Displaying publications 21 - 40 of 137 in total

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  1. Chemical compositions of the rhizome oils of two Alpinia species of Malaysia
    Sirat HM, Basar N, Jani NA
    Nat Prod Res, 2011 Jun;25(10):982-6.
    PMID: 21644178 DOI: 10.1080/14786419.2010.529079
    The essential oils obtained by hydrodistillation of the rhizomes of Alpinia aquatica Rosc. syn. Alpinia melanocarpa and Alpinia malaccensis Roscoe were analysed by capillary gas chromatography and gas chromatography-mass spectrometry. Eighteen compounds, representing 98.4% of the essential oil were identified in A. aquatica rhizome oil, with β-sesquiphellandrene in 36.5% being the major constituent, while 20 compounds representing 99.7% of the rhizome oil of A. malaccensis were identified, among which methyl (E)-cinnamate (78.2%) was the major constituent.
    Matched MeSH terms: Chromatography, Gas
  2. Recent developments and applications of liquid phase microextraction in fruits and vegetables analysis
    Abdulra'uf LB, Sirhan AY, Huat Tan G
    J Sep Sci, 2012 Dec;35(24):3540-53.
    PMID: 23225719 DOI: 10.1002/jssc.201200427
    The sample preparation step has been identified as the bottleneck of analytical methodology in chemical analysis. Therefore, there is need for the development of cost-effective, easy to operate, and environmentally friendly miniaturized sample preparation technique. The microextraction techniques combine extraction, isolation, concentration, and introduction of analytes into analytical instrument, to a single and uninterrupted step, and improve sample throughput. The use of liquid-phase microextraction techniques for the analysis of pesticide residues in fruits and vegetables are discussed with the focus on the methodologies employed by different researchers and their analytical performances. Analytes are extracted using water-immiscible solvents and are desorbed into gas chromatography, liquid chromatography, or capillary electrophoresis for identification and quantitation.
    Matched MeSH terms: Chromatography, Gas
  3. Survey of the Anopheles maculatus complex (Diptera: Culicidae) in peninsular Malaysia by analysis of cuticular lipids
    Kittayapong P, Clark JM, Edman JD, Lavine BK, Marion JR, Brooks M
    J Med Entomol, 1993 Nov;30(6):969-74.
    PMID: 8271255
    Anopheles maculatus Theobald sensu lato is a species complex now consisting of eight sibling species; An. maculatus is still represented by two cytologically distinct forms; i.e., the widely distributed sensu strictu or B, and E from southern Thailand and adjacent areas in northern Malaysia. Cuticular lipid profiles in conjunction with principal component analysis was used to separate An. maculatus form E from sensu stricto form B in a preliminary survey of the An. maculatus complex at five locations spanning peninsular Malaysia. The relative rank orders, from the areas of the five gas chromatographic peaks used to determine lipid differences for specimens from peninsular Malaysia, matched well with those from cytogenetically identified colony specimens of An. maculatus forms B and E. The two-dimensional principal component pattern of specimens identified as form E was highly clumped, which indicated that very similar cuticular lipids were present within this putative malaria vector. Both forms coexisted in peninsular Malaysia, but form E may be dominant except in the south.
    Matched MeSH terms: Chromatography, Gas
  4. The fatty acid composition of cooking oils and fats used in Malaya
    Chong YH, Mills GL
    Med J Malaya, 1966 Dec;21(2):125-7.
    PMID: 4227381
    Matched MeSH terms: Chromatography, Gas
  5. Fulltext Surface Thermo-Dynamic Characterization of Poly (Vinylidene Chloride-Co-Acrylonitrile) (P(VDC-co-AN)) Using Inverse-Gas Chromatography and Investigation of Visual Traits Using Computer Vision Image Processing Algorithms
    Kakani V, Kim H, Basivi PK, Pasupuleti VR
    Polymers (Basel), 2020 Jul 23;12(8).
