High-performance liquid chromatography coupled with electrochemical detection

Measurements of octopamine in insects have almost exclusively been made using the radioenzymatic assay. However, recent advances have now resulted in the availability of high performance liquid chromatography coupled with electrochemical detection for the measurements of catecholamines, monoamines and their metabolites (20,21 ). This technique affords the advantage of estimating several compounds simultaneously in a single sample. One may anticipate an increase in the use of this technique in the near future. 

Mesenteric effluents were collected at 1-min intervals up to 10 min during and following periarterial nerve stimulation. Coronary effluents were collected for 3 min at 15-sec intervals. In both cases samples were collected in plastic tubes containing 0.01 N perchloric acid and 0.025% EDTA, and stored at — 70°C until analysis. All samples were analyzed within 3 weeks. NE was determined by high-performance liquid chromatography coupled with electrochemical detection (Imamura et al., 1994). None of the drugs used in our experiments interfered with the NE assay. 

Gazdik, Z., O. Zitka, J. Petrlova et al. 2008. Determination of vitamin C (ascorbic acid) using high performance liquid chromatography coupled with electrochemical detection. Sensors 8 7097-7112. 

Boyer, G.L. and Goddard, G.D., High performance liquid chromatography coupled with post-column electrochemical oxidation for the detection of PSP toxins, Nat. Toxins, 7, 353, 1999. 

Imperato, A., and Di Chiara, G. Transtriatal dialysis coupled to reverse-phase high performance liquid chromatography with electrochemical detection A new method for the study of the in vivo release of endogenous dopamine and metabolites. J Neurosci A.966-911, 1984. 

Fujitomo, H., Nishino, I., Ueno, K., Umeda, T. (1993). Determination of the enantiomers of a new 1,4-dihydropyridine calcium antagonist in dog plasma by achiral/chiral coupled high-performance liquid chromatography with electrochemical detection. J. Pharm. Sci. 82, 319-322, 1300. 

Amperometric sensing of selected species in liquids is widely extended with an enormous variety of materials and applications, which include electrochemical detection coupled with high-performance liquid chromatography and flux injection analysis. In these cases, high sensitivity and high reproducibility are required. These properties are conditioned by electrode fouling associated to formation of solid deposits and adsorbates on the electrode surface. As a result, the electrode experiences memory effects with concomitant loss of analytical performance. 

Heybroek, W.M. Caulfield, M. Johnston, A. IVu-ner, 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.BiomedAnal., 1990, 8, 1021-1027 Chen, Z.R. Bochner, F. Somogyi, A. Simultaneous determination of codeine, norcodeine and morphine in biological fluids by high-performance liquid chromatography with fluorescence detection. J.Chromatogr., 1989, 491, 367-378... 

Fig. 1 Chromatograms of a standard solution of monoamine transmitters and their metabolites at (A) a poly(para-aminobenzoic acid) modified electrode and (B) a bare glassy carbon electrode. (1) Norepinephrine, (2) epinephrine, (3) dopamine, (4) 3,4-dihydroxyphenol acetic acid, (5) serotonin, (6) 5-hydroxyindole acetic acid, and (7) homovanillic acid. Source From Study on the effect of electromagnetic impulse on neurotransmitter metabolism in nerve cells by high performance liquid chromatography-electrochemical detection coupled with microdialysis, in Anal. Biochem. ...

It is practical to carry out analysis on on-line systems with two detectors. Since quantitative capabilities of UV-Vis absorption spectroscopy are typically greater than those of MS, in some protocols, UV absorption detectors are used to carry out quantitative analysis (after separation on a chromatographic column) while MS data are used for qualitative analysis (peak assignment) [3]. In one study, the effluent from a high-performance liquid chromatography (HPLC) instmment was transferred to the UV detector. After UV detection, the flow was split, and part of it was transferred to the ESI-MS system [4]. Using LC separations coupled with UV and MS is also useful in the characterization of products of electrochemical reactions, and considered complementary to on-line monitoring [5, 6]. 

Sanchez-Ortega, A. et al.. Solid-phase microextraction coupled with high performance liquid chromatography using online diode-array and electrochemical detection for the determination of fenitrothion and its main metabolites in environmental water samples, /. Chromatogr. A, 1094, 70, 2005. 

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