Displaying publications 1 - 20 of 154 in total

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  1. Zinc(II) salphen complex-based fluorescence optical sensor for biogenic amine detection
    Sahudin MA, Su'ait MS, Tan LL, Lee YH, Abd Karim NH
    Anal Bioanal Chem, 2019 Sep;411(24):6449-6461.
    PMID: 31392436 DOI: 10.1007/s00216-019-02025-4
    Biogenic amines have attracted interest among researchers because of their importance as biomarkers in determining the quality of food freshness in the food industry. A rapid and simple technique that is able to detect biogenic amines is needed. In this work, a new optical sensing material for one of the biogenic amines, histamine, based on a new zinc(II) salphen complex was developed. The binding of zinc(II) complexes without an electron-withdrawing group (complex 1) and with electron-withdrawing groups (F, complex 2; Cl, complex 3) to histamine resulted in enhancement of fluorescence. All complexes exhibited high affinity for histamine [binding constant of (7.14 ± 0.80) × 104, (3.33 ± 0.03) × 105, and (2.35 ± 0.14) × 105 M-1, respectively]. Complex 2 was chosen as the sensing material for further development of an optical sensor for biogenic amines in the following step since it displayed enhanced optical properties in comparison with complexes 1 and 3. The optical sensor for biogenic amines used silica microparticles as the immobilisation support and histamine as the analyte. The optical sensor had a limit of detection for histamine of 4.4 × 10-12 M, with a linear working range between 1.0 × 10-11 and 1.0 × 10-6 M (R2 = 0.9844). The sensor showed good reproducibility, with a low relative standard deviation (5.5 %). In addition, the sensor exhibited good selectivity towards histamine and cadaverine over other amines, such as 1,2-phenylenediamine, triethylamine, and trimethylamine. Recovery and real sample studies suggested that complex 2 could be a promising biogenic amine optical sensing material that can be applied in the food industry, especially in controlling the safety of food for it to remain fresh and healthy for consumption.
    Matched MeSH terms: Spectrophotometry, Ultraviolet/instrumentation*
  2. Study and fabrication of europium picrate triethylene glycol complex
    Saleh MI, Kusrini E, Mohd Sarjidan MA, Abd Majid WH
    Spectrochim Acta A Mol Biomol Spectrosc, 2011 Jan;78(1):52-8.
    PMID: 21030294 DOI: 10.1016/j.saa.2010.08.029
    A mononuclear of [Eu(NO3)(Pic)(H2O)2(EO3)](Pic)·(0.73)H2O complex, where EO3=trietraethylene glycol and Pic=picrate anion, shows a red emission when used as an active layer in a single layer of ITO/EO3-Eu-Pic/Al configuration. The crystal structure of the complex consists of [Eu(NO3)(Pic)(H2O)2(EO3)]+ cation and [Pic]- anion. The Eu(III) ion is coordinated to the 10 oxygen atoms from one EO3 ligand, one Pic anion, one nitrate anion, and two water molecules. The complex is crystallized in triclinic with space group P-1. The hybrids in thin films I and II were prepared in the respective order solution concentrations of 15 and 20 mg/mL the emissive center. Comparing the photoluminescence (PL) and electroluminescence (EL) spectra, we can find that all emissions come from the characteristic transitions of the Eu(III) ion. The EL spectra of both thin films showed the occurrence of the most intense red-light emission around at 612 nm. Comparison of organic light-emitting device (OLED) current intensity characteristics as a function of voltage (I-V) show that the thin film I is better than those found for the thin film II. The thickness of the emitting layer is an important factor to control the current-voltage curve. The sharp and intense emission of the complex at low voltage indicates that the complex is a suitable and promising candidate for red-emitting materials.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  3. Fulltext Synthesis and characterization of polyethylene glycol mediated silver nanoparticles by the green method
    Shameli K, Ahmad MB, Jazayeri SD, Sedaghat S, Shabanzadeh P, Jahangirian H, et al.
    Int J Mol Sci, 2012;13(6):6639-50.
