Potentiometric Detection of Carboxylic Acids, Phosphate Esters, and Nucleotides in Liquid Chromatography Using Anion-Selective Coated-Wire Electrodes

• Published in: Analytical chemistry (Washington) 2000-05, Vol.72 (9), p.2029-2034
• Main Authors: Picioreanu, S, Poels, I, Frank, J, van Dam, J. C, van Dedem, G. W. K, Nagels, L. J
• Format: Article
• Language: English
• Subjects: Algorithms; Analytical biochemistry: general aspects, technics, instrumentation; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Carboxylic Acids - chemistry; Chromatography, Liquid; Electrodes; Fundamental and applied biological sciences. Psychology; Nucleotides - chemistry; Phosphates - chemistry; Potentiometry; Reproducibility of Results
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac991294d

An all-solid-state ion-selective membrane electrode incorporating a lipophilic anion exchanger was used in a flow-through potentiometric detector for the LC determination of organic anions of biological interest. Different metabolic intermediates (mono-, di-. and tricarboxylic acids, sugar phosphates, and nucleotides) were detected sensitively after separation on a pellicular anion-exchange chromatographic column. The electrode was coated by directly casting the electroactive mixture on a glassy carbon support of 3 mm diameter and used in a wall-jet-type flow cell. The analysis conditions were optimized to obtain both efficient separation and sensitive detection. Calibration curves showed a logarithmic dependence on the injected concentration for concentrations higher than 5.0 × 10-5 M and a linear dependence for injected concentrations below this value. Under isocratic conditions, detection limits of 5.0 × 10-7 M (25 pmol) were attained when a sodium hydroxide solution was used as an eluent. No suppressor system was needed in this case. The relative standard deviation for consecutive injections was 0.3% (n = 15), and the electrode lifetime was at least 2 months. The utility of potentiometric detection is further demonstrated in a gradient elution separation for single-run analysis of a synthetic mixture of biochemical compounds containing carboxylic acids, phosphate esters, and nucleotides.