Ammonium ion concentration

Nitrogen compounds These also arise from both natural and synthetic sources. Thus ammonia is formed in the atmosphere during electrical storms, but increases in the ammonium ion concentration in rainfall over Europe in recent years are attributed to increased use of artiflcial fertilisers. Ammonium compounds in solution may increase the wettability of a metaland the action of ammonia and its compounds in causing season cracking , a type of stress-corrosion cracking of cold-worked brass, is well documented. 

The ammonium ion concentration may be monitored with a cation selective glass electrode or an neutral carrier based ion-selective electrode The pH may... 

Degobbis [60] studied the storage of seawater samples for ammonia determination. The effects of freezing, filtration, addition of preservatives, and type of container on the concentration of ammonium ions in samples stored for up to a few weeks were investigated. Both rapid and slow freezing were equally effective in stabilising ammonium ion concentration, and the addition of phenol as a preservative was effective in stabilising non-frozen samples for up to two weeks. 

Zhang s group [82] recently presented a novel CL sensor combined with FIA for ammonium ion determination. It is based on reaction between luminol, immobilized electrostatically on an anion-exchange column, and chlorine, electrochem-ically generated online via a Pt electrode from hydrochloric acid in a coulometric cell. Ammonium ion reacts with the chlorine and decreases the produced CL intensity. The system responds linearly to ammonium ion concentration in a range of 1.0-100 pM, with a detection limit of 0.4 pM. A complete analysis can be performed in 1 min, being satisfactorily applied to the analysis of rainwater. 

The extraliposomal ammonium ion concentration [(NH4)jJ yj ] was measured as ammonia with the ammonia electrode at pH 13.5. Under these conditions, all ammonium ions are converted to ammonia and no leakage of intraliposomal ammonium ion occurred during the measurement. For measurements of total ammonium ion plus ammonia present in both intraliposome aqueous phase and external medium ammonia [(NH4)jJ g4i y +(NH4)Jpg j ] the liposomes were sonicated under acidic conditions (pH 1.5-2.0) using the Transonic 460/H bath sonicator in sealed vials for 45 minutes. Then, in order to convert ammonium ion to ammonia, NaOH was added to bring the pH to... 

Ion chromatography is a convenient method for simultaneous determination of alkali, alkaline earth and ammonium ion concentrations in solution. The identity of the analytes is set by the retention times and quantation is carried out by a detector. Conductivity is frequently used, after chemical suppression of the eluate, by which chloride counterions were exchanged by hydroxide. UVV spectrophotometric measurement of hydroxide ions at 200 nm was proposed as an alternative method to suppressed conductivity. Both methods... 

Reflectance measurements provided an excellent means for building an ammonium ion sensor involving immobilization of a colorimetric acid-base indicator in the flow-cell depicted schematically in Fig. 3.38.C. The cell was furnished with a microporous PTFE membrane supported on the inner surface of the light window. The detection limit achieved was found to depend on the constant of the immobilized acid-base indicator used it was lO M for /7-Xylenol Blue (pAT, = 2.0). The response time was related to the ammonium ion concentration and ranged from 1 to 60 min. The sensor remained stable for over 6 months and was used to determine the analyte in real samples consisting of purified waste water, which was taken from a tank where the water was collected for release into the mimicipal waste water treatment plant. Since no significant interference fi-om acid compounds such as carbon dioxide or acetic acid was encountered, the sensor proved to be applicable to real samples after pH adjustment. The ammonium concentrations provided by the sensor were consistent with those obtained by ion chromatography, a spectrophotometric assay and an ammonia-selective electrode [269]. 

The ratio of a-D-xylopyranosyl to D-apiosyl derivatives in the reaction products with the enzyme from L. minor seems to remain constant after efficient purification of the enzyme447 or under treatment with a variety of inhibitors, but the ratio is affected by the ammonium-ion concentration.447 This suggests that the same enzyme, or closely related ones, participate in both of the reactions. A similar observation has been reported for the parsley enzyme.4473... 

The acid and base analogs of ammonia as a solvent is specified by this equilibrium as NH41 and NH inns. All substances which undergo ammonolysis and hence bring about an increase in the ammonium ion concentration yield acitl solutions Thus P S, dissolves in liquid ammonia to give an acid solution as follows. 

The intermediate portion, called the rinse, shows a maximum in ammonium ion concentration and a steadily decreasing chloride ion concentration. 

By applying the steady-state approximation to the ammonium ion concentration, we calculate the rate law... 

Urea concentration is most frequently determined during a catalytic reaction with urease (Eq. (27.1)) and subsequent measurement of ammonium ions concentration ... 

On the basis of the ion-exchange mechanism, the color change of the ionsensing film occurs according to the ammonium ion concentration change. 

Next, find the ammonium ion concentration (from NH4CI) needed to keep the hydroxide ion concentration at or below 8.4 x 10 5 M. 

Calculate the ammonia concentration and the ammonium ion concentration in each of the following solutions ... 

Thus, the ammonium ion concentration decreases at more negative potentials. Since N-H vibrations of NH are not observed under our experimental conditions, it is proposed that the decomposition reaction of ammonium ion occurs in the diffuse layer. 

Bada, J.L. and Miller, S.L., 1968a. Ammonium ion concentration in the primitive ocean. Science, 159 423—425. 

The conditional solubility product of magnesium ammonium phosphate, struvite (MgNH4P04[s)) illustrates a situation where more than one of the dissolving species is affected by solution pH. These species are the ammonium ion NH4+) and the phosphate ion (P04 ). Because an increase in pH will decrease the ammonium ion concentration and increase the phosphate ion concentration, it follows that there should be a pH value where the solubility of MgNH4p04(s) is a minimum, that is, the pH where the product [Mg +][NH4 ][P04 ] is a minimum. Where is this point ... 

Monochloramine predominates at pH >7.5, whereas dichloramine prevails down to pH 5, except at high ammonium ion concentrations, where it is destroyed by the following reaction (Fair et al., 1948) ... 

Figure 3. The model s prediction of growth-rate (solid line) dependence on ammonium-ion concentration is compared to experimental data. The data and the model predictions indicate that more than a single system is responsible for ammonium-ion uptake, assimilation, or both.

Figure 8. Transient response of the computer cell to a step-change in exterruil ammonium-ion concentration O, response to step-decrease (2.5 mg/L to 1.4 mg/L) A. response to step-increase (1.4 mg/L to 2.5 mg/L). The relative rate corresponds to the average growth rate during that cell generation.

Ion mobility spectrometers with hydrated proton ion chemistry is exquisitely sensitive to ammonia, and two teams have sought to engineer IMS-based analyzers for ammonia in water." ° " In the earlier development," ammonia was thermally purged through a silicone membrane, and the limit of detection in this approach was 1.2 mg/L. The membrane was free of memory effects, and pH was controllable and permitted determination of ammonium ion concentrations. The system was engineered to avoid biofouling. 

The strong acid concentrations agreed with the free acid concentrations within the error limits of the measurements. Thus weak acids, with the exception of carbonic acid, did not influence the pH. The weak acid concentration agreed with the ammonium ion concentrations within error limits. Other weak acids may hav been present in concentrations below the uncertainty in the NH and weak acid concentrations. The sum of unidentified acids could have been present at an average concentration of less than 5 yM. 

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