Displaying publications 1 - 20 of 78 in total

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  1. Flow injection determination of free fatty acids in vegetable oils using capacitively coupled contactless conductivity detection
    Makahleh A, Saad B
    Anal Chim Acta, 2011 May 23;694(1-2):90-4.
    PMID: 21565307 DOI: 10.1016/j.aca.2011.03.033
    A single line flow injection analysis (FIA) method that incorporated a preconcentrator column packed with C(18) particles and capacitively coupled contactless conductivity detector (C(4)D) was developed for the determination of free fatty acid (FFA) in vegetable oils. The carrier stream was methanol/1.5 mM sodium acetate (pH 8) 80:20 (v/v) at a flow rate of 1.0 mL min(-1). Calibration curve was well correlated (r(2)=0.9995) within the range of 1-200 mg L(-1) FFA (expressed as palmitic acid). Sampling rate of 40-60 h(-1) was achieved. Good agreement was found between the standard non-aqueous titrimetry method and the proposed method when applied to the determination of FFA in palm (crude, olein, and refined, bleached and deodorised) and other vegetable (soybean, rice bran, walnut, corn and olive) oils. The proposed method offers distinct advantages over the official method, especially in terms of simplicity, high sampling rate, economy of solvents and sample, offering considerable promise as a low cost automated system that needs minimum human intervention over long periods of time.
  2. Fulltext Correction to: the Effect of Cross-Linking Efficiency of Drug-Loaded Novel Freeze Gelated Chitosan Templates for Periodontal Tissue Regeneration
    Qasim SSB, Nogueira LP, Fawzy AS, Daood U
    AAPS PharmSciTech, 2020 Sep 01;21(7):250.
    PMID: 32875436 DOI: 10.1208/s12249-020-01778-x
    The correct spelling of the second author's name is Liebert Parreiras Nogueira.
  3. Fulltext The Effect of Cross-linking Efficiency of Drug-Loaded Novel Freeze Gelated Chitosan Templates for Periodontal Tissue Regeneration
    Qasim SSB, Nogueria LP, Fawzy AS, Daood U
    AAPS PharmSciTech, 2020 Jun 16;21(5):173.
    PMID: 32548717 DOI: 10.1208/s12249-020-01708-x
    Innovative strategies for periodontal regeneration have been the focus of research clusters across the globe for decades. In order to overcome the drawbacks of currently available options, investigators have suggested a novel concept of functionally graded membrane (FGM) templates with different structural and morphological gradients. Chitosan (CH) has been used in the past for similar purpose. However, the composite formulation of composite and tetracycline when cross-linked with glutaraldehyde have received little attention. Therefore, the purpose of the study was to investigate the drug loading and release characteristics of novel freeze gelated chitosan templates at different percentages of glutaraldehyde. These were cross-linked with 0.1 and 1% glutaraldehyde and loaded with doxycycline hyclate. The electron micrographs depicted porous morphology of neat templates. After cross-linking, these templates showed compressed ultrastructures. Computerized tomography analysis showed that the templates had 88 to 92% porosity with average pore diameter decreased from 78 to 44.9 μm with increasing concentration. Fourier transform infrared spectroscopy showed alterations in the glycosidic segment of chitosan fingerprint region which after drug loading showed a dominant doxycycline spectral composite profile. Interestingly, swelling profile was not affected by cross-linking either at 0.1 and 1% glutaraldehyde and template showed a swelling ratio of 80%, which gained equilibrium after 15 min. The drug release pattern also showed a 40 μg/mL of release after 24 h. These doxycycline-loaded templates show their tendency to be used in a functionally graded membrane facing the defect site.
  4. Rapid tea catechins and caffeine determination by HPLC using microwave-assisted extraction and silica monolithic column
    Rahim AA, Nofrizal S, Saad B
    Food Chem, 2014 Mar 15;147:262-8.
