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1.
A novel sensitive and simple method for rapid and selective extraction, preconcentration and determination of iron (as its
bathophenanthroline complex) and copper (as its neocuproine complex) using octadecyl silica cartridges and dual wavelength
spectrophotometry is presented. The dual wavelength method (533 nm for the iron-bathophenanthroline and 454 nm for the copper-neocuproine
as the analytical wavelength) is used to eliminate spectral interferences. Extraction efficiency and the influence of flow
rates of sample solution and eluent, pH, amount of neocuproine, bathophenanthroline and hydroxylamine hydrochloride, type
and least amount of eluent for elution of iron and copper complexes from cartridge, break-through volume and limit of detection
are evaluated. The effects of various cationic and anionic interferences on percent recovery of iron and copper are also studied.
Extraction efficiencies >95% are obtained by elution of cartridges with minimal amount of organic solvent. Iron and copper
were determined in the range of 3–100 ng mL−1. The limits of detection are 0.98 and 1.13 ng mL−1 for iron and copper, respectively. The proposed method is applied successfully to the determination of both analytes in river,
tap and well water samples.
Author for correspondence. E-mail: yyamini@modares.ac.ir
Received September 18, 2002; accepted December 12, 2002
Published online May 5, 2003 相似文献
2.
Mir Ali Farajzadeh Mortaza Ebrahimi Ali Ranji Elham Feyz Vali Bejani Amir Abbas Matin 《Mikrochimica acta》2006,153(1-2):73-78
High performance liquid chromatography (HPLC) and gas chromatography (GC) are introduced for analysis of polymer lubricants
(stearamide, oleamide and erucamide). In the HPLC method, a reverse phase octadecylsilane (ODS) column along with acetonitrile/methanol
(60:40) as a mobile phase were used. Detection of analytes was performed by a UV detector at 202 nm. The analysis time was
less than 8 min. In the GC method, polar capillary column and flame ionization detector (FID) were used for separations and
detection, respectively. The analysis time by GC was longer than HPLC and was about 30 min. Limits of detection, linear range
and repeatability of both methods are similar, but determination of oleamide in real samples by HPLC method is difficult due
to complexity of the initial part of HPLC chromatogram in polyethylene samples. That problem is not observed in the GC method.
Detection limits in both methods for all analytes are lower than 0.003% which are much lower than the amount of lubricants
in commercial polymers (0.05–0.2%). 相似文献
3.
Nahid Emad 《Numerical Algorithms》1996,11(1):159-179
We make use of the Padé approximants and the Krylov sequencex, Ax,,...,A
m–1
x in the projection methods to compute a few Ritz values of a large hermitian matrixA of ordern. This process consists in approaching the poles ofR
x()=((I–A)–1
x,x), the mean value of the resolvant ofA, by those of [m–1/m]Rx(), where [m–1/m]Rx() is the Padé approximant of orderm of the functionR
x(). This is equivalent to approaching some eigenvalues ofA by the roots of the polynomial of degreem of the denominator of [m–1/m]Rx(). This projection method, called the Padé-Rayleigh-Ritz (PRR) method, provides a simple way to determine the minimum polynomial ofx in the Krylov subspace methods for the symmetrical case. The numerical stability of the PRR method can be ensured if the projection subspacem is sufficiently small. The mainly expensive portion of this method is its projection phase, which is composed of the matrix-vector multiplications and, consequently, is well suited for parallel computing. This is also true when the matrices are sparse, as recently demonstrated, especially on massively parallel machines. This paper points out a relationship between the PRR and Lanczos methods and presents a theoretical comparison between them with regard to stability and parallelism. We then try to justify the use of this method under some assumptions. 相似文献
4.
Mehrzad Mehran William J. Cooper Nahid Golkar Michael G. Nickelsen Eric R. Mittlefehldt Edward Guthrie Walter Jennings 《Journal of separation science》1991,14(11):745-750
The retention behavior of a heterogeneous group of solutes has been examined on seven different stationary phases under isothermal and temperature-programmed conditions. Both ΔHv (enthalpy of solute vaporization from the stationary phase) and ΔSv (entropy of solute vaporization from the stationary phase) values were determined for each solute – stationary phase combination under isothermal conditions. Both program rate and carrier gas velocity were shown to affect solute elution order. Unless these and other experimental factors discussed are controlled, column equivalency studies based on solute elution order have dubious value. 相似文献
5.
The partial least squares (PLS-1) calibration model based on spectrophotometric measurement, for the simultaneous determination of CN− and SCN− ions is described. The method is based on the difference in the rate of the reaction between CN− and SCN− ions with chloramine-T in a pH 4.0 buffer solution and at 30 °C. The produced cyanogen chloride (CNCl) reacts with pyridine and the product condenses with barbituric acid and forms a final colored product. The absorption kinetic profiles of the solutions were monitored by measuring absorbance at 578 nm in the time range 20-180 s after initiation of the reaction with 2 s intervals. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 31 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 10.0-900.0 and 50.0-1200.0 ng mL−1 for CN− and SCN− ions, respectively. The proposed method was successfully applied to the simultaneous determination of cyanide and thiocyanate in water samples. 相似文献
6.
7.
8.
Thermodynamic simulation of performance of a dual cycle with stroke length and volumetric efficiency
This article presents finite-time thermodynamics analysis of an irreversible air standard dual cycle. An irreversible dual cycle model which is more close to practice is established. In this model, the effects of stroke length and volume efficiency by considering the nonlinear relation between the specific heats of working fluid and its temperature, the frictional loss, the internal irreversibility, and heat transfer loss are analyzed. The results show that if compression ratio is less than certain value, the power output increases with increasing stroke length, while if compression ratio exceeds certain value, the power output first increases and then starts to decrease with increasing stroke length. With further increase in compression ratio, the increase of stroke length results in decreasing the power output. The results also show that, throughout the compression ratio range, the power output increases with the increasing volumetric efficiency. The results obtained in this study are of importance to provide good guidance for performance evaluation and improvement of practical internal combustion engines. 相似文献
9.
10.
Application of a dispersive micro‐solid‐phase extraction method for pre‐concentration and ultra‐trace determination of cadmium ions in water and biological samples
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Mohammad Behbahani Ali Veisi Fariborz Omidi Aminreza Noghrehabadi Ali Esrafili Mohammad Hossein Ebrahimi 《应用有机金属化学》2018,32(3)
A method for the trace determination of cadmium ions in water, human urine and human blood serum samples using ultrasonic‐assisted dispersive micro‐solid‐phase extraction (UA‐D‐μSPE) was developed. Silica‐coated magnetic nanoparticles were coated with polythiophene, and the resulting sorbent was characterized using thermogravimetry, differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X‐ray diffraction. Following UA‐D‐μSPE, cadmium ions were quantified using graphite furnace atomic absorption spectrometry. A Box–Behnken design was used for optimization of important sorption and desorption parameters in UA‐D‐μSPE: in the sorption step, pH of solution, sorption amount and sonication time for sorption; in the desorption step, concentration of eluent, volume of eluent and sonication time. The optimum conditions for the method were: pH of solution, 7.5; sonication time for sorption, 3 min; sorption amount, 35 mg; type and concentration of eluent, HCl and 1.1 mol l?1; volume of eluent, 360 μl; sonication time for desorption, 110 s. Under the optimized conditions the limit of detection and relative standard deviation for the detection of cadmium ions by UA‐D‐μSPE were found to be 0.8 ng l?1 and <6%, respectively. 相似文献