Simultaneous Determination Of Nitrate Research Articles

Simultaneous determination of nitrate, chemical oxygen demand and turbidity in water based on UV-Vis absorption spectrometry combined with interval analysis.

In this paper, a new method for simultaneous determination of nitrate, COD and turbidity in water based on UV-Vis absorption spectrometry combined with interval analysis was studied. By analyzing the spectral absorption characteristics of nitrate, COD, and turbidity standard solutions and the mixtures of them, the absorption spectra in the range of 225-260nm, 260-320nm and 320-700nm were selected as the characteristic spectra of nitrate, COD and turbidity, respectively. Multiplicative scatter correction was employed to compensate turbidity of the absorption spectra of the mixture solutions in the wavelength range of 225-320nm. Then, the spectra after turbidity compensation in the range of 225-260nm was compensated for COD using the method of spectral difference. The original spectra in the range of 320-700nm, the turbidity compensated spectra in the range of 260-320nm, and the COD compensated spectra in the range of 225-260nm were analyzed by PLS algorithm in order to calculate the concentrations of nitrate, COD and turbidity in the mixture solutions. The results showed that this method could simultaneously and accurately determine the concentrations of nitrate, COD and turbidity. After interval analysis, all the correlation coefficients (R2) between the predicted values and the true values of nitrate, COD and turbidity were higher than 0.9, and root mean square error (RMSE) of predicted values were between 0.696 and 2.337.

Simultaneous determination of nitrate and nitrite in vegetables by poly(vinylimidazole-co-ethylene dimethacrylate) monolithic capillary liquid chromatography with UV detection

Simultaneous determination of nitrate (NO3‾) and nitrite (NO2‾) in vegetables was performed on a poly(1-vinylimidazole-co-ethylene dimethacrylate) (VIM-EDMA) monolithic column by capillary liquid chromatography (LC) with UV detection. Good linearity (0.5−100 μg mL-1 i.e. 12.5 −2500 μg g-1 in vegetables) was obtained with coefficient of determination > 0.996. Limits of detection (signal-to-noise ratio: S/N= 3) were estimated at 0.06 and 0.05 μg mL-1, which corresponded to 1.50 and 1.25 μg g-1 for NO2‾ and NO3‾, respectively, in vegetables. The limits of quantification (S/N= 10) were estimated at 0.17 and 0.16 μg mL-1 (4.25 and 4.00 μg g-1 in vegetables) for NO2‾ and NO3‾, respectively. Although the detection limits were relatively higher than other LC-UV techniques, this proposed method offered satisfactory sensitivity for complying the Acceptable Daily Intake (ADI) levels set by EU to monitor the occurrence of NO2‾ and NO3‾in vegetables. The intra-day/inter-day precision (0.14−3.35%/0.06−6.93%) and accuracy (90.33−103.32%/96.00−101.26%) were also examined for method validation. No obvious carry-over and decline of separation efficiency were observed for more than 200 analyses of real samples. The occurrence of NO2‾ and NO3‾in various vegetable samples was investigated to demonstrate the potential of utilizing the developed polymeric monolith-based capillary LC-UV method for food safety application.

Simultaneous determination of nitrate, nitrite and phosphate in environmental samples by high performance liquid chromatography with UV detection

An HPLC method using anUVdetector was developed for the simultaneous determination of nitrites, nitrates and phosphates in environmental samples. Chromatographic separation was achieved isocratically on a Phenomenex Synergi Polar-RP LC column using acetonitrile and acidified water (pH 2.7) at 60:40 v/v as mobile phase. Baseline resolution of all the three analytes was achieved within 3 min. The developed method was applied to water samples obtained from the wastewater treatment plant in Gaborone, Botswana. The use ofHPLC technique in this study demonstrated its ability to carry out a simultaneous determination of NO 2 – , NO 3 – and PO 4 3– in water samples. The treatment plant was found to be functioning within expectations, removing 97.6% NO 2 – , 88.0% NO 3 – and 90.9% PO 4 3– from the received wastewater.Results of the developed method were comparable with those of the traditional ion chromatography method, showing accuracy values between 95.22%and 98.04 %. The precision of the method for the determination of all analytes was determined by RSD values, all of which were lower than 5%. The method is of low cost, fast, has an easy procedure and avoids the use of many reagents – some of which may be hazardous. Keywords: HPLC-UV, simultaneous determination, nitrate, nitrite, phosphate

