Nitrites, in urine

Colorimetric Assay for Nitrites in Urine The niEite ion is rapidly eliminated from blood and it is best to assay urine in cases of suspected overdose. 

III)/multiwalled carbon nanotubes (Fe P/MWCNTs) composites showed well-enough resolved peaks to allow the simultaneous analyses of ascorbic acid, dopamine, uric acid, and nitrite in urine and serum samples [186]. This result was assigned to the 71-interaction between the analytes and MWCNT, as well as the synergic effects of Fe "P and MWCNTs. 

Singh, J., Elberling, J. A., Hemphill, D. G., and Holmstrom, J. The measurement of nitrite in adulterated urine samples by high-performance ion chromatography, J. Anal. Toxicol., 23, 137, 1999. 

Quantification of total /V-nitroso compounds in urine and gastric juice is achieved by combining photolytic denitrosation with TEA. Nitrite interference is effectively eliminated with sulfamic acid (H2NSO3H)605. 

Excretion of 7V-nitrosodiethanolamine in urine was evident in Sprague-Dawley rats receiving diethanolamine via the skin (100-400 mg/animal) and sodium nitrite in the drinking water (2000 ppm [mg/L]) for six days but not in the absence of sodium nitrite (Preussmann et al, 1981). 7V-Nitrosodiethanolamine was detected in a gastric rinse of rats treated with 100 pmol diethanolamine [59 mg/kg bw] and 400 pmol sodium nitrite [153 mg/kg bw] by gavage (Konishi et al, 1987). No evidence of formation of /V-nitrosodiethanolamine in vivo was found, however, in B6C3Fi mice treated with diethanolamine (160 mg/kg bw per day) and sodium nitrite (140 ppm in drinking-water 40 mg/kg bw) (Stott et al, 2000). 

Diethanolamine is metabolized by biosynthetic routes common to endogenous alkanolamines (ethanolamine and choline) and incorporated into phospholipids. It is excreted predominantly unchanged with a half-life of approximately one week in urine. In the absence of sodium nitrite, no conversion to TV-nitrosodiethanolamine is observed. Diethanolamine competitively inhibits the cellular uptake of choline in vitro and hepatic changes in choline homeostasis, consistent with choline deficiency, are observed in vivo. 

A-Nitrosodiethanolamine has been detected in urine (1-150 pg per animal) of male Sprague-Dawley rats given nitrite in their drinking water following skin treatment with diethanolamine (100-400 mg per rat) (Preussmann et al, 1981). 

Determination of oxidized amino acids in urine is usually performed by isotope dilution gas chromatography-mass spectrometry (L9). DOPA is estimated by HPLC separation of acid protein hydrolysates with fluorescence detection (excitation 280 nm, emission at 320 nm) (A15). Other methods are based on borate-hydrochloric acid difference spectroscopy (this method suffers interference from tyrosine and tryptophan) (W2), derivatization of DOPA with nitrite and subsequent coulometric determination (W3), and fluorometric detection after derivatization with ethylenediamine (A15). 3-Hydroxylysine is quantitated by HPLC with 9-fluorenylmethyl chloroformate precolumn derivatization (M25) of amino acids obtained by gas-phase hydrolysis of proteins (F21). Other general methods to detect amino acid damage are mass spectometry methods applied to protein hydrolysates, such as tandem mass spectrometry (F6). 

Nitrates are well absorbed from the gastrointestinal tract producing peak blood levels only 40 min after ingestion. They may also be absorbed through abraded or damaged skin. Nitrates are converted to nitrites by various bacteria in the stomach and intestines of animals and humans. Approximately 14-31% of nitrate is excreted via the kidneys. The mean renal clearance for nitrates is 26 ml min About 40% is excreted as nitrites in the urine. It is also recycled through the saliva. 

The Chemstrip and Multistix strips for bilirubin in urine are highly specific tests and have a low incidence of falsepositive results. However, medications that color the urine red or that give a red color in an acid medium, such as phenazopyridine, can produce a false-positive reading. Large quantities of ascorbic acid or of nitrite also worsen the detection limit of the test. In practice, bilirubin is rarely measured in urine. 

Tsai S-CJ, ElSohly MA, Dubrovsky T, Twarowska B, Towt J, Salamone SJ, Determination of five abused drugs in nitrite-adulterated urine by immunoassays and gas chromatography mass spectrometry. J Anal Toxicol 1998 22 474-80. 

Tsai JSC, ElSohly MA, Tsai S-F, Murphy TP, Twarowska B, Salamone SJ. Investigation of nitrite adulteration on the immunoassay and GC-MS analysis of cannabinoids in urine specimens. J Anal Toxicol 2000 24 708-14. 

Several biochemical tests have been developed for screening mine for the presence of bacteria. A common dipstick test detects the presence of nitrite in the urine, which is formed by bacteria that rednce nitrate normally present in the urine. False-positive tests are nncommon. False-negative tests are more common and freqnently are cansed by the presence of gram-positive organisms or P. aeruginosa that do not reduce nitrate. Other causes of false tests include low urinary pEf, frequent voiding, and dilute urine. 

A. Specific levels. Blood levels are not commercially available. With the use of a nitrite dipstick (normally used to detect bacteria in urine), nitrite can be detected in the serum of patients intoxicated by alkyl nitrites. 

Watanabe-Suzuki K, Nozawa H, Suzuki O, and Ishii A (2003) Sensitive analysis of alkyl alcohols as decomposition products of alkyl nitrites in human whole blood and urine by headspace capillary GC with cryogenic oven trapping. Journal of Chromatographic Science 41 63-66. 

As with blood, urine analysis is used in clinical studies, and the relative concentrations of various ionic species are of great importance in both disease diagnostic and drug metabolism studies. For example, IC is used to determine urine oxalate concentrations. Urinary oxalate levels are an important parameter in urolithiasis research (kidney stones). Other anions that can be determined in urine using IC include phosphate, sulfate, bromide, citrate, nitrate, nitrite, and thiosulfate. As with blood and serum samples, both ultrafiltration and centrifugation are often used as sample cleanup steps. 

Afkhami et al. [162] used a graphite paste electrode containing MWCNT modified by the electrodeposition of gold NPs from a HAuCl solution to successfully determine cefixime, methadone [163], and nitrite [164] in a pharmaceutical form, in urine and saliva in several food stuffs and water samples, respectively. Fe203... 

Selected Ion chromatogram showing negative ions at miz 46, 47, 62, and 63 obtained by derivatizing nitrite and nitrate plus Internal standards ( N02 and NOi) In urine. [From D. Tsikas, Anai Chem. 2000, 72, 4064 Anal. Chem. 2010, 52, 2585.]... 

Excess tyrosine in the serum and urine can be detected by chromatography. It can be measured fluorimetrically in serum by its reaction with a-nitroso-jS-naphthol and nitrite in the presence of nitric acid. Tyrosine can be detected in urine by the Millon reaction when it gives a red colour with mercuric nitrate in nitric acid containing a trace of nitrous acid. 

Guaiacum, 2 per cent, in alcohol. With HgOg, it is a reagent for peroxidases, and hsemoglobin in urine. With acetic acid, it is a reagent for nitrite in saliva. 

---