Normal-phase high-performance liquid chromatography

Shulka, High performance liquid chromatography, normal phase, reverse phase detection methodology, in New Trends in Lipid and Lipoprotein Analyses (J. L. Sebedio and E. G Perkins, eds.), AOCS Press, Champaign, IL, 1995, p. 38. 

K.-M. Chu, S.-M. Sliieh, S.-H. Wu and O. Y.-P. Hu, Enantiomeric separation of a cardiotonic agent pimobendan and its major active metabolite, UD-CG 212 BS, by coupled achiral-cliiral normal-phase high-performance liquid chromatography , 7. Chromatogr. Sci 30 171-176(1992). 

The most common approaches to sulfonylurea determinations involve high-performance liquid chromatography (HPLC). The earliest reported methods utilized normal-phase liquid chromatography (LC) with photoconductivity detection this type of detector demonstrated undesirably long equilibration times and is no longer... 

Lee, S. T. and Olesik, S. V., Normal-phase high-performance liquid chromatography using enhanced fluidity liquid mobile phases, /. Chromatogr. A, 707, 217, 1995. 

Jandera, P., Holcapek, M., Theodoridis, G. (1998). Investigation of chromatographic behavior of alcohol ethoxylate surfactants in normal-phase and reversed-phase systems using high-performance liquid chromatography-mass spectrometry. J. Chromatogr. A 813(2), 299-311. 

Enantiomers of the 8,9-dichloro-2,3,4,4 ,5,6-hexahydro-177-pyrazino[l,2-tf]quinoxalin-5-one (structure 249 Rz = R3 = Cl R1 = R4 = H) could be separated by normal-phase, chiral high-performance liquid chromatography (HPLC) with increased retention and separation factors if ethoxynonafluorobutane was used as solvent, instead of -hexane <2001JCH(918)293>. 

Ahel M, Giger W, Molnar E, Ibric S (2000) Determination of nonylphenol polyethoxylates and their lipophilic metabolites in sewage effluents by normal-phase high-performance liquid chromatography and fluorescence detection. Croat Chem Acta 73 209-227... 

Aboul-Enein and Ali [78] compared the chiral resolution of miconazole and two other azole compounds by high performance liquid chromatography using normal-phase amylose chiral stationary phases. The resolution of the enantiomers of ( )-econazole, ( )-miconazole, and (i)-sulconazole was achieved on different normal-phase chiral amylose columns, Chiralpak AD, AS, and AR. The mobile phase used was hexane-isopropanol-diethylamine (400 99 1). The flow rates of the mobile phase used were 0.50 and 1 mL/min. The separation factor (a) values for the resolved enantiomers of econazole, miconazole, and sulconazole in the chiral phases were in the range 1.63-1.04 the resolution factors Rs values varied from 5.68 to 0.32. 

Thick-layer silica gel chromatography can also be employed [7], although most separations are now accomplished by high-performance liquid chromatography. Resolution of complex mixtures often requires both normal and reverse phase modes [19]. A further dimension is added, when bioactivity is correlated with spectroscopically-monitored chromatographic profiles. 

Product ester ee was determined by isocratic normal-phase high-performance liquid chromatography using a Chiralcel OD-H (250 mm x 4.6 mm) column and a 98 % hexanes/2 % isopropanol mobile phase at 1.75 mL min and 25 °C. The undesired (/ )-ester and desired (5)-ester were quantified using their characteristic retention times of 10.3 min and 21 min respectively during elution. 

Assay of the reaction mixture. The samples were then resuspended in 1.5 mL isopropanol and assayed to determine both the yield and ee by chiral normal phase high-performance liquid chromatography (HPLC). A 250 mm x 4.6 mm Chiralpak AD-H column was used with an eluant of 95 5 heptane/ethanol, a flow rate of 3 mL min a temperature of 10 °C and a detection wavelength of 210 nm. 

Chiral analysis for ee determination was by normal-phase high-performance liquid chromatography with a Chiralcel OD-H column using 98 % hexanes/2 % 2-propanol at 1 mL min 25 °C and monitoring at 265 nm. 

