Coulometric array detector

Another application utilizing the coulometric array detector is the simultaneous determination of biogenic amines, kynurenine, and indole derivatives of tryptophan. The method employed a CIS column with a phosphate-acetate mobile phase (pH 4.1) containing methanol and sodium octyl sulphonate (Vaarman et al., 2002). 

Achilli, G., Cellerino, G. P., Melzi d Eril, G. V., and Tagliaro, F. (1996). Determination of illicit drugs and related substances by high-performance liquid chromatography with an electrochemical coulometric-array detector. J. Chromatogr. A 729 273-277. 

The coulometric array detection mimics the diode array detector if two peaks are eluted together, they can be electrochemically and spectrophotometrically resolved and quantified. While a diode array detector relies on the different UV-Vis spectra of various compounds and characterizes analytes on the basis of their retention times and spectroscopic features, the coulometric array detector takes advantage of the variability of the voltammograms for diverse analytes and typifies them based on retention time and reaction potential. 

Larcher, R., Nicolini, G., Puecher, C., Bertoldi, D., Moser, S., Favaro, G. (2007). Determination of volatile phenols in wine using high-performance liquid chromatography with a coulometric array detector. Anal. Chim. Acta, 582, 55-60. 

Figure 4.24 Analysis of the four volatile phenols (VPs) in a wine sample by HPLC-Coulometric array detector using 8 electrodes...

Recently, an indirect method to measure the free radical scavenging activity of extracts and, thus, their antioxidant activity has been developed using HPLC coupled to a coulometric array detector system [61]. This was developed to characterise the overall antioxidant activity status of fruit and vegetables. A significant positive linear correlation was demonstrated between the total antioxidant activity determined by using the oxygen radical absorbance capacity assay and that measured using the electrochemical data obtained from the coulometric array detectors. 

V. Rizzo, G.M. d Eril, G. Achilli and G.P. Cellerino, Determination of neurochemicals in biological fluids by using an automated high-performance liquid chromatographic system with a coulometric array detector, J. Chromatogr., 1991, 536, 229-236. 

Coulometry has been used tor detection in liquid chromatography (Section 28C-6). A relatively recent innovation is the coulometric array detector that con-... 

Microcoulometric titration is used as the detection mode in some commercial sulfur-specific analysers. Sulfur in PP and waxes (range from 0.6 to 6 ppm S) were determined by means of an oxidative coulometric procedure [537]. The coulometric electrochemical array detector was used for determining a variety of synthetic phenolic antioxidants (PG, THBP, TBHQ, NDGA, BHA, OG, Ionox 100, BHT, DG) in food and oils [538],... 

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. 

Having optimised the efficiency of a chromatographic separation the quality of the chromatography can be controlled by applying certain system suitability tests. One of these is the calculation of theoretical plates for a column and there are two other main parameters for assessing performance peak symmetry and the resolution between critical pairs of peaks. A third performance test, the peak purity parameter, can be applied where two-dimensional detectors such as diode or coulometric array or mass spectrometry detectors are being used. The reproducibility of peak retention times is also an important parameter for controlling performance. 

The detection system consisted of a coulometric electfochemical cell preceded by a diode array detector followed in series by a fluorescence detector. 

Ferruzzi, M.G., Sander L.C., Rock C.L., and Schwartz S.J. 1998. Carotenoid determination in biological microsamples using liquid chromatography with a coulometric electrochemical array detector. Anal. Biochem. 256 74-81. 

Gamache, P.H., McCabe, D.R., Parevez, H., Parvez, S., and Acworth, I.N. 1997. The measurement of markers of oxidative damage, antioxidants and related compounds using HPLC and coulometric array analysis. In Columetric Electrode Array Detectors for HPCL (l.N. Acworth, M. Naoi, S. Parvez, and H. Parvez, eds.) pp. 91-119. VSP Publications, Zeist, The Netherlands. 

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... 

IN Acworth, M Naoi, H Parvez, S Parvez. Coulometric Electrode Array Detectors for HPLC. Utrecht, The Netherlands VSP, 1997, pp 1-382. 

Cheng, M. H., Lipsey, A. I., Lee, J., and Gamache, P. H. (1991). Automated analysis of urinary VMA, HVA, and 5-HIAA by gradient HPLC using an array of eight coulometric electrochemical detectors. Lab. Robot. Auto. 4 297-303. 

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. 

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... 

Kristal, B.S. et al., High-performance liquid chromatography separations coupled with coulometric electrode array detectors A unique approach to metabolomics, Methods Mol. Biol., 358,159, 2007. 

SPE, solid-phase extraction LLE, liquid-liquid extraction SPME, solid-phase microextraction DAD, diode-array detector CD, coulometric detector ED, electrochemical detector FD, fluorescence detector MS, mass spectrometry IT, ion trap TOP, time-of-flight. 

---