    PMID: 22837654 DOI: 10.3390/ijms13066639
    The roles of green chemistry in nanotechnology and nanoscience fields are very significant in the synthesis of diverse nanomaterials. Herein, we report a green chemistry method for synthesized colloidal silver nanoparticles (Ag NPs) in polymeric media. The colloidal Ag NPs were synthesized in an aqueous solution using silver nitrate, polyethylene glycol (PEG), and β-D-glucose as a silver precursor, stabilizer, and reducing agent, respectively. The properties of synthesized colloidal Ag NPs were studied at different reaction times. The ultraviolet-visible spectra were in excellent agreement with the obtained nanostructure studies performed by transmission electron microscopy (TEM) and their size distributions. The Ag NPs were characterized by utilizing X-ray diffraction (XRD), zeta potential measurements and Fourier transform infrared (FT-IR). The use of green chemistry reagents, such as glucose, provides green and economic features to this work.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  4. Fulltext Spectroscopic (UV/VIS, Raman) and Electrophoresis Study of Cytosine-Guanine Oligonucleotide DNA Influenced by Magnetic Field
    Banihashemian SM, Periasamy V, Boon Tong G, Abdul Rahman S
    PLoS One, 2016;11(3):e0149488.
    PMID: 26999445 DOI: 10.1371/journal.pone.0149488
    Studying the effect of a magnetic field on oligonucleotide DNA can provide a novel DNA manipulation technique for potential application in bioengineering and medicine. In this work, the optical and electrochemical response of a 100 bases oligonucleotides DNA, cytosine-guanine (CG100), is investigated via exposure to different magnetic fields (250, 500, 750, and 1000 mT). As a result of the optical response of CG100 to the magnetic field, the ultra-violet-visible spectrum indicated a slight variation in the band gap of CG100 of about 0.3 eV. Raman spectroscopy showed a significant deviation in hydrogen and phosphate bonds' vibration after exposure to the magnetic field. Oligonucleotide DNA mobility was investigated in the external electric field using the gel electrophoresis technique, which revealed a small decrease in the migration of CG100 after exposure to the magnetic field.
    Matched MeSH terms: Spectrophotometry, Ultraviolet/methods*
  5. Fulltext Environmental Synthesis of Few Layers Graphene Sheets Using Ultrasonic Exfoliation with Enhanced Electrical and Thermal Properties
    Noroozi M, Zakaria A, Radiman S, Abdul Wahab Z
    PLoS One, 2016;11(4):e0152699.
    PMID: 27064575 DOI: 10.1371/journal.pone.0152699
    In this paper, we report how few layers graphene that can be produced in large quantity with low defect ratio from exfoliation of graphite by using a high intensity probe sonication in water containing liquid hand soap and PVP. It was founded that the graphene powder obtained by this simple exfoliation method after the heat treatment had an excellent exfoliation into a single or layered graphene sheets. The UV-visible spectroscopy, FESEM, TEM, X-ray powder diffraction and Raman spectroscopy was used to analyse the graphene product. The thermal diffusivity of the samples was analysed using a highly accurate thermal-wave cavity photothermal technique. The data obtained showed excellent enhancement in the thermal diffusivity of the graphene dispersion. This well-dispersed graphene was then used to fabricate an electrically conductive polymer-graphene film composite. The results demonstrated that this low cost and environmental friendly technique allowed to the production of high quality layered graphene sheets, improved the thermal and electrical properties. This may find use in the wide range of applications based on graphene.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  6. New alkaloids from Phoebe grandis (Nees) Merr
    Awang K, Mukhtar MR, Hadi AH, Litaudon M, Latip J, Abdullah NR
    Nat Prod Res, 2006 May 20;20(6):567-72.
    PMID: 16835089
    The alkaloidal extract of the leaves of Phoebe grandis (nees) merr. have provided two new minor alkaloids; phoebegrandine D (1), a proaporphine-tryptamine dimer, and phoebegrandine E (2), an indoloquinolizidine. This is the first report on the occurrence of an indoloquinolizidine in the Phoebe species. The crude extract also exhibited antiplasmodial activity (IC50<8 microg mL-1). The structures of the novel compounds were elucidated by spectroscopic methods, notably 2D NMR and HRMS.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  7. Simultaneous determination of ofloxacin and ornidazole in pharmaceutical preparations by capillary zone electrophoresis
    See KL, Elbashir AA, Saad B, Ali AS, Aboul-Enein HY
    Biomed Chromatogr, 2009 Dec;23(12):1283-90.
