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排序方式: 共有217条查询结果,搜索用时 31 毫秒
81.
Y Abdollahi A Zakaria KA Matori K Shameli H Jahangirian M Rezayi T Abdollahi 《Chemistry Central journal》2012,6(1):100-5
ABSTRACT: BACKGROUND: The interactions of p-cresol photocatalytic degradation components were studied by response surface methodology. The study was designed by central composite design using the irradiation time, pH, the amount of photocatalyst and the p-cresol concentration as variables. The design was performed to obtain photodegradation % as actual responses. The actual responses were fitted with linear, two factor interactions, cubic and [left-to-right mark] quadratic model to select an appropriate model. The selected model was validated by analysis of variance which provided evidences such as high F-value (845.09), very low P-value (<.0.0001), non-significant lack of fit, the coefficient of R-squared (R2 = 0.999), adjusted R-squared (Radj2 = 0.998), predicted R-squared (Rpred2 = 0.994) and the adequate precision (95.94). RESULTS: From the validated model demonstrated that the component had interaction with irradiation time under 180 min of the time while the interaction with pH was above pH 9. Moreover, photocatalyst and p-cresol had interaction at minimal amount of photocatalyst (< 0.8 g/L) and 100 mg/L p-cresol. CONCLUSION: These variables are interdependent and should be simultaneously considered during the photodegradation process, which is one of the advantages of the response surface methodology over the traditional laboratory method. 相似文献
82.
Shahab Shariati Yadollah Yamini Mohammad Faraji Abolfazl Saleh 《Mikrochimica acta》2009,165(1-2):65-72
An on-line solid phase extraction method coupled to ICP-OES was developed for the simultaneous determination of Ce(III), La(III), Sm(III), Y(III), Yb(III), Dy(III), Hf(IV), Zr(IV) and Th(IV) ions in aqueous samples. The ions forming hydrophobic complexes with 3,5,7,2?,4?-pentahydroxy flavone (morin) and were retained on an octadecyl silica (C18) minicolumn. The adsorbed chelates were subsequently eluted from the column and directly transferred into the plasma with 80% (v/v) propanol:H2O solution for the simultaneous determination of the metal ions. Different parameters affecting the ICP-OES signal intensities and extraction efficiency including pH of the solution, concentration of the chelating agent, flow rate and type of the eluent, loading rate and ionic strength were evaluated and optimized. The calibration graphs were linear in the range of 0.2–100 μg L?1 and limit of detections for the extraction and determination of the ions in the aqueous sample (25 mL) were in the range 0.10–0.46 μg L?1. The enhancement factors of the method for the metal ions obtained were in the range of 23 to 242 (V Sample?=?25 mL) and the precision expressed as relative standard deviations (RSD %) was below 6.9%. Finally, the method was successfully applied to determine the target analytes in natural water samples. 相似文献
83.
A simple and reliable method is presented for the rapid extraction, separation, preconcentration, and determination of iron as its bathophenanthroline complex by the use of octadecylsilica membrane disks and spectrophotometry. We evaluted extraction efficiency, the influence of sample matrix, type and optimum amount of extractant, flow rates of sample solution and eluent, pH, amounts of bathophenanthroline and hydroxylamine hydrochloride, breakthrough volume, and limit of detection. We also studied the effects of various cationic interferences on percent recovery of iron. Complete elution of the complex from disks was obtained with a minimal amount of solvent. The limit of detection of the proposed method is 0.080 ppb. The method was applied to the recovery and determination of iron in natural waters. 相似文献
84.
Tohid Farajpour Yadollah Bayat Mahdi Abdollahi Mohammad Hosein Keshavarz 《Polymer Science Series A》2016,58(2):186-195
Effect of adding millable polyurethane as adhesion promoter to the ethylene-propylene-diene terpolymer as well as to the terpolymer modified by grafting of maleic anhydride on the adhesion between the terpolymer and polyurethane coating was studied. The results of peel test and water contact angle measurements showed that surface and bulk modification of terpolymer cause a significant improvement in its adhesion properties. The effect of the composition of the polymer blends on the loss tangent was studied to evaluate the extent of polymer compatibility and damping characteristics. Results demonstrated that modification of terpolymer with maleic anhydride can improve its compatibility with polyurethane, which was further confirmed by the results of the mechanical and morphological study. 相似文献
85.
Phase-transfer-catalyzed, highly versatile, and high-yielding protocol for the synthesis of 2,4,5-triaryl-1H-imidazoles was developed through response surface methodology (RSM). The effects of different solvents, reaction paths, and phase-transfer catalysts (PTCs) in different concentrations were envisioned. Three independent variables (catalyst, catalyst loading, and solvent volume) identified by one-factor-at-a-time (OFAT) study were screened through full factorial design at two levels. The analysis of variance results suggested the significance of catalyst PEG400 and solvent glacial acetic acid at 5 h reaction. The optimum reaction conditions suggested by the RSM were the use of PEG400 (10.61 mol%) and glacial acetic acid (10.71 mL) for 5 h cycloocondensation. The experimental yield of 4,5-diphenyl-2-nitrophenyl-1H-imidazole (97%) was in agreement with predicted yield (97.5%). 相似文献
86.