    PMID: 24206716 DOI: 10.1016/j.foodchem.2013.09.131
    A rapid reversed-phase high performance liquid chromatographic method using a monolithic column for the determination of eight catechin monomers and caffeine was developed. Using a mobile phase of water:acetonitrile:methanol (83:6:11) at a flow rate of 1.4 mL min(-1), the catechins and caffeine were isocratically separated in about 7 min. The limits of detection and quantification were in the range of 0.11-0.29 and 0.33-0.87 mg L(-1), respectively. Satisfactory recoveries were obtained (94.2-105.2 ± 1.8%) for all samples when spiked at three concentrations (5, 40 and 70 mg L(-1)). In combination with microwave-assisted extraction (MAE), the method was applied to the determination of the catechins and caffeine in eleven tea samples (6 green, 3 black and 2 oolong teas). Relatively high levels of caffeine were found in black tea, but higher levels of the catechins, especially epigallocatechin gallate (EGCG) were found in green teas.
  5. Flow injection potentiometric determination of paraquat in formulations and biological samples
    Saad B, Ariffin M, Saleh MI
    Talanta, 1998 Dec;47(5):1231-6.
    PMID: 18967428
    A flow injection potentiometric method for the rapid determination of paraquat in herbicide formulations and biological samples is described. It is based on the utilization of a flow-through potentiometric detector containing polyvinyl chloride-immobilised octamethylcyclotetrasiloxane, a lipophilic plasticizer (tetra-n-undecyl 3,3',4,4'-benzophenone tetracarboxylate) and membrane additive potassium tetrakis(4-chlorophenyl)borate. The detector was minimally interfered by the presence of constituents such as Na(+), K(+), Ca(2+), Mg(2+), glucose, urea, lactic and citric acids at physiological levels, respectively. Good correlation between results of the proposed method and HPLC for the formulation samples was found, while results for the determination of paraquat in biological samples such as urine, vomitus and stomach washout was less satisfactory.
  6. Vortex- and CO2 -gas-assisted liquid-liquid microextraction with salt addition for the high-performance liquid chromatographic determination of furanic compounds in concentrated juices and dried fruits
    Abu-Bakar NB, Makahleh A, Saad B
    J Sep Sci, 2016 Mar;39(5):947-55.
    PMID: 26718308 DOI: 10.1002/jssc.201501109
    A novel microextraction method based on vortex- and CO2 -assisted liquid-liquid microextraction with salt addition for the isolation of furanic compounds (5-hydroxymethyl-2-furaldehyde, 5-methyl-2-furaldehyde, 2-furaldehyde, 3-furaldehyde, 2-furoic and 3-furoic acids) was developed. Purging the sample with CO2 was applied after vortexing to enhance the phase separation and mass transfer of the analytes. The optimum extraction conditions were: extraction solvent (volume), propyl acetate (125 μL); sample pH, 2.4; vortexing time, 45 s; salt concentration, 25% w/v and purging time, 5 min. The analytes were separated using an ODS Hypersil C18 column (250×4.6 mm i.d, 5 μm) under gradient flow. The proposed method showed good linearities (r(2) >0.999), low detection limits (0.08-1.9 μg/L) and good recoveries (80.7-122%). The validated method was successfully applied for the determination of the furanic compounds in concentrated juice (mango, date, orange, pomegranate, roselle, mangosteen and soursop) and dried fruit (prune, date and apricot paste) samples.
  7. Vortex-assisted liquid-liquid microextraction coupled with high performance liquid chromatography for the determination of furfurals and patulin in fruit juices
    Abu-Bakar NB, Makahleh A, Saad B
    Talanta, 2014 Mar;120:47-54.
