Liquid chromatography electrochemical detection

Liquid chromatography was performed on symmetry 5 p.m (100 X 4.6 mm i.d) column at 40°C. The mobile phase consisted of acetronitrile 0.043 M H PO (36 63, v/v) adjusted to pH 6.7 with 5 M NaOH and pumped at a flow rate of 1.2 ml/min. Detection of clarithromycin and azithromycin as an internal standard (I.S) was monitored on an electrochemical detector operated at a potential of 0.85 Volt. Each analysis required no longer than 14 min. Quantitation over the range of 0.05 - 5.0 p.g/ml was made by correlating peak area ratio of the dmg to that of the I.S versus concentration. A linear relationship was verified as indicated by a correlation coefficient, r, better than 0.999. 

Micellar gradient elution liquid chromatography with electrochemical detection with sodium dodecyl sulfate has been used to separate phenols [186]. 

Because of this lack of resolving power, much electroanalytical research is aimed at providing increased selectivity. This can be accomplished in two ways. First, electrochemistry can be combined with another technique which provides the selectivity. Examples of this approach are liquid chromatography with electrochemical detection (LCEC) and electrochemical enzyme immunoassay (EEIA). The other approach is to modify the electrochemical reaction at the electrode to enhance selectivity. This... 

Monitoring enzyme catalyzed reactions by voltammetry and amperometry is an extremely active area of bioelectrochemical interest. Whereas liquid chromatography provides selectivity, the use of enzymes to generate electroactive products provides specificity to electroanalytical techniques. In essence, enzymes are used as a derivatiz-ing agent to convert a nonelectroactive species into an electroactive species. Alternatively, electrochemistry has been used as a sensitive method to follow enzymatic reactions and to determine enzyme activity. Enzyme-linked immunoassays with electrochemical detection have been reported to provide even greater specificity and sensitivity than other enzyme linked electrochemical techniques. 

Kojima, T., Nishina, T., Kitamura, M., Kamatani, N. and Nishioka, K. (1989). Reversed-phase high-performance liquid-chromatography of 2,8-dihydroxyadenine in serum and urine with electrochemical detection. Clin. Chim. Acta 181, 109-114. 

Shigenaga, M.K., Park, J.W., Cundy, K.C., Cimeno, C.J. and Ames, B.N. (1990). In pim oxidative DNA damage, measurement of 8-hydroxy-2 -deoxyguanosine in DNA and urine by high-performance liquid chromatography with electrochemical detection. Meth. Enzymol. 186, 521-530. 

Long, H., Zhu, Y. X., and Kissinger, P. T. (2003). Liquid chromatography with multi-channel electrochemical detection for the determination of natural phenolic compounds. Chin. J. Anal. Chem. 31, 631-634. 

Biochemical analyses of 6-OHDA-injected animals revealed a 93 percent depletion of dopamine. The tissue was assayed using electrochemical detection following separation by high-pressure liquid chromatography (Felice et al. 1978). recorded as ng/mg protein in the nucleus accumbens and compared to control rats with sham lesions (sham=65.5 4.4, lesion=4.9 1.5 t(39)=23.4). A lesion was defined as complete if 75 percent or more of the dopamine was determined to be depleted from the nucleus accumbens compared to mean sham group values. 

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. 

High-performance liquid chromatography (HPLC) with a micellar mobile phase or with a selective pre-column or reaction detection system has also been used to determine alkylenebis(dithiocarbamaes). ° Zineb and mancozeb residues in feed were determined by ion-pair HPLC with ultraviolet (UV) detection at 272 nm. These compounds were converted to water-soluble sodium salts with ethylenediaminetetra-acetic acid (EDTA) and sodium hydroxide. The extracts were ion-pair methylated with tetrabuthylammonium hydrogensulfate (ion-pair reagent) in a chloroform-hexane solvent mixture at pH 6.5-8.S. The use of an electrochemical detector has also been reported. ... 

Caliguri, E. J, Capella, P., Bottari, L., and Mefford, I. N., High-speed microbore liquid chromatography with electrochemical detection using 3 p C18 packing, Anal. Chem., 57, 2423, 1985. 

Mishin, V. M., Koivisto, T., and Lieber, C. S., The determination of cytochrome P450 2E1 -dependent p-nitrophenol hydroxylation by high-performance liquid chromatography with electrochemical detection, Anal. Biochem., 233,212,1996. 

Figure 1 Electrochemical detection of catechol, acetaminophen, and 4-methyl catechol, demonstrating the selectivity of differential pulse detection vs. constant potential detection. (A) Catechol, (B) acetaminophen, and (C) 4-methylcatechol were separated by reversed phase liquid chromatography and detected by amperometry on a carbon fiber electrode. In the upper trace, a constant potential of +0.6 V was used. In the lower trace, a base potential of +425 mV and a pulse amplitude of +50 mV were used. An Ag/AgCl reference electrode was employed. Note that acetaminophen responds much more strongly than catechol or 4-methylcatechol under the differential pulse conditions, allowing highly selective detection. (Reproduced with permission from St. Claire, III, R. L. and Jorgenson, J. W., J. Chromatogr. Sci. 23, 186, 1985. Preston Publications, A Division of Preston Industries, Inc.)...

Wang, J., Electrochemical detection for liquid chromatography, in HPLC Detection Newer Methods, Patonay, G., Ed.,VCH Publishers, New York, 1992, chap. 5. 

Kafil, J. B., Cheng, H.-Y., and Last, T. A., Quantitation of nucleic acids at the picogram level using high-performance liquid chromatography with electrochemical detection, Anal. Chem., 58, 285, 1986. 

Mayer, W. J. and Greenberg, M. S., Determination of some carbamate pesticides by high-performance liquid chromatography with electrochemical detection, ]. Chromatogr., 208, 295, 1981. 

Vandeberg, P. J. and Johnson, D. C., Pulsed electrochemical detection of cysteine, cystine, methionine, and glutathione at gold electrodes following their separation by liquid chromatography, Anal. Chem., 65, 2713, 1993. 

Feubolt, R. and Klein, H., Determination of sulphite and ascorbic acid by high-performance liquid chromatography withe electrochemical detection,. Chromatogr., 640, 271, 1993. 

W. R. LaCourse, Pulsed Electrochemical Detection in High Performance Liquid Chromatography, John Wiley Sons, Inc., New York, NY (1997). 

In these flow systems a certain kind of separation, be it pre-concentration or a more sophisticated separation such as chromatography, of individual analyte components preceeds the detection in treating the subject we shall distinguish between the techniques for gaseous samples and those for liquid samples, while concentrating on electrochemical detection. 

ECD = electrochemical detection FID = flame ionization detector GC = gas chromatography HPLC = high performance liquid chromatography M = molar NaOH = sodium hydroxide NR = not reported rpm = revolutions per minute... 

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. 

J.H. Pei and X.Y. Li, Xanthine and hypoxanthine sensors based on xanthine oxidase immobilized on a CuPtCl6 chemically modified electrode and liquid chromatography electrochemical detection. Anal. Chim. Acta 414, 205-213 (2000). 

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