کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10549508 | 965614 | 2005 | 7 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Determination of the dissociation constants (pKa) of secondary and tertiary amines in organic media by capillary electrophoresis and their role in the electrophoretic mobility order inversion
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی آنالیزی یا شیمی تجزیه
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چکیده انگلیسی
Non-aqueous capillary electrophoresis (NACE) may provide a selectivity enhancement in separations since the analyte dissociation constants (pKa) in organic media are different from those in aqueous solutions. In this work, we have studied the inversion in mobility order observed in the separation of tertiary (imipramine (IMI) and amitryptiline (AMI)) and secondary amines (desipramine (DES) and nortryptiline (NOR)) in water, methanol, and acetonitrile. We have determined the pKa values in those solvents and the variation of dissociation constants with the temperature. From these data, and applying the Van't Hoff equation, we have calculated the thermodynamic parameters ÎH and ÎS. The pKa values found in methanol for DES, NOR, IMI, and AMI were 10.80, 10.79, 10.38, and 10.33, respectively. On the other hand, in acetonitrile an opposite relation was found since the values were 20.60, 20.67, 20.74, and 20.81 for DES, NOR, IMI, and AMI. This is the reason why a migration order inversion is observed in NACE for these solvents. The thermodynamic parameters were evaluated and presented a tendency that can be correlated with that observed for pKa values.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Chromatography A - Volume 1068, Issue 1, 11 March 2005, Pages 99-105
Journal: Journal of Chromatography A - Volume 1068, Issue 1, 11 March 2005, Pages 99-105
نویسندگان
Marcelo Delmar Cantu, Sandro Hillebrand, Emanuel Carrilho,