during electrochemical oxidation, which allowed to construct the proposed structure of by-products.

A validation method development for simultaneous LC-ESI-TOF/MS analysis of some pharmaceuticals in Tangkas river-Malaysia

Pharmaceuticals are synthetic or natural chemicals that can be found in prescription medicines, over-the-counter therapeutic drugs and veterinary drugs. The occurrence of pharmaceuticals in the environment and the water cycle at trace levels (in the range of nanograms to low micrograms per litre) has been widely discussed and published in literature in the past decade. The increase in detection is largely attributable to the advances in analytical techniques and instrumentation. This paper describes development, optimisation and validation of a method for the simultaneous analysis of 7 multi-class pharmaceuticals (caffeine (CAF), Prazosin (PRZ), enalapril maleate (ENL), carbamazepine (CBZ), nifedipine (NFD), levonorgestrel (LNG), simvastatin (SMV)) using solid phase extraction (SPE cartridges Oasis HLB) followed by liquid chromatography-time-of-flight/mass spectrometry (LC-ESI-TOF/MS). Its linearity, 0.5-250 µg L-1, provided determination coefficients (R2) above 0.99 for all compounds. The Instrumental Quantification Limits (IQLs) for all pharmaceuticals ranged from 0.5-5 µg L-1 in the solvent as a standard mixture (i.e., direct injection). The extraction efficiency (EE%) was more than 40% and 60% in river and deionised water for most of compounds, respectively. Limit of quantification (LOQ) for all pharmaceutic als ranged from 13-800 ng L -1 in spiked river water. The inter and intra day precision of the method, calculated as the relative standard deviation (RSD%), 2.33-22.3% and 0.6-9.9%, respectively, except for caffeine, which has a RSD% of 20.1% at 50 µg L-1. Matrix effect was investigated and ranged from 10-41%. Out of seven pharmaceuticals, six pharmaceutical compounds were detected in the river water sample.

Controlled Release Electrochemical Synthesis and Cytotoxicity Study of Copper(II) Nanoparticles in Copper(II) Decanoate Complex

In the present study, a controlled release electrochemical (CRE) technique based on the controlled release of Cu2+ ion from Cu anode in the presence of decanoic acid (HDe) has been used to synthesize Cu(II) decanoate (CuDe2) complex. The effect of applied voltages (1–10V) and electrolyte concentrations (0.1–2.0M CH3COONH4) during the electrolysis on the nanoparticles obtained was studied using TEM. The results reveal that small-sized nanoparticles (2±1nm) were obtained by using lowest applied voltage and CH3COONH4 concentration (1V and 0.1M, respectively). The smallest nanoparticle obtained was then used in the cytotoxicity study against A549 and HeLa cells. The synthesized complex gives moderate cytotoxic effect on the selected cells (IC50=15.85μM and 20.89μM, respectively) and low cytotoxic effect on normal cells (IMR90). Apoptosis is the mode of cell death based on the apoptosis assay that has been conducted.

Effect of Applied Voltage on Slow-Release of Cu(II) Ions on the Synthesis of Copper(II) Stearate Complex by Electrochemical Technique

ion from electrochemical oxidation of a Cu anode in the presence of stearic acid (HSt) and an aqueous solution of ammonium acetate (CH 3 COONH 4 ) (0.1 mol L-1) as supporting electrolyte has been used to synthesize Cu(II) stearate (Cu(II)St) complex. Different values of applied voltages (1, 5 and 10 V) were used during the synthesis to study the effect of applied voltage on the particle size of the Cu nanoparticles and morphology of the synthesized Cu(II)St complex. By using 1 V of applied voltage, small Cu nanoparticle was produced with an average particle size of 2.49 ± 0.82 nm, followed by 5 V (3.61 ± 1.18 nm) and 10 V (6.64 ± 2.72 nm). Another advantage of using 1 V of the applied voltage is the formation of well-shaped petal-like structures of the Cu(II)St complex compared to the synthesis using 5 V and 10 V which inhibit the formation of well-shaped petal-like structure. This proves that the slow-release electrochemical synthesis using lower value of applied voltage has successfully resulted in the formation of small size Cu nanoparticles.

Decolorization of landfill leachate using electrochemical oxidation technique

The study was carried out to investigate the electrochemical oxidation of landfill leachate from the Jeram sanitary landfill leachate using charcoal base metallic composite electrodes. The control parameters used were applied voltage, Cl− concentration (as supporting electrolyte) and pH of the solution. The optimum conditions obtained were NaCl concentration of 1.5 % (w/v), applied voltage of 10 V, operating time 180 min and C60CG Co10PVC15 electrode as an anode.15 Electrochemical treatment using charcoal base metallic composite electrode was able to remove color up to 79%.

Penilaian pengekstrakan erapan bar untuk pengekstrakan herbisid triazin menggunakan pendekatan reka bentuk komposit berpusat

A (PDMS)-coated stir bar was prepared for a glass jacket-free stir bar sorptive extraction (SBSE) configuration by adhesion technique for the extraction of triazine herbicides prior to quantification using a gas chromatography-flame ionization detector (GC-FID). A central composite design (CCD) was used in the optimization of extraction and desorption conditions. At optimum conditions, values of factors were set as pH 8.5, with no addition of NaCl, for 25 minutes of extraction time, and 24 minutes of desorption time. Under optimal experimental conditions, the proposed method has linear ranges at 0.1 – 100 µgL-1 with correlation of determination (R2), ranging from 0.9991 – 0.9995, respectively. The limit of detection (LODs) and limit of quantification (LOQs) of three triazines were found to be ranging from 0.015 – 0.023 µgL-1 and 0.047 – 0.060 µgL-1, respectively.