    PMID: 24468341 DOI: 10.1016/j.talanta.2013.11.081
    A fast and simple solvent microextraction technique using salting out-vortex-assisted liquid-liquid microextraction (salting out-VALLME) was developed for the extraction of furfurals (2-furfural (2-F), 3-furfural (3-F), 5-methylfurfural (5-MF) and 5-hydroxymethylfurfural (5-HMF)) and patulin (PAT) in fruit juice samples. The optimum extraction conditions for 5 mL sample were: extraction solvent, 1-hexanol; volume of extractant, 200 µL; vortex time, 45 s; salt addition, 20%. The simultaneous determination of the furfurals and PAT were investigated using high performance liquid chromatography coupled with diode array detector (HPLC-DAD). The separation was performed using ODS Hypersil C18 column (4.6 mm i.d × 250 mm, 5 μm) under gradient elution. The detection wavelengths used for all compounds were 280 nm except for 3-F (210 nm). The furfurals and PAT were successfully separated in less than 9 min. Good linearities (r(2)>0.99) were obtained within the range 1-5000 μg L(-1) for all compounds except for 3-F (10-5000 µg L(-1)) and PAT (0.5-100 μg L(-1)). The limits of detection (0.28-3.2 µg L(-1)) were estimated at S/N ratio of 3. The validated salting out-VALLME-HPLC method was applied for the analysis of furfurals and PAT in fruit juice samples (apple, mango and grape).
  8. Capillary electrophoresis with capacitively coupled contactless conductivity detection for the determination of cis/trans isomers of octadec-9-enoic acid and other long chain fatty acids
    Wong YF, Saad B, Makahleh A
    J Chromatogr A, 2013 May 17;1290:82-90.
    PMID: 23578483 DOI: 10.1016/j.chroma.2013.03.014
    A capillary electrophoresis (CE)-capacitively coupled contactless conductivity detection (C(4)D) method for the simultaneous separation of eleven underivatized fatty acids (FAs), namely, lauric, myristic, tridecanoic (internal standard), pentadecanoic, palmitic, stearic, oleic, elaidic, linoleic, linolenic and arachidic acids is described. The separation was carried out in normal polarity mode at 20 °C, 30 kV and using hydrodynamic injection (50 mbar for 1 s). The separation was achieved in a bare fused-silica capillary (70 cm × 75 μm i.d.) using a background electrolyte of methyl-β-cyclodextrin (~6 mM) and heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (~8 mM) dissolved in a mixture of Na2HPO4/KH2PO4 (5 mM, pH 7.4):ACN:MeOH:n-octanol (3:4:2.5:0.5, v/v/v/v). C(4)D parameters were set at fixed amplitude of 100 V and frequency of 1000 kHz. The developed method was validated. Calibration curves of the ten FAs were well correlated (r(2)>0.99) within the range of 5-250 μg mL(-1) for lauric acid, and 3-250 μg mL(-1) for the other FAs. The method was simple and sensitive with detection limits (S/N=3) of 0.9-1.9 μg mL(-1) and good relative standard deviations of intra- and inter-day for migration times and peak areas (≤9.7%) were achieved. The method was applied to the determination of FAs in margarine samples. The proposed method offers distinct advantages over the GC and HPLC methods, especially in terms of simplicity (without derivatization) and sensitivity.
  9. In-vial liquid-liquid microextraction-capillary electrophoresis method for the determination of phenolic acids in vegetable oils
    Abu Bakar NB, Makahleh A, Saad B
    Anal Chim Acta, 2012 Sep 12;742:59-66.
    PMID: 22884208 DOI: 10.1016/j.aca.2012.02.045
    An in-vial liquid-liquid microextraction method was developed for the selective extraction of the phenolic acids (caffeic, gallic, cinnamic, ferulic, chlorogenic, syringic, vanillic, benzoic, p-hydroxybenzoic, 2,4-dihydroxybenzoic, o-coumaric, m-coumaric and p-coumaric) in vegetable oil samples. The optimised extraction conditions for 20 g sample were: volume of diluent (n-hexane), 2 mL; extractant, methanol: 5 mM sodium hydroxide (60:40; v/v); volume of extractant, 300 μL (twice); vortex, 1 min; centrifugation, 5 min. Recoveries for the studied phenolic acids were 80.1-119.5%. The simultaneous determination of the phenolic acid extracts was investigated by capillary electrophoresis (CE). Separations were carried out on a bare fused-silica capillary (50 μm i.d.× 40 cm length) involving 25 mM sodium tetraborate (pH 9.15) and 5% methanol as CE background electrolyte in the normal polarity mode, voltage of 30 kV, temperature of 25°C, injection time of 4s (50 mbar) and electropherograms were recorded at 200 nm. The phenolic acids were successfully separated in less than 10 min. The validated in-vial LLME-CE method was applied to the determination of phenolic acids in vegetable oil samples (extra virgin olive oil, virgin olive oil, pure olive oil, walnut oil and grapeseed oil). The developed method shows significant advantages over the current methods as lengthy evaporation step is not required.