Summary Octadecyl-bonded silica membrane disks were employed for the extraction of anionic surfactants from water. Methanol was used for eluting the surfactants from the disks. Extraction efficiencies of more than 95% with relative standard deviations of less than 5% were achieved. 相似文献
87.
Yadollah Maham Tjoon T. Teng Loren G. Hepler Alan E. Mather 《Journal of solution chemistry》1994,23(2):195-205
We have measured densities of binary mixtures of water with monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) over the full range of compositions and over the temperature range from 25 to 80°C. Results of these measurements have been used in calculating excess molar volumes and partial molar volumes. Knowledge of the volumetric properties of these mixtures is useful in connection with industrial treatment of acidic gases; derived excess molar volumes and partial molar volumes can be used as a basis for understanding some of the molecular interactions in water-organic mixtures.Presented at the Symposium, 76th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65th birthday. 相似文献
88.
A simple method has been developed for rapid and selective extraction, preconcentration and determination of trace amounts of beryllium. The extraction is carried out by octadecyl silica cartridge, modified with quinalizarine as a chelating agent. The effect of different parameters, such as sample matrix, flowrates of sample solution and eluent, pH, type and least amount of eluent for elution of Be(+2) ions from cartridge, breakthrough volume and limit of detection, were evaluated. Also, the effects of various cationic and anionic interferences on percent recovery of Be(+2) were studied. Be(+2) was extracted from solution at pH 6-6.6 and was eluted from modified cartridge with 5 ml of 0.5 M HNO(3). Extraction efficiencies >99% were obtained by elution of the cartridges with minimal amount of eluent. A preconcentration factor of 200 and a detection limit of 200 ng per 1000 ml were obtained. The method was applied to the recovery and determination of Be(+2) in different water and alloy samples. 相似文献
89.
Mehdi Ashraf-Khorassani Mohsen Barzegar Yadolah Yamini 《Journal of separation science》1995,18(8):472-476
Supercritical fluid extraction was coupled directly with high performance liquid chromatograph. The system was evaluated for direct injection of supercritical CO2 and modified supercritical CO2 at high pressure and temperature onto a HPLC system with varying mobile phase compositions and flow rates. Injection of 9 μL supercritical CO2 onto the HPLC using methanol/water mobile phases from 100% methanol to 80% with a flow of 1.0 mL/min did not adversely affect the baseline of UV detector. However at higher percentages of water, CO2 solubility in the mobile phase decreased and caused baseline interferences on the UV detector. At higher HPLC mobile phase flow rates, supercritical CO2 was injected to higher percentages of water without any effect on the UV baseline. Also, increasing the extraction pressure or modifier concentration did not change the results. Separations of polynuclear aromatic hydrocarbons and linear alkenebenzene sulfonate test mixtures were obtained using on-line SFE/HPLC interfaced system. 相似文献
90.
Hassan Karami Mir Fazlollah Mousavi Yadollah Yamini Mojtaba Shamsipur 《Mikrochimica acta》2006,154(3-4):221-228
A new simple flow injection analysis (FIA) system is described for on-line preconcentration by solid phase extraction and
simultaneous determination of Hf and Zr in different samples using inductively coupled plasma atomic emission spectroscopy
with a charge coupling detector (CCD). Quinalizarin (QA) was loaded on an octadecyl silica-polyethylene mini-column for the
retention of Hf and Zr ions in complexed form. A 0.3 M ammonium acetate was used as buffer for providing suitable conditions
for complexation and increasing reproducibility. Retained ions on the solid phase were then eluted by a solution containing
3.0 M HCl and 0.5 M HNO3. In this work, for reducing bandwidths of eluted ions, elution of minicolumn was carried out from opposite direction. The
same solution was used as both carrier and eluent, in order to increase the reproducibility. The eluted ions were introduced
into the conventional nebulizer of ICP–AES instrument. Effects of different parameters, including instrumental parameters
of ICP and FIA were optimized. An enrichment factor of 330 for each analyte ion was obtained at a concentration level of 80 ppb.
The detection limits of the proposed method for Hf and Zr were 0.16 ng mL−1 and 0.04 ng mL−1 respectively. The ability of the method for the recovery of Hf and Zr ions was tested in the presence of several diverse
metal ions in a synthetic mixture and some real matrices. It was also applied to the determination of Zr and Hf ions in a
standard soil and in a standard alloy as real samples. 相似文献