Measurement of acid dissociation constants and ionic mobilities of 3-nitro-tyrosine and 3-chloro-tyrosine by capillary zone electrophoresis

The ionization constant (pKa) and limiting ionic mobility of 3-chlorotyrosine (CT) and 3-nitrotyrosine (NT) were determined in capillary zone electrophoresis (CZE) in a wide pH range. Measurements were carried out in a poly(ionic liquid) (PIL) modified capillary at a low pH (1.80–4.00) and a bare fused capillary at an upper pH (3.00–11.00). Electrostatic interaction between analytes and inner wall was suppressed dramatically. Furthermore, parameters usually empirically assumed were calculated from a simple theoretical model. Besides pKa and limiting ionic mobility, diameter of the hydrated ion was calculated as well. The former were inserted into the database of Peakmaster software, whose predictions led to satisfactory agreement with experimental runs.

Graphical abstractThe dissociation constant (pKa) and limiting mobility of 3-chlorotyrosine (CT) and 3-nitrotyrosine (NT) obtained were inserted into database in Peakmaster, whose prediction led to satisfactory agreement with experimental runs.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► This article reported limiting mobilities and pKa values of 3-nitrotyrosine and 3-chlorotyrosine. ► Once tested the data in Peakmaster 5.2, satisfactory agreement with experimental results was obtained. ► The calculation was improved by a simple theoretical model instead of an empirical assumption usually used.