    PMID: 32717780 DOI: 10.3390/polym12081631
    The Inverse Gas Chromatography (IGC) technique has been employed for the surface thermo-dynamic characterization of the polymer Poly(vinylidene chloride-co-acrylonitrile) (P(VDC-co-AN)) in its pure form. IGC attributes, such as London dispersive surface energy, Gibbs free energy, and Guttman Lewis acid-base parameters were analyzed for the polymer (P(VDC-co-AN)). The London dispersive surface free energy ( γ S L ) was calculated using the Schultz and Dorris-Gray method. The maximum surface energy value of (P(VDC-co-AN )) is found to be 29.93 mJ·m - 2 and 24.15 mJ·m - 2 in both methods respectively. In our analysis, it is observed that the γ S L values decline linearly with an increase in temperature. The Guttman-Lewis acid-base parameter K a , K b values were estimated to be 0.13 and 0.49. Additionally, the surface character S value and the correlation coefficient were estimated to be 3.77 and 0.98 respectively. After the thermo-dynamic surface characterization, the (P(VDC-co-AN)) polymer overall surface character is found to be basic. The substantial results revealed that the (P(VDC-co-AN)) polymer surface contains more basic sites than acidic sites and, hence, can closely associate in acidic media. Additionally, visual traits of the polymer (P(VDC-co-AN)) were investigated by employing Computer Vision and Image Processing (CVIP) techniques on Scanning Electron Microscopy (SEM) images captured at resolutions ×50, ×200 and ×500. Several visual traits, such as intricate patterns, surface morphology, texture/roughness, particle area distribution ( D A ), directionality ( D P ), mean average particle area ( μ a v g ) and mean average particle standard deviation ( σ a v g ), were investigated on the polymer's purest form. This collective study facilitates the researches to explore the pure form of the polymer Poly(vinylidene chloride-co-acrylonitrile) (P(VDC-co-AN )) in both chemical and visual perspective.
    Matched MeSH terms: Chromatography, Gas
  6. Fulltext Trans fatty acids in selected bakery products and its potential dietary exposure
    Siti Nurshahbani, S., Azrina, A.
    International Food Research Journal, 2014;21(6):2175-2181.
    MyJurnal
    High intake of trans fatty acids (TFA) may cause adverse changes in blood lipids as shown in many epidemiological studies. The major sources of TFA in human diet come from bakery products such as cookies, cakes, muffins, breads and pastries. In this study, total fat of baked products was determined using Soxhlet method while TFA content was determined on gas chromatograph using a highly polar capillary column and flame ionization detector. Exposure to TFA from the baked product was estimated based on Food Consumption Statistics of Malaysia 2003. High level of TFA was observed in muffins (3.21-7.34 g per 100 g food) followed by pastries (2.90-6.03 g per 100 g food) and cakes (2.26-8.36 g per 100 g food) regardless of products having brand name or not. Among the TFA isomers, trans 18:1 6t was the most abundant followed by trans 18:1 9t, trans 16:1 9t, trans 18:2 and small quantities of trans 18:1 11t. Exposure to TFA based on the Malaysian Food Consumption Statistics 2003 of the baked products was ranging from 0.14-0.18 g/day. Even with the low estimated exposure, actual intake of baked products must be monitored closely as other high fat food as these products is one of main contributor to TFA in the diet following their high frequency of daily intake.
    Matched MeSH terms: Chromatography, Gas
  7. Fulltext Characterization of agarwood incense using gas chromatography - mass spectrometry (GC-MS) coupled with Solid Phase Micro Extraction (SPME) and Gas Chromatography - Flame Ionization Detector (GC-FID)
    Nurlaila Ismail, Mohd Hezri Fazalul Rahiman, Mohd Nasir Taib, Mastura Ibrahim, Seema Zareen, Saiful Nizam Tajuddin
    Scientific Research Journal, 2015;12(2):0-0.
    MyJurnal
    This paper presents the application of Solid Phase Micro Extraction (SPME) coupled with Gas Chromatography - Mass Spectrometry (GC-MS) and Gas Chromatography - Flame Ionization Detector (GC-FID) in characterizing the agarwood incense. The work involved three types of SPME fibres at 30 minute sampling time. The fibres are 50/30 μm divinylbenzene-carboxen-polydimethysiloxane (DVB-CAR-PDMS), 65 μm polydi methylsiloxane-divinylbenzene (PDMS-DVB) and 85 μm carboxen-polydimethyl siloxane (CAR-PDMS). The results showed that among the many compounds extracted by GC-MS coupled with SPME, six compounds were substantially found in high quality agarwood incense due to their high percentage area (%). They are β-maaliene, α-elemol, β-selinene, 10-epi-γ-eudesmol, agarospirol and caryophellene oxide. The finding offers a new approach for establishing the volatile profile of agarwood incense components as well as for agarwood grading and discrimination.
