Coulometric electrode array detection

Krach, C. and Sontag, G. Determination of some heterocyclic aromatic amines in soup cubes by ion-pair chromatography with coulometric electrode array detection. Anal. Chim. Acta 2000, 417, 77-83. 

Gerbl, U., Cichna, M., Zsivkovits, M., Knasmuller, S., and Sontag, G. 2004. Determination of heterocychc aromatic amines in beef extract, cooked meat and rat urine by liquid chromatography with coulometric electrode array detection. J. Chromatogr. 802 107-113. 

Nurmi, T. and Adlercreutz, H., Sensitive HPLC method for profiling phytoestrogens using coulometric electrode array detection Application to plasma analysis. Anal Biochem., 11 A, 110-117, 1999. 

Penalvo, J.L. and Nurmi, T., Application of coulometric electrode array detection to the analysis of isoflavonoids and hgnans, J. Pharm. Biomed. Anal., 41 1497, 2006. 

UV detection, diode-array detector (DAD) and fluorescence have been the detection techniques used, coupled to HPLC for the analysis of OTC. UV detection is set at 355 nm [49-51], 350 nm [40], or at 353 nm [52], Using the diode array detector [49] offers advantages that the target peak can be identified by its retention time and absorption spectrum. Compared to UV detection, fluorescence detection is generally more specific and is less interfered by other compounds in the sample matrix [51]. A HPLC method with electrochemical detection has also been suggested recently. Zhao et al. [53] described HPLC with a coulometric electrode array system for the analysis of OTC, TC, CTC, DC, and methacycline (MC) in ovine milk. An amper-ometric detection coupled with HPLC was developed by Kazemifard and Moore [54] for the determination of tetracyclines in pharmaceutical formulations. 

Many published articles on HPLC-ECD refer to the use of one of three voltammetric detectors (amperometric, coulometric, or polarographic). More detailed information on principles and techniques of various electrochemical detection modes can be obtained from the recent book, Coulometric Electrode Array Detectors for HPLC (34). There are also two electrode array detectors, the coulometric electrode array system and the CoulArray detector, currently available. Both detectors offer the qualitative data of PDA and the extreme sensitivity of ECD (34). The... 

Roy, S., Venojarvi, M., Khanna, S., and Sen, C. K. (2002). Simultaneous detection of tocopherols and tocotrienols in biological samples using HPLC-coulometric electrode array. Methods Enzymol. 352 326-332. 

Iodide in urine [39] and catecholamines [40,41] are example of analytes recently detected electrochemically and studied under IPC conditions. Pulsed amperometric detection on a gold electrode was used to detect etimicin [42] and gentamicin [43] in commercial samples, thus avoiding tedious pre-column derivatization. Heterocyclic aromatic amines in soup cubes [44] were determined by a coulometric electrode array detector, and the coulometric detection of a quinone-bearing drug candidate [45] allowed the study of electrochemical properties. 

Electrochemical detection is very sensitive for the compounds that can be oxidized or reduced at low-voltage potentials. Therefore, it could also be applied in the HPLC analysis of phenolic acids that are present in natural samples at very low concentrations. With the recent advances in electrochemical detection, multi-electrode array detection is becoming a powerful tool for detecting phenolic acids and flavonoids in a wide range of samples. The multi-channel coulometric detection system may serve as a highly sensitive way for the overall characterization of antioxidants the coulometric efficiency of each element of the array allows a complete voltametiic resolution of analytes as a function of their reaction (redox) potential. Some peaks may be resolved by the detector, even if they are unresolved when they leave the HPLC column. ... 

I. N. Acworth and M. Bowers, An Introduction to HPLC-Based Electrochemical Detection From Single Electrode to Multi-Electrode Arrays, in Coulometric Electrode Array Detectors for HPLC. Progress in HPLC-HPCE. 6, ed. I. N. Acworth, M. Naoi, S. Parvez and H. Parvez, 1997, VSP Publications, The Netherlands, pp. 3-50. 

Cullison, J.K. and Gamache, P.H. (1997) Qualitative, utility of coulometric array detection theoretical and applied aspects, in Coulometric Electrode Array Detectors in HPLC, Progress in HPLC-HPCE, vol. 6 (eds I.N. Acworth, M. Naoi, H. Parvez and S. Parvez), VSP, Zeist. 

Three Dimensional Graphs Demonstrating the Difference between Amperometric and Coulometric Detection Employing an Electrode Array Courtesy of the Analyst. 

The advent of the porous carbon electrode made coulometric detection possible and thus opened the way for an effective electrode array detector. An example of the application of the detector to monitoring... 

Multichannel electrochemical coulometric detection or coulometric array detection has been developed so that different potentials are applied on the electrodes. A number of chromatograms (8, 12, or 16) can be recorded simultaneously. Flavonoids can have several oxidation processes across the array of potentials, giving characteristic profiles for identification. Methods were developed for the... 

The use of multielectrode BCD in combination with SPE using Ci8 material and HPLC separation was described for the identification of 27 phenolic compoimds in water samples [64]. The multielectrode consisted of four coulometric array cells, each containing four electrochemical detector cells. These employed porous graphite-working sensors with palladium as reference and coimter electrodes were arranged in series after the analytical column. Tap water and mineral water were analyzed the authors reported very low detection limits for the phenols. 

Screen-printing methods have been used to fabricate a 16-electrode microwell array of carbon electrodes [30]. The polycarbonate-supported conducting tracks were sandwiched between a solid lower block and an upper block of teflon that was drilled to create microwells above each of the 16 electrodes. A silver wire, anodized in chloride, was inserted from the top to allow amperometric/coulometric measurements. This array was applied to antibiotic susceptibility testing with one strain of E. coli, using bacterial respiratory activity changes to compare responses to 17 antibiotics. The use of ferricyanide reduction (and detection by oxidation of ferrocya-nide) rather than oxygen consumption as an indicator of respiratory activity allows this method to be used with bacteria that do not respire aerobically. 

---