Carotenoids electrochemical detection

Brown MJ, Ferruzzi MG, Nguyen ML, Cooper DA, Eldridge AL, Schwartz SJ and White WS. 2004. Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection. Am J Clin Nutr 80 396-403. 

All of the fat-soluble vitamins, including provitamin carotenoids, exhibit some form of electrochemical activity. Both amperometry and coulometry have been applied to electrochemical detection. In amperometric detectors, only a small proportion (usually <20%) of the electroactive solute is reduced or oxidized at the surface of a glassy carbon or similar nonporous electrode in coulometric detectors, the solute is completely reduced or oxidized within the pores of a graphite electrode. The operation of an electrochemical detector requires a semiaqueous or alcoholic mobile phase to support the electrolyte needed to conduct a current. This restricts its use to reverse-phase HPLC (but not NARP) unless the electrolyte is added postcolumn. Electrochemical detection is incompatible with NARP chromatography, because the mobile phase is insufficiently polar to dissolve the electrolyte. A stringent requirement for electrochemical detection is that the solvent delivery system be virtually pulse-free. 

Often, low levels of carotenoids in biological samples provide significant challenges in quantification by HPLC-PDA alone. Electrochemical detection (ECD) has been successful in quantifying low concentrations of carotenoids (MacCrehan and Schonberger, 1987 Finckh et ah, 1995 Yamashita and Yamamoto, 1997). More information about ECD can be found in Chapter 2. ECD has also been successful in quantifying carotenoid isomers in foods, plasma, prostate tissue, cervical tissue, and buccal mucosal cells (Ferruzzi et ah, 1998,2001 Allen et ah, 2003 Unlu et ah, 2007). Electrochemical array detection for all-irans - 3-carotene has been reported to be 10 fmol on column, which is approximately 100-1000 times more sensitive than UVA is detectors (Ferruzzi et ah, 1998). 

Finckh, B. Kontush, A. Commentz, J. Flubner, C. Burdelski, M. Kohlschiitter, A. 1995. Monitoring of ubiquinol-10, ubiquinone-10, carotenoids, and tocopherols in neonatal plasma microsamples using high-performance liquid chromatography with coulometric electrochemical detection. Anal. Biochem. 232 210-216. Fleshman, M.K. Cope, K.A. Novotny, J.A. Riedl, K. Schwartz, S.J. Jones, P.J. Baer, D.J. Harrison, E.H. 2010. Efficiency of intestinal absorption of P-carotene (BC) is not correlated with cholesterol (CHL) absorption in humans. FASEB J. 24S 539.4. 

The detection and quantification of tocopherols, carotenoids, and chlorophylls in vegetable oil were effectively used for authentication pnrposes. The presence of tocopherols, carotenoids, and chlorophylls influence the oxidative stability of vegetable oils and their potential health benefits. Puspitasari-Nienaber et demonstrated the application of a rapid and reliable analysis method of direct injection of C-30 RP-NPLC with electrochemical detection for the simultaneous analysis of the above mentioned substances. Aliquots of vegetable oils were dissolved in appropriate solvents and injected directly without saponification, thus preventing sample loss or component degradation. Thus the effective separation of tocopherols, carotenoids, and chlorophylls was achieved. 

The highest sensitivity and selectivity in vitamin E LC assays are obtained by using fluorescence or electrochemical detection. In the former, excitation at the low wavelength (205 nm) leads to improved detection limits but at the expense of selectivity, compared with the use of 295 nm. Electrochemical detection in the oxidation mode (amperometry or coulometry) is another factor 20 times more sensitive. In routine practice, however, most vitamin E assays employ the less sensitive absorbance detection at 292-295 nm (variable wavelength instrument) or 280 nm (fixed wavelength detectors). If retinol and carotenoids are included, a programmable multichannel detector, preferably a diode array instrument, is needed. As noted previously, combined LC assays for vitamins A, E, and carotenoids are now in common use for clinical chemistry and can measure about a dozen components within a 10 min run. The NIST and UK EQAS external quality assurance schemes permit interlaboratory comparisons of performance for these assays. 

Lessin WJ, Catigani GL, Schwartz SJ (1997) Quantification of cis-trans isomers of provitamin A carotenoids in fresh and processed fruits and vegetables. J Agric Food Chem 45 3728 MacCrehan WA, Schonberger E (1987) Determination of retinol, a-tocopherol, and a-carotene in serum by liquid chromatography with absorbance and electrochemical detection. Clin Chem 33 1585... 

B Finckh, A Kontush, J Commentz, C Hiibner, M Burdelski, A Kohlschiitter. Monitoring of ubiquinol-10, ubiquinone-10, carotenoids, and tocopherols in neonatal plasma microsamples using high-performance hquid chromatography with coulometric electrochemical detection. Anal Biochem 232 210-216, 1995. 

Puspitasari-Nienaber, N.L. Ferruzzi, M.G. Schwartz, S.J. 2002. Simultaneous detection of tocopherols, carotenoids, and chlorophylls in vegetable oils by direct injection C30 RP-HPLC with coulometric electrochemical array detection. J. Am. Oil Chem. Soc. 79 633 640. 

Several comprehensive reviews have been published on the existing chromatographic methods for the analysis of lipophilic antioxidants (tocopherols, tocotrienols, and carotenoids) in various sample matrices (Abidi, 2000 Aust et al., 2001) on electrochemical approaches in the sensing of natural or biological antioxidants and antioxidant capacity (mainly polyphenols and vitamins C and E) using cyclic voltammetry on flow injection analysis (FIA) with amperometric detection in food and biological samples (Blasco et al., 2007) and on chemiluminescence (CL) and fluorescence (FL) methods for the analysis of oxidative stability, antioxidant activity, and lipid hydroperoxide content in edible oils (Christodouleas et al., 2012). 

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