Ammonia, determination

Methods of EGA using selective sorption, condensation of effluent gases, infrared absorption and thermoparticulate analysis have been reviewed by Lodding [144]. The use of simple gas burette systems should not be forgotten and an Orsat gas analysis apparatus can provide useful measurements in studies of the decomposition of formates [169]. Problems have been encountered in the determination of water released Kiss et al. [170—172] have measured the formation of this compound from infrared analyses of the acetylene evolved following reaction of water with calcium carbide. Kinetic data may be obtained by wet methods ammonia, determined by titration after absorption in an aqueous solution, has been used to measure a—time values for the decomposition of ammonium salts in a fluidized bed [173],... 

The above discussion does not mean that the use of urease and subsequently the use of an ammonia electrode is not practicable for a urea determination. Unfortunately, the commercial company that produced the urea analyzer, chose a conductivity procedure, which happens to be unsuitable for the laboratory of Neonatology. Had they chosen the ammonia electrode, which happens to be a relatively good electrode, and is especially specific, since only ammonia and not potassium can pass an air space, then the instrument could have been made highly specific for urea. In this case an ammonia determination would be done initially and then subtracted by the computer, from the amount which has been generated subsequently. In any case, with present technology, sensitivity is not adequate to use less than approximately 15fil of serum. 

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. 

Haywood and Huyser s [43] study of the indophenol blue reaction for ammonia determination showed the effect of pH variation on the final colour and emphasised the necessity for the efficient buffering to obtain reproducible results. The optimum conditions found by the authors (pH 10.8 and using sodium nitroprusside) were similar to those used by Solorzano [37]. Haywood and Huyser also replaced acetone with sodium nitroprusside. 

Particularly in autoanalyser methods this wide variation in chloride content of the sample can lead to serious salt errors and, indeed, in the extreme case, can lead to negative peaks in samples that are known to contain ammonia. Salt errors originate because of the changes of pH, ionic strength and optical properties with salinity. This phenomenon is not limited to ammonia determination by autoanalyser methods it has, as will be discussed later, also been observed in the automated determination of phosphate in estuarine samples by molybdenum blue methods. 

Mertens etal. [11] and Stevens [12] designed semiautomated versions of the micro Kjeldahl which avoided the distillation step altogether. In their versions, after the digestion step the digestion solution was diluted and the ammonia determined with an ammonia probe. The limitation on the sensitivity, then, is the sensitivity of the ammonia probe. This limits the method to the more productive oceanic waters. 

Figure 5 shows that the experimental sums of ethylenediamine and ammonia formed fall below the theoretical curve during the early stages of the reaction. This discrepancy may be caused by an error in the method of ammonia determination mentioned earlier. The amount of ammonia in the gas stream coming from the reaction solution would be less than the amount of ammonia being formed in the reaction solution during the early stages of the reaction, until the reaction solution becomes saturated with ammonia. 

The phenyl azide so obtained was reacted with phenylmagnesium bromide to give diazoaminobenzene, which, in turn, was split into aniline and ammonia. Determination of the isotope content of the reaction products proved that the only linear formula that fits is that in which the extreme nitrogen is the isotope 15N ... 

Methionine and glycylmethionine interfered in the ammonia determination, and although color developed, no ammonia yields are reported for these compounds. A fine precipitate also appeared on nesslerizing some of the irradiated glycylglycine solutions, which prevented their analysis. The ammonia yields for glycine solutions were so low they were at the... 

A method [17] has been described for the determination of nitrate and nitrite nitrogen and ammonium ions in the 2 M potassium chloride extracts of moist soils. Firstly, an aliquot of the extract is made alkaline and the released ammonia determined via an ammonia-selective probe or titrimetrically. The nitrate in the ammonia-free extract is then reduced to ammonia with Devarda s alloy and the ammonia removed by distillation and determined titrimetrically. The concentration of nitrite in the extract is then determined spectrophoto-metrically as the red dye formed by coupling diazotised sulfanilic acid with N naphthylethylenediamine hydro chloride. 

This gas-phase reaction is run at less than 300°C and under 250 bar in the presence of hydrogen and nickel catalysts with various promoters such as Co, Fe, and Re. Excess ammonia determines the selectivity, and secondary reactions can give higher amines such as piperazine. One of the key advantages of this process is the absence of the chloride by-products46. 

If, however, the precipitate of diphenylurea is too small to weigh accurately, it is converted to ammonia and determined colorimetrically by the Nessler method. In this procedure, the filter paper is removed from the funnel and placed in a small beaker 4 ml. pure sulphuric acid (66° Be) are added, allowing this to flow slowly over the platinum spiral and through the funnel so as to wash off all traces of adherent precipitate. To the mixture obtained in this way 10 mgm. mercuric sulphate are added and the whole is then kept near boiling temperature for 2 hours. After allowing to cool, 20 ml. distilled water are added and the mixture is transferred to a 200-ml. flask containing 0-25 gm. sodium thiosulphate dissolved in 100 ml. water to remove the mercury. The beaker is washed with water which is added to the contents of the flask until the total volume is about 150 ml. and the ammonia determined in this. 

