Ammonia, interference

Note Ammonia interferes with the reaction and must be removed from the layer completely before appUcation of the reagent. 

Ammonia. Ammonia interferes with existing acid gas removal processes because it can pass on through the scrubbers and then solidify on cyrogenic surfaces or it can go with the acid gases and poison the sulfur conversion catalysts. If ammonia is absorbed into an aqueous stream, then this aqueous stream must be... 

Ferretti, J.A., Calesso, D.F. and Hermon, T.R. (2000). Evaluation of methods to remove ammonia interference in marine sediment toxicity tests. Environmental Toxicology and Chemistry 19, pp. 1935-1941. 

This method can measure the concentration of NH3-N in water in the range 0.03 to 1400 mg/L. Color and turbidity do not affect the measurement. Distillation of sample, therefore, is not necessary. High concentration of dissolved solids in the sample, however, can cause error. Also, certain complex forming ions, such as mercury or silver, which form complex with ammonia, interfere with the test. Presence of amines in the sample can give high value. 

Petty et al. (29) developed an FI A procedure for the determination of total amino acids in seawater. Total dissolved amino acids can be determined with a detection limit of 0.01 yM and a sampling rate of 150 per hour with the manifold shown in Figure 8. The amino acids are determined as fluorescent isoindoles (41), which are formed by reaction of primary amines with 1,2-benzenedicarbaldehyde (o-phthaldialdehyde) and mer-captoethanol. The fluorescence quantum yields of the isoindoles formed from most amino acids are similar 41, 42), and the sensitivity of the FI A analysis is similar for most amino acids (29). Ammonia also forms a fluorescent product with 1,2-benzenedicarbaldehyde, but its fluorescence quantum yield is about a factor of 15 lower (29, 42). The ammonia interference is low, therefore, in most areas of the ocean. 

Sodium benzoate decreased urea production in ammonia challenged rats (Maswoswe et al. 1986) and hyperammonemic mice (O Connor et al. 1987). Valproate, a widely used antiepileptic dmg, has a hyperammonemic effect in Wistar rats (Ferrier et al. 1988) and may therefore predispose to ammonia intoxication. Ammonia interferes with the metabolism of pent-4-enoic acid in cultured rat hepatocytes and may dramatically potentiate its toxicity (Coude and Grimber 1984). 

Fluorescamine (Udenfriend et al., 1972 Weigele et al., 1972) was adapted for use with seawater samples by North (1975), Packard and Dortch (1975) and Zika (1977). It may be employed to make some distinction between free amino acids and peptides or proteins by changing the reaction pH from 9.0 to 7.0, respectively. The reaction takes place at room temperature with only low ammonia interference. On the other hand, fluorescamine is unstable in aqueous solutions and the relative fluorescence intensities for the various amino acids vary over a wide range (Zika, 1977). 

Stabilized protein bands are excised and hydrolyzed in constant-boiling hydrochloric acid containing thioglycolic acid. The hydrolysate is evaporated, and the residue is dissolved and used for amino acid analysis. This procedure has not been highly successful with conventional amino acid analyzers, mainly because of the large amounts of ammonia released from the gel during hydrolysis. The ammonia interferes with the analysis of lysine and histidine by both ninhydrin and o-phthalaldehyde. Fluorescamine yields low fluorescence with ammonia, and, although an ammonia peak appears, it does not interfere with the analysis of the basic amino acids. 

Ammonia interferes in the determination. However, its equivalent signal is a mere 5 % of the glycine response over the entire linear range of the method. If necessary, a correction may be applied after parallel determinations of the ammonia content (see Chapter 10). Samples with primary amine concentrations exceeding the linear range, e.g., from anoxic pore... 

Sulfide, cyanide, and ammonia interfere with the determination by reacting directly with the measuring membrane of the electrode. After acidification with sulfuric acid the hydrogen cyanide and hydrogen sulfide can be carefully purged out (imder hood), eliminating their interfering effect. 

Pseudomonas sp.. The characteristics of the two sensors are given in Tables 4.2 and S.l. The en me sensor has a better performance than the bacterial sensor, in terms of both re nse time and concentration range. The purification of the enzyme takes about a week, and the purified enzyme will keep for years without decomposing. This is not the case for the bacteria, which require periodic culture and harvesting. The bacterial sensor is, however, less sensitive to pH and temperature, but is the least selective since it is also sensitive to urea. Ammonia interferes with the response of both the enzyme and the bacterial electrodes, as they both use the same pNHa transducer. 

The precipitated acetyHde must be decomposed with hydrochloric acid after the titration as a safety measure. Concentrated solutions of silver nitrate or silver perchlorate form soluble complexes of silver acetyHde (89). Ammonia and hydrogen sulfide interfere with the silver nitrate method which is less... 

Qualitative Analysis. Nitric acid may be detected by the classical brown-ring test, the copper-turnings test, the reduction of nitrate to ammonia by active metal or alloy, or the nitrogen precipitation test. Nitrous acid or nitrites interfere with most of these tests, but such interference may be eliminated by acidifying with sulfuric acid, adding ammonium sulfate crystals, and evaporating to alow volume. 

Ammonia.. The most rehable results for ammonia are obtained from fresh samples. Storage of acidified samples at 4°C is the best way to minimi2e losses if prompt analysis is impossible. The sample acidity is neutrali2ed prior to analysis. Ammonia concentrations of 10 -0.5 M can be determined potentiometricaHy with the gas-sensing, ion-selective electrode. Volatile amines are the only known interferents. 

The most common colorimetric technique involves a reaction between ammonia and a reagent containing mercuric iodide in potassium iodide (Messier reagent) to form a reddish-brown complex. Turbidity, color, and hardness are possible interferences that can be removed by preliminary distiHation at pH 9.5. 

An isolated acetoxyl function would be expected to be converted into the alkoxide of the corresponding steroidal alcohol in the course of a metal-ammonia reduction. Curiously, this conversion is not complete, even in the presence of excess metal. When a completely deacetylated product is desired, the crude reduction product is commonly hydrolyzed with alkali. This incomplete reduction of an acetoxyl function does not appear to interfere with a desired reduction elsewhere in a molecule, but the amount of metal to be consumed by the ester must be known in order to calculate the quantity of reducing agent to be used. In several cases, an isolated acetoxyl group appears to consume approximately 2 g-atoms of lithium, even though a portion of the acetate remains unreduced. Presumably, the unchanged acetate escapes reduction because of precipitation of the steroid from solution or because of conversion of the acetate function to its lithium enolate by lithium amide. 

Precipitated hydantoin must be washed with sufficient water to remove any residual ammonia, which can interfere with subsequent reactions. If an ammonia odor or yellow color persists after the initial water washes, additional washes should be performed. 

Note When combined with thin-layer chromatographic separation the reagent provides a specific detection method for nitrate and nitrite. The color development is often completed within a few minutes on silica gel plates. In the absence of ammonia vapor traces of oxides of nitrogen in the laboratory atmosphere can slowly cause the background to become reddish-brown. The simultaneous presence of the following ions in the chromatogram zones interferes with the detection of nitrate/nitrite I , 10J, IO4, MoO and H2PO2. 

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