Spectrophotometric Determination Of Nitrate Research Articles

Technical note: An open-source, low-cost system for continuous monitoring of low nitrate concentrations in soil and open water

Abstract. Nitrate (NO3-), mainly leaching with soil porewater, is the primary nonpoint source pollutant of groundwater worldwide. Obtaining real-time information on nitrate levels in soils would allow for gaining a better understanding of the sources and transport dynamics of nitrate through the unsaturated zone. However, conventional nitrate detection techniques (e.g., soil sample analysis) necessitate costly, laboratory-grade equipment for analysis, along with human resources, resulting in a laborious and time-intensive procedure. These drawbacks raise the need to develop cost-effective and automated systems for in situ nitrate measurements in field conditions. This study presents the development of a low-cost, portable, automated system for field measurements of nitrate in soil porewater and open water bodies. The system is based on the spectrophotometric determination of nitrate using a single reagent. The system design and processing software are openly accessible, including a building guide, to allow duplicating or changing the system according to user-specific needs. Three field tests, conducted over 5 weeks, validated the system's measurement capabilities within the range of 0–10 ppm NO3-–N with a low RMSE of <0.2 ppm NO3-–N when comparing the results to standard laboratory nitrate analysis. Data derived from such a system allow for tracking of the temporal variation in soil nitrate, thus opening new possibilities for diverse soil and nutrient management studies.

Spectrophotometric determination of nitrate in small volume of seawater samples using a simple resorcinol method.

A simple resorcinol method to determine nitrate (NO3-) in seawater using a microplate reader with a 48-well plate was established. The method involved the nitration of resorcinol in sulfuric acid to form a pink product that was detected at 505nm. Reagent concentrations were optimized, and the effect of salinity on NO3- determination was investigated. The detection limit of this method was 0.8µM, while the upper limit of the linear range was 100µM. The recoveries ranged from 91.5 to 109.7% for spiked seawater samples with different salinities. The proposed method was compared with two reference methods, and the results revealed a good correlation. Compared to conventional methods that require the preparation of reactants, the proposed method used aqueous solutions as reagents for the reaction, which was simpler and more convenient. Compared to the methods that used organic solvents for the direct determination of NO3-, the proposed method was suitable for estuarine and coastal water samples with large salinity variations. All results indicated that the proposed method can satisfy the requirements of laboratory analysis and demonstrate high application potential for use in field determination.

Spectrophotometric determination of nitrate in hypersaline waters after optimization based on the Box-Behnken design

Monitoring dissolved nitrate (NO3−) concentrations is essential for conservation efforts in aquatic ecosystems. Spectrophotometric methods are a widely accepted approach for NO3− analysis. They detect NO3− as a colored diazo complex after reduction to nitrite (NO2−) and its consequent reaction with the so-called Griess reagent. This method is commonly used for freshwater and saline water samples, even though it requires applying a heavy metal in powder form (cadmium) or high concentrations of heavy metal salts (vanadium-III), as a reductant. There has been little discussion about applying these methods for hypersaline samples. This study optimizes an existing method for use in high saline conditions based on the Griess reaction. Five factors were studied: incubation temperature, reaction time, concentration of EDTA, concentration of trisodium citrate, and concentration of reductant (VCl3). Optimal conditions were obtained by using the Box-Behnken design and included using VCl3 17.5 mM, trisodium citrate 70 mM, and an incubation temperature of 60 °C for 40 min. These conditions provided a linear range from 0.55 μM to 50 μM NO3−. The method showed a moderate precision (ranging from 4.3% to 15.4%). The proposed protocol was tested with hypersaline natural samples and showed recovery rates between 92.6% and 100.1%. This protocol for NO3− determination is the first specifically described for hypersaline samples.