    PMID: 19488980 DOI: 10.1002/bmc.1251
    A simple, rapid and validated capillary electrophoretic method has been developed for the separation and determination of ofloxacin and ornidazole in pharmaceutical formulations with detection at 230 nm. Optimal conditions for the quantitative separations were investigated. Analysis times shorter than 4 min were obtained using a background electrolyte solution consisting of 25 mmol/L phosphoric acid adjusted with 1 M Tris buffer to pH 8.5, with hydrodynamic injection of 5 s and 20 kV separation voltage. The validation criteria for accuracy, precision, linearity and limits of detection and quantitation were examined and discussed. An excellent linearity was obtained in concentration range 25-250 microg/mL. The detection limits for ofloxacin and ornidazole were 1.03 +/- 0.11 and 1.80 +/- 0.06 microg/mL, respectively. The proposed method has been applied for the analysis of ofloxacin and ornidazole both individually and in a combined dosage tablet formulation. The proposed validated method showed recoveries between 96.16 and 105.23% of the nominal contents.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  8. Simultaneous determination of atenolol, chlorthalidone and amiloride in pharmaceutical preparations by capillary zone electrophoresis with ultraviolet detection
    Al Azzam KM, Saad B, Aboul-Enein HY
    Biomed Chromatogr, 2010 Sep;24(9):977-81.
    PMID: 20066730 DOI: 10.1002/bmc.1395
    Capillary zone electrophoresis methods for the simultaneous determination of the beta-blocker drugs, atenolol, chlorthalidone and amiloride, in pharmaceutical formulations have been developed. The influences of several factors (buffer pH, concentration, applied voltage, capillary temperature and injection time) were studied. Using phenobarbital as internal standard, the analytes were all separated in less than 4 min. The separation was carried out in normal polarity mode at 25 degrees C, 25 kV and using hydrodynamic injection (10 s). The separation was effected in an uncoated fused-silica capillary (75 mum i.d. x 52 cm) and a background electrolyte of 25 mm H(3)PO(4) adjusted with 1 m NaOH solution (pH 9.0) and detection at 198 nm. The method was validated with respect to linearity, limit of detection and quantification, accuracy, precision and selectivity. Calibration curves were linear over the range 1-250 microg/mL for atenolol and chlorthalidone and from 2.5-250 microg/mL for amiloride. The relative standard deviations of intra- and inter-day migration times and corrected peak areas were less than 6.0%. The method showed good precision and accuracy and was successfully applied to the simultaneous determination of atenolol, chlorthalidone and amiloride in various pharmaceutical tablets formulations.
    Matched MeSH terms: Spectrophotometry, Ultraviolet/methods*
  9. Fulltext A Colorimetric pH Sensor Based on Clitoria sp and Brassica sp for Monitoring of Food Spoilage Using Chromametry
    Ahmad NA, Yook Heng L, Salam F, Mat Zaid MH, Abu Hanifah S
    Sensors (Basel), 2019 Nov 05;19(21).
    PMID: 31694284 DOI: 10.3390/s19214813
    A developed colorimetric pH sensor film based on edible materials for real-time monitoring of food freshness is described. The mixed natural dyes from edible plants Clitoria sp and Brassica sp were extracted and incorporated into ι-carrageenan film as a colorimetric pH sensor film for monitoring food spoilage and its freshness. The color changes of the developed colorimetric sensor film were measured with chromametry and UV-vis spectroscopy, respectively. Experimental results show that colorimetric pH sensor film demonstrated statistically significant differences (p < 0.05) between CIE-L*a*b* coordinates color system indicated that the developed colorimetric sensor film was able to give a gradual change in color over a wide pH range. The color of the colorimetric sensor film also changes discretely and linearly with factors that contribute to food spoilage using shrimp and durian samples. Moreover, the developed colorimetric pH sensor film has the potential to be used as a safe, non-destructive testing and also a flexibly visual method for direct assessment of food freshness indicator during storage.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  10. Fulltext Optimization and Validation of RP-HPLC-UV/Vis Method for Determination Phenolic Compounds in Several Personal Care Products
    Akkbik M, Assim ZB, Ahmad FB
    Int J Anal Chem, 2011;2011:858153.
