Home List of Titles Measurement of the limiting equivalent conductivities and mobilities of the most prevalent ionic species of EGTA (EGTA 2- and EGTA 3-) for use in electrophysiological experiments
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/231169
- Measurement of the limiting equivalent conductivities and mobilities of the most prevalent ionic species of EGTA (EGTA 2- and EGTA 3-) for use in electrophysiological experiments
- Keramidas, Angelo; Kuhlmann, Levin; Moorhouse, Andrew J.; Barry, Peter H.
- In many experimental biological situations, chelating agents like EGTA (ethylene glycol-bis-(β-amino-ethyl ether) N,N,N',N'-tetra-acetic acid) are commonly used to control or suppress the concentration of divalent ions like Ca 2+. The evaluation of liquid junction potentials in electrophysiological measurements, and particularly in patch-clamp situations, requires information about the ions within the solution. Where there is a significant concentration of EGTA present, it is necessary to know the values of the relative mobility of at least the most predominant ionic species of EGTA in order to complete these calculations. EGTA, with four negative charges with different pK(a)s, can therefore exist as four differently charged ions in solution (EGTA -, EGTA 2-, EGTA 3- and EGTA 4-) or as uncharged, although between pH 5.5 and 8 it is almost exclusively EGTA 2-. We have measured limiting equivalent conductivities of the most common ionic forms of EGTA (EGTA 2-and EGTA 3-) encountered at physiological pHs. These were 35.9±0.7 and 56±2.5 S cm 2 equiv -1 respectively. Their mobilities relative to K + were 0.24±0.01 for EGTA 2- and 0.25±0.01 for EGTA 3-. Thus for typical electrophysiological solutions, the contribution of EGTA to the liquid junction potential should be small (e.g. ~0.4 mV).
- Publication type
- Journal article
- Journal of Neuroscience Methods, Vol. 89, no. 1 (Jul 1999), pp. 41-47
- Publication year
- FOR Code(s)
- 1109 Neurosciences; 1702 Cognitive Sciences
- Conductivities; EGTA; Ion mobilities; Liquid junction potentials; Patch-clamp
- Publisher URL
- Copyright © 1999 Elsevier Science B.V.
- Peer reviewed