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Highest Selectivity (highest + selectivity)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Analysis of flavonoids by CE using capacitively coupled contactless conductivity detection

ELECTROPHORESIS, Issue 5 2007
Stefan Bachmann
Abstract A CE method employing capacitively coupled contactless conductivity (C4D) compared to indirect UV-detection was developed for the analysis of phytochemically relevant flavonoids, such as 6-hydroxyflavone, biochanin A, hesperetin and naringenin. To ensure fast separation at highest selectivity, sensitivity and peak symmetry, the pH value and the concentration of the running BGE had to be optimized regarding both co- and counter-EOF mode. Optimum conditions were found to be 1.0 and 5.0,mM chromate BGE (pH,9.50) in the counter- and co-EOF mode, respectively. Validation of the established CE-C4D method pointed out to be approximately seven times more sensitive compared to indirect UV-detection applying the same conditions. The lower LOD defined at an S/N of 3:1 was found between 0.12 and 0.21,µg/mL for the analytes of interest using C4D and between 0.77 and 1.20,µg/mL using indirect UV-detection. Compared to an earlier published CE method employing direct UV-detection, C4D was found to be approximately two times more sensitive. Due to the lower baseline noise, C4D showed an excellent regression coefficient >0.99 compared to 0.93 when using indirect UV detection calibrating within a concentration range between 1 and 10,µg/mL. The influence of the sugar moiety on the conductivity of a flavonoid was studied upon the analysis of the aglycon hesperetin and the rutinosid hesperidin. The sugar moiety in hesperedin shows a higher conductivity compared to hesperetin. Finally, the optimized established CE-C4D method was applied to the determination and quantification of naringenin in Sinupret®. [source]

The Use of N -Type Ligands in the Enantioselective Liquid,Liquid Extraction of Underivatized Amino Acids

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2010
Bastiaan J. V. Verkuijl
Abstract The first palladium based extraction system using chiral N -based ligands in the enantioselective liquid,liquid extraction (ELLE) of underivatized amino acids, is presented. The system shows the highest selectivity for the ELLE of methionine with metal complexes as hosts reported to date. Furthermore, the host can be prepared in situ from commercially available compounds. The dependency of the system on parameters such as pH, organic solvent, and temperature has been established. The intrinsic selectivity was deduced by determination of the association constants of the palladium complex with the tryptophan enantiomers. [source]

Enantiomeric separation of aminoglutethimide by capillary electrophoresis using native cyclodextrins in single and dual systems

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2003
Adel M. Abushoffa
Abstract Aminoglutethimide (AGT) is one of the few examples of chiral drugs that can be enantioseparated by capillary electrophoresis using any of the three native cyclodextrins: ,-, ,-, or ,-CD. A complete resolution of the enantiomers of this compound in cationic form could be achieved with each of the three CDs, using a pH 3 phosphoric acid-triethanolamine buffer. Affinity constants for AGT enantiomers with the three native CDs were determined, confirming that the highest selectivity was given by ,-CD while the strongest complexation was obtained with ,-CD. However, an opposite affinity pattern was observed with the latter. Selectivity was lower for AGT enantiomers in dual CD systems, compared to that obtained with a single selector at its optimal concentration, which confirms that dual systems are of more limited interest when the two selectors have a similar effect on the analyte mobility. These results are in good agreement with those predicted using recently developed mathematical models. [source]

Studies on the Novel Calix [4] pyrrole and Its High Selectivity for p -Nitrophenol

CHINESE JOURNAL OF CHEMISTRY, Issue 7 2001
Xun-Cheng Su
Abstract Synthesis of novel neutral molecule receptor calix [4] pyrrole (2) from pyrrole and tropinone has been described and its ability of binding neutral molecules was tested. Spectroscopic titrations indicate that receptor 2 shows the highest selectivity for p -nitrophenol among m,o,p -nitrophenols due to the coincidence between the host's binding sites and the guest's geometry. [source]