[en] Polymeric materials are used in many food contact applications as packaging material. The presence of residual toluene in this food packaging material can migrate into food and thus affect the quality of food. In this study, a manual headspace analysis was successfully designed and developed. The determination of residual toluene was carried out with standard addition method and multiple headspace extraction, MHE) method using gas chromatography-flame ionization detector, GC-FID). Identification of toluene was performed by comparison of its retention time with standard toluene and GC-MS. It was found that the suitable heating temperature was 180 degree Celsius with an optimum heating time of 10 minutes. The study also found that the concentration of residual toluene in multicolored sample was higher compared to mono colored sample whereas residual toluene in sample analyzed using standard addition method was higher compared to MHE method. However, comparison with the results obtained from De Paris laboratory, France found that MHE method gave higher accuracy for sample with low analyte concentration. On the other hand, lower accuracy was obtained for sample with high concentration of residual toluene due to systematic errors. Comparison between determination methods showed that MHE method is more precise compared to standard addition method. (author)

[en] Nickel possess characteristics similar to noble metals, apart from being easily deactivated by carbon deposition and poisoning. In this study, the activity of prepared nickel based catalysts doped with selected elements (Mg, Zr, Mo, Mn, Co, Fe, and Cu) that were presumed to help nickel active sites has been investigated for the CO₂ elimination in the presence of H₂ in the hopes for a menthanate reaction. With the addition of lanthanide series as co-dopant in the catalyst, the synthesized catalysts were tested for its catalytic activity and reproducibility by FTIR spectroscopy. It was found that only several elements can boost CO₂ elimination, namely magnesium, cobalt and ferum, with cobalt showing the highest conversion for both ratios, Ni/ Co/ Pr 60:30:10 and 60:10:30. Furthermore, Ni/ Co/ Pr with the ratio of 60:30:10 was proven superior as it yielded highest CH₄ in the lowest conversion temperature of approximately 350 degree Celsius. Further characterization on Ni/ Co/ Pr with the ratio of 60:30:10 showed the supremacy towards the conversion of CO₂ to CH₄. Single point BET analysis showed that Ni/ Co/ Pr did not have any changes in the surface area, as it did not adsorb CO₂. This statement is in agreement with the XRD and EDX results obtained whereby there are no traces of carbon deposition. From TPD results showed CO₂ desorption peaks at low and high temperature indicated intermediate bonding of CO₂ on the surface of the catalyst. This shows the presence of dopant will result in the enhancement of CO₂ elimination to a 100 %. (author)

[en] Activated carbon has been known as an excellent adsorbent and is widely used due to its large adsorption capacity. Activation condition and types of activation influence the surface area and porosity of the activated carbon produced. In this study, palm kernel shells and commercially activated carbon were used. To convert palm kernel shells into coal, two methods were employed, namely chemical activation and physical activation. For chemical activation, two activating agents, zinc chloride and potassium carbonate, were used. The activated carbons were analyzed using Fourier Transform Infrared (FTIR) spectroscopy, single point BET and free emission scanning electron microscopy (FESEM). The commercial activated carbon was also characterized. FTIR results indicate that all the palm kernel shells were successfully converted to carbon. Single point BET surface area of all the carbons prepared were obtained. From FESEM micrograph, the chemically activated palm kernel shells shows well highly defined cavities and pores. This study also shows that palm kernel shells can be used to be a better source of high surface area carbon. (author)

[en] A selective and sensitive method for simultaneous determination of lead and zinc by adsorptive differential pulse cathodic stripping voltammetry is presented. The method is based on adsorptive accumulation of the complexes of Pb (II) and Zn (II) ions with Dopamine onto hanging mercury drop electrode (HMDE), followed by reduction of adsorbed species by differential pulse cathodic stripping voltammetry. Optimal conditions were obtained at pH 10.0, Dopamine concentration of 1.0 x 10^-4 M, accumulation potential of 0.0 V (vs. Ag/ AgCl), accumulation time of 10 s, scan rate of 10 mV/ s. Under the optimized conditions, a linear calibration curve was established for the concentration of Pb (II) and Zn (II) in the range of 5-150 and 5-250 ng/ mL, respectively, with a detection limit of 0.5 ng/ mL Pb (II) and 1.8 ng/ mL Zn (II). The procedure was successfully applied to the simultaneous determination of both ions in some real samples. (author)

[en] Surface sediment samples from the mangrove forest of Setiu river were analyzed for the grain size analysis in order to understand better the accretion processes in the mangrove environment. There is a significant (P<0.05) relationship between sediment characteristics with the seasonal changes with a decreasing mean particle size occurring during monsoon seasons. Thhe accretion rate in this study was determined using ²³⁰Th_excess and an average accretion rate of about 0.61 cm yr^-1 was obtained. Those fairly high average accretion rates obtained indicating that this mangrove may be still prograding and in an immature stage with an estimated age of 163 years. (author)