    Matched MeSH terms: Chromatography, Gas
  8. Fulltext Fatty acid composition of five Malaysian biscuits (cream crackers) with special reference to trans-fatty acids
    Neo, Y.P., Tan, C.H., Ariffin, A.
    International Food Research Journal, 2007;14(3):197-204.
    MyJurnal
    The fatty acid composition and trans fatty acids (TFA) contents of samples of five Malaysian cream crackers biscuit brands were determined by gas-liquid chromatography, using a 60 m Supelco SP2340 fused silica capillary column and flame ionization detection. The identities of the fatty acids were established by comparing their retention times with authentic standards from Supelco. The results were expressed as relative percentages. The total saturated fatty acids (SFA) in the samples ranged from 48.90% to 54.87% of total fatty acids. As for the polyunsaturated fatty acids (PUFA), the total PUFA in the samples ranged from 9.97% to 11.73% of total fatty acids. Total trans fatty acids (TFA) ranged from 0.17% to 0.77% of total fatty acids. The monotrans 18:2 tc or 18:2 ct isomer content ranged from 0.07% to 0.10% of total fatty acids and the ditrans 18:2 isomer (9t, 12t) was not detected. The results indicate that all the fat sources of the 5 sample crackers biscuit brands were palm oil based.
    Matched MeSH terms: Chromatography, Gas
  9. Fulltext Efficacy of ginger oil and extract combined with gum arabic on anthracnose and quality of papaya fruit during cold storage
    Ali A, Hei GK, Keat YW
    J Food Sci Technol, 2016 Mar;53(3):1435-44.
    PMID: 27570268 DOI: 10.1007/s13197-015-2124-5
    Effect of 2.0 % ginger oil (GO) and 1.5 % ginger extract (GE) in combination with 10.0 % gum arabic (GA) was evaluated for the postharvest control of anthracnose and maintaining quality of Eksotika II papaya fruit during storage at 12 ± 1 °C and 80-85 % RH. Antifungal compounds present in GO and GE were analyzed using gas chromatography and GO was found to contain α-pinene, 1, 8-cineole and borneol, while only borneol was present in GE due to different extraction methods applied. The highest antifungal activity was shown in 2.0 % GO combined with 10 % GA, which significantly (P 
    Matched MeSH terms: Chromatography, Gas
  10. Fulltext Surface Energy Mapping of Modified Silica Using IGC Technique at Finite Dilution
    Ngeow YW, Williams DR, Chapman AV, Heng JYY
    ACS Omega, 2020 May 12;5(18):10266-10275.
    PMID: 32426583 DOI: 10.1021/acsomega.9b03920
    The reinforcing silica filler, which can be more than 40% of an elastomer composite, plays a key role to achieve the desired mechanical properties in elastomer vulcanizates. However, the highly hydrophilic nature of silica surface causes silica particle aggregation. It remained a challenge for many tire manufacturers when using silica-filled elastomer compounds. Here, the silica surface energy changes when the surface is modified with coupling or noncoupling silanes; coupling silanes can covalently bond the silica to the elastomers. The surface energy of silica was determined using inverse gas chromatography (IGC) at finite dilution (FD-IGC) and found to be reduced by up to 50% when the silica surface was silanized. The spatial distribution of silica aggregates within the tire matrix is determined by transmission electron microscopy (TEM) and a direct correlation between aggregate size (silica microdispersion) and work of cohesion from IGC is reported, highlighting surface energy and work of cohesion being excellent indicators of the degree of dispersion of silica aggregates.
    Matched MeSH terms: Chromatography, Gas
  11. Palm-Based Neopentyl Glycol Diester: A Potential Green Insulating Oil
    Raof NA, Yunus R, Rashid U, Azis N, Yaakub Z
    Protein Pept Lett, 2018;25(2):171-179.
