Quantification of nitrite and nitrate in human urine and plasma as pentafluorobenzyl derivatives by gas chromatography—mass spectrometry using their 15N-labelled analogs
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SUMMARY 1. The present study investigated whether a low nitrate/nitrite diet could minimize variability in the measurement of endogenous plasma and urine nitric oxide (NO) metabolites, nitrate and nitrite (NO x ) in normal subjects. 2. Nitrate and nitrite concentrations were measured in plasma and urine as indicators of NO production in six subjects during a free diet and then during a low nitrate/nitrite diet for 6 days. 3. The plasma concentration and 24 h urine NO x /creatinine ratio were significantly lower on the low nitrate/nitrite diet than on the free diet ( P < 0.01). Nitric oxide production appeared to vary greatly within and between subjects, but these variations were substantially decreased by the fourth day of a low nitrate/ nitrite diet. 4. Human plasma and urine NO x measurements should be determined after a low nitrate/nitrite diet for at least 4 days.
Dietary Nitrate
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In this study, a novel method has been developed for the simultaneous detection of nitrate and nitrite using CdTe quantum dot-enhanced chemiluminescence(CL) from peroxynitrous acid-carbonate(ONOOH-Na2CO3), coupled with the reduction of nitrate in the presence of copperized cadmium column. The corresponding linear regression equation of nitrite was established in the range of 0.3–75μM, the detection limit(S/N = 3) was 0.12 μM, and the relative standard deviation(RSD) for seven repeated measurements of 1.0 μM nitrite was 1.9%; the corresponding linear regression equation of nitrate was established in the range of 1.0–100 μM, the detection limit(S/N = 3) was 0.26 μM, and the relative standard deviation(RSD) for seven repeated measurements of 1.0 μM nitrate was 1.5%. Moreover, this proposed method has been successfully applied to detect nitrite and nitrate in human urine with good accuracy and precision. Good agreements were obtained for the determination of nitrite and nitrate in human urine between the present approach and the standard spectrophotometric method. The recoveries were found to fall in the range between 94% and 105% for nitrite, 96.6% and 110.4% for nitrate.
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Flow injection analysis
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Abstract This article uses and validates the analytical methods for the determination of aniline and 3,3’-dichlorobenzidine in soil by gas chromatography-mass spectrometry, and discusses the determination of semi volatile organic compounds in soil by gas chromatography-mass spectrometry. The feasibility of the application. The results showed that the semi volatile organic compounds aniline and 3,3’-dichlorobenzidine target corresponding to the internal standard response value and concentration showed a good linear relationship, the correlation coefficient was between 0.9997 and 0.9983 respectively; the detection limit was 0.04 mg, respectively/kg and 0.04mg/kg, the limits of quantification are 0.2mg/kg and 0.2mg/kg; the relative standard deviations of the two semi-volatile organic compounds in the precision are 2.5∼16.9% and 3.6∼6.2%, respectively; the accuracy is 2 The recovery rates of these volatile organic compounds were 64.5-83.9% and 72.6-74.3%, respectively. The verification results show that the linear relationship, detection limit, precision and accuracy all meet the requirements of “Determination of Semi-volatile Organic Compounds in Soils and Sediments by Gas Chromatography-Mass Spectrometry” (HJ 834-2017). Using gas chromatography-mass spectrometry technology can achieve fast, accurate and sensitive detection of target substances, and can meet the detection requirements of trace semi-volatile organic compounds, so this method can be better applied to the detection of soil and other environments.
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Twelve healthy volunteers ingested orally 7-10.5 g of NH4NO3 in a single dose and 12 others received 9.5 g of NaNO3 intravenously in about 60 min. Samples of blood, saliva and urine were collected just before administration of nitrate and at various times afterwards during a 24 h period. Saliva and urine were analysed for volatile NA, nitrate and nitrite. Blood was analysed for nitrate. Neither in urine nor in saliva were NA other than NDMA detected. Of the 188 urine samples, only 13% contained more than 0.1 microgram NDMA/kg, the highest level being 0.5 microgram/kg. In 92% of the 179 saliva samples, less than 0.5 microgram NDMA/1 was found. The saliva of 1 person contained 0.7-8.9 microgram NDMA/1. Nitrate levels in blood rose sharply during the first hour after intravenous nitrate administration and 2 hours after oral intake, reaching peak values of ca. 6 mmol/1. Peak values for NO-3 + NO-2 in saliva, which were reached 2-6 hours after intake, varied strongly between individuals, ranging from 4 to 43 mmol/1. Nitrite was detected in 26% of the urine samples. There was no correlation between NDMA contents and nitrite in urine. An average of 75% of administered nitrate was excreted in urine in 24 h. However, nitrate contents in blood, urine and saliva after 24 h were still higher than before the nitrate intake.
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The fate of ingested nitrate and nitrite was investigated in rats by carrying out single and multiple dose feeding studies with 15N-labelled nitrate and nitrite. By 72 hr after discontinuation of administration of the 15N-labelled compounds, about 60–70% of the dose was excreted in the urine, and 10–20% was eliminated in the feces. Residual 15N remaining in the bbody carcass was about 10% following single dose experiments and 3–4% following continuous feeding trials. One-half or more of the excreted 15N was not analyzable chemically as nitrate or nitrite. On the basis of chemical analysis, about 30% of the dose was excreted in urine as nitrate plus nitrite; excretion in the feces was low. Negligible amounts of nitrate-N or nitrite-N were found in blood and organs of the animals. Most of the nonnitrate-15N and nonnitrite-15N was excreted, like nitrate-N and nitrite-N, rather rapidly from the body.
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An environmental friendly method was developed based on reversed flow injection(r-FIA) with UV-induced reduction of nitrate to nitrite and spectrophotometric detection.Sample or standard solutions were mixed with a phosphate buffer solution containing diethylenetriaminepentaacetate(DTPA),and then passed through a UV reduction reactor equipped with an 8 W low pressure mercury lamp,where the nitrate was reduced to nitrite.The formed nitrite was detected with spectrophotometric method through Griess reaction.Less than 20 μmol/L of nitrite showed no effect on the nitrate analysis.Reduction efficiency over 80% was obtained.The detection limit of the proposed method was 0.053 μmol/L and linear range was 0.2-40 μmol/L.A sample of 20 μmol/L nitrate was continually measured for 48 times,and a RSD of 2.22% was obtained.The recoveries of drinking waters were between 90.9%-100.6%.
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