    PMID: 21760792 DOI: 10.1155/2011/858153
    An HPLC method with ultraviolet-visible spectrophotometry detection has been optimized and validated for the simultaneous determination of phenolic compounds, such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) as antioxidants, and octyl methyl cinnamate (OMC) as UVB-filter in several personal care products. The dynamic range was between 1 to 250 mg/L with relative standard deviation less than 0.25% (n = 4). Limits of detection for BHA, BHT, and OMC were 0.196, 0.170, and 0.478 mg/L, respectively. While limits of quantification for BHA, BHT, and OMC were 0.593, 0.515, and 1.448 mg/L, respectively. The recovery for BHA, BHT, and OMC was ranged from 92.1-105.9%, 83.2-108.9%, and 87.3-103.7%, respectively. The concentration ranges of BHA, BHT, and OMC in 12 commercial personal care samples were 0.13-4.85, 0.16-2.30, and 0.12-65.5 mg/g, respectively. The concentrations of phenolic compounds in these personal care samples were below than maximum allowable concentration in personal care formulation, that is, 0.0004-10 mg/g, 0.002-5 mg/g, and up to 100 mg/g for BHA, BHT, and OMC, respectively.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  11. Synthesis, characterization and dna binding studies of [ruthenium(ii)(bpy)2 l]2+ where l are derivatives of imidazo[4,5-f]-1,10-phenanthrolines
    Ting T, Crouse K, Ahmad H
    Sains Malaysiana, 2015;44:619-628.
    Three novel ruthenium(II) complexes of the general formula [Ru(II)(bpy)2
    L]2+ were synthesized, where L =
    1,10-phenanthroline derivatives of position 2 imidazole having 3,4-didecyloxy-phenyl (ddip), 3,4-ditetradecyloxy-phenyl
    (dtip) and 3,4-dihexadecyloxy-phenyl (dhip). All complexes were characterized by elemental analysis, 1
    H-NMR and ESI-MS.
    Their photophysical properties have also been studied by UV-visible spectroscopy and fluorescence spectroscopy. The
    complexes exhibit Ru(II) metal centered emission at approximately 610 nm in acetonitrile solution at room temperature. DNA
    binding studies were carried out by UV-visible titration, luminescence titration and viscosity studies. The results indicated
    that [Ru(bpy)2
    (ddip)]2+ binds to CT-DNA by partial intercalation mode, while [Ru(bpy)2
    (dtip)]2+ and [Ru(bpy)2
    (dhip)]2+
    bind intercalatively via extended ligands.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  12. Nanocrystalline cellulose decorated quantum dots based tyrosinase biosensor for phenol determination
    Manan FAA, Hong WW, Abdullah J, Yusof NA, Ahmad I
    Mater Sci Eng C Mater Biol Appl, 2019 Jun;99:37-46.
    PMID: 30889711 DOI: 10.1016/j.msec.2019.01.082
    Novel biosensor architecture based on nanocrystalline cellulose (NCC)/CdS quantum dots (QDs) nanocomposite was developed for phenol determination. This nanocomposite was prepared with slight modification of nanocrystalline cellulose (NCC) with cationic surfactant of cetyltriammonium bromide (CTAB) and further decorated with 3-mercaptopropionic acid (3-MPA) capped CdS QDs. The nanocomposite material was then employed as scaffold for immobilization of tyrosinase enzyme (Tyr). The electrocatalytic response of Tyr/CTAB-NCC/QDs nanocomposite towards phenol was evaluated using differential pulse voltammetry (DPV). The current response obtained is proportional to the concentration of phenol which attributed to the reduction of o-quinone produced at the surface of the modified electrode. Under the optimal conditions, the biosensor exhibits good linearity towards phenol in the concentration range of 5-40 μM (R2 = 0.9904) with sensitivity and limit of detection (LOD) of 0.078 μA/μM and 0.082 μM, respectively.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  13. Fulltext From Green Remediation to Polymer Hybrid Fabrication with Improved Optical Band Gaps
    Brza MA, Aziz SB, Anuar H, Al Hazza MHF
    Int J Mol Sci, 2019 Aug 11;20(16).
