Detection of Vitamin

The electrode was then modified by depositing tiny droplets of water-insoluble 1,2-dibromocyclohexane (DBCH) on the electrode. The altered voltammetry is shown in Fig. 9.11 (trace C) in the absence of vitamin B12 in solution no voltam-metric response from DBCH is seen (trace B). 

The choice of a BPPG electrode for the experiment described is partly since the material needs to be inactive with respect to the reduction of DBCH. The reduction of allylbromides has a high overpotential on carbon electrodes as compared to, say, silver electrodes. Additionally, the flat surface allows droplets of the oily DBCH to be formed on the electrode surface. 

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H Indyk. The photoinduced reduction and simultaneous fluorescence detection of vitamin K, with HPLC. J Micronutr Anal 4 61-70, 1988. 

HG Daood, PA Biacs, MA Dakar, F Hajdu. Paired-ion chromatography and photodiode-array detection of vitamin C and organic acids. J Chromatogr Sci 32 481-487, 1994. 

Terpstra M. and Gruetter R. (2004). 1H NMR detection of vitamin C in human brain in vivo. Magn Reson. Med. 51 225-229. 

Natadisastra G, Wittpenn JR, West KP Jr, Muhilal, and Sommer A (1987) Impression cytology for detection of vitamin A deficiency. Archives of Ophthalmology 105,1224-8. 

Hollis B. Detection of vitamin D and its major metabolites. In Feldman DD, Glorieux FH, Pike JW, eds. Vitamin D. New York Academic Press, 1997 587-606. 

Colombo ML, Corsini A, Mossa A, Sala L, Stanca M. Supercritical carbon dioxide extraction, fluorimetric and electochemical high performance liquid chromatographic detection of vitamin E from Hordeum vulgare L. Phytochem Anal 1998 9 192-195. 

Wang J, Xing D. Detection of vitamin C-induced singlet oxygen formation in oxidized LDL using MCLA as a chemiluminescence probe. Acta Biochim Biophys Sin 2002 34 11-5... 

Detection of vitamin A and its derivatives is most conveniently performed by monitoring fluorescence however, UV detection is also... 

H. Wei and Y. Cheng, Separation and Detection of Vitamins B1 (Thiamine), B2 (Riboflavine), B6 (Pyridoxine) and Nicotinamide in Compound Vitamin B Tablets with Use of Micellar TLC, Yaowu-Fenxi-Zazhi, 10 371 (1990). 

Wardas and Pyka separated vitamins D2, D3, acid of vitamin A, and oL-a-tocopherol by NP-TLC and RP-TLC. Vitamins D2 and D3 could not be separated by NP-TLC and RP-TLC. Eleven visualizing reagents were used for detection of vitamins on TLC plates. It was found that more advantageous visualizing effects for all investigated vitamins were... 

Fig. 118. Limit of detection of vitamin D on a 0.25 mm thick silica gel layer after spraying with SbClg-rea-gent and warming inspected in UV-light (365 nm) [8]...

Table 45. Detection of vitamin D on silica gel GF m spray reagents [8] (Layer spread 0.25 mm thick and activated)...

Haroon et al. (38) developed a dual electrode system for the detection of vitamin K compounds. The device utilized two sequential generator/detector electrodes. Vitamin K was electrolyzed at the first electrode and the reaction products were then detected electrochemically at a second electrode. The minimum mass of vitamin that they claim could be detected was 100 pg. They applied their system to the analysis of rat liver extracts and claimed it was superior in both sensitivity and specificity to the UV detector. 

Y Haroon, DS Bacon, JA Sadowski. Reduction of quinones with zinc metal in the presence of zinc ions application of post-column reactor for the fluorimetric detection of vitamin K compounds. Biomed Chromatogr 2(l) 4-8, 1987. 

The simultaneous determination of fat-soluble vitamins is possible, thus, simultaneous analysis of retinol, tocopherols, as well as other carotenoids present in milk, among other products, can be achieved by ultra-performance liquid chromatography (UPLC) with detection at 325, 292, and 450 nm, respectively. Another possibility is to select a compromise wavelength, in which the overall sensitivity is acceptable. For instance, 265 nm can be employed for the detection of vitamins E and D in foods using an RP method. In addition, the sample preparation method has to be carefully selected, given that several compounds are involved. In general, compromise conditions should be selected to have a maximum... 

MS/MS detection was shown to be a useful tool for the simultaneous determination of vitamins using stable isotope-labeled internal standards for their quantification in nutritional formulations [9]. Nevertheless, it is difficult to optimize the ionization and detection conditions, due to the different nature of the vitamins analyzed. Thus, frequently, compromise conditions have to be selected. Another critical factor for the multiple separation and detection of vitamins is the pH. In general, low pH values should be used, although the best conditions should be optimized in each... 

Chen (1965) examined several fluorescent dyes for the detection of vitamin D on thin-layer chromatograms. When the fluorescence was visualized under light having wavelengths of 365 and 254 mji, significant differences were observed in the nature of the fluorescence for a number of sterols. This method afforded a good qualitative differentia-... 

Tomcik P, Banks CE, Davies TJ et al (2004) A self-catalytic carbon paste electrode for the detection of vitamin B-12. Anal Chem 76 161-165... 

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