Electrode ammonia-selective

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]. 

Ammonium chloride is analyzed by treatment with formaldehyde (neutralized with NaOH) and the product HCl formed is analyzed by titration using an acid-base color indicator such as phenolphthalein. Alternatively, it may be mixed with caustic soda solution and distdled. The distillate may be analyzed for NH3 by titration with H2SO4 or by colorimetric Nesslerization or with an ammonia-selective electrode (APHA, AWWA, WEF. 1995. Standard Methods for the Examination of Water and Wastewater. 19th ed. Washington, DC, American Pubhc Health Association). The presence of ammonia or any other ammonium compound would interfere in the test. The moisture content in NH4CI may be determined by Karl—Fischer method. 

Elemental composition Be 49.11%, N 50.89%. Analysis may be performed by treatment with HCl. The soluble BeCL solution is then measured for Be by AA or ICP techniques. The ammonia liberated is determined by titrimetry, colorimetry or by ammonia-selective electrode (see Ammonia). 

Elemental composition Na 58.93%, N 35.90%, H 5.17%. The compound may he decomposed cautiously with water (reaction is violent) under cooling to yield sodium hydroxide and ammonia. (Or it may he decomposed with anhyrous alcohol to form ammonia and sodium alcoholate. The alcoholate then may he treated with water to form sodium hydroxide). Ammonia liberated is dissolved in water and the solution is measured using an ammonia-selective electrode. Alternatively, ammonia is collected over horic acid solution containing a small quantity of methyl red indicator. The solution is titrated with a standard solution of sulfuric acid. Sodium hydroxide is measured hy titration with a standard solution of hydrochloric or sulfuric acid. 

The cation exchange capacity (CEC) of the saponite was determined from the ammonium content in solution after exchange with NaOH using an ammonia selective electrode. 

The gas-sensing electrodes also are used for the potentiometric measurement of biologically important species. An enzyme is immobilized at or near the gas probe. The gas sensor measures the amount of characteristic gas produced by the reaction of the analyzed substance with the enzyme. For example, an enzyme electrode for urea [NH2C(0)NH2] determination is constructed by the immobilization of urease onto the surface of an ammonia-selective electrode. When the electrode is inserted into a solution that contains urea, the enzyme catalyzes its conversion to ammonia ... 

Fig. 4.23. Manifolds used for speciation analysis of solid samples. (A) Mercury speciation (as Hg- and PhHgH). (B) Nitrogen speciation (as ammonia and urea). GLS gas-liquid separator, MWS microwave system, ISE ammonia-selective electrode, RE reference electrode, WB water bath thermostat. Other abbreviations as in previous figures. (Reproduced with permission of Elsevier.)...

Saliva Freeze at -20 °C for up to 2 weeks, or for 1 hour at 4 °C, or analyze immediately Membrane based ammonia- selective electrode Not reported Not reported Huizenga et al. 1994... 

Asparaginase (glutaminase) L-Asparagine+ (L-glutamine+ ) + H2O -> L-aspartate (L-glutamate ) + N H4 Leukemia Spectrophotometry, potentiometry (ammonia-selective electrode), or microcalorimetry One unit liberates 1.0 pmol of ammonia from L-asparagine (or L-glutamine) per min at pH 8.6 and 37°C... 

Ammonia-selective electrode These electrodes are electrochemical cells in which a potentiometric signal is correlated with the concentration of ammonia Chromatographic techniques Methods that involve the separation of components in a mixture e.g., gas chromatography, liquid chromatography, and ion chromatography FIA... 

Ammonia (distillation, titrimetric, ammonia-selective electrode, phenate method) nitrite (ion chromatography, colorimetric) nitrate (ultraviolet spectrophotometric screening, nitrate electrode, reduction) organic (Kjeldahl, persulfate method) lodimetric and modifications, membrane electrode Acid digestion, colorimetric methods Gravimetric, atomic absorption spectrometry, colorimetric Colorimetry, iodometric, ion-selective electrode Gravimetric, turbidimetric, colorimetric... 

Potentiometric determination using ammonia selective electrode... 

If an ammonia selective electrode is available, it can be used for measuring [ammonium]... 

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