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ID 114228
Title Alternative
Determination of Acid Dissociation Constants of Degradable Catecholamines by CZE
Author
Itoh, Daichi Tokushima University
Keywords
catecholamines
acid dissociation constants
capillary zone electrophoresis
degradable compounds
Content Type
Journal Article
Description
塩基性溶液中で分解性を有する4種類のカテコールアミンについて,キャピラリーゾーン電気泳動法(CZE)の電気泳動移動度の変化により酸解離定数を決定した.カテコールアミンは塩基性溶液中で分解するため,エレクトロフェログラム上で分解生成物に対応するCZEピークが検出された.泳動緩衝液のpH上昇に伴い,エレクトロフェログラム上のカテコールアミンのピーク高さは分解反応により減少したが,検出されたピークの有効電気泳動移動度を用いてカテコールアミンの酸解離定数を決定することができた.測定された有効電気泳動移動度から,ドーパミンは弱酸性〜弱塩基性pH領域で陽イオン,pH>10の塩基性pH領域で陰イオンであり,測定pH範囲では2段階で連続的に酸解離することが示唆された.CZEによる解析法は分解反応物を生成する系であっても解析が可能という特長を活用して,有効電気泳動移動度の解析によりドーパミンの酸解離定数としてpKa1=9.12±0.03,pKa2=10.85±0.16が得られた.
Description Alternative
The acid dissociation constants (pKa) of four catecholamines were determined through changes in the effective electrophoretic mobility by capillary zone electrophoresis (CZE). The catecholamines are degradable in alkaline aqueous solutions, and the CZE peaks corresponding to the degraded species from the catecholamine were detected in the electropherogram. Although the peak height of the catecholamine in the electropherogram decreased under alkaline pH conditions, the acid dissociation constants of catecholamines were determined based on the peak of the catecholamine detected. The effective electrophoretic mobility of dopamine (μeff,DA), as an example, was positive at weakly acidic to weakly alkaline pH conditions, suggesting that dopamine was positively charged by protonation. The μeff,DA value decreased with increasing pH of the separation buffer, and the value was negative at alkaline pH conditions of pH > 10; the protonated dopamine dissociates at two steps, and it becomes anionic. Two steps of the acid dissociation constants were determined through changes in the effective electrophoretic mobility; pKa1 = 9.12±0.03 and pKa2 = 10.85±0.16 were determined for dopamine.
Journal Title
BUNSEKI KAGAKU
ISSN
05251931
NCID
AA11681958
Publisher
日本分析化学会
Volume
68
Issue
11
Start Page
871
End Page
876
Published Date
2019-11-05
EDB ID
DOI (Published Version)
URL ( Publisher's Version )
FullText File
language
jpn
TextVersion
Publisher
departments
Science and Technology