Home About us Contact
|
Home About us Contact | ||
|
|
||
Coexisting Substances (coexisting + substance)
Selected AbstractsRapid and sensitive determination of phosphorus-containing amino acid herbicides in soil samples by capillary zone electrophoresis with diode laser-induced fluorescence detectionELECTROPHORESIS, Issue 23 2005Eva Orejuela Abstract A straightforward and sensitive method has been developed for the analysis of phosphorus-containing amino acid herbicides (glufosinate and aminomethylphosphonic acid, the major metabolite of glyphosate) in soil samples. For this purpose, the analytical features of two indocyanine fluorescent dyes, sulfoindocyanine succinimidyl ester (Cy5) and 1-ethyl-1-[5-(N -succinimidyl-oxycarbonyl)pentyl]-3,3,3,3-tetramethyl-indodicarbocyanine chloride, as labeling reagents for the determination of these herbicides by CZE with diode LIF detection were investigated. Practical aspects related to the labeling chemistry and CZE separation showed that the two probes behave similarly, Cy5 being the best choice for the determination of these herbicides on account of its higher sensitivity. The optimum procedure includes a derivatization step of the pesticides at 25°C for 30,min and direct injection to CZE analysis, which is conducted within about 14,min using ACN in the running buffer. The lowest detectable analyte concentration ranged from 0.025 to 0.18,µg/L with a precision of 3.6,5.4%. These results indicate that indocyanine fluorescence dyes are useful as rapid and sensitive labels for the determination of these herbicides when compared with typical fluorescein dyes such as FITC and 5-(4,6-dichloro- s -triazin-2-ylamino) fluorescein, because they provide faster labeling reactions even at room temperature and the excess of reagent practically does not interfere the determination. Finally, the Cy5 method was successfully applied to soil samples without a preliminary clean-up procedure, and the herbicides were measured without any interference from coexisting substances. The recoveries of these compounds in these samples at fortification levels of 100,500,ng/g were 90,93%. [source] Spectrofluorimetric determination of vitamin B1 using horseradish peroxidase as catalyst in the presence of hydrogen peroxideLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 2 2009Mir Azam Khan Abstract In this work a new spectrofluorimetric method for the determination of vitamin B1, based on the catalytic activity of horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H2O2), has been developed. Non-fluorescent vitamin B1 was easily converted through catalytic oxidation in alkaline medium into a fluorescent compound, even without exposure to light. The linear range for vitamin B1 observed was 0.026,16.83 µg/mL (RSD = 1.75%). The correlation coefficient for the calibration curve and limit of detection were found to be 0.9964 and 0.015 µg/mL, respectively. The developed method is practical, simple, sensitive and relatively free from interference by coexisting substances and has been successfully applied for the determination of vitamin B1 in pharmaceutical preparations. Copyright © 2008 John Wiley & Sons, Ltd. [source] Square Wave Voltammetric Label-free Determination of the Natural Protein Material Silk FibroinCHINESE JOURNAL OF CHEMISTRY, Issue 11 2008Ming-Ming MA The electrochemical behavior of silk fibroin (SF) was investigated by cyclic voltammetry and square wave voltammetry in 0.01 mol/L HCl for the first time. Within the potential scan range of 0.0 to1.2 V (vs. SCE), two oxidative peaks at 0.91 V (Pa,1) and 0.43 V (Pa,2) as well as one reductive peak at 0.24 V (Pc ) were observed on cyclic voltammogram at scan rate of 0.2 V/s. The peak current of the peak Pa,1 was linear with SF concentration in the range of 5.8×10,8 to 1.1×10,6 mol/L, with the limit of detection 3.0×10,8 mol/L (S/N=3). The proposed method was of high selectivity without the interferences from the coexisting substances such as another natural protein material sericin and other small molecular substances. It was applied to the determination of SF in raw silk liquid samples without any pre-separation and pre-purification. [source] Second-order Scattering and Frequency Doubling Scattering Spectra of Thallium(III)-Methotrexate System and Its Analytical ApplicationCHINESE JOURNAL OF CHEMISTRY, Issue 9 2008Cun-Xian XI Abstract In pH 4.9 Britton-Robinson buffer solution, methotrexate (MTX) reacted with thallium(III) to form a 3:1 chelate. This resulted in great enhancement of second-order scattering (SOS) spectra and frequency doubling scattering (FDS) spectra and appearance of new SOS and FDS spectra. Their maximum wavelengths were located at 520 and 390 nm, respectively. The increments of scattering intensities (,I) were directly proportional to the concentrations of MTX in the ranges of 0.022,2.0 µg·mL,1 (SOS method) and 0.008,2.5 µg·mL,1 (FDS method). The methods exhibited high sensitivities. The detection limits for MTX were 7.4 ng·mL,1 (SOS method) and 2.3 ng·mL,1 (FDS method), respectively. The optimum conditions of the reaction, the influencing factors and the effects of coexisting substances were investigated. A highly sensitive, simple and fast method for the determination of MTX has been developed. The method can be applied satisfactorily to the determination of MTX in human serum samples. In this work, the charge distribution of MTX was calculated by a CNDO quantum chemistry method. In addition, the reaction mechanism was discussed. [source] | ||||||||||