Umi K. Ahmad and Sumathy Rajendran
Department of Chemistry, Faculty of Science,
Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia
A micellar electrokinetic chromatography (MEKC) method was developed for the simultaneous determination of five common energetic compounds namely octrahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 1,3,5-hexahydro-1,3,5-trinitrotriazine (RDX), 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN) and 2,4-dinitrotoluene (2,4-DNT). In this preliminary study, an electrolyte composed of 2.5 mM sodium tetraborate and 12.5 mM boric acid containing 50 mM sodium dodecyl sulfate (SDS) was chosen as the running buffer with 5% organic modifier (ACN:MeOH, 1:1). Separation runs were carried out at positive (anodic injection) at 30 kV with a constant temperature of 25°C and was performed using a fused-silica capillary of total length 112 cm (104 cm effective length) and 50 µm I.D. The developed MEKC method was coupled with a simple cartridge solid phase extraction (SPE) system as the off-line extraction and pre-concentration method to enhance the detection limit of the technique. The SPE cartridges were constructed from SPE material, LiChrolut EN. In the absence of SPE, the detection limits obtained for the analytes were in the range of 11 – 32 ppm. By coupling the separation with pre-concentration using SPE, the detection limits for detecting these five explosives in water sample were lowered by more than 1000 times with good percentage recovery (> 87%). In order to test the possibility to apply the developed method to real cases, post-blast water samples were analyzed and their results were compared with those obtained with high performance liquid chromatography (HPLC). The post-blast water samples which were collected from Baling Bom training range, Ipoh contained RDX in the range of 0.05 – 0.17 ppm with no analytes detected in some samples.
An ESR Study of Trapped Electron on High Surface Area Carbon
from Palm Kernel Shells.
Abdul Rahim Yacob, Ratna Sari Dewi Dasril, Mohd. Khairul Asyraf A.M.,
and Vicnisvarri Inderan
Chemistry Department, Science Faculty,
Universiti Teknologi Malaysia 81310Skudai Johor.
Palm kernel shells, an agricultural by-product, has been found to be a suitable starting material for the preparation of economical high surface area activated carbon. It was found that the palm kernel shell’s activated carbon contain a high carbon content of 75% and with low ash content of 1%. Palm kernel shells were converted to high surface area activated carbon via both physical and chemical methods. In this study, chemical activation was carried using zinc chloride as the activating agent while characterization was carried using FTIR, single point BET surface area, FESEM and N2 adsorption. Due its porosity and high surface area activated carbon, its property in trapping electrons was studied using ESR. For this study, the sample was first degassed and hydrogen gas was introduced. The sample was then UV irradiated and the activity observed. A singlet peak which corresponds to trap free electron with the g-value of 2.0235 was observed throughout the 90 minutes of UV irradiation. Deviation from the free electron g-value of 2.0023 indicates some contribution of the p-orbital from carbon. As the irradiation time increases, the peak intensity reduces while the g-value slightly shifted. The reduction of the singlet peak intensity is most probably due to the pairing out of the additional electrons, whilst shifted g-value indicates less contribution with the p-orbital of carbon atom during the hyperfine interaction. No interaction from hydrogen atom was however observed. This experiment shows that carbon is not capable to trapped electrons at its pores and the cavities, but continuously pairing them out through time.
Effect of Substrate Temperature and Deposition Time on the Sizes of Silicon Nanodots Grown on Corning Glass (7059) Substrate
Imam Sumpono, Lim Qiao Jie and Samsudi Sakrani
Ibnu Sina Institute for Fundamental Science Studies,
Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia
The growth of silicon nanodots is investigated using a self-assembly method of deposition, in particular RF magnetron sputtering. The dots with sizes ranging between 80 - 160 nm were grown on corning glass (7059) substrate at the following conditions: Fixed setting of 100W RF power and 5 sccm argon flow rate, and varying substrate temperatures and deposition times. The surface morphology was characterized using a non-contact dynamic mode of AFM (model SPI3800N). Observation from AFM images revealed the average dot sizes which decreased with increasing substrate temperatures, except for deposition time 600 s and substrate temperature 200°C. The average dots sizes were also found to vary in an increasing and decreasing manner with deposition times for the samples under study. Analysis from photoluminescence measurements gave the band gap energies around 1.79 eV which was greater than the band gap energy of bulk silicon (1.12 eV). The results showed strong indication of the nanodot size dependency on both substrate temperature and deposition time.