Spectrophotometric determination of nitrate in vegetables using phenol

A rapid and sensitive spectrophotometric method for the determination of nitrate in vegetables is described. The method is based on the measurement of the absorbance of yellow sodium nitrophenoxide formed via the reaction of phenol with the vegetable-based nitrate in presence of sulphuric acid. The analytical concentration of the acid has marked effect on the nitrate determined. The colour development was rapid and remained stable overnight. Analysis of six vegetable samples containing nitrate gave satisfactory mean recoveries of 76 to 123% in 18 determinations. The proposed method is reproducible and sensitive to lower level concentrations. Journal of Applied Sciences and Environmental Management Vol. 10(1) 2006: 79-82

Spectrophotometric Determination of Nitrate with a Single Reagent

A spectrophotometric procedure for determination of nitrate in water, soil extracts, and a variety of other sample types is described using one reagent solution which is easily prepared and stored. Sample and equipment requirements are minimal. Reduced chemical hazard, simplicity, and versatility represent improvements over existing methods. Limit of detection is 0.01 µg N mL−1 (0.72 μM ) or less, depending on the matrix.

Spectrophotometric Determination of Nitrate in Polluted Water Using a New Coupling Reagent

Spectrophotometric Determination of Nitrate in Polluted Water Using a New Coupling Reagent

Spectrophotometric determination of nitrate and nitrite in natural water samples based on an oxime formation reaction of phenol.

The spectrophotometric method for the determination of nitrate reported by Velghe and Clays was modified.The modified method was applied to the determination of nitrate and nitrite in natural water samples(well, river, and seawater).In the modified method, a sodium chloride solution was used instead of hydrohloric acid as the source of chloride for reducing nitrate.The sensitivity of this method was comparable to that of ion chromatography and that of HPLC with UV detection.The results obtained by the proposed method were in good agreement with those obtained by the chromatographic methods.The proposed method could be applied to the determination of nitrate of low concentration levels in seawater sample.

Spectrophotometric determination of nitrate and nitrite in water and some fruit samples using column preconcentration

A sensitive analytical method for the simultaneous assay of nitrate and nitrite in water and some fruit samples is presented. The method is based on nitrite determination using the diazotization-coupling reaction by column preconcentration and on the reduction of nitrate to nitrite using the Cd–Cu reductor column. Nitrite is diazotized with sulfanilamide (SAM) in the pH range 2.0–5.0, sulfamethizole (SM) in pH 1.8–5.6 and sulfadimidine (SD) in pH 1.8–4.0 in a hydrochloric acid medium to form water-soluble colourless diazonium cations. These cations were coupled with sodium 1-naphthol-4-sulfonate (NS) in the pH range 9.0–12.0 for the SAM–NS system, pH 8.6–12.0 for the SM–NS system and pH 9.4–12.0 for the SD–NS system to be retained on naphthalene-tetradecyldimethylbenzylammonium (TDBA)–iodide (I) adsorbent packed in a column. The solid mass is dissolved out from the column with 5 ml of dimethylformamide (DMF) and the absorbance is measured by a spectrophotometer at 543 nm for SAM–NS, 537 nm for SM–NS and 530 nm for SD–NS. The calibration graph was linear over 30–600 ng NO 2-N and 22–450 ng NO 3-N in 15 ml of final aqueous solution (i.e. 2–40 ng NO 2-N ml −1 and 1.5–30 ng NO 3-N ml −1 in aqueous sample) for three systems. The detection limits were 1.4 ng NO 2-N ml −1 and 1.1 ng NO 3-N ml −1 for SAM–NS, 1.2 ng NO 2-N ml −1 and 0.89 ng NO 3-N ml −1 for SM–NS, 1.0 ng NO 2-N ml −1 and 0.75 ng NO 3-N ml −1 for SD–NS, respectively. The concentration factor is eight for SAM–NS and SM–NS, and 12 for SD–NS. Interferences from various foreign ions have been examined and the method was successfully applied to the determination of low levels of nitrate and nitrite in water and some fruit samples.