  10. Comparative study on oxidative decomposition behavior of vegetable oils and its correlation with iodine value using thermogravimetric analysis
    Saad B, Wai WT, Lim BP
    J Oleo Sci, 2008;57(4):257-61.
    PMID: 18332590
    A comparative study of oxidative decomposition behavior of a wide range of vegetable oils and its correlation to iodine value (IV) using thermogravimetric analysis (TGA) was described. The oxidative decomposition of saturated fatty acids shows weight loss before 385 degrees C while oxidative decomposition of unsaturated fatty acids shows lower rate of weight loss (dWt/dt) compared to saturated fatty acids due to the oxidation process ('up taking ' of oxygen) involving breaking down of double bond to form primary and secondary oxidation products, which leads to some weight gain in the sample before being decomposed. The relative differences in the dWt/dt (%/min) of the both fatty acids give different decomposition steps in TGA thermogram, enabling IV to be determined through the percentage weight loss of saturated fatty acids per 100% of total sample weight (excluding weight loss from moisture and volatile compounds). Therefore, TGA method can be used as an alternative method for IV determination with no sample pre-dilution and solvent consumption. Using the TGA methods, good correlation (r = 0.9889) with standard AOCS method was achieved.
  11. Vortex-assisted liquid-liquid-liquid microextraction (VALLLME) technique: A new microextraction approach for direct liquid chromatography and capillary electrophoresis analysis
    Makahleh A, Yap HF, Saad B
    Talanta, 2015 Oct 01;143:394-401.
    PMID: 26078176 DOI: 10.1016/j.talanta.2015.05.011
    A new, rapid and sensitive microextraction technique named vortex-assisted liquid-liquid-liquid microextraction (VALLLME) is proposed. The complete extraction process involves two steps. First, a vortex-assisted liquid-liquid microextraction (VALLME) procedure was used to extract the analytes from a relatively large volume of sample (donor phase) to a small volume of organic solvent (intermediate phase). Next, a micro-vortex-assisted liquid-liquid extraction (µ-VALLE) was used to extract the target analytes from the intermediate phase to a smaller volume of aqueous solution (acceptor phase). The final extract (acceptor phase) can be directly injected into the high performance liquid chromatography or capillary electrophoresis units without any further treatments. The selection of the intermediate phase and the manipulation of pH are key parameters that ensure good extraction efficiency of the technique. The proposed technique has been successfully applied for the determination of carvedilol (used as model analyte) in biological fluid samples. The optimum extraction conditions were: toluene as intermediate phase (150 μL); pH of the donor phase, 9.5; vortex time of the VALLME, 45 s (maximum speed, 2500 rpm); 0.1M HCl (15 μL) as acceptor phase; vortexing time of the µ-VALLME, 75 s (maximum stirring speed, 2500 rpm) and salt concentration in the donor phase, 5% (w/v). Under these conditions, enrichment factors of 51- and 418-fold for VALLME step and VALLLME procedure, respectively, were achieved.
  12. Determination of α-ketoglutaric and pyruvic acids in urine as potential biomarkers for diabetic II and liver cancer
    Makahleh A, Ben-Hander GM, Saad B
    Bioanalysis, 2015;7(6):713-23.
    PMID: 25871588 DOI: 10.4155/bio.14.307
    BACKGROUND: A simple and sensitive hollow fiber-liquid phase microextraction with in situ derivatization method was developed for the determination of α-ketoglutaric (α-KG) and pyruvic acids (PA) in small-volume urine samples. 2,4,6-trichloro phenyl hydrazine was used as derivatization agent.
