Determination of nitrate and nitrite at the parts per billion level by chemiluminescence

Cox, Robert D.

doi:10.1021/ac50052a028

Cited by 216 publications

(119 citation statements)

References 22 publications

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“…In this highly acidic solution the nitrous acid can be further protonated producing H 2 NO 2 +, which is in equilibrium with the nitrosonium cation (NO + ). Cox [33] had shown that even in acetic acid, NO is not…”

Section: Discussionmentioning

confidence: 99%

Measurement of plasma nitrite by chemiluminescence without interference of S-, N-nitroso and nitrated species

Nagababu

Rifkind

2007

Free Radical Biology and Medicine

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Recent studies have demonstrated that plasma nitrite (NO 2 -) reflects endothelial nitric oxide synthase activity and it has been proposed as a prognostic marker for cardiovascular disease. In addition, NO 2 -itself has been shown to have biological activities thought to be triggered by reduction back to NO in blood and tissues. The development of sensitive and reproducible methods for the quantitative determination of plasma NO 2 -is, therefore, of great importance. Ozone-based chemiluminescence assays have been shown to be highly sensitive for the determination of nanomolar quantities of NO and NO related species in biological fluids. We report here an improved direct chemiluminescence method for the determination of plasma NO 2 -without interference of other nitric oxide related species such as nitrate, S-nitrosothiols, N-nitrosamines, nitrated proteins and nitrated lipids. The method involves a reaction system consisting of glacial acetic acid and ascorbic acid in the purge vessel of the NO analyzer. Under these acidic conditions NO 2 -is stoichiometrically reduced to NO by ascorbic acid. Fasting human plasma NO 2 -values were found in the range of 56-210 nM (mean =110 ± 36 nM). This method has high sensitivity with an accuracy of 97% and high precision (C.V <10%) for determination of plasma nitrite. The present method is simple and highly specific for plasma NO 2 -. It is particularly suited to evaluate vasculature endothelial NO production that predicts the risks for cardiovascular disease.

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Section: Discussionmentioning

confidence: 99%

Measurement of plasma nitrite by chemiluminescence without interference of S-, N-nitroso and nitrated species

Nagababu

Rifkind

2007

Free Radical Biology and Medicine

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“…We found in the earlier work that the reducing power of copperized cadmium deteriorated with use because of contact with air bubbles accidentally introduced into the coil, and the reproducible regeneration of the reductant was rather difficult. Thus, homogeneous procedures, employing reducing agents, such as iron(II)-molybdate, 6,15 vanadium(III) chloride, 8 titanium(III) chloride, 11,12 and hydrazine sulfate, [16][17][18] appear to be more suitable for flow systems. The reagents all reduce nitrate to NO, except for hydrazine sulfate.…”

Section: Chemical and Fia Variables For Nitrate Determinationmentioning

confidence: 99%

“…4,5 The spectrophotometric method can provide reliable results for natural water samples, but suffers from interferences from suspended and colored substances in the samples. Cox 6 proposed a chemiluminescence analysis technique, which is more highly sensitive and free from these interferences. The technique is based on the chemical reduction of nitrate and nitrite to NO and detection via a chemiluminescence reaction of NO with ozone.…”

Section: Introductionmentioning

confidence: 99%

Flow-Injection Analysis Method for the Determination of Nitrite and Nitrate in Natural Water Samples Using a Chemiluminescence NOx Monitor

Kanda

Taira

2003

ANAL. SCI.

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The determination of nitrite and nitrate in aqueous environmental samples is of considerable interest in research concerning hydrological chemistry, chemical oceanography, and atmospheric chemistry. Nitrate is an essential nutrient which controls the biomass in natural water; the amount also indicates the extent of pollution and eutrophication of the aquatic environment. Nitrite is a nitrogen-cycle intermediate and a useful indicator of the equilibrium state of the oxidative and reductive pathways of the nitrogen cycle. Also, nitric acid and nitrous acid are very important trace constituents of the atmosphere in both the gaseous and particulate phases. Nitric acid is a major NOx sink in photochemical air pollution. Nitrous acid is recognized as a major source of a very reactive hydroxyl radical, which is a key intermediate for all photochemical oxidant formations. These gases and particulates are precursors of acid rain, and are deposited on the ground mainly by wet precipitation, such as rain and snow.Among many analytical methods proposed for the determination of nitrate and nitrite, a widely used method for analyses of natural water samples is based on the reduction of nitrate to nitrite and a subsequent spectrophotometric determination via the Griess reaction, 1-3 which involves the diazotization of sulfanilic acid and successive coupling with 1-naphthylamine. Though numerous modifications have been suggested, primarily based on changing either the reagent being diazotized or coupled, sulfanilamide or sulfanilic acid and N-(1-naphtyl)ethylenediamine are the most popular couples. 4,5 The spectrophotometric method can provide reliable results for natural water samples, but suffers from interferences from suspended and colored substances in the samples. Cox 6 proposed a chemiluminescence analysis technique, which is more highly sensitive and free from these interferences. The technique is based on the chemical reduction of nitrate and nitrite to NO and detection via a chemiluminescence reaction of NO with ozone. Garside 7 first applied this technique to seawater analyses. Braman and Hendrix 8 reported on an application used for environmental water samples. These methods used NaI for reducing nitrite to NO, and iron(II)-molybdate or vanadium(III) for reducing nitrate to NO. The reduction procedures in these methods require highly acidic conditions and/or operation at a relatively high temperature. In the monitoring method of ambient gaseous HNO2, 9 we employed ascorbic acid in a dilute H2SO4 for reducing nitrite to NO. This reagent is easy to handle and the reaction is rapid and quantitative at low nitrite levels. By reducing nitrate to nitrite with an alkaline hydrazine solution, the measurement system was further developed to a gaseous HNO3 monitoring method. 10The coupling of the chemiluminescence detection with a flowinjection technique (FIA) would permit the development of sensitive, precise, rapid, and high throughput methodologies having a wide dynamic range. Aoki and Wakabayashi 11 reported a chemilumine...

