Copper(II) complexation properties and surfactant activity of 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid and N-(2-hydroxyethyl)piperazine-N '-2-hydroxypropanesulfonic acid pH buffers which may affect trace metal speciation in in vitro studies

• Type: Article in International Scientific Journal
• Date: 1998

Authors

Vasconcelos, MTSD (Author) Other; Azenha, MAGO (Author) Other; Almeida, CMR (Author) Other

Journal

Title: Analytical Biochemistry

Vol. 265

Pages: 193-201

ISSN: 0003-2697

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 29 Citations

Scopus - 30 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-001-6J5

DOI: 10.1006/abio.1998.2884

Abstract (EN): Disadvantages of the some zwitterionic pH buffers are (i) that they can interact with metal ions as well as protons, and (ii) that they may have a surfactant effect in chemical or in vitro biological or biochemical studies. This has to be taken into account when a buffer is selected. Here, the copper-complexing capacity and the surfactant activity of three compounds, 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO), N-(2-hydroxyethyl)piperazine-N'-(2-hydroxypropanesulfonic acid) (HEPPSO), and piperazine-Ni,N'-bis(2-ethanesulfonic acid) (Pipes), were investigated. Global stability constants (log beta(abc)) of copper(II)-buffer complexes were determined, at 25 degrees C, 0.5 M ionic strength, and at 0.8 mM buffer concentration, by pH and pCu ion-selective electrode measurements. Here, beta(abc) corresponds to the equilibrium: aCu(2+) + bL(-) + cH(+) <-> (CUaLbHc)((2a-b+c)); HL = DIPSO or HEPPSO; c: +1 = proton; -1 = hydroxide. Using SUPERQUAD constants were calculated, giving: DIPSO: log beta(110) = 5.02, log beta(120) 8.99, log beta(130) = 13.0, log beta(140) = 16.3, log beta(14-1) = 9.26, log beta(14-2) = 0.645, log beta(150) = 20.5, log beta(160) = 24.3, log beta(16-1) 16.1, log beta(16-2) = 8.98; HEPPSO: log beta(110) = 4.29, log beta(120) = 8.35, log beta(130) = 12.1, log beta(140) = 15.9, log beta(150) = 19.6, log beta(160) = 23.4, log beta(16-1) = 14.9. The pK(a) values were determined at higher buffer concentrations, giving a value 7.33 for DIPSO and 7.84 for HEPPSO at 2.0 mM buffer concentration. Effects of buffer concentration on stability and acidity constants were investigated and compared with measurements using voltammetric and potentiometric stripping analysis, confirming no copper(II) complexation by Pipes. Surfactant activities were determined using alternating current polarography, confirming marked surface activity of 10 mM of DIPSO or HEPPSO. (C) 1998 Academic Press.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9