Reversed phase chromatographic separation and isolation of tautomers of naphthoquinoneoximes by HPLC. Effect of ph of mobile phase on separation of 3-chloro-2-hydroxy-4-naphthoquinone-1-oxime
2014
Shinde, Yogesh | Salunke-Gawali, Sunita
Reversed phase HPLC separation and isolation of isomers of 3-chloro-2-hydroxy-4-naphthoquinone-1-oxime was investigated. At pH 7 with acetonitrile as a mobile phase, no separation occurs. Using various buffer solutions the pH of the mobile phase was maintained and the effect was studied between pH ∼ 2.5 and ∼10.5. Two distinct peaks are observed in chromatograms in the pH range studied. These peaks are assigned to para-tautomer 3,3-chloro-2-hydroxy-4-naphthoquinone-1-oxime and ortho-tautomer 4,3-chloro-4-hydroxy-2-naphthoquinone-1-oxime. Tautomeric equilibrium was found in acidic pH of mobile phase, whereas at pH 6.8 and basic pH of mobile phase the tautomers are well separated from each other. Isolation of the tautomers was carried out by preparative HPLC technique. The solids of tautomers 3 and 4 were obtained as ammonium acetate adducts.
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