Electrosynthesis of Benzoic Acid from Chlorobenzene by
Carbon Dioxide Fixation Method
Aishah Abdul Jalil1, Hartini Mohd Aris1, Normala Suliman1, Norhuda Abdul Manaf1,
Nur Hanis Hayati Hairom1, Mohd Razif Harun1and Sugeng Triwahyono2
1Faculty of Chemical and Natural Resources Engineering,
2Ibnu Sina Institute for Fundamental Science Studies,
Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia
An alternative dechlorination method of chlorobenzenes by using a simple electrolysis system via carbon dioxide fixation technique has been developed. Electrolysis of chlorobenzene was carried out in a one-compartment cell fitted with an aluminium anode and a platinum cathode. Reaction in an N,N-dimethylformamide (DMF) solution containing 0.1M of tetrapropylammonium bromide (TPAB) at 0oC, 100 Ncc/min of CO2 flow rate and 120 mA/cm2 of current density was found to be the optimum conditions of this electrocarboxylation, which gave 72% yield of benzoic acid. This conditions was then applied to 1,2-dichlorobenzene and 1,3-dichlorobenzene in order to convert it to their corresponding benzoic acids.
Influence of Surfactant Types on Correlation of Retention Factor
and Hydrophobicity of Selected Triazole Fungicides
in Micellar Electrokinetic Chromatography
Wan Aini Wan Ibrahim, Dadan Hermawan, Mohamed Noor Hasan and Mohd Marsin Sanagi
Separation Science Research Group (SSRG)
Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia,
81310 UTM Skudai, Johor, Malaysia
Application of micellar electrokinetic chromatography (MEKC) in quantitative structure-retention relationship (QSRR) has been studied for selected triazole fungicides. Effect of different surfactant types and concentrations of bile salts and sodium dodecyl sulfate on the correlation between logarithm of retention/capacity factor (log k) in MEKC and logarithm of distribution coefficient between 1-octanol and water (log Pow) was investigated. Five standard fungicides (cyproconazole, bromuconazole, epoxiconazole, bitertanol and difenoconazole) with known log Pow values from 2.9 to 4.3 were used for constructing the calibration curve of log Pow against the MEKC retention factor, log k. High correlations were observed between hydrophobicity (log Pow) and log k in MEKC using two bile salt surfactants viz. sodium cholate and sodium deoxycholate and mixed bile salt systems, with correlation coefficient of linear regression greater than 0.98, due to the similar hydrogen bonding interaction patterns between bile salts MEKC systems and the 1-octanol-water system.
Design and Characterization of Resistance Heating for Czochralski Crystal Growth
Hamdan H.K. and Mohammad Radzi Sudin
Physics Department, Faculty of Science, Universiti Teknologi Malaysia,
81310 UTM Skudai, Johor, Malaysia
A resistance heating for Czochralski crystal growth system has been constructed. The vertical tube resistance furnace with outside diameter of 240.00 0.05 mm, inside diameter of 100.00 0.05 mm and high of 290.00 0.05 mm is placed in the chamber. Wire Super Kanthal A-1 of diameter 2.05 0.05 mm and resistance of 9.70 0.05 is used for resistance furnace. Two thermocouples type- K are used to control and measure the temperature inside resistance furnace. The temperature control has been interface to computer for monitoring the crystal growth process. A high alternating current of 23.71 0.05 ampere is used to resistance furnace for reaching high temperature quickly. The maximum temperature of the resistance furnace is 1300.00 0.05 °C. The temperature gradient of resistance furnace are found between 1.00 0.05 °C/cm to 5.00 0.05 °C/cm.