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“…[5][6][7] In this method, both nitrate and nitrite are reduced to nitrous oxide in a highly acidic solution of sulfuric acid containing iron(II) ammonium sulfate and ammonium molybdate. Nitrous oxide in the solution is carried to a drying tube and reacts with ozone, resulting in chemiluminescence.…”

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confidence: 99%

Onboard Determination of Submicromolar Nitrate in Seawater by Anion-Exchange Chromatography with Lithium Chloride Eluent

2006

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Nitrogen is an essential element for phytoplankton growth in aquatic environments. Nitrate is the main nutrient supporting this production in the open ocean, and the supply of nitrate often controls primary production in oligotrophic areas. Excluding the high-latitude and eastern equatorial regions of the Pacific, the surface waters of the North and South Pacific Ocean from about 40˚ N to 40˚ S are relatively depleted in nitrate. In the North Pacific subtropical gyre, nitrate concentrations are typically below 10 nmol/l.1 To understand the nitrogen cycles in the open ocean ecosystem, a sensitive analytical method to determine the nanomolar levels of nitrate in seawater is essential.The standard method of nitrate determination in seawater is based on a flow-injection technique with spectrophotometric detection. [2][3][4] In this method, nitrate is first reduced to nitrite in a copperized cadmium column.Nitrite is coupled with sulfanilamide to form a diazonium cation. This diazonium reacts with N-1-naphtylethylenediamine dihydrochloride, forming a purple azo dye whose absorbance is measured at 550 nm. Next, the nitrite is measured independently according to the same method without reduction. Nitrate is then calculated from the difference in the concentration between [nitrate + nitrite] and nitrite. This method can be conventionally applied to the determination of nitrate and nitrite on board; its detection limit is about 50 nmol/l as [nitrate + nitrite].A more sensitive method of nitrate analysis has been developed by utilizing the chemiluminescence of nitrogen monoxide. [5][6][7] In this method, both nitrate and nitrite are reduced to nitrous oxide in a highly acidic solution of sulfuric acid containing iron(II) ammonium sulfate and ammonium molybdate. Nitrous oxide in the solution is carried to a drying tube and reacts with ozone, resulting in chemiluminescence. The detection limit is around 2 nmol/l. This measurement method also requires nitrate reduction to nitrite. By this method, Cavender-Bares et al. 8 measured 2 to 10 nmol/l concentrations of [nitrate + nitrite] in surface seawater that were below the detection limit of the standard method using azo dye formation. They revealed the vertical gradients of [nitrate + nitrite] in the North Atlantic Ocean.As a simple method, direct UV determination 2,4,9 has also been examined, but often encounters interference by bromide or organic compounds, such as humic substances, which also have UV absorbance in a wavelength range similar to that of nitrate. Capillary electrophoresis 10,11 is very useful because it gives high efficiency in the separation of analytes, and enables rapid analysis and the direct injection of seawater. However, the small injection volume and short path length of the detector results in a poor detection limit for nitrate and nitrite.Ion chromatography (IC) 12 is advantageous in the determination of nitrite and nitrate because these anions can be separated from other ions, such as bromide and organic substances. However, with highly ionic mat...

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Determination of nitrate and nitrite at the parts per billion level by chemiluminescence

Cited by 216 publications

References 22 publications

Measurement of plasma nitrite by chemiluminescence without interference of S-, N-nitroso and nitrated species

Measurement of plasma nitrite by chemiluminescence without interference of S-, N-nitroso and nitrated species

Flow-Injection Analysis Method for the Determination of Nitrite and Nitrate in Natural Water Samples Using a Chemiluminescence NOx Monitor

Onboard Determination of Submicromolar Nitrate in Seawater by Anion-Exchange Chromatography with Lithium Chloride Eluent

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