Spectrophotometric determination of nitrate and nitrite in soil and water samples with a diazotizable aromatic amine and coupling agent using column preconcentration on naphthalene supported with ion-pair of tetradecyldimethylbenzylammonium and iodide

Composite diazotization-coupling reagents containing sulfanilamide (SAM), sulfapyridine (SP) or sulfathiazole (ST) as the diazotizable aromatic amines and sodium 1-naphthol-4-sulfonate (NS) as the coupling agent using column preconcentration on naphthalene-tetradecyldimethylbenzylammonium(TDBA)-iodide adsorbent have been used for the spectrometric determination of trace nitrate and nitrite in soil and water samples. Nitrite ion reacts with SAM in the pH range 2.0–5.0, SP in the pH range 2.0–2.5 and ST in the pH range 2.0–3.3 in HCl medium to form water-soluble colourless diazonium cations. These cations were coupled with NS in the pH range 9.0–12.0 for the SAM system, 9.6–12.0 for the SP system and 8.5–12.0 for the ST system to be retained on naphthalene-TDBA-I material packed in a column. The solid mass is dissolved from the column with 5 ml of dimethylformamide and the absorbance is measured spectrometerically at 543 nm for SAM-NS, 533 nm for SP-NS and 535 nm for ST-NS. Nitrate is reduced to nitrite by a copper-coated cadmium reductor column and the nitrite is then treated with the diazotization-coupling reagent by column preconcentration. The absorbance due to the sum of nitrate and nitrite is measured and nitrate is determined by difference. The calibration graph was linear over the range 2–40 ng NO 2 −-N ml −1 and 1.5–30 ng NO 3 −-N ml −1 in aqueous samples for the SAM and ST systems and 2–48 ng NO 2 −-N ml −1 and 1.5–36 ng NO 3 −-N ml −1 in aqueous samples for the SP system, respectively. The sensitivity, accuracy and precision of the systems decreased in the order ST⪢SAM⪢SP. The detection limits were 1.4 ng NO 2 −-N ml −1 and 1.1 ng NO 3 −-N ml −1 for SAM, 1.6 ng NO 2 −-N ml −1 and 1.2 ng NO 3 −-N ml −1 for SP, and 1.0 ng NO 2 −-N ml −1 and 0.75 ng NO 3 −-N ml −1 for ST, respectively. The preconcentration factors are 8, 5 and 6 for SAM-NS, SP-NS and ST-NS, respectively. Interferences from various foreign ions have been studied and the methods have been applied to the determination of ng ml −1 levels of nitrite and nitrate in soil and water samples. The mean recovery was 95–102% for all three systems.

Spectrophotometric Determination of Nitrate in Baby Foods: Collaborative Study

A collaborative study was conducted of a spectrophotometric method for determination of nitrate after cadmium reduction to nitrite in baby foods containing meat. Thirty-one municipal and 2 industrial food laboratories participated in the study. The study design involved 2 baby food matrices. Samples of both matrices were prepared at 3 concentration levels between 52 and 309 mg NaNO3/kg as blind duplicates. A blank without added nitrate was also included. The outlier percentage of the results was very low (4.3%). It was typical for the method that recoveries were slightly > 100%. Recoveries for baby foods varied between 113.3 and 116.9%, and were acceptable for control purposes. The relative standard deviations for repeatability were 5.0-18.1%. The relative standard deviations for reproducibility were 8.3-21.6%. Three collaborators also evaluated liquid chromatographic technique for nitrate determinations. These preliminary results are presented but are not analyzed statistically. The spectrophotometric method was adopted first action by AOAC INTERNATIONAL.

Pyrolysis-flow-injection analysis-spectrophotometric determination of amino acids in aqueous solutions

A method is described for the determination of proline, cysteine, alanine and tyrosine in aqueous mixtures based on their pyrolitic conversion to nitrogen-containing compounds. These compounds undergo through peroxodisulphate digestion with a heated capillary tube containing a platinum wire in a closed flow system. Subsequent mixing of aliquots of the digest and a Malachite Green chromogenic reagent solution in a symmetrical system allowed the spectrophotometric determination of nitrate at 650 nm. The method is reproducible and accurate.

