T. Stora et al., METAL-ION TRACE DETECTION BY A CHELATOR-MODIFIED GOLD ELECTRODE - A COMPARISON OF SURFACE TO BULK AFFINITY, Langmuir, 13(20), 1997, pp. 5211-5214
The binding of metal ions to self-assembled nitrilotriacetic acid (NTA
)-modified thioalkane monolayers was monitored by impedance spectrosco
py via a capacitance change of the blocking gold electrode. Binding to
a fluorescent NTA-derivative and the native NTA, measured in bulk by
fluorescence quenching and isothermal titration calorimetry, was deter
mined for comparison. Surface and bulk absolute dissociation constants
K-abs of metal ion-NTA complexes for these three derivatives showed n
o significant differences. Cu2+ concentrations as low as 0.5 nM (30 pp
t) could be detected by impedance spectroscopy. This concept of metal
ion trace detection might be further extended to other chelating group
s for use in future applications.