HPLC with electrochemical detection

Nasr, M.M. Single-puff particle-size analysis of edbuterol metered-dose inhalers (MDIs) by high-pressure liquid chromatography with electrochemical detection (HPLC-EC). Pharm.Res., 1993,10,1381—1384... 

Fundamentally, trace analysis is possible with a range of different procedures. In the organic pollutant determination, chromatographic methods such as GC, GC-MS, HPLC and, more recently immunoassay and to a greater degree, the coupling of HPLC with electrochemical detection (HPLC-EC) (see below) take precedence (cf. )... 

Urinary creatinine can be analyzed by HPLC using a variety of columns. Detection methods include absorption, fluorescence after postcolumn derivatization, MS, and some other methods. The application of biosensors in HPLC could improve detection, and, in many cases, allows the detection of solutes otherwise undetectable by the common method. Review of the recent literature revealed that the method of choice for the measurement of creatinine has been RP-HPLC. Cg and Cig columns and UV or electrochemical detection (ED) with isocratic elution or gradient elution were mostly used. ... 

Hjemdahl, P., Daleskog, M., and Kahan, T., 1979, Determination of plasma catecholamines by HPLC with electrochemical detection comparison with a radioenzymatic method. Life Sciences 25 131-138. 

W.L. Childress, I.S. Krull and C.M. Selavka, Determination of deoxynivalenol (DON, vomitoxin) in wheat by high-performance liquid chromatography with photolysis and electrochemical detection (HPLC-hv-EC), J. Chromatogr. ScL, 1990, 28, 76-82. 

C.M. Riley, A.K. Runyan and J. Graham-Pole, Determination of doxorubicin in plasma and urine by high-perfomance liquid chromatography with electrochemical detection (HPLC-EC). Application to the clinical pharmacokinetics of doxorubicin in patients with osteogenic sarcoma. Anal. Lett., 1987, 20, 97-116. 

E.J. Eisenberg, P. Conzentino, G.G. Liversidge and K.C. Cundy, Determination of allopurinol and oxypurinol in rat plasma, intestinal wash, and bile by high-performance liquid chromatography with electrochemical detection (HPLC/EC) following automated solid phase extraction, Pharm. Res., 1991, 8, 653-655. 

Gonzalez de la Huebra, M.J., Vincent, U. and von Holst, C. (2007) Sample preparation strategy for the simultaneous determination of macrolide antibiotics in animal feeding stuffs by liquid chromatography with electrochemical detection (HPLC-ECD). J. Pham. Biomed. Anal, 43, 1628-1637. 

Chromatographic methods including thin-layer, hplc, and gc methods have been developed. In addition to developments ia the types of columns and eluents for hplc appHcations, a significant amount of work has been done ia the kiads of detectioa methods for the vitamin. These detectioa methods iaclude direct detectioa by uv, fluoresceace after post-column reduction of the quiaone to the hydroquinone, and electrochemical detection. Quantitative gc methods have been developed for the vitamin but have found limited appHcations. However, gc methods coupled with highly sensitive detection methods such as gc/ms do represent a powerful analytical tool (20). 

Therefore, hplc methods seem more effective. By usiag a combiaed uv and electrochemical detection technique (52), the gem-chlotinated cyclohexadienones, the chlorophenols, and the phenoxyphenols present ia the chlorination mixtures can be determined with great accuracy. 

Knowledge of the identity of phenolic compounds in food facilitates the analysis and discussion of potential antioxidant effects. Thus studies of phenolic compounds as antioxidants in food should usually by accompanied by the identification and quantification of the phenols. Reversed-phase HPLC combined with UV-VIS or electrochemical detection is the most common method for quantification of individual flavonoids and phenolic acids in foods (Merken and Beecher, 2000 Mattila and Kumpulainen, 2002), whereas HPLC combined with mass spectrometry has been used for identification of phenolic compounds (Justesen et al, 1998). Normal-phase HPLC combined with mass spectrometry has been used to identify monomeric and dimeric proanthocyanidins (Lazarus et al, 1999). Flavonoids are usually quantified as aglycones by HPLC, and samples containing flavonoid glycosides are therefore hydrolysed before analysis (Nuutila et al, 2002). 

The on-line measurement of reducing capacity can be performed with either a single or a series of electrochemical detectors, and linear correlations have been demonstrated between total antioxidative activities determined by the electrochemical detection and those determined by DPPH- reduction or by the ORAC assay (Guo et al, 1997 Peyrat-Maillard et al, 2000). The reducing capacity must also be quantified by post-column reactions, either with DPPH- or by the reduction of phosphomolybdenum complexes followed by UV-VIS-detection (Bandoniene and Murkovic, 2002 Cardenosa et al, 2002). A combination of HPLC and semi-automatic ORAC analysis has also been described (Caldwell, 2001). 

Whilst for the analysis of plant material for cannabinoids both GC and HPLC are commonly used, in analytical procedures the employment of GC-based methods prevails for human forensic samples. Nonetheless, the usage of HPLC becomes more and more of interest in this field especially in combination with MS [115-120]. Besides the usage of deuterated samples as internal standards Fisher et al. [121] describe the use of a dibrominated THC-COOH (see 7.5). The usage of Thermospray-MS and electrochemical detection provide good performance and can replace the still-used conventional UV detector. Another advantage in the employment of HPLC rather than GC could be the integration of SPE cartridges, which are needed for sample preparation in the HPLC-system. 

Sontag, G., Friedrich, O., Kainz, G., and Jorg, E. (1989). Determination of phenolic compounds by HPLC with electrochemical detection. Proc. EUR 5th Food Chem. Conference, Agric. Food Chem. Consum. 2, 703-707. 

Acetochlor and its metabolites are extracted from plant and animal materials with aqueous acetonitrile. After filtration and evaporation of the solvent, the extracted residue is hydrolyzed with base, and the hydrolysis products, EMA and HEMA (Figure 1), are steam distilled into dilute acid. The distillate is adjusted to a basic pH, and EMA and HEMA are extracted with dichloromethane. EMA and HEMA are partitioned into aqueous-methanolic HCl solution. Following separation from dichloromethane, additional methanol is added, and HEMA is converted to methylated HEMA (MEMA) over 12 h. The pH of the sample solution is adjusted to the range of the HPLC mobile phase, and EMA and MEMA are separated by reversed phase HPLC and quantitated using electrochemical detection. 

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. ... 

Kynaston, J. A., Fleming, S. C., Laker, M. F. and Pearson, A. D. J., Simultaneous quantification of mannitol, 3-O-methyl glucose and lactulose in urine by HPLC with pulsed electrochemical detection, for use in studies of intestinal permeability, Clin. Chem., 39, 453, 1993. 

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