Determination of carbon-centered radicals in aqueous solution by liquid chromatography with fluorescence detection

1990 ◽  
Vol 62 (21) ◽  
pp. 2275-2283 ◽  
Author(s):  
David J. Kieber ◽  
Neil V. Blough
1994 ◽  
Vol 77 (3) ◽  
pp. 758-760
Author(s):  
Ugo R Cieri

Abstract A procedure is presented for the determination of reserpine in tablets by liquid chromatography (LC) that is a slight modification of a method presented in a previous publication. The sample is extracted with methanol, and solutions are filtered through filter paper. For LC, a 7.5 cm column is used; the mobile phase is methanol containing a small volume of an aqueous solution of the sodium salt of 1-pentanesulfonic acid. Detection is by fluorescence with 280 nm excitation and 360 nm emission. Two commercial samples containing 0.1 and 0.25 mg reserpine were analyzed. For each sample, 2 determinations were made on a ground composite. Ten tablets were also analyzed individually. A linearity study was conducted, with solutions ranging in concentration from 80 to 120% of the amount present in the reference solution.


2020 ◽  
Vol 16 (5) ◽  
pp. 748-756
Author(s):  
Mir Waqas Alam ◽  
Tentu Nageswara Rao ◽  
Yarasani Prashanthi ◽  
Vourse Sridhar ◽  
Adil Alshoaibi ◽  
...  

Background: Herbicides are very beneficial in the crop yield with the aid of controlling weeds within the agriculture, but several herbicides are chronic in soil. Objective: In this study, nanoparticles and the packages of synthesized novel silica nanoparticles were studied for the preconcentration of herbicides. Methods: These nanoparticles prepared by the Stöber mechanism were purified and functionalized. Nanoparticles thus prepared successfully were used as supporting material for the preconcentration of residues of herbicides in the water. Results: Preconcentration was achieved by preparing the silica-based solid-phase-extraction cartridges. Nanoparticles used for this purpose were within the range of 50-250 nm. An SPE cartridge was prepared by packing 200 mg of silica nanoparticle in the empty cartridge of diameter 5.5 cm and length 0.6 cm in between PTFE frits. Aqueous solutions of 0.1 μg/ml of herbicides were prepared separately, and 10 ml of the solution was passed through the cartridge at the rate of 0.2 ml/min. After passing 10 ml volume of the aqueous solution, residues adsorbed on the cartridge were eluted using 2 ml of acetonitrile. The eluate was injected to determine the herbicide residue adsorbed on the SPE cartridge. Conclusion: In the study, it was found that greater than 90% of the herbicide residues were trapped on silica nanoparticle-based SPE cartridge. An analytical method was developed for the simultaneous determination of these herbicides. The residues were quantified by LC-MS/MS with ESI mode.


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