The determination of ammonia in boiler feed-water with an ammonium-selective glass electrode

Abstract

An investigation has been made into the accuracy of ammonium-selective (ammonium-responsive) glass electrodes for determining ammonia (10 to 1000 pgl-l) in boiler feed-water and similar high-purity water samples from power stations. The electrode potential follows the Nernst equation in samples containing up to 10 000 mg 1-1 of ammonia, the pH of which is controlled between 8.0 and 8.4 by the addition of triethanolaminehydrochloric acid buffer solution. However, interfering species in the buffer solution cause a detectable deviation from Nernstian response at low ammonia concentrations (less than 1000 pg 1-1). By use of a calomel -0.1 N hydrochloric acid reference electrode, reproducible results have been obtained in static buffered solutions containing 10 to 1000 pgl-1 of ammonia. Of the other impurities likely to be present in power-station waters only sodium caused a serious effect (100 pgl-1 of sodium is equivalent to 25 pg1-1 of ammonia). The within-batch standard deviations of analytical results were 2, 7, 17 and 33 t concentrations of 10, 100, 500 and 1000 pg 1-1 of ammonia, respect-&: &. aDetails of a recommended analytical procedure for discrete samples are given, and the application of the ammonium-selective electrode to continuous on-stream analysis is briefly discussed.* The term "static" refers throughout this paper t o the system in which the electrodes are immersed in a magnetically stirred, buffered solution of the sample contained in a polythene beaker.

Ion selective electrodes, potentiometry, and potentiometric titrations

“…The ammonia sensing electrode based on pH shift of "immobilized" NH4CI surrounding a pH sensing glass electrode has been evaluated and found numerous applications (68,180,261,353,650,1188). Ammonia can also be monitored by following the equilibrium NH4+ at fixed pH using cationic glass or neutral carrier electrodes (361,772,794). Improved or new enzyme-coupled electrodes include those for urea (397), D-amino acids and asparagine (392), 1-phenylalanine (396), glutamine (393), and penicillin (886).…”

A microfluidic chip for ammonium sensing incorporating ion-selective membranes formed by surface tension forces

“…Inspired by the rst work, the ammonium ISE was then demonstrated utilizing ammonium specic glass membrane. 6 ISE membranes can be fabricated using a variety of materials, including solids, organic liquids and polymeric lms. However, polyvinyl chloride (PVC) membranes have attracted particular attention due to their permeability, plasticity and ease of fabrication.…”

The interpretation of non-ideal calibrations of ion-selective electrodes

“…The long term stability of Ilosvay reagent also has been a major problem. This is witnessed by the fact that numerous formulations exist for Ilovsay reagent (5)(6)(7)(8)(9). Additional information has been published on the formation of copper acetylides (10) and on the copper-catalyzed oxidation of hydroxylamine (11).…”