Amperometric detection vitamins

Amperometric detection in the oxidative mode produced on-column detection limits of 0.07, 4.3, and 0.19 ng for retinol, vitamin D3, and a-tocopherol, respectively (143). A limitation of amperometric detection in vitamin E assays is that it cannot measure a-tocopheryl acetate, owing to the absence of the oxidizable hydroxyl group. 

Fig. 10 HPLC chromatograms of supercritical fluid extracts of (A) an unfortified wheat sample and (B) a vitamin A-fortified bran-based ready-to-eat breakfast cereal. Column, 5-/rm Altex C8 (octyl) (150 X 4.6-mm ID) mobile phase, acetonitrile/2-propanol/aqueous 25 mM sodium perchlorate (45 45 10), 2.0 ml/min amperometric detection (oxidative mode), glassy carbon electrode, +1.2 V, vs saturated calomel electrode. Peak (1) retinyl palmitate. (Reprinted from Ref. 90, Copyright 1997, with the kind permission of Elsevier Science-NL, Sara Burgerhartstraat 25, 1055 KV Amsterdam, The Netherlands.)...

MM Delgado Zamarreno, A Sanchez Perez, MC Gomez Perez, MA Fernandez Moro, J Hernandez Mendez. Determination of vitamins A, E and K, in milk by high-performance liquid chromatography with dual amperometric detection. Analyst 120 2489-2492, 1995. 

J. P. Hart, M. D. Norman, and C. J. Lacey, Voltammetric behavior of vitamins D2 and D3 at a glassy carbon electrode and their determination in pharmaceutical products by using liquid chromatography with amperometric detection, Analyst, 777 1441 (1992). 

Iodide in vitamin tablets can be found by amperometric detection [88]. Nonaqueous eluents of methanol-containing ammonium perchlorate, which are relatively oxidant resistant, have been used in conjunction with a silica column to detect a wide range of drugs [89]. The use of higher potentials not possible in totally aqueous mobile phases allows for the detection of secondary and tertiary aliphatic amines 462 drugs have been detected in this manner. For compounds that are not electroactive, a procedure using a postcolumn photolysis can generate electroactive species [90] for penicillins [91], proteins [92], and barbiturates [93]. 

B Yang, J Mo, X Yang, L Wang. Separation and determination of chlorphenamine maleate, acetaminophen and vitamin C of cold medicines by capillary electrophoresis with amperometric detection. Sepu 17 477-479, 1999. 

In amperometric detection, initially the naphthoquinone nucleus of the K vitamins has been reduced to the corresponding hydroquinone by applying a sufficiently... 

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). 

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. 

The concentration of sulfite in wine is expected to be in the low ppm range however, the sample matrix includes a wide variety of materials including several carboxylic acids, ethanol, sugars, and many other components. A search of the literature for sulfite determinations by ion chromatography yielded several references [1-22] describing a variety of separation methods, matrixes, and detection methods. Detection methods included ICP-AE [1], amperometric [3,5,9] refractive index [17], fluoro-metric [8,14] UV [12] and other methods. The sample type ranged from vitamins... 

The reduction of benzyl bromide mediated by vitamin B12r, CoTSPc, and Co(salem) in a microemulsion under homogeneous conditions, resulted in products derived from the resulting radicals and anions . The reactions were mediated by Co species . Priyantha and Tambalo employed GCE coated with Co TPP or Ee TPP as electrocatalytic amperometric sensors for the detection of herbicides including 2,3-dichlorophenoxyacetic acid ... 

Li, G Fan, C. and Xing, C. (1997) Preliminary study on separation of three vitamins by capillary zone electrophoresis and micellar electrokinetic chromatography with amperometric electrochemical detection. Se Pu, 15, 65-66. 

Hu, Q., Zhou, T.S., Zhang, L. etal. (2001) Separation and determination of three water-soluble vitamins in pharmaceutical preparations and food by micellar electrokinetic chromatography with amperometric electrochemical detection. Anal Chim. Acta, 437, 123-129. 

Z Liu, T Li, J Li, E Wang. Detection of menadione sodium bisulfite (vitamin Kj) by reversed-phase high performance liquid chromatography with series dual-electrode amperometric detector. Anal Chim Acta 338 57-62, 1997. 

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