Nozaki O, Ohba Y, Imai K. 1988. Determination of serum estradiol by normal-phase high-performance liquid chromatography with peroxyojalate chemiluminescence detection. Anal Chim Acta 205 255-260. 

High-performance liquid chromatography (HPLC) techniques are widely used for separation of phenolic compounds. Both reverse- and normal-phase HPLC methods have been used to separate and quantify PAs but have enjoyed only limited success. In reverse-phase HPLC, PAs smaller than trimers are well separated, while higher oligomers and polymers are co-eluted as a broad unresolved peak [8,13,37]. For our reverse-phase analyses, HPLC separation was achieved using a reverse phase. Cl8, 5 (Jtm 4.6 X 250 mm column (J. T. Baker, http //www.mallbaker.com/). Samples were eluted with a water/acetonitrile gradient, 95 5 to 30 70 in 65 min, at a flow rate of 0.8 mL/min. The water was adjusted with acetic acid to a final concentration of 0.1%. All mass spectra were acquired using a Bruker Esquire LC-MS equipped with an electrospray ionization source in the positive mode. 

Normal phase (NP) was the original mode of high-performance liquid chromatography (HPLC) reported. This uses a polar stationary phase (e.g. sihca, alumina) and non-polar mobile phase. It can also be referred to as adsorption... 

Cheynier, V. et al.. Size separation of condensed tannins by normal-phase high-performance liquid chromatography. In Methods in Enzymology, Volume 299. Oxidants and Antioxidants. Part A. (ed. L. Packer), Academic Press, San Diego, 1999, p. 178. 

Zhang Q, van der Klift EJ, Janssen HG, van Beek TA. An on-line normal-phase high performance liquid chromatography method for the rapid detechon of radical scavengers in non-polar food matrixes. Journal of Chromatography A. 2009 1216 7268-7274. 

Currently, high-performance liquid chromatography (HPLC) methods have been widely used in the analysis of tocopherols and tocotrienols in food and nutrition areas. Each form of tocopherol and tocotrienol can be separated and quantified individually using HPLC with either a UV or fluorescence detector. The interferences are largely reduced after separation by HPLC. Therefore, the sensitivity and specificity of HPLC methods are much higher than those obtained with the colorimetric, polarimetric, and GC methods. Also, sample preparation in the HPLC methods is simpler and more efficiently duplicated than in the older methods. Many HPLC methods for the quantification of tocopherols and tocotrienols in various foods and biological samples have been reported. Method number 992.03 of the AOAC International Official Methods of Analysis provides an HPLC method to determine vitamin E in milk-based infant formula. It could probably be said that HPLC methods have become dominant in the analysis of tocopherols and tocotrienols. Therefore, the analytical protocols for tocopherols and tocotrienols in this unit are focused on HPLC methods. Normal and reversed-phase HPLC methods are discussed in the separation and quantification of tocopherols and tocotrienols (see Basic Protocol). Sample... 

Development of fast, accurate, and reproducible high-performance liquid chromatography (HPLC) methods has offset the use of traditional open-column and TLC methods in modern chlorophyll separation and analysis. A number of normal and reversed-phase methods have been developed for analysis of chlorophyll derivatives in food samples (unit F4.4), with octadecyl-bonded stationary phase (C]8) techniques predominating in the literature (Schwartz and Lorenzo, 1990). Inclusion of buffer salts such as ammonium acetate in the mobile phase is often useful, as this provides a proton equilibrium suitable for ionizable chlorophyllides and pheophorbides (Almela et al., 2000). 

KC Amoldsson, P Kaufmann. Lipid class analysis by normal phase high performance liquid chromatography, development and optimization using multivariate methods. Chromatographia 38 317-324, 1994. 

PRN Carvalho, CH Collins, DB Rodriguez-Amaya. Comparison of provitamin A determination by normal-phase gravity-flow column chromatography and reversed-phase high performance liquid chromatography. Chromatographia 33 133-137, 1992. 

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