    PMID: 31405255 DOI: 10.3390/ijms20163910
    The present work proposed a novel approach for transferring high-risk heavy metals tometal complexes via green chemistry remediation. The method of remediation of heavy metals developed in the present work is a great challenge for global environmental sciences and engineering because it is a totally environmentally friendly procedure in which black tea extract solution is used. The FTIR study indicates that black tea contains enough functional groups (OH and NH), polyphenols and conjugated double bonds. The synthesis of copper complex was confirmed by the UV-vis, XRD and FTIR spectroscopic studies. The XRD and FTIR analysis reveals the formation of complexation between Cu metal complexes and Poly (Vinyl Alcohol) (PVA) host matrix. The study of optical parameters indicates that PVA-based hybrids exhibit a small optical band gap, which is close to inorganic-based materials. It was noted that the absorption edge shifted to lower photon energy. When Cu metal complexes were added to PVA polymer, the refractive index was significantly tuned. The band gap shifts from 6.2 eV to 1.4 eV for PVA incorporated with 45 mL of Cu metal complexes. The nature of the electronic transition in hybrid materials was examined based on the Taucs model, while a close inspection of the optical dielectric loss was also performed in order to estimate the optical band gap. The obtained band gaps of the present work reveal that polymer hybrids with sufficient film-forming capability could be useful to overcome the drawbacks associated with conjugated polymers. Based on the XRD results and band gap values, the structure-property relationships were discussed in detail.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  14. Fulltext Robust Synthesis of Ciprofloxacin-Capped Metallic Nanoparticles and Their Urease Inhibitory Assay
    Nisar M, Khan SA, Qayum M, Khan A, Farooq U, Jaafar HZ, et al.
    Molecules, 2016 Mar 25;21(4):411.
    PMID: 27023506 DOI: 10.3390/molecules21040411
    The fluoroquinolone antibacterial drug ciprofloxacin (cip) has been used to cap metallic (silver and gold) nanoparticles by a robust one pot synthetic method under optimized conditions, using NaBH₄ as a mild reducing agent. Metallic nanoparticles (MNPs) showed constancy against variations in pH, table salt (NaCl) solution, and heat. Capping with metal ions (Ag/Au-cip) has significant implications for the solubility, pharmacokinetics and bioavailability of fluoroquinolone molecules. The metallic nanoparticles were characterized by several techniques such as ultraviolet visible spectroscopy (UV), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) methods. The nanoparticles synthesized using silver and gold were subjected to energy dispersive X-ray tests in order to show their metallic composition. The NH moiety of the piperazine group capped the Ag/Au surfaces, as revealed by spectroscopic studies. The synthesized nanoparticles were also assessed for urease inhibition potential. Fascinatingly, both Ag-cip and Au-cip NPs exhibited significant urease enzyme inhibitory potential, with IC50 = 1.181 ± 0.02 µg/mL and 52.55 ± 2.3 µg/mL, compared to ciprofloxacin (IC50 = 82.95 ± 1.62 µg/mL). MNPs also exhibited significant antibacterial activity against selected bacterial strains.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  15. Bionanocomposites of regenerated cellulose/zeolite prepared using environmentally benign ionic liquid solvent
    Soheilmoghaddam M, Wahit MU, Tuck Whye W, Ibrahim Akos N, Heidar Pour R, Ali Yussuf A
    Carbohydr Polym, 2014 Jun 15;106:326-34.
    PMID: 24721086 DOI: 10.1016/j.carbpol.2014.02.085
    Bionanocomposite films based on regenerated cellulose (RC) and incorporated with zeolite at different concentrations were fabricated by dissolving cellulose in 1-ethyl-3-methylimidazolium chloride (EMIMCl) ionic liquid using a simple green method. The interactions between the zeolite and the cellulose matrix were confirmed by Fourier transform infrared spectra. Mechanical properties of the nanocomposite films significantly improved as compared with the pure regenerated cellulose film, without the loss of extensibility. Zeolite incorporation enhanced the thermal stability and char yield of the nanocomposites. The scanning electron microscopy and transmission electron microscopy showed that zeolite was uniformly dispersed in the regenerated cellulose matrix. In vitro cytotoxicity test demonstrated that both RC and RC/zeolite nanocomposite films are cytocompatible. These results indicate that the prepared nanocomposites have potential applications in biodegradable packaging, membranes and biomedical areas.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  16. Fulltext Early-stage cervical cancer diagnosis based on an ultra-sensitive electrochemical DNA nanobiosensor for HPV-18 detection in real samples
    Mahmoodi P, Rezayi M, Rasouli E, Avan A, Gholami M, Ghayour Mobarhan M, et al.