The determination of ammonia in blood is carried out enzymatically, which is considered to be specific, precise and simple. (48) Serious mistakes can easily occur during the preanalytical phase of ammonia determination, making it imperative to comply with the standardized method of taking a blood sample, (s. p. 91) EDTA blood should be taken with the addition of sodium borate and L-serine. Furthermore, elevated serum y-GT activity and increased thrombocytes cause the ammonia level to rise, as does cigarette smoking prior to blood collection. Even minor haemolysis (e. g. in the event of prolonged transport) will spoil the blood for ammonia determination, since the ammonia concentration of erythrocytes is three times that found in plasma. Besides these interfering factors, ammonia concentration is influenced by (7.) the metabolic performance of the urea cycle, (2.) the extrahepatic formation and elimination of ammonia, and (5.) the acid-base status. 

Thus, the enzyme can be coupled to ammonia electrodes, field effect transistors or chemical methods of ammonia determination [115]. Alternatively, a bi-enz5mie system can be applied combining glutaminase with glutamate oxidase (Eq. (11.4)) ... 

The ambient concentrations of ammonia determined at Whiteface Mountain, New York, in 1982 ranged from approximately 0.3-5 ppb, with the hourly median and mean values both determined as 2.2 ppb (Kelly et al. 1984). Ammonia concentrations in mral Thurber, Nevada, ranged from approximately 0.5 to 2 ppb (Farmer and Dawson 1982). In the atmosphere over the world s oceans, ammonia concentrations ranged from approximately 0.28 to 5.6 ppb (Georgii and Gravenhorst 1977). 

All chemical shifts expressed in ppm from liquid ammonia, determined by means of external MeNO-./Cr(acac)3. (INDO/S-SOS method) 401.6, 409.7, 374.8 and 338.7, respectively <84OMR(22)209>. Table 5 UV absorption maxima. Calculated shifts... 

Weber (1930). Weber measured the volume of ionization of several amines in aqueous solution but does not appear to have measured the volume of ionization of ammonia. To avoid using a volume of ionization of ammonia determined by others, there being oonsidetable scatter in the values, Weber s results were reduced assuming that the volume of the reaction CH NH, + CH,NH + NE, in aqueous solution is... 

MPFS analyzer for ammonia determination. MP solenoid micropump PMT photomultiplier RC reaction coil. 

T. Tsuboi, Y. Hirano, Y. Shibata, S. Motomizu, Sensitivity improvement of ammonia determination based on flow-injection indophenol spectrophotometry with manganese(II) ion as a catalyst and analysis of exhaust gas of thermal power plant. Anal. Sci. 18 (2002) 1141-1144. 

Analysis of filtered Baltic Sea samples of about 0.5 pmol/L spiked to nominally I, 2 and 3/tmol/L ammonia and analysed in three independent analytical runs resulted in a mean standard deviation of 0.092 pmol/L or 2.7 % Hansen and Johannsen, unpublished). Similar results have been reported by Riley et al. (1972) and Solorzano (1969). The recent ICES intercomparison exercise (Aminot and Kirkwood, 1995) showed an overall relative standard deviation of more than 20 %, indicating that, despite good precision of ammonia measurements within one laboratory, the inter-laboratory precision is comparatively poor. This is probably due to the ease of contamination in preparations of zero water and standards as well as in the handling of samples for ammonia determinations. 

The analysis of unfiltered samples yields the total amount of nitrogen. By subtracting the concentration of nitrate -i- nitrite and ammonia determined separately, the amount of organically bound nitrogen is obtained. 

The electrode in Figure 23-13a is a glass electrode that responds to the ammonium ion formed by the reaction shown in the upper part of Equation 23-23. The electrode in Figure 23-13b is an ammonia gas probe that responds to the molecular ammonia in equilibrium with the ammonium ion. Unfortunately, both electrodes have limitations. The glass electrode responds to all monovalent cations, and its selectivity coefficients for NHi over Na and are such that interference occurs in most biological media (such as blood). The ammonia gas probe has a different problem — the pH of the probe is incompatible with the enzyme. The enzyme requires a pH of about 7 for maximum catalytic activity, but the sensor s maximum response occurs at a pH that is greater than 8 to 9 (where essentially all of the NH4 has been converted to NH3). Thus, the sensitivity of the electrode is limited. Both limitations are overcome by use of a fixed-bed enzyme system where the sample at a pH of about 7 is pumped over the enzyme. The resulting solution is then made alkaline and the liberated ammonia determined with an ammonia gas probe. Automated instruments (see Chapter 33) based on this technique have been on the market for several years. 

Trimethylamine determination is shown schematically in Figure 34.4. It differs that system used for TVB-N and ammonia determination in that there is a third channel running through the peristaltic pump that brings FA solution into a mixing coil, where it meets the injected sample (extraction), and from there it sequesters all the non-TMA volatile bases, ammonia, and nontertiary amines in the FA prior to alkalinization. TMA is thus left as the only base diffusing across the semipermeable membrane. A similar system has been used to determine TMAO in fish extracts (Ruiz-Capillas et al., 2001a). Bromocresol purple has been assayed as an indicator for FIA determination of DMA. 

The content of free ammonia in this product is obtained from the total ammonia determined as above for ammonium bicarbonate, using 20 ml of the spirit and 50 ml of N acid, and deducting the equivalent of combined ammonia. The ammonium carbonate is determined by precipitating it as barium carbonate from 20 ml with 25 ml of N sodium hydroxide and an excess of barium chloride solution at 70°, adding, after cooling, neutral formaldehyde to fix the ammonia and titrating the excess of alkali with N acid to the grey colour of thymol blue indicator. 1 ml N = 0 04805 g... 

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