Nitrate and Nitrite Determination in Gunshot Residue Samples by Capillary Electrophoresis in Acidic Run Buffer,

Simultaneous determination of nitrate and nitrite in gunshot residue has been conducted by capillary electrophoresis using an acidic run buffer (pH 3.5). In previously developed capillary electrophoretic methods, alkaline pH separation buffers were used where nitrite and nitrate possess similar electrophoretic mobility. In this study, the electroosmotic flow has been reversed by using low pH running buffer without any additives. As a result of reversing the electroosmotic flow, very fast analysis has been actualized, well-defined and separated ion peaks emerge in less than 4min. Besides, the limit of detection was improved by employing large volume sample stacking. Limit of detection values were 6.7 and 4.3μM for nitrate and nitrite, respectively. In traditional procedure, mechanical agitation is employed for extraction, while in this work the extraction efficiency of ultrasound mixing for 30min was found sufficient. The proposed method was successfully applied to authentic gunshot residue samples.

Simultaneous Determination of Nitrate and Nitrite in Wrapper by High-Performance Liquid Chromatography with Cloud-Point Extraction

Simultaneous Determination of Nitrate and Nitrite in Wrapper by High-Performance Liquid Chromatography with Cloud-Point Extraction

A Simple and High Resolution Ion-Pair HPLC Method for Separation and Simultaneous Determination of Nitrate and Thiocyanate in Different Water Samples

An ion-pair reversed-phase high-performance liquid chromatography method with isocratic elution and ultraviolet detection was developed and validated for the separation and simultaneous determination of nitrate and thiocyanate. The separation was performed on a C18 analytical column with mobile phase containing 0.08 mM hexadecyltrimethylammonium bromide as an ion-pair reagent, 40 mM of acetate buffer and 30% methanol at pH 3.2. The detection was monitored at 206 nm. The response was linear from 1 to 10 mM for nitrate, with a detection limit of 0.05 mM, and 1 to 10 mM for thiocyanate, with a detection limit of 0.31 mM. Calibration curves were found to be linear in these concentration ranges with correlation coefficient better than 0.99.

The simultaneous determination of chloride, nitrate and sulphate by isotachophoresis using bromide as a leading ion

A new method has been devised to allow the determination of small inorganic anions using isotachophoresis. This method makes use of indium(III) as a counter ion to manipulate the effective mobilities of inorganic anion species by means of complexation reactions. This new procedure successfully allowed the simultaneous determination of nitrate, chloride and sulphate to be realised on a capillary scale instrument and in a chip-based separation device. The electrolyte system developed to allow the separation to be achieved employed a 10 mM bromide-based leading electrolyte containing 1.25 mM indium(III) at pH 3.15 and a terminating electrolyte of cyanoacetic acid.

Nitrogen Cycling in Natural Waters using In Situ, Reagentless UV Spectrophotometry with Simultaneous Determination of Nitrate and Nitrite

Reliable, high temporal, and spatial resolution data is essential for enhancing our understanding of aquatic nitrogen biogeochemical cycling. This paper describes a novel UV spectrophotometric sensor (ProPS, TriOS GmbH, Oldenburg, Germany) for the real time, in situ, high resolution simultaneous mapping of nitrate/nitrite (linearity 0.01 - 6 mg N L(-1), RSD's NO3-N 4-10%, NO2-N 7-14%) in fresh and estuarine waters. Good agreement (t test at p = 0.05) was found with MOOS-1 certified reference material and with reference segmented flow analysis data. River Taw deployments identified a diurnal cycle for NO3-N (0.22-0.63 mg L(-1), RSD 3.9%) and for NO2-N (0.01-0.28 mg L(-1), RSD 12.4%) with the photo-oxidation of dissolved organic nitrogen a source of diurnal nitrate/nitrite, and a large cyclical amplitude (30-62% of mean nitrate/nitrite). In situ Tamar Estuary nitrate/nitrite concentrations, mapped through the salinity gradient, were strongly correlated with suspended particulate material and inversely correlated with dissolved oxygen and pH, indicating midestuarine, bacterially mediated nitrification/denitrification, with the raised estuarine nitrite also significantly correlated with particulate organic nitrogen. Such previously unquantified inputs have important implications for N loadings calculated from coarse scale sampling and laboratory analysis, pollution assessment, and our understanding of the biological rhythms of aquatic organisms.