    PMID: 29359647 DOI: 10.2174/0929866525666180122095056
    BACKGROUND: The transesterification of high oleic palm oil methyl ester (HOPME) with neopentyl glycol (NPG) has been investigated. The present study revealed the application of low-pressure technology as a new synthesis method to produce NPG diesters. Single variable optimization and response surface methodology (RSM) were implemented to optimize the experimental conditions to achieve the maximum composition (wt%) of NPG diesters.

    OBJECTIVE: The main objective of this study was to optimize the production of NPG diesters and to characterize the optimized esters with typical chemical, physical and electrical properties to study its potential as insulating oil.

    METHODS: The transesterification reaction between HOPME and NPG was conducted in a 1L three-neck flask reactor at specified temperature, pressure, molar ratio and catalyst concentration. For the optimization, four factors have been studied and the diester product was characterized by using gas chromatography (GC) analysis. The synthesized esters were then characterized with typical properties of transformer oil such as flash point, pour point, viscosity and breakdown voltage and were compared with mineral insulating oil and commercial NPG dioleate. For formulation, different samples of NPG diesters with different concentration of pour point depressant were prepared and each sample was tested for its pour point measurement.

    RESULTS: The optimum conditions inferred from the analyses were: molar ratio of HOPME to NPG of 2:1.3, temperature = 182°C, pressure = 0.6 mbar and catalyst concentration of 1.2%. The synthesized NPG diesters showed very important improvement in fire safety compared to mineral oil with flash point of 300°C and 155°C, respectively. NPG diesters also exhibit a relatively good viscosity of 21 cSt. The most striking observation to emerge from the data comparison with NPG diester was the breakdown voltage, which was higher than mineral oil and definitely in conformance to the IEC 61099 limit at 67.5 kV. The formulation of synthesized NPD diesters with VISCOPLEX® pour point depressant has successfully increased the pour point of NPG diester from -14°C to -48°C.

    CONCLUSION: The reaction time for the transesterification of HOPME with NPG to produce NPG diester was successfully reduced to 1 hour from the 14 hours required in the earlier synthesis method. The main highlight of this study was the excess reactant which is no longer methyl ester but the alcohol (NPG). The optimum reaction conditions for the synthesis were molar ratio of 2:1.13 for NPG:HOPME, 182°C, 0.6 mbar and catalyst concentration of 1.2 wt%. The maximum NPG diester yield of 87 wt% was consistent with the predicted yield of 87.7 wt% obtained from RSM. The synthesized diester exhibited better insulating properties than the commercial products especially with regards to the breakdown voltage, flash point and moisture content.

    Matched MeSH terms: Chromatography, Gas
  12. Simultaneous quantification of free fatty acids, free sterols, squalene, and acylglycerol molecular species in palm oil by high-temperature gas chromatography--flame ionization detection
    Lau HL, Puah CW, Choo YM, Ma AN, Chuah CH
    Lipids, 2005 May;40(5):523-8.
    PMID: 16094863
    This paper discusses a rapid GC-FID technique for the simultaneous quantitative analysis of FFA, MAG, DAG, TAG, sterols, and squalene in vegetable oils, with special reference to palm oil. The FFA content determined had a lower SE compared with a conventional titrimetric method. Squalene and individual sterols, consisting of beta-sitosterol, stigmasterol, campesterol, and cholesterol, were accurately quantified without any losses. This was achieved through elimination of tedious conventional sample pretreatments, such as saponification and preparative TLC. With this technique, the separation of individual MAG, consisting of 16:0, 18:0, and 18:1 FA, and the DAG species, consisting of the 1,2(2,3)- and 1,3-positions, was sufficient to enable their quantification. This technique enabled the TAG to be determined according to their carbon numbers in the range of C44 to C56. Comparisons were made with conventional methods, and the results were in good agreement with those reported in the literature.
    Matched MeSH terms: Chromatography, Gas/methods*
  13. Effects of some non-steroidal anti-inflammatory drugs (NSAIDS) on steroidogenesis in rat and porcine testis
    Kwan TK, Foong SL, Lim YT, Gower DB
    Biochem. Mol. Biol. Int., 1993 Nov;31(4):733-43.