    J Nanobiotechnology, 2020 Jan 13;18(1):11.
    PMID: 31931815 DOI: 10.1186/s12951-020-0577-9
    BACKGROUND: In several years ago, infection with human papillomaviruses (HPVs), have been prevalent in the worlds especially HPV type 18, can lead to cervical cancer. Therefore, rapid, accurate, and early diagnosis of HPV for successful treatment is essential. The present study describes the development of a selective and sensitive electrochemical biosensor base on DNA, for early detection of HPV-18. For this purpose, a nanocomposite of reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWCNTs) were electrodeposited on a screen-printed carbon electrode (SPCE). Then, Au nanoparticles (AuNPs) were dropped on a modified SPCE. Subsequently, single strand DNA (ssDNA) probe was immobilized on the modified electrode. The link attached between AuNPs and probe ssDNA provided by L-cysteine via functionalizing AuNPs (Cys-AuNPs). The differential pulse voltammetry (DPV) assay was also used to electrochemical measurement. The measurement was based on the oxidation signals of anthraquninone-2-sulfonic acid monohydrate sodium salt (AQMS) before and after hybridization between the probe and target DNA.

    RESULTS: The calibration curve showed a linear range between 0.01 fM to 0.01 nM with a limit of detection 0.05 fM. The results showed that the optimum concentration for DNA probe was 5 µM. The good performance of the proposed biosensor was achieved through hybridization of DNA probe-modified SPCE with extracted DNA from clinical samples.

    CONCLUSIONS: According to the investigated results, this biosensor can be introduced as a proprietary, accurate, sensitive, and rapid diagnostic method of HPV 18 in the polymerase chain reaction (PCR) of real samples.

    Matched MeSH terms: Spectrophotometry, Ultraviolet
  17. Optimization of lignin production from empty fruit bunch via liquefaction with ionic liquid
    Sidik DA, Ngadi N, Amin NA
    Bioresour Technol, 2013 May;135:690-6.
    PMID: 23186683 DOI: 10.1016/j.biortech.2012.09.041
    The production of lignin from empty fruit bunch (EFB) has been carried out using liquefaction method with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid (IL), in presence of sulfuric acid (H2SO4) as a catalyst. Response surface methodology (RSM) based on a factorial Central Composite Design (CCD) was employed to identify the optimum condition for lignin yield. The result indicated that the second order model was adequate for all the independent variables on the response with R(2)=0.8609. The optimum temperature, time, ionic liquid to EFB ratio, and catalyst concentration were 150.5 °C, 151 min, 3:1 wt/wt and 4.73 wt%, respectively for lignin yield=26.6%. The presence of lignin liquefied product was confirmed by UV-Vis and FTIR analysis. It was also demonstrated lignin extraction from lignocellulosic using recycled IL gave sufficient performance.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  18. Microcrystalline cellulose/metal-organic framework hybrid as a sorbent for dispersive micro-solid phase extraction of chlorophenols in water samples
    Ghaemi F, Amiri A
    J Chromatogr A, 2020 Aug 30;1626:461386.
