Urine ammonia determination

Sample preparation Condition a 300 mg Bond Elut Certify SPE cartridge with 2 mL MeOH and 2 mL water. 5 mL Urine -i- 1 mL concentrated HCl, vortex, heat at 120° for 30 min, cool, adjust pH to between 7.0 and 8.0 with 10 M KOH. 5 mL Urine or hydrolyzed urine + nalorphine, add to the SPE cartridge, wash with 2 mL water, wash with 1 mL pH 4 acetate buffer, wash with 2 mL MeOH, elute with 2 mL dichloromethane isopro-pemol 80 20 containing 2% ammonia. Evaporate the eluate to dryness imder a stream of nitrogen, reconstitute the residue in 0.5-1 mL pentane dichlorometheine 90 10. (Use unhydrolyzed urine to determine diamorphine and unconjugated compoimds.)... 

B. Other useful laboratory studies include electrolytes, glucose, BUN, creatinine, calcium, ammonia, liver transaminases, bilirubin, prothrombin time (PT), amylase, serum osmolality and osmolar gap (see p 32 serum levels > 1500 mg/L may increase the osmolar gap by 10 mOsm/L or more), arterial blood gases or oximetry, and EGG monitoring. Valproic acid may cause a falsepositive urine ketone determination. 

Possible applications of enzyme electrodes include the determination of urea in blood (Equation (20)) and for which the optimum pH is about 7 at which 99.7 per cent of the ammonia product exists as NH4 cation, the only form among the species generated that elicits a potential response from the Beckman cation-selective glass electrode. Any sodium or potassium ion interference introduced with the enzyme (or substrate) can easily be detected because of the large positive potential reading that it causes. In such instances Dowex 50 cation exchanger may be used to remove the interferences beforehand [372]. Average differences between the urea values in blood and urine as determined by the urea-urease electrode and a spectrophotometric technique were 2.8 and 2.3 per cent m/m, respectively [373]. 

Nitrogen compounds commonly determined are creatinine, urea, and uric acid. Creatinine is an end product of the energy process occurring within the muscles, and is thus related to muscle mass. Creatinine in urine is commonly used as an indicator and correction factor of dilution in urine. Creatinine in serum is an indicator of the filtration capacity of the kidney. Urea is the end product of the nitrogen luea cycle, starting with carbon dioxide and ammonia, and is the bulk compoimd of urine. The production of uric acid is associated with the disease gout. In some cases, it appears that the excess of uric acid is a consequence of impaired renal excretion of this substance. 

As the one of the main end products of protein metabolism in living organisms, urea is a primary source of organic nitrogen in soil (from animal urine, fertilizers, etc.). Monitoring the level of urea is important for medicine, as well as for environmental protection. Urease is an enzyme that breaks the carbon-nitrogen bond of amides to form carbon dioxide, ammonia and water. This enzyme is widely used for determination of urea in... 

Willis 93) extracted lead directly from 200 ml of urine with APDC into 1.5 ml of methyl-n-amyl ketone. He was able to determine as little as 0.02 ppm of lead. Kopito and Shwachman 141>, on the other hand, co-precipitate the lead from urine with bismuth nitrate by adding ammonia. The precipitated bismuth hydroxide is dissolved in acid and this solution is aspirated. Coprecipitation of the lead is not quantitative, and so standards should be prepared in the same manner. It should be possible to employ this procedure with protein free filtrates of blood without the necessity of close pH control. 

The presence of hexamethylenediamine (4c) in hydrolyzed human urine is indicative of exposure to hexamethylene diisocyanate. The diamine was determined after derivatization with heptafluorobutyric anhydride followed by GC-CI-MS, using ammonia as the ionizing reagent and deuterated hexamethylenediamine as internal standard LOD 0.5 j.ig/L urine97. 