    PMID: 8298502
    Using the rapid gas chromatographic steroid profiling technique, a number of metabolites of pregnenolone have been separated and quantified after incubation of this steroid with adult rat and neonatal porcine testicular homogenates. It was shown that the 5-ene-3 beta-hydroxy- and the 4-en-3-oxosteroid pathways for androgen biosynthesis were operating in both species, although the former pathway appeared to be more important in porcine testis. This tissue was characterised by the formation of several odorous, and pheromonal, 16-androstenes, which were quantitatively more important than the androgens. Three non-steroidal anti-inflammatory drugs (NSAIDS) caused dose-related inhibition of androgen and 16-androstene biosynthesis when co-incubated with pregnenolone. The order of potency was flurbiprofen > indomethacin > > > aspirin. The possibility that the NSAIDS may interfere with cytochrome P-450 is discussed, since several steroid-transforming enzymes, known to be dependent on this cytochrome for their activity, were markedly inhibited.
    Matched MeSH terms: Chromatography, Gas/methods
  14. Analytical GC-FID Method for the Determination of Organic Solvents in Radiopharmaceuticals
    Hassan H, Othman MF, Zakaria ZA, Saad FFA, Abdul Razak HR
    Curr Radiopharm, 2021;14(2):131-144.
    PMID: 33115398 DOI: 10.2174/1874471013999201027215704
    BACKGROUND: Organic solvents play an indispensable role in most of the radiopharmaceutical production stages. It is almost impossible to remove them entirely in the final formulation of the product.

    OBJECTIVE: In this presented work, an analytical method by gas chromatography coupled with flame ionization detection (GC-FID) has been developed to determine organic solvents in radiopharmaceutical samples. The effect of injection holding time, temperature variation in the injection port, and the column temperature on the analysis time and resolution (R ≥ 1.5) of ethanol and acetonitrile was studied extensively.

    METHODS: The experimental conditions were optimized with the aid of further statistical analysis; thence, the proposed method was validated following the International Council for Harmonisation (ICH) Q2 (R1) guideline.

    RESULTS: The proposed analytical method surpassed the acceptance criteria including the linearity > 0.990 (correlation coefficient of R2), precision < 2%, LOD, and LOQ, accuracy > 90% for all solvents. The separation between ethanol and acetonitrile was acceptable with a resolution R > 1.5. Further statistical analysis of Oneway ANOVA revealed that the increment in injection holding time and variation of temperature at the injection port did not significantly affect the analysis time. Nevertheless, the variation in injection port temperature substantially influenced the resolution of ethanol and acetonitrile peaks (p < 0.05).

    CONCLUSION: The proposed analytical method has been successfully implemented to determine the organic solvent in the [18F]fluoro-ethyl-tyrosine ([18F]FET), [18F]fluoromisonidazole ([18F]FMISO), and [18F]fluorothymidine ([18F]FLT).

    Matched MeSH terms: Chromatography, Gas/methods*
  15. Chemometric techniques in oil classification from oil spill fingerprinting
    Ismail A, Toriman ME, Juahir H, Kassim AM, Zain SM, Ahmad WKW, et al.
    Mar Pollut Bull, 2016 Oct 15;111(1-2):339-346.
    PMID: 27397593 DOI: 10.1016/j.marpolbul.2016.06.089
    Extended use of GC-FID and GC-MS in oil spill fingerprinting and matching is significantly important for oil classification from the oil spill sources collected from various areas of Peninsular Malaysia and Sabah (East Malaysia). Oil spill fingerprinting from GC-FID and GC-MS coupled with chemometric techniques (discriminant analysis and principal component analysis) is used as a diagnostic tool to classify the types of oil polluting the water. Clustering and discrimination of oil spill compounds in the water from the actual site of oil spill events are divided into four groups viz. diesel, Heavy Fuel Oil (HFO), Mixture Oil containing Light Fuel Oil (MOLFO) and Waste Oil (WO) according to the similarity of their intrinsic chemical properties. Principal component analysis (PCA) demonstrates that diesel, HFO, MOLFO and WO are types of oil or oil products from complex oil mixtures with a total variance of 85.34% and are identified with various anthropogenic activities related to either intentional releasing of oil or accidental discharge of oil into the environment. Our results show that the use of chemometric techniques is significant in providing independent validation for classifying the types of spilled oil in the investigation of oil spill pollution in Malaysia. This, in consequence would result in cost and time saving in identification of the oil spill sources.
