Photometric detection of cyclodextrins in liquid chromatography by using iodine generated electrochemically in-situ
2005
Hiroi, Toshiya | Jin, Jiye | Takeuchi, Toyohide
A method has been developed for photometric detection of cyclodextrins (CD) in liquid chromatography using iodine (I₂) generated electrochemically in-situ. Iodide ion in the mobile phase was electrochemically oxidized to I₂ which was subsequently reacted with I⁻, in an electrochemical flow cell, forming I ₃⁻ . The absorbance of I ₃⁻ was found to be greatly enhanced when CD were present in the mobile phase. The absorbance enhancement was caused by the change in the mole fraction of I ₃⁻ , because of the inclusion reaction of I ₃⁻ with CD. On the basis of this phenomenon, CD were detected by means of a photodiode-array UV–visible detector positioned downstream of the electrochemical flow cell. The signals were found to be linearly dependent on CD concentration. Because the formation constants of I ₃⁻ with CD decrease in the order α-CD>β-CD>γ-CD, α-CD was most detectable by the method. Detection limits were 1.0 μmol L⁻¹ for α-CD, 65 μmol L⁻¹ for monoG1-β-CD, 100 μmol L⁻¹ for β-CD, and 200 μmol L⁻¹ for γ-CD.
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