High-performance nitrate-selective electrodes containing immobilized amino acid betaines as sensors.
Ten nitrate-selective electrodes based upon rubbery membranes containing various betaine salts as sensors covalently bound to a cross-linked polystyrene-block-polybutadiene-block-polystyrene (SBS) polymer have been produced. The membranes were robust, highly selective, and effective over a pH range of 2-8. The best nitrate-selective electrode fabricated contained 10% m/m dicumyl peroxide, 40% 2-nitrophenyloctyl ether, 6.5% triallyl leucine betaine chloride and 43.5% SBS. The characteristics of this electrode were a linear Nernstian range of 1 x 10(-1) to 5 x 10(-6) mol dm(-3) NO3-, a limit of detection of 3.4 x 10(-7) mol dm(-3) NO3-, and a selectivity coefficient for nitrate against chloride, K(NO3-,Cl-)pot, of 3.4 x 10(-3). These figures represent a significant improvement on current commercial nitrate sensors. Response times were 1 min or less; stability of response and electrode lifetime in continuous use was also very satisfactory.
Le Goff
Thierry
T
Plymouth Environmental Research Centre, Department of Environmental Sciences, University of Plymouth, UK.
Braven
Jim
J
Ebdon
Les
L
Scholefield
David
D
D000596:Amino Acids / Q000032:analysis*; D001622:Betaine / Q000032:analysis*; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D009566:Nitrates / Q000032:analysis*
D000596:Amino Acids; D007202:Indicators and Reagents; D009566:Nitrates; D001622:Betaine