Surfactant-modified graphite surfaces in biological analysis: ionic strength and ion charge effects.
Previous work with rough pyrolytic graphite and glassy carbon electrodes demonstrated that surfactant assembly at these two structurally and chemically different surfaces was similar, with surfactants adsorbing head on. Improvement in response of biological molecules was attributed to the formation of a dynamic, renewable surface. Furthermore, surfactants provided a favorable hydrophobic-hydrophilic environment for the response of selected catechols. Surfactants could also be used to control selectivity if needed. In this work ionic strength and cation charge effects on response of catechols in surfactant solutions are investigated. The results illustrate the relative importance of electrostatic and hydrophobic interactions at graphite to the response of probes with combined hydrophobic and hydrophilic properties. Furthermore, the results show that although catechol-surface interactions are significantly affected by ionic strength and electrolyte charge, surfactant-surface and surfactant-probe interactions are not significantly affected, indicating that surfactants serve as an effective ionic buffer. The results presented here indicate that surfactant assembly at the surface is best at low ionic strength. These results also verify the importance of a favorable hydrophobic and hydrophilic environment to catechol response which can be provided by the surfactants when needed.
Jaramillo
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Department of Chemistry, University of Florida, Gainesville 32611-2046.
Marino
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Brajter-Toth
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D015102:3,4-Dihydroxyphenylacetic Acid / Q000737:chemistry; D004298:Dopamine / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D004573:Electrolytes; D006108:Graphite / Q000737:chemistry*; D007700:Kinetics; D009994:Osmolar Concentration; D013501:Surface-Active Agents / Q000737:chemistry*
D004573:Electrolytes; D013501:Surface-Active Agents; D015102:3,4-Dihydroxyphenylacetic Acid; D006108:Graphite; D004298:Dopamine