Spectrophotometric determination of nitrate and nitrite in natural water and sea-water

Nitrate and nitrite in natural waters are determined spectrophotometrically by passage through an amalgamated zinc reductor at pH 3.4 into iron(III)-Ferrozine solution. Interference by high levels of nitrite is eliminated by treatment with azide. Levels as low as 0.2 μg ml (expressed as nitrogen) can be determined with a precision of ± 3%.

A simple procedure for standard additions in flow injection analysis : Spectrophotometric Determination of Nitrate in Plant Extracts

The standard additions method with constant sample volumes is readily achieved in a flow injection system if zone sampling is used to select segments with different concentration levels from the dispersed zone of a known standard, and these segments are merged with the sample zone. This system requires a single standard solution, is suitable for routine large-scale analyses, and does not need complex equipmnt. The number of sequence and level of additions are chosen in accordance with the required sampling rate, the speed of the method and the mean analyte content in the samples. Details of system design, stability and potential are discussd. As an applicaion, this system was used in the spectrophotometric determination of nitrate in plant extracts where the standard additions method is required to overcome the matrix effect. The results, based on twelve additions per sample (about 100 measurements per hour) agree with those obtained by the corresponding manual procedure.

Spectrophotometric determination of nitrate in vegetable products using 2-sec-butylphenol.

A procedure is described for the determination of nitrate in vegetable products, based on the quantitative reaction of nitrate and 2-sec-butylphenol in sulphuric acid (5 + 7), and the subsequent extraction and measurement of the yellow complex formed in alkaline medium. The colour reaction is sensitive and stable and absorbances measured at 418 nm obey Beer's law for concentrations of nitrate-nitrogen between 0.13 and 2.50 µg ml–1. Various possible interferents in vegetable products do not interfere with the nitration of 2-sec-butylphenol. Recoveries of nitrate from vegetable products were satisfactory and the standard deviation for the whole procedure was 1.41% for the 42 determinations; the detection limit of the method is 1.3 p.p.m. for nitratenitrogen.

Analytical methods for nitrate and nitrite in feeds. 1. Spectrophotometric determination of nitrate with o-cresol

The o-cresol procedure which is used for determining nitrate in feeds is tested for precision. The treatment of the samples and the course of analysis are rationalized. The method is recommended as a standard procedure for biological materials; it is suited as a reference technique in elaborating new analytical procedures.

Spectrophotometric determination of nitrate in water in the μg 1 -1 range

Spectrophotometric determination of nitrate in water in the μg 1 -1 range

A fast determination of nitrate in rain and surface waters by means of UV spectrophotometry

Organic substances are the main interference in the direct U.V. spectrophotometric determination of nitrate at 210 nm. An active carbon filter (Filopur) is therefore proposed which adsorbs all organic interferences. With this filter the U.V. spectrophotometric method gives the same results as the Na-salicylate method. The reproducibility is generally better than 5 %. One determination takes 50 s.

Spectrophotometric determination of nitrate using a difference method

Spectrophotometric determination of nitrate using a difference method

Spectrophotometric determination of nitrate in the presence of chloride

Spectrophotometric determination of nitrate in the presence of chloride

Spectrophotometric determination of nitrate and/or nitrite using brucine sulfate

硝酸イオンによるブルシンの発色は硫酸の存在量約64%で極大を示した.また温度の影響も無視できなかった.亜硝酸イオンの場合は硫酸の最約8%でも反応したが,検量線が直線性になるためには適量の硫酸と過塩素酸との共存が必要であった.種々検討の結果,定量法として次の条件が得られた. (1) 硝酸イオン溶液2mlにブルシン溶液0.3mlと濃硫酸4mlとを添加し適温に加熱後,405mμの吸光度を測定する.検量線は0.05～2.5ppm NO-3-Nの間で直線性を示した. (2) 亜硝酸イオン溶液5mlにブルシン溶液0.5mlと濃硫酸0.5mlならびに過塩素酸2.5mlとを添加し,適温に放置後430mμの吸光度を測定する.検量線は0.2～8.0ppmNO-2-Nの閥で直線性を示した.