    RESULTS: Under the optimum extraction conditions, enrichment factors of 742 and 400 for α-KG and PA, respectively, were achieved. Calibration curves were linear over the range 1 to 1000 ng/ml (r(2) ≥ 0.998). Detection and quantitation limits were 0.03 and 0.02, and 0.10 and 0.05 ng/ml for α-KG and PA, respectively.
    CONCLUSION: The concentrations in diabetic II and liver cancer samples were significantly lower than those from healthy people, showing their potential as biomarkers for these diseases.
  13. Salting-out assisted liquid-liquid extraction coupled with hydrophilic interaction chromatography for the determination of biguanides in biological and environmental samples
    Alshishani A, Salhimi SM, Saad B
    J Chromatogr B Analyt Technol Biomed Life Sci, 2018 Jan 15;1073:51-59.
    PMID: 29241085 DOI: 10.1016/j.jchromb.2017.12.013
    A new salting-out assisted liquid-liquid extraction (SALLE) sample preparation method for the determination of the polar anti-diabetic biguanide drugs (metformin, buformin and phenformin) in blood plasma, urine and lake water samples were developed. The SALLE was performed by mixing samples (plasma (0.2mL), urine or lake water (1.0mL)) with acetonitrile (0.4mL for plasma, 0.5mL for urine or lake water), sodium hydroxide powder was then added for the phase separation. The effects of type of salting-out reagent, type of extraction solvent, volumes of acetonitrile and sample, amount of sodium hydroxide, vortexing and centrifugation times on the extraction efficiency were investigated. The upper layer, containing the biguanides, was directly injected into a HPLC unit using ZIC-HILIC column (150mm×2.1mm×3.5μm) and was detected at 236nm. The method was validated and calibration curves were linear with r2>0.99 over the range of 20-2000μgL-1for plasma and 5-2000μgL-1for urine and lake water samples. The limits of detection were in the range (3.8-5.6)μgL-1, (0.8-1.5)μgL-1and (0.3-0.8)μgL-1for plasma, urine and lake water, respectively. The accuracies in the three matrices were within 87.3-103%, 87.4-109%, 82.2-109% of the nominal concentration for metformin, buformin and phenformin, respectively. The relative standard deviation for inter- and intra -day precision were in the range of 1.0-17% for all analytes in the three matrices.
  14. Hollow fiber liquid-phase microextraction combined with high performance liquid chromatography for the determination of trace mitiglinide in biological fluids
    Hadi H, Makahleh A, Saad B
    J Chromatogr B Analyt Technol Biomed Life Sci, 2012 May 1;895-896:131-6.
    PMID: 22503735 DOI: 10.1016/j.jchromb.2012.03.031
    A hollow fiber liquid phase microextraction (HF-LPME) in conjunction with reversed phase HPLC-UV method was developed for the extraction and determination of trace amounts of the antidiabetic drug, mitiglinide (MIT) in biological fluids. The drug was extracted from 10 mL aqueous sample (donor phase (DP)) into an organic phase impregnated in the pores of hollow fiber, followed by the back extraction into a second aqueous solution (acceptor phase (AP)) located in the lumen of the hollow fiber. Parameters influencing the extraction efficiency including the kind of organic solvent, composition of DP and AP, extraction time, stirring rate and salt addition were investigated and optimized. Under the optimized extraction conditions, high enrichment factors (210-fold), good linearity (5-1000 ng mL(-1)) and detection limit lower than 1.38 ng mL(-1) were achieved. Recoveries of spiked samples were in the range (88.3-96.3%) and (92.0-99.3%) for urine and plasma samples, respectively. The percent relative standard deviation (n=9) for the extraction and determination of three concentration levels (100, 400 and 800 ng mL(-1)) of MIT were less than 10.6% and 13.6% for urine and plasma samples, respectively. The developed method is simple, sensitive and has been successfully applied to the analysis of MIT in biological fluids.