[en] An electrochemical biosensor based on the immobilisation of alkaline phosphatase was developed for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D). The biosensor was constructed from the immobilization of alkaline phosphatase enzyme onto a screen-printed electrode (SPE). The ascorbic acid 2-phosphate (AA2P) was used as substrate for the enzymic reaction. The enzyme was entrapped in a hybrid sol-gel/ chitosan material with certain fixed composition. The determination of toxicity of 2,4-D pesticides quantitatively and qualitatively could be carried out by the inhibition of the alkaline phosphatase. A potential of +600 mV was suitable to be used for the oxidation of the products from the enzyme-substrate reaction, where the reaction pH was at 8.5. The linear response range of the biosensor to the AA2P substrates was 10 μM - 80 μM. The inhibition of the alkaline phosphatase enzyme of the 2,4-D biosensor was maximum at 80 ppm 2,4-D (50 % inhibition). (author)

[en] The adsorption of chlorimuron-ethyl and metsulfuron-methyl herbicide in four types of soil samples taken from an oil palm estate in Selangor has been investigated at two different depths (0-10 cm and 20-30 cm) using a batch technique. The adsorption behavior of both herbicides was evaluated using Freundlich and linear adsorption isotherms. Results indicate that soils from KLG 3 and KLG 4 stations exhibited significant stronger adsorption affinity for both herbicides (p<0.05). The adsorption affinity of chlorimuron-ethyl is stronger than metsulfuron-methyl in all soils studied and the adsorption affinity decreased with soil depth. Comparison of the soil physicochemical properties revealed that the organic matter content of KLG 3 and KLG 4 soils are significantly different from other soils although their pH values were similar. In agreement with previously reported studies, organic matter content and pH exert a dominant role in controlling the adsorption of sulfonylurea herbicides in the four soils studied. Thus it could be concluded that the varying adsorption coefficient values observed in the present study could be attributed to the differences in soil properties. (author)

[en] Accelerated solvent extraction (ASE) has been successfully used in the analysis of a wide range of chemicals from many sample matrices. However, the main problem with accelerated solvent extraction is low selectivity towards the analyte because during the extraction process, many interfering components are co-extracted together with target analytes and thus requires post-extraction clean-up processes. In this study, a selective accelerated solvent extraction with clean-up step incorporated inside the extraction cell was developed for the analysis of polycyclic aromatic hydrocarbons (PAHs) and sterols in soil. PAHs (naphthalene, acenaphthene, anthracene, pyrene) and sterols (coprostanol, cholestrol, stigmasterol, stigmastanol) were extracted separately using two elution steps. The selectivity and efficiency of this approach were evaluated using several sorbents and proper choice of solvents. Using polar sorbents, PAHs were recovered in the first extraction using n-hexane while sterols were recovered in the second extraction using a more polar solvent such as methanol, isopropanol, acetone and mixture of DCM: MeOH (40:60, v/ v). Recoveries for PAHs ranged from 76.5-99.2 % and sterols from 83.7-91.4 % using silica as the sorbent, n-hexane as the first eluent, and methanol as the second eluent. (author)

[en] Capillary electrophoresis (CE) of nine peptides namely, bradykinin, bradykinin fragment 1-5, substance P, Arg⁸-vasopressin, luteinizing hormone-releasing hormone (LHRH), bombesin, leucine-enkephalin, methionine-enkephalin and oxytocin were carried out using 0.5 % and 1.0 % formic acid (FA) as the separation buffers, added with acetonitrile (ACN) and triethylamine (TEA) as an additive at low pH. The electrophoretic behaviour of these peptides was examined at different concentration of TEA (0, 10, 20, 30, 40 and 50 mM), and ACN (30, 40, 50, 60, 70 %) at their respective measured final pH. The results showed that all nine peptides were fully resolved with addition of 10 - 20 mM TEA. Peak efficiency was improved significantly by increasing TEA concentration up to 40 mM where 800 000 m^-1 was obtained. Without TEA, the closely related enkephalins were co-migrating. Interestingly, by addition of as little as 5 mM TEA has sufficient to separate them almost at baseline. Increasing ACN to 40 % has shortened the analysis time by ca. 1 min. However, further increase of ACN can cause peak broadening and current instability. (author)

[en] The residual styrene and other volatile organic compounds (VOCs) present in the polystyrene food packaging are of concern as these compounds have the potential to migrate into the food in contact. This work describes a method for quantitative determination of VOCs, namely styrene, toluene, ethyl benzene, iso-propylbenzene and n-propylbenzene that have migrated from polystyrene food packaging into food stimulant by gas chromatography-flame ionization detection (GC-FID). Headspace solid phase micro extraction (HS-SPME) technique was applied for migration test using water as food stimulant. The effects of extraction variables including sample volume, eluotropic strength, extraction temperature, extraction time, desorption time, sample agitation, and salt addition on the amounts of the extracted analyses were studied to obtain the optimal HS-SPME conditions. The optimized method was applied to test the VOCs migrated from polystyrene bowls and cups at storage temperatures ranging from 24 to 80 degree Celsius for 30 min. Styrene and ethyl benzene were found to migrate from the samples into the food stimulant. The migration of analyze was found to be strongly dependent upon the storage temperature. The HS-SPME is useful as an alternative method to determine the migration of VOCs from food packaging material into food stimulant. (author)