Anion-selective electrodes based on long-chain methyltrialkylammonium salts

Area of Science:

• Analytical Chemistry
• Electrochemistry
• Materials Science

Background:

• Conventional methyltridodecylammonium (MTDDA) is used in anion-selective electrodes (ISEs).
• There is a need for improved ligands in ISEs for enhanced selectivity and accuracy.
• The Hofmeister regime describes anion interactions, but deviations are observed with novel materials.

Purpose of the Study:

• To synthesize and evaluate new methyltrialkylammonium salts with longer alkyl chains (n=16, 18, 20) as ligands for ISEs.
• To assess the performance of ISEs incorporating these novel ligands for anion sensing.
• To compare the efficacy of the new ligands against the conventional MTDDA.

Main Methods:

• Synthesis of methyltrialkylammonium salts with n=16, 18, and 20.
• Fabrication of ISEs using synthesized ammonium salts and an alcoholic plasticizer.
• Characterization of ISEs' fundamental properties (slope sensitivity, impedance, time response).
• Evaluation of chloride selectivity against various anions and application in blood serum analysis.

Main Results:

• ISEs with ligands n=12, 16, and 18 demonstrated sufficient performance for practical applications.
• Ligands with n=16 and n=18 showed significantly improved chloride selectivity over lipophilic and hydrophilic anions compared to MTDDA.
• Selectivity improvement factors of 20 (n=16) and 15 (n=18) for perchlorate were observed.
• Application in blood serum chloride analysis resulted in a 2-6 fold improvement in accuracy.

Conclusions:

• Methyltrialkylammonium salts with alkyl chain lengths of n=16 and n=18 offer significant advantages over MTDDA for chloride ISEs.
• These novel ligands demonstrate enhanced selectivity and accuracy, potentially becoming new standards for chloride sensing.
• The developed ISEs show promise for reliable chloride analysis in biological samples.