    Matched MeSH terms: Chromatography, Gas/methods
  16. New magnetic oil palm fiber activated carbon-reinforced polypyrrole solid phase extraction combined with gas chromatography-electron capture detection for determination of organochlorine pesticides in water samples
    Marsin FM, Wan Ibrahim WA, Nodeh HR, Sanagi MM
    J Chromatogr A, 2020 Feb 08;1612:460638.
    PMID: 31676087 DOI: 10.1016/j.chroma.2019.460638
    Magnetic solid phase extraction (MSPE) employing oil-palm fiber activated carbon (OPAC) modified with magnetite (Fe3O4) and polypyrrole (OPAC-Fe3O4-PPy) was successfully used for the determination of two organochlorine pesticides (OCPs), namely endosulfan and dieldrin in environmental water samples. Analysis was performed using gas chromatography with micro-electron capture detection (GC-μECD). The effects of three preparation variables, namely Fe3O4:OPAC ratio, amount of pyrrole monomer, and amount of FeCl3 oxidant were optimized using Box-Behnken design (BBD) (R2 < 0.99, p-value < 0.001%). The optimum conditions were as follows: Fe3O4:OPAC ratio of 2:1 w/w, 1 g of FeCl3 and 100 μL of pyrrole monomer. The experimental results obtained agreed satisfactorily with the model prediction (> 90% agreement). Optimized OPAC-Fe3O4-PPy composite was characterized using field emission scanning electron microscope, vibrating sample magnetometer and Fourier transform infrared spectroscopy. Four numerical parameters of MSPE procedure was optimized using BBD. The significance of the MSPE parameters were salt addition > sample solution pH > extraction time and desorption time. Under the optimized conditions (extraction time: 90 s, desorption time: 10 min, salt: 0%, and pH: 5.8), the method demonstrated good linearity (25-1000 ng L-1) with coefficients of determination, R2 > 0.991, and low detection limits for both endosulfan (7.3 ng L-1) and dieldrin (8.6 ng L-1). The method showed high analyte recoveries in the range of 98.6-103.5% for environmental water samples. The proposed OPAC-Fe3O4-PPy MSPE method offered good features such as sustainability, simplicity, and rapid extraction.
    Matched MeSH terms: Chromatography, Gas*
  17. Sterols as biomarkers in the surface microlayer of the estuarine areas
    Alsalahi MA, Latif MT, Ali MM, Dominick D, Khan MF, Mustaffa NI, et al.
    Mar Pollut Bull, 2015 Apr 15;93(1-2):278-83.
    PMID: 25682566 DOI: 10.1016/j.marpolbul.2015.01.011
    This study aims to determine the concentration of sterols used as biomarkers in the surface microlayer (SML) in estuarine areas of the Selangor River, Malaysia. Samples were collected during different seasons through the use of a rotation drum. The analysis of sterols was performed using gas chromatography equipped with a flame ionisation detector (GC-FID). The results showed that the concentrations of total sterols in the SML ranged from 107.06 to 505.55 ng L(-1). The total sterol concentration was found to be higher in the wet season. Cholesterol was found to be the most abundant sterols component in the SML. The diagnostic ratios of sterols show the influence of natural sources and waste on the contribution of sterols in the SML. Further analysis, using principal component analysis (PCA), showed distinct inputs of sterols derived from human activity (40.58%), terrigenous and plant inputs (22.59%) as well as phytoplankton and marine inputs (17.35%).
    Matched MeSH terms: Chromatography, Gas
  18. Antioxidant activity of Piper nigrum L. essential oil extracted by supercritical CO₂ extraction and hydro-distillation
    Bagheri H, Abdul Manap MY, Solati Z
    Talanta, 2014 Apr;121:220-8.