AC Conductivity of Ca0.8Ba0.2Cu3Ti4O12 Ceramic Sample
M. Mazni, W. D. W. Yusoff, C. P. Walter, S. A. Halim, Z. A. Talib
Department of Physics, Faculty of Science,
Universiti Putra Malaysia,
43400 UPM Serdang, Selangor
Ca0.8Ba0.2Cu3Ti4O12 (CBCTO) ceramics has been doped on Ca site with Barium and was prepared using solid state reaction technique. Dielectric measurement was done from 30oC to 250oC in frequency range of 10-2 Hz to 106 Hz. XRD pattern shows single phase with cubic structure. Two relaxation dispersions of the electrical parameters were found in complex impedance plot and conductivity plot due to grain boundary at low frequency and bulk at high frequency. It can be seen that the conductivity, σ is increasing with increasing temperatures. From Arrhenius plot of conductivity data, the activation energy, Ea for grain boundary region are 0.53 eV and 0.22 eV for bulk region.
The Study of Precipitated Cu-Zn-Al Catalyst via pH Titration Analysis
Nur Fadhilah Idrisa, Salamiah Zakariaa, Nurain Nasrudinb, Robert Schlöglc and Sharifah Bee Abd Hamidb.
aNanoC Sdn Bhd, 29 Jalan PJU 3/47, Sunway Technology Park,
47810 Petaling Jaya, Selangor, Malaysia
bCombinatorial Technology and Catalysis Research Centre,
Universiti Malaya, 50603 Kuala Lumpur, Malaysia,
cFritz-Haber Institute der Max Planck-Gesselschaft,
Faradayweg 4-6, 14195 Berlin, Germany.
The used of conventionally precipitated Cu-Zn-Al catalyst has been studied to increase the activity for reaction like methanol synthesis. Controlling the precipitation is crucial in determining the final dispersion of active sites in catalyst. Thus, the initial understanding of process changes through precipitation in multi components system is very useful. A series of titration experiment was carried out in order to gain deeper insight into the precipitation reaction of the complex ternary system by investigation of single metal, binary and ternary system during pH increment. Samples at relevant pH plateaus were taken and analyzed using XRD for phase identification and the content of Cu in solution was inspected by in-situ UV-Vis method. Spontaneous nucleation at pH increment was observed for single Cu and Zn systems exhibited crystalline precursors and oxolation to crystalline metal oxide at higher pH. The Al showed a partial oxolation to bayerite because the molecular species was unstable at higher concentration. The binary and ternary systems showed a complicated mixture of phase formation at respective pH plateaus. Nevertheless, it is clearly observed that Cu species was less soluble allowing it to be first precipitated leaving other elements to buffer the system. The final conclusion can be made that the precipitation has substantially occurred step-wise and not by co-precipitation. Therefore, the fast precipitation is essential to improve the system preventing sequential precipitation in order to control the process and finding the correct nucleation and growth kinetics.
Mo-V-Te-Nb-Mn-O Catalyst for Selective Oxidation of Propane to Acrylic Acid: Effect Promoter Loadings to Surface Modification
aRosliza Mohd Salim, aFazliana Abd Hamid, bNoor Azeerah Abas,
aLooi Ming Hoong and aSharifah Bee Abd Hamid
aCombinatorial Technology and Catalysis Research Centre (COMBICAT),
University of Malaya, 50603 Kuala Lumpur, Malaysia
bNanoC Sdn Bhd, 29 Jalan PJU 3/47, Sunway Technology Park, 47810 Petaling Jaya, Selangor, Malaysia
Manganese promoted catalysts were prepared at a fixed composition of Mo1V0.3Te0.23Nb0.125Mn≤nOx (n =0.0005, 0.005, 0.05) by slurry method and tested for the selective oxidation of propane to acrylic acid. The catalysts with moderate metal loading shows better activity than the rest with up to 49% yield to acrylic acid. By dispersing the active material onto SiO2, the catalysts become more selective but less active whereas without SiO2 the catalyst turn out to be more active but less selective to acrylic acid. The leaching treatment does affect the catalyst activity but the bulk structure remained unchanged. The systems have been investigated by XRD, SEM, IR, TG and DSC to further understand the relationship between the physical-chemical properties of the catalysts to their corresponding catalytic performance.
Effect of Platinum and Tungsten Oxide Metal Loading on
n-Pentane Isomerization over HZSM-5 Based Catalyst