The ammonia content of the air was determined using a Drager detector tube, which is not very accurate, particularly at low concentrations. In theory the acidic nature of of peat suggests it should bind ammonia far better than the other Utters. However, the results obtained indicate that the use of peat freshens up the cowshed air only if the manure removal and urine separation systems are working efficiently. 

UREASE. Enzyme present in low-percentages in jackbean and soybean water soluble, its action is inhibited by heavy-metal ions. Its principal use is in the determination of urea in urine, blood, and other body fluids it splits urea into ammonia and carbon dioxide or ammonium carbonate. 

Paracetamol—Cresol-ammonia test. To 0.5 ml of urine add 0.5 ml of hydrochloric acid and heat for 10 minutes at 100° to 2 drops of the mixture add 10 ml of water, 1 ml of 1 % o-cresol in water, and 4 ml of 2M ammonium hydroxide. A blue colour appears if paracetamol is present. The test is very sensitive and can detect therapeutic concentrations. The presence of the parent drug and its conjugated metabolites can be detected for several days after overdose. If a positive result is obtained, a plasma-paracetamol determination should be carried out immediately (p. 23). 

Ammonia/Urea Serum, urine Biochemical Conventional Sequential determination. 150... 

Because of the high selectivity and sensitivity of the postcolumn fluorescence detection of histidine with OPA, the present HPLC method is applicable to a specific and rapid assay of histidine in human semm, blood, and urine after simple pretreatment. A recent paper demonstrated that the postcolumn detection with OPA was applicable to the simultaneous assays of histidine and its major metabolites cis- and frawi-urocanic acids) in human stratum corneum. " The postcolumn detection system was also applicable to the flow injection analysis (FIA) method for the assay of histidine in semm and urine. The FIA method enabled us to determine histidine in blood after pretreatment of the sample with A-ethylmaleimide (masking reagent of glutathione).These methods are useful in the diagnosis of histidinanemia, one of hereditary metabolic disorders characterized by a virtual deficiency of histidine ammonia-lyase. 

Beckett and Triggs were interested in the determination of nicotine and its main metabolite cotinine in urine. An acidified urine was extracted with diethyl ether to remove impurities, the urine was made alkaline with sodium hydroxide and the nicotine extracted with diethyl ether. Cotinine was extracted from urine with methylene chloride after basification of the sample with ammonia. On concentration of the solution, the gas chromatography was carried out on a packed column treated with KOH using Carbowax 20 M as stationary phase. A relative recovery of 95-100 % for the two alkaloids was obtained with respect to their internal standard, chlorophentermine for nicotine and lignocaine for cotinine, which were added to the urine at the start of the assay procedure. Typical chromatograms are given in Figure 4. 

There are tests that measure ammonia/ammonium ion in blood and urine however, these tests would probably not tell you whether you have been exposed because ammonia is normally found in the body. If you were exposed to harmful amounts of ammonia, you would notice it immediately because of the strong, unpleasant, and irritating smell, the strong taste, and because of skin, eye, nose, or throat irritation. Exposure detection levels and methods for determining ammonia levels in biological materials are discussed in Chapters 3 and 7. 

When ammonia is found in biological materials at physiological pH (7.2), most of it (99%) will be found as ammonium ion, due to its pK of 9.2. This is an important consideration for any subsequent analysis. The determination of ammonia (as dissolved NH3 and ammonium ion) in blood, plasma, or semm is of value in detecting existing or impending hepatic coma and Reyes Syndrome (Meyerhoff and Robins 1980 Tietz 1970). The determination of ammonia in urine had historically been used as an indicator of the kidney s ability to produce ammonia however, this procedure has been replaced by more modem and accurate tests for kidney function. Procedures for the determination of ammonia in biological samples are found in Table 7-1. Ammonia is also tested for in calculi (abnormal concretions in the body formed of mineral deposits, often found in the gall bladder, kidney, or bladder) (Tietz 1970) however, this is not a quantitative test and is not included in Table 7-1. 

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