    PMID: 24607131 DOI: 10.1016/j.talanta.2014.01.007
    The aim of this study was to optimize the antioxidant activity of Piper nigrum L. essential oil extracted using the supercritical carbon dioxide (SC-CO₂) technique. Response surface methodology was applied using a three-factor central composite design to evaluate the effects of three independent extraction variables: pressure of 15-30 MPa, temperature of 40-50 °C and dynamic extraction time of 40-80 min. The DPPH radical scavenging method was used to evaluate the antioxidant activity of the extracts. The results showed that the best antioxidant activity was achieved at 30 MPa, 40 °C and 40 min. The extracts were analyzed by GC-FID and GC-MS. The main components extracted using SC-CO₂ extraction in optimum conditions were β-caryophyllene (25.38 ± 0.62%), limonene (15.64 ± 0.15%), sabinene (13.63 ± 0.21%), 3-carene (9.34 ± 0.04%), β-pinene (7.27 ± 0.05%), and α-pinene (4.25 ± 0.06%). The essential oil obtained through this technique was compared with the essential oil obtained using hydro-distillation. For the essential oil obtained by hydro-distillation, the most abundant compounds were β-caryophyllene (18.64 ± 0.84%), limonene (14.95 ± 0.13%), sabinene (13.19 ± 0.17%), 3-carene (8.56 ± 0.11%), β-pinene (9.71 ± 0.12%), and α-pinene (7.96 ± 0.14%). Radical scavenging activity of the extracts obtained by SC-CO₂ and hydro-distillation showed an EC₅₀ of 103.28 and 316.27 µg mL(-1) respectively.
    Matched MeSH terms: Chromatography, Gas
  19. Thermodynamics and inhibition studies of lipozyme TL IM in biodiesel production via enzymatic transesterification
    Khor GK, Sim JH, Kamaruddin AH, Uzir MH
    Bioresour Technol, 2010 Aug;101(16):6558-61.
    PMID: 20363621 DOI: 10.1016/j.biortech.2010.03.047
    In order to characterize enzyme activity and stability corresponding to temperature effects, thermodynamic studies on commercial immobilized lipase have been carried out via enzymatic transesterification. An optimum temperature of 40 degrees C was obtained in the reaction. The decreasing reaction rates beyond the optimum temperature indicated the occurrence of reversible enzyme deactivation. Thermodynamic studies on lipase denaturation exhibited a first-order kinetics pattern, with considerable stability through time shown by the lipase as well. The activation and deactivation energies were 22.15 kJ mol(-1) and 45.18 kJ mol(-1), respectively, implying more energy was required for the irreversible denaturation of the enzyme to occur. At water content of 0.42%, the initial reaction rate and FAME yield displayed optimum values of 3.317 g/L min and 98%, respectively.
    Matched MeSH terms: Chromatography, Gas
  20. Multiple use of waste catalysts with and without regeneration for waste polymer cracking
    Salmiaton A, Garforth AA
    Waste Manag, 2011 Jun;31(6):1139-45.
    PMID: 21324661 DOI: 10.1016/j.wasman.2011.01.025
    Waste plastics contain a substantial number of valuable chemicals. The wastes from post-consumer as well as from industrial production can be recycled to valuable chemical feedstock, which can be used in refineries and/or petrochemical industries. This chemical recycling process is an ideal approach in recycling the waste for a better environment. Polymer cracking using a laboratory fluidized bed reactor concentrated on the used highly contaminated catalyst, E-Cat 2. Even though E-Cat 2 had low activity due to fewer acid sites, the products yielded were similar with amorphous ASA and were far better than thermal cracking. The high levels of heavy metals, namely nickel and vanadium, deposited during their lifetime as an FCC catalyst, did not greatly affect on the catalyst activity. It was also shown that E-Cat 2 could be used with and without regeneration. Although there was more deactivation when there was no regeneration step, the yield of gases (C(2)-C(7)) remained fairly constant. For the first time, these results indicate that "waste" FCC catalyst (E-Cat) is a good candidate for future feedstock recycling of polymer waste. The major benefits of using E-Cat are a low market price, the ability to tolerate reuse and regeneration capacity.
    Matched MeSH terms: Chromatography, Gas
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