    PMID: 32797858 DOI: 10.1016/j.chroma.2020.461386
    In this study, the microcrystalline cellulose/metal-organic framework 199 hybrid (MCC/MOF-199) was applied as sorbent for the dispersive micro-solid phase-extraction (D-μSPE) of chlorophenols. The D-μSPE method combined with high-performance liquid chromatography- ultraviolet detection (HPLC-UV) was employed to determine of four chlorophenols including 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,3-dichlorophenol (2,3-DCP), and 2,5-dichlorophenol (2,5-DCP) in aqueous. The main parameters of the D-μSPE process that influence the extraction (i.e. the amount of sorbent, elution condition, extraction time, and pH) were investigated and optimized. Based on the outputs, the presence of MCC on the surface of MOF-199 leads to improve the properties of MOF-199 and the MCC/MOF-199 has the highest sorption capacity, durability, and porosity in comparison with MCC and MOF-199. According to the validation study at the optimized conditions, the linearity for the analytes was achieved in the range from 0.1 to 200 ng mL-1 for 2-CP and 4-CP and 0.15 to 200 ng mL-1 for 2,3-DCP and 2,5-DCP with correlation coefficients between 0.9928 and 0.9965. The limits of detection calculated at S/N=3 were in the range of 0.03-0.05 ng mL-1. Besides, the relative standard deviations (RSDs) for three spiking levels (0.2, 10,100 ng mL-1) do not exceed 6.8% and extraction recoveries are between 81.0% and 88.3%. Finally, the D-μSPE-HPLC-UV method was successfully applied to the analysis of CPs in real water samples (mineral, river and wastewater samples) with good recoveries (95.8 to 99.5%) and satisfactory precisions (RSD < 6.8%).
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  19. Fulltext Low concentration of silver nanoparticles not only enhances the activity of horseradish peroxidase but alter the structure also
    Karim Z, Adnan R, Ansari MS
    PLoS One, 2012;7(7):e41422.
    PMID: 22848490 DOI: 10.1371/journal.pone.0041422
    Chemical synthesis of Ag-NPs was carried out using reduction method. The reduction mechanistic approach of silver ions was found to be a basic clue for the formation of the Ag-NPs. The nanoparticles were characterized by UV-vis, FT-IR and TEM analysis. We had designed some experiments in support of our hypothesis, "low concentrations of novel nanoparticles (silver and gold) increases the activity of plant peroxidases and alter their structure also", we had used Ag-NPs and HRP as models. The immobilization/interaction experiment had demonstrated the specific concentration range of the Ag-NPs and within this range, an increase in HRP activity was reported. At 0.08 mM concentration of Ag-NPs, 50% increase in the activity yield was found. The U.V-vis spectra had demonstrated the increase in the absorbance of HRP within the reported concentration range (0.06-0.12 mM). Above and below this concentration range there was a decrease in the activity of HRP. The results that we had found from the fluorescence spectra were also in favor of our hypothesis. There was a maximum increase in ellipticity and α-helix contents in the presence of 0.08 mM concentration of Ag-NPs, demonstrated by circular dichroism (CD) spectra. Finally, incubation of a plant peroxidase, HRP with Ag-NPs, within the reported concentration range not only enhances the activity but also alter the structure.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  20. Supramolecular phosphatases formed by the self-assembly of the bis(Zn²⁺-cyclen) complex, copper(II), and barbital derivatives in water
    Zulkefeli M, Hisamatsu Y, Suzuki A, Miyazawa Y, Shiro M, Aoki S
    Chem Asian J, 2014 Oct;9(10):2831-41.
    PMID: 25080369 DOI: 10.1002/asia.201402513
    In our previous paper, we reported that a dimeric Zn(2+) complex with a 2,2'-bipyridyl linker (Zn2L(1)), cyanuric acid (CA), and a Cu(2+) ion automatically assemble in aqueous solution to form 4:4:4 complex 3, which selectively catalyzes the hydrolysis of mono(4-nitrophenyl)phosphate (MNP) at neutral pH. Herein, we report that the use of barbital (Bar) instead of CA for the self-assembly with Zn2L(1) and Cu(2+) induces 2:2:2 complexation of these components, and not the 4:4:4 complex, to form supramolecular complex 6 a, the structure and equilibrium characteristics of which were studied by analytical and physical measurements. The finding show that 6 a also accelerates the hydrolysis of MNP, similarly to 3. Moreover, inspired by the crystal structure of 6 a, we prepared barbital units that contain functional groups on their side chains in an attempt to produce supramolecular phosphatases that possess functional groups near the Cu2(μ-OH)2 catalytic core so as to mimic the catalytic center of alkaline phosphatase (AP).
    Matched MeSH terms: Spectrophotometry, Ultraviolet
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