Use of Griess Reagent Containing Vanadium(III) for Post-Column Derivatization and Simultaneous Determination of Nitrite and Nitrate in Baby Food

An ion chromatographic method with post-column derivatization and spectrophotometric detection is presented for the determination of nitrate and nitrite (NOx) in baby food. NOx residues found naturally or added as preservatives were extracted from baby foods and determined by using ion chromatography with post-column derivatization and spectrophotometric detection. Nitrate was reduced to nitrite online by post-column reduction using vanadium(lll) chloride and heat. Nitrite reacted with Griess reagent to produce a dye that was detected at 525 nm. The use of V(III) and heat to promote the reduction of nitrate to nitrite online is a novel feature of this detection system. The determination of incurred NOx residues in samples by using AOAC Method 993.03 yielded results comparable to those obtained by ion chromatography with spectrophotometric detection. The toxic and carcinogenic metal cadmium used in the AOAC Method to reduce the nitrate to nitrite was avoided. The proposed method provides simultaneous determination of nitrate and nitrite. Average recoveries of nitrate and nitrite residues ranged from 82 to 107% for fortification levels of 25-400 ppm.

Simultaneous determination of nitrate and nitrite in biological fluids by capillary electrophoresis and preliminary study on their determination by microchip capillary electrophoresis

In order to develop a highly sensitive and high-throughput screening method for nitrogen monoxide metabolites in biological fluids, we have investigated the simultaneous determination of nitrite and nitrate, using capillary electrophoresis and microchip capillary electrophoresis. In capillary zone electrophoresis, a running buffer based on human serum components with high ionic strength has been developed for the determination of nitrite and nitrate in human serum and human saliva. We obtained successful separation of nitrite and nitrate in the serum and the saliva within 7 min under optimum analytical conditions. Linear calibration curves for nitrite and nitrate for both peak height and area were obtained by a standard addition method. The limits of detection obtained at a signal-to-noise ratio (S/N) of 3 for nitrite and nitrate in the serum were 2.6 and 1.5 microM, respectively. The values of the relative standard deviation of peak height for the serum with 9.2 microM nitrite and 20.9 microM nitrate were 5.7 and 4.1%, respectively. For on-site analysis with high-throughput screening, a microchip capillary electrophoresis method using a microchip made of quartz with a UV detector was developed. In this high-throughput format, using a running buffer with an electroosmotic flow modifier, the peaks of nitrite and nitrate in an artificial serum sample were obtained within 8 s. In high-resolution mode, using the buffer without electroosmotic flow modifier, the separation of nitrite and nitrate was obtained within 15 s. In high-resolution mode, using an artificial serum sample with 50 microM NO2- and 50 microM NO3-, the limits of detection (S/N = 3) of 41 microM for NO2- and 26 microM for NO3- were obtained. The method was applied to human serum and saliva. We obtained peaks due to nitrite and nitrate in 10-fold diluted saliva.

Simultaneous determination of nitrate and nitrite in biological fluids by capillary electrophoresis and preliminary study on their determination by microchip capillary electrophoresis

In order to develop a highly sensitive and high-throughput screening method for nitrogen monoxide metabolites in biological fluids, we have investigated the simultaneous determination of nitrite and nitrate, using capillary electrophoresis and microchip capillary electrophoresis. In capillary zone electrophoresis, a running buffer based on human serum components with high ionic strength has been developed for the determination of nitrite and nitrate in human serum and human saliva. We obtained successful separation of nitrite and nitrate in the serum and the saliva within 7 min under optimum analytical conditions. Linear calibration curves for nitrite and nitrate for both peak height and area were obtained by a standard addition method. The limits of detection obtained at a signal-to-noise ratio ( S/ N) of 3 for nitrite and nitrate in the serum were 2.6 and 1.5 μM, respectively. The values of the relative standard deviation of peak height for the serum with 9.2 μM nitrite and 20.9 μM nitrate were 5.7 and 4.1%, respectively. For on-site analysis with high-throughput screening, a microchip capillary electrophoresis method using a microchip made of quartz with a UV detector was developed. In this high-throughput format, using a running buffer with an electroosmotic flow modifier, the peaks of nitrite and nitrate in an artificial serum sample were obtained within 8 s. In high-resolution mode, using the buffer without electroosmotic flow modifier, the separation of nitrite and nitrate was obtained within 15 s. In high-resolