Electrochemical detection simultaneous analysis

Lurie, I.S. McGuiness, K. The quantitation of heroin and selected basic impurities via reversed phase HPLC. II. The analysis of adulterated samples. J.Liq.Chromatogr., 1987,10, 2189-2204 [UV detection electrochemical detection simultaneous acetaminophen, acetylcodeine, acetylmorphine, acetyl-procaine, aminopyrene, amitriptyline, antipyrene, barbital, benztropine, caffeine, cocaine, codeine, diamorphine, diazepam, diphenhydramine, dipyrone, ephedrine, ethylmorphine, lidocaine, meconin, methamphetamine, methap3rrilene, methaqualone, monoacetylmorphine, morphine, nalorphine (IS), niacinamide, noscapine, papaverine, phenacetin, phenmetrazine, phenobarbital, phenolphthsdein, procaine, propanophenone, propoxyphene, pyrilamine, quinidine, quinine, salicylamide, salicylic acid, secobarbital, strychnine, tartaric acid, tetracaine, thebaine, tripelennamine, tropacocaine, vitamin Bj, vitamin B3]... 

Another recent development is the advent of pulse amperometry in which the potential is repeatedly pulsed between two (or more) values. The current at each potential or the difference between these two currents ( differential pulse amperometry ) can be used to advantage for a number of applications. Similar advantages can result from the simultaneous monitoring of two (or more) electrodes poised at different potentials. In the remainder of this chapter it will be shown how the basic concepts of amperometry can be applied to various liquid chromatography detectors. There is not one universal electrochemical detector for liquid chromatography, but, rather, a family of different devices that have advantages for particular applications. Electrochemical detection has also been employed with flow injection analysis (where there is no chromatographic separation), in capillary electrophoresis, and in continuous-flow sensors. 

Immusoft is a software that has been developed to perform computer-driven assays in our microchips. This software has a user-friendly graphical user interface, and it enables control of the pump, the valves and the electrochemical detection system, as well as the development of specific assay protocols, the running of simultaneous or sequential experiments in eight parallel microchannels, the automatic read-out of the results and the processing of the obtained data. These different functions are managed by way of three main menus, named Method, Analysis and Results, and the software also comprises two additional items dedicated to the setting of the computing parameters and to the maintenance of the instrumentation. 

Fig. 2.23 Simultaneous analysis by using electrochemical and conductivity detection. Concentrations are 300gg L 1 sulphide, 500pgL 1 cyanide, lmg...

The determination of catecholamines requires a highly sensitive and selective assay procedure capable of measuring very low levels of catecholamines that may be present. In past years, a number of methods have been reported for measurement of catecholamines in both plasma and body tissues. A few of these papers have reported simultaneous measurement of more than two catecholamine analytes. One of them utilized Used UV for endpoint detection and the samples were chromatographed on a reversed-phase phenyl analytical column. The procedure was slow and cumbersome because ofdue to the use of a complicated liquid-liquid extraction and each chromatographic run lasted more than 25 min with a detection Umit of 5-10 ng on-column. Other sensitive HPLC methods reported in the literature use electrochemical detection with detection limits 12, 6, 12, 18, and 12 pg for noradrenaline, dopamine, serotonin, 5-hydroxyindoleace-tic acid, and homovanillic acid, respectively. The method used very a complicated mobile phase in terms of its composition while whilst the low pH of 3.1 used might jeopardize the chemical stability of the column. Analysis time was approximately 30 min. Recently reported HPLC methods utilize amperometric end-point detection. 

Buu NT, Angers M, Chevalier D, Kuchel O. A new method for the simultaneous analysis of free and sulfoconjugated normetanephrine, metanephrine, and 3-methoxytyramine in human urine by HPLC with electrochemical detection. J Lab Clin Med 1984 104 425-32. 

The chlorophenols, cyclohexadienones, benzoquinones and chlorophenoxy-phenols are analysed using UV detection. Simultaneous electrochemical detection enables specific analysis of electro active compounds in reduction. 

Betto, P Meneguz, A. Ricciarello, G. Pichini, S. Simultaneous high-performance liquid chromatographic analysis of buspirone and its metabolite l-(2-pyrimidinyl)-piperazine in plasma using electrochemical detection. J.Chromatogr., 1992, 576, 117-121... 

Band, C.J. Band, P.R. Deschamps, M. Besner, J.-G. Goldman, A.J. Human pharmacokinetic study of immediate-release (codeine phosphate) and sustained-release (codeine contin) codeine. J.Clin. Pharmacol., 1994, 34, 938-943 [electrochemical detection SPE plasma ethylmorphine (IS)] Papadoyannis, I. Zotou, A. Samanidou, V. Theodoridis, G. Zougrou, F. Comparative study of different solid-phase extraction cartric es in the simultaneous RP-HPLC analysis of morphine and codeine in biological fluids. J.Liq.Chromatogn, 1993,16, 3017—3040 [simultaneous caffeine, morphine, quinine, strychnine SPE urine plasma LOD 10-20 ng/mL]... 

Heybroek, W.M. Caulfield, M. Johnston, A. Himer, P. Automatic on-line extraction coupled with electrochemical detection as an improved method for the HPLC co-analysis of codeine and morphine in plasma and gastric juice. J.Pharm.Biomed.Anal., 1990, 8, 1021-1027 Chen, Z.R. Bochner, F. Somog3d, A. Simultaneous determination of codeine, norcodeine and morphine in biological fluids by high-performance hquid chromatography with fluorescence detection. J.Chromatogr., 1989, 491, 367-378... 

Bachman, W.J. Stewart, J.T. HPLC-photolysis-electrochemical detection in pharmaceutical analysis application to the determination of spironolactone and hydrochlorothiazide in tablets. J.Chromatogr.Sci., 1990, 28, 123-128 [post-column reaction electrochemical detection tablets simultaneous spironolactone]... 

The detection and quantification of tocopherols, carotenoids, and chlorophylls in vegetable oil were effectively used for authentication pnrposes. The presence of tocopherols, carotenoids, and chlorophylls influence the oxidative stability of vegetable oils and their potential health benefits. Puspitasari-Nienaber et demonstrated the application of a rapid and reliable analysis method of direct injection of C-30 RP-NPLC with electrochemical detection for the simultaneous analysis of the above mentioned substances. Aliquots of vegetable oils were dissolved in appropriate solvents and injected directly without saponification, thus preventing sample loss or component degradation. Thus the effective separation of tocopherols, carotenoids, and chlorophylls was achieved. 

M. Chicharro, A. Zapardiel, E. Bermejo and A. Sanchez, Multiresidue analysis of pesticides in environmental waters by capillary electrophoresis using simultaneous UV and electrochemical detection. Electroanalysis, 16, 311-318, 2004. 

Yuan B, Huang J, Sun J, You T (2009) A novel technique for NACE coupled with simultaneous electrochemiluminescence and electrochemical detection for fast analysis of tertiary amines. Electrophoresis 30(3) 479-486. doi 10.1002/elps.200800253... 

Li X, Zhu D, You T (2011) Simultaneous analysis of six cardiovascular drugs by capillary electrophoresis coupled with electrochemical and electrochemiluminescence detection, using a chemometrical optimization approach. Electrophoresis 32(16) 2139-2147. doi 10.1002/elps.201100074... 

Numerous detection strategies have also been developed for biosensing applications based on combining electrochemistry with SPR detection. Although most of the combined electrochemical and SPR studies utiUzed uniform electrode surfaces with traditional SPR detection, there have been several examples of combined electrochemical systems with SPR imaging, where the optical response of various locations on the electrode surface are investigated simultaneously. Simultaneous electrochemical and SPR analysis has been extensively used in the characterization of various conducting and electroactive polymer films to provide information about polymer assembly, redox transformations, electrochemicaUy catalyzed processes and others applications [48, 49]. 

D.C. Titus, T.F. August, K.C. Yeh, R. Eisenhandler, W.F. Bayne and D.G. Musson, Simultaneous high-performance liquid chromatographic analysis of carbidopa, levodopa and 3-O-methyldopa in plasma and carbidopa, levodopa and dopamine in urine using electrochemical detection, J. Chromatogr., 1990, 534, 87-100. 

A.I. Bouquillon, D. Freeman and D.E. Moulin, Simultaneous solid-phase extrmaction and chromatographic analysis of morphine and hydromorphone in plasma by high-performance liquid chromatography with electrochemical detection, J. Chromatogr., 1992, 577, 354-357,... 

Limits of detection for absorbance detectors (325 nm) with conventional (5 qm particle size) C18 columns and methanol water mobile phases are typically 0.35 pmol (0.1 ng) at a 5 1 signal noise ratio. Even low serum retinol concentrations as found in vitamin A deficiency (0.35 to 0.7 iM, i.e., 10 to 20 Ag/dL) require sample volumes of only 1 pL Nonetheless, fiuorescence detection can give even lower limits of detection (0.07 pmol, 20 pg in tear fluid (111) 5-pL sample sizes have been used for routine plasma assays (112). Electrochemical detection has also been used for simultaneous analysis of retinol and tocopherol (113,114). Microbore columns and smaller packing particle sizes could give improved limits of detection (115,116) but require low-dispersion fittings and detector cells. The requirements for plasma retinol quantitation are not so stringent that use of these techniques has become popular. 

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