University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Pre-column extraction

Classification: Manifold process -> Pre-column extraction

Citations 4

"Automatic Determination Of N-methylcarbamate Pesticides By Using A Liquid Liquid Extractor Derivatization Module Coupled Online To A Gas Chromatograph Equipped With A Flame Ionization Detector"
J. Chromatogr. A 1993 Volume 633, Issue 1-2 Pages 169-176
E. Ballesteros, M. Gallego and M. Valcárcel

Abstract: A continuous extraction system for the continuous introduction of carbamate pesticide derivatives into a gas-liquid chromatograph was developed. The hydrolysis products of aryl N-methylcarbamates (phenols) were extracted with or without derivatization in a continuous fashion by using ethyl acetate or acetic anhydride in n-hexane, respectively. The acetylated phenolic portion of N-methylcarbamates is highly selective, which was taken advantage of to identify six pesticides (propoxur, carbofuran, carbaryl, aminocarb, benthiocarb and methiocarb). The chromatographic responses obtained were linear between 0.2 and 160 mg/l of the different N-methylcarbamates, and the relative standard deviation was 1.9-3.9%.
Carbamates, N-methyl Pesticides GC Sample preparation Flame ionization

"Automated Determination Of Levodopa And Carbidopa In Plasma By High Performance Liquid Chromatography-electrochemical Detection Using An On- Line Flow Injection Analysis Sample Pretreatment Unit"
J. Chromatogr. B 1997 Volume 698, Issue 1-2 Pages 201-207
A. Tolokán, I. Klebovich, K. Balogh-Nemes and G. Horvai*

Abstract: An automated analytical procedure is described for the parallel determination of L-3,4-dihydroxyphenylalanine (levodopa, L-dopa, LD) and the analogous hydrazine compound carbidopa (CD) in dog plasma by ion-pair high performance liquid chromatography with electrochemical detection (HPLC-ED). After deproteinization of the plasma samples with perchloric acid the catecholamines were extracted from the supernatant by adsorption on a small column filled with alumina. The extraction and redissolution were automatically performed in a flow injection analysis unit (FIA) coupled to the HPLC system. The performance of the whole system was tested on dog plasma samples including specimens taken after oral administration of the anti-Parkinsonism drug Duellin, which is a combination tablet of levodopa and carbidopa.
l-Dopa Carbidopa Blood Plasma HPLC Electrochemical analysis Sample preparation Sample preparation

"Online Phase-transfer Catalysed Dansylation Of Phenolic Compounds Followed By Normal-phase Liquid Chromatography With Fluorescence Detection"
J. Pharm. Biomed. Anal. 1992 Volume 10, Issue 5 Pages 335-341
J. J. Halvax*, G. Wiese, W. P. Van Bennekom and A. Bult

Abstract: A study of the online phase-transfer catalyzed dansylation of phenolic compounds is presented. The extraction-dansylation is performed in the extraction coil of a home-made flow injection extraction unit. After phase separation, the organic phase is fed to a normal-phase liquid chromatographic system with fluorescence detection. Ethynyloestradiol, oestradiol and paracetamol are used as test compounds. The influence of temperature on the reaction is examined. Calibration graphs showed good linearity (r greater than 0.996) and limits of detection are satisfactory (8 x 10^-7 M for ethynyloestradiol, 2 x 10^-6 M for oestradiol and 5 x 10^-7 M for paracetamol). The method is not applicable for the assay of oxychinoline, phenylephrine and morphine.
Ethynyloestradiol Oestradiol Acetaminophen HPLC Fluorescence Sample preparation

"Aminopropyl-silica As An Advantageous Alternative To Nonpolar Sorbents For Continuous Cleanup/preconcentration Of Vitamin D-3 Metabolites"
Chromatographia 1998 Volume 47, Issue 7-8 Pages 367-372
F. Ortiz Boyer, J. M. Fernández Romero, M. D. Luque de Castro and J. M. Quesada

Abstract: A new procedure for continuous cleanup and concentration of hydroxyvitamin D3 metabolites prior to their separation by HPLC and UV-detection is reported. The process is based on the use of aminopropyl-silica as solid-phase sorbent as an alternative to the use of nonpolar sorbents. The improvement thus achieved has been tested by comparing the results with those obtained using octadecyl-C18 as non-polar sorbent. The comparison has been based on the calibration graphs (linear range, detection and quantitation limits), precision and multiple standard addition method.
Previtamin D(3) 7-Hydrocholesterol 25-Hydroxyvitamin D3 Calcitriol 24,25-Dihydroxyvitamin D3 Blood Plasma Blood Serum HPLC