Abstract
A range of ion-selective electrodes (ISEs) for the determination of nitrate has been produced based upon rubbery membranes having covalently bound betaine salt sensor molecules. The best performing electrode contained N,N,N-triallyl leucine betaine (6.5 % m/m) covalently bound to polystyrene-block-polybutadiene-block-polystyrene (SBS) (43.5% m/m), with 2-nitrophenyIoctyl ether (2-NPOE) as solvent mediator (40 % m/m) and dicumyl peroxide (DCP) as free radical initiator (10% m/m). The Nemstian slope was -59.1 mV per decade over a linear range of 1 x 10'^-5 x 10"^ mol dm'^ nitrate, a limit of detection of 0.34 pmol dm'^ nitrate and a selectivity coefiBcient for nitrate against chloride ( ^ ° N 0 3 . , CI-) of 3.4 X IQ"^. The speed of response was less than 1 minute over the linear Nerastian range. The lifetime in the laboratory exceeded 5 months with no potentiometric drift over the linear Nemstian range. Temperafure dependency (0-25°C), pH range (2-12) and a selection of interfering anions (F', CI", B r , T, SCN, CIO4", HCO3", NO2", S04^ phthalate) were studied. A field evaluation by continuous immersion in both agricultural drainage weirs and a river were undertaken. The nitrate results obtained with the ISEs compared very favourably (R^=0.99) with those obtained with a segmented-flow instmment in a concentration range 0.47-16 ppm nitrate-N. The electrodes perfonned continuously for over 5 months in mnoff water from a field and over 2 months in river water. The ISEs did not require recalibration and no deterioration in performance or fouling of the membrane surface was observed. A preliminary investigation of a phosphate ionophore based upon a heterocyclic macrocycle was also undertaken. This work, based on previous literature, resulted in a dibasic phosphate electrode having a linear Nemstian range from 3 x lO"'' to 1 x 10"^ mol dm'^, a slope of -27 mV per activity decade and a Umit of detection of 1 x 10"^ mol dm"^ HP04^".
Awarding Institution(s)
University of Plymouth
Document Type
Thesis
Publication Date
2000
Deposit Date
June 2024
Additional Links
Recommended Citation
Le Goff, T. (2000) DEVELOPMENT OF NOVEL SENSORS FOR ANIONS OF ENVIRONMENTAL INTEREST. Thesis. University of Plymouth. Available at: http://dx.doi.org/10.24382/1507