  15. An integrative review of negative emotions of older adults in later life
    Adolfo CS, Albougami ASB, Roque MY, Aruta JJBR, Almazan JU
    Nurs Forum, 2022 Nov;57(6):1452-1464.
    PMID: 35962773 DOI: 10.1111/nuf.12785
    BACKGROUND: Older adults are one of the most vulnerable populations requiring scientific, psychological, and clinical attention. Although several studies have explored psychoemotional needs in later life, one critical gap in the literature is a shortage of studies comprehensively reviewing negative emotional experiences and their antecedents associated with later life.

    AIM: This integrative review aims to identify negative emotional experiences during older adult years.

    METHODS: This review of articles from Medline, CINAHL, Science Direct, Web of Science, ProQuest, and Taylor and Francis synthesized negative emotional experiences during older adult years. Across these six electronic databases, we searched and identified 17 relevant articles from 2005 to 2020 containing quantitative, qualitative, and mixed-method studies.

    RESULTS: Based on the review, we identified five negative emotions (sadness, anxiety, frustration, anger, and loneliness). These negative emotions were rooted in marital problems, separation from families, medical problems, physical functioning and disability, and financial limitations. Additionally, we identified common antecedents of negative emotions.

    CONCLUSION: At the center of numerous interventions, older adults are reinvigorated to understand the antecedents of negative emotions. The complex array of emotions, specifically regrets and frustration in later life, is depicted by more negativity than positivity. Such array of emotions could help develop strategies to prevent the causes of regret and frustration that nurses see when working with older adults in a clinical practice setting.

  16. Zeolite Linde Type L as micro-solid phase extraction sorbent for the high performance liquid chromatography determination of ochratoxin A in coffee and cereal
    Lee TP, Saad B, Ng EP, Salleh B
    J Chromatogr A, 2012 May 11;1237:46-54.
    PMID: 22444432 DOI: 10.1016/j.chroma.2012.03.031
    Zeolite Linde Type L (LTL) crystals with different length, diameter and particle size (nanosized LTL, rod LTL, cylinder LTL and needle LTL) were synthesized, characterized and were used as sorbent in the micro-solid phase extraction of ochratoxin A (OTA) before the high performance liquid chromatography detection. Under the optimized conditions, the detection limits of OTA for coffee and cereal were 0.09 ng g(-1) and 0.03 ng g(-1), respectively, while the quantification limits were 0.28 ng g(-1) and 0.08 ng g(-1), respectively. The recoveries of OTA of coffee and cereal spiked at 0.5, 10 and 25 ng g(-1) ranged from 91.7 to 101.0%. The proposed method was applied to forty-five samples of coffee and cereal. The presence of OTA was found in twenty-five samples, ranging from 0.28 to 9.33 ng g(-1).
  17. High performance liquid chromatographic determination of aflatoxins in chilli, peanut and rice using silica based monolithic column
    Khayoon WS, Saad B, Lee TP, Salleh B
    Food Chem, 2012 Jul 15;133(2):489-96.
    PMID: 25683424 DOI: 10.1016/j.foodchem.2012.01.010
    A simple and rapid high performance liquid chromatographic with fluorescence detection method for the determination of the aflatoxin B1, B2, G1 and G2 in peanuts, rice and chilli was developed. The sample was extracted using acetonitrile:water (90:10, v/v%) and then purified by using ISOLUTE® multimode solid phase extraction. After the pre-column derivatisation, the analytes were separated within 3.7 min using Chromolith® performance RP-18e (100-4.6mm) monolithic column. To assess the possible effects of endogenous components in the food items, matrix-matched calibration was used for the quantification and validation. The recoveries of aflatoxins that were spiked into food samples were 86.38-104.5% and RSDs were <4.4%. The method was applied to the determination of aflatoxins in peanut (9), rice (5) and chilli (10) samples. Liquid chromatography-tandem mass spectrometry analysis using triple quadruple analyser and operated in the multiple reaction monitoring modes on the contaminated samples was performed for confirmation.
