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Voltammetric determination of dopamine in the presence of ascorbic and uric acids using partial least squares regression: determination of dopamine in human urine and plasma

100%
Bahram M., Farhadi K., Arjmand F.
Open Chemistry
|
2009
|
vol. 7
|
issue 3
524-531
EN
A new differential pulse voltammetric method for dopamine determination at a bare glassy carbon electrode has been developed. Dopamine, ascorbic acid (AA) and uric acid (UA) usually coexist in physiological samples. Because AA and UA can be oxidized at potentials close to that of DA it is difficult to determine dopamine electrochemically, although resolution can be achieved using modified electrodes. Additionally, oxidized dopamine mediates AA oxidation and the electrode surface can be easily fouled by the AA oxidation product. In this work a chemometrics strategy, partial least squares (PLS) regression, has been applied to determine dopamine in the presence of AA and UA without electrode modification. The method is based on the electrooxidation of dopamine at a glassy carbon electrode in pH 7 phosphate buffer. The dopamine calibration curve was linear over the range of 1–313 μM and the limit of detection was 0.25 μM. The relative standard error (RSE %) was 5.28%. The method has been successfully applied to the measurement of dopamine in human plasma and urine. [...]
2
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Dispersive liquid-liquid microextraction and liquid chromatographic determination of pentachlorophenol in water

100%
Farhadi K., Farajzadeh M., Matin A., Hashemi P.
Open Chemistry
|
2009
|
vol. 7
|
issue 3
369-374
EN
A simple and sensitive dispersive liquid-liquid microextraction method for extraction and preconcentration of pentachlorophenol (PCP) in water samples is presented. After adjusting the sample pH to 3, extraction was performed in the presence of 1% W/V sodium chloride by injecting 1 mL acetone as disperser solvent containing 15 μL tetrachloroethylene as extraction solvent. The proposed DLLME method was followed by HPLC-DAD for determination of PCP. It has good linearity (0.994) with wide linear dynamic range (0.1–1000 μg L−1) and low detection limit (0.03 μg L−1), which makes it suitable for determination of PCP in water samples. [...]
3
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Simultaneous kinetic spectrophotometric determination of Cu(II), Co(II) and Ni(II) using partial least squares (PLS) regression

88%
Bahram M., Farhadi K., Afkhami A., Shokatynia D., Arjmand F.
Open Chemistry
|
2009
|
vol. 7
|
issue 3
375-381
EN
A partial least squares (PLS-1) calibration model based on kinetic-spectrophotometric measurement, for the simultaneous determination of Cu(II), Ni(II) and Co(II) ions is described. The method was based on the difference in the rate of the reaction between Co(II), Ni(II) and Cu(II) ions with 1-(2-pyridylazo)2-naphthol in a pH 5.8 buffer solution and in micellar media at 25°C. The absorption kinetic profiles of the solutions were monitored by measuring the absorbance at 570 nm at 2 s intervals during the time range of 0–10 min after initiation of the reaction. The experimental calibration matrix for the partial least squares (PLS-1) model was designed with 30 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 0.1-2 μg mL−1 for each cation. The proposed method was successfully applied to the simultaneous determination of Cu(II), Ni(II) and Co(II) ions in water and in synthetic alloy samples. [...]
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