  18. Molecularly imprinted polymer as sorbent in micro-solid phase extraction of ochratoxin A in coffee, grape juice and urine
    Lee TP, Saad B, Khayoon WS, Salleh B
    Talanta, 2012 Jan 15;88:129-35.
    PMID: 22265478 DOI: 10.1016/j.talanta.2011.10.021
    A simple, environmental friendly and selective sample preparation technique employing porous membrane protected micro-solid phase extraction (μ-SPE) loaded with molecularly imprinted polymer (MIP) for the determination of ochratoxin A (OTA) is described. After the extraction, the analyte was desorbed using ultrasonication and was analyzed using high performance liquid chromatography. Under the optimized conditions, the detection limits of OTA for coffee, grape juice and urine were 0.06 ng g(-1), 0.02 and 0.02 ng mL(-1), respectively while the quantification limits were 0.19 ng g(-1), 0.06 and 0.08 ng mL(-1), respectively. The recoveries of OTA from coffee spiked at 1, 25 and 50 ng g(-1), grape juice and urine samples at 1, 25 and 50 ng mL(-1) ranged from 90.6 to 101.5%. The proposed method was applied to thirty-eight samples of coffee, grape juice and urine and the presence of OTA was found in eighteen samples. The levels found, however, were all below the legal limits.
  19. Electro polymerized 4-vinyl pyridine on 2B pencil graphite as ionophore for cadmium (II)
    Wee Ling JL, Khan A, Saad B, Ab Ghani S
    Talanta, 2012 Jan 15;88:477-83.
    PMID: 22265529 DOI: 10.1016/j.talanta.2011.11.018
    A new poly(4-vinyl pyridine) (P4VP) based cadmium (Cd)-ion selective electrode (ISE) was developed. The 4-vinyl pyridine (4VP) was first polymerized electrochemically on the surface of graphite, later characterized by FTIR, SEM/EDX and then optimized as ISE for Cd. At optimal pH 6.4, slope of 27.7±0.8mVdecade(-1), linear concentration range of 1×10(-7) to 1.0×10(-1)M Cd(2+) and limit of detection (S/N=3) of 2.51×10(-8)M were obtained. The ISE was very selective towards Cd(2+), with K(pot)<1×10(-2) in the presence of the usual cations and anions in water samples. Response time and shelf life of less than 1min and 90 days, respectively, were observed. Its application was tested in various types of samples.
  20. Hollow fiber liquid-phase microextraction coupled with gas chromatography-flame ionization detection for the profiling of fatty acids in vegetable oils
    Siang GH, Makahleh A, Saad B, Lim BP
    J Chromatogr A, 2010 Dec 24;1217(52):8073-8.
    PMID: 21081239 DOI: 10.1016/j.chroma.2010.10.052
    The development of a two phase hollow fiber liquid-phase microextraction technique, followed by gas-chromatography-flame ionization detection (GC-FID) for the profiling of the fatty acids (FAs) (lauric, myristic, palmitic, stearic, palmitoleic, oleic, linoleic, linolenic and arachidic) in vegetable oils is described. Heptadecanoic acid methyl ester was used as the internal standard. The FAs were transesterified to their corresponding methyl esters prior to the extraction. Extraction parameters such as type of extracting solvent, temperature, extraction time, stirring speed and salt addition were studied and optimized. Recommended conditions were extraction solvent, n-tridecane; extraction time, 35 min; extraction temperature, ambient; without addition of salt. Enrichment factors varying from 37 to 115 were achieved. Calibration curves for the nine FAs were well correlated (r(2)>0.994) within the range of 10-5000 μg L(-1). The limit of detection (signal:noise, 3) was 4.73-13.21 ng L(-1). The method was successfully applied to the profiling of the FAs in palm oils (crude, olein, kernel, and carotino cooking oil) and other vegetable oils (soybean, olive, coconut, rice bran and pumpkin). The encouraging enrichments achieved offer an interesting option for the profiling of the minor and major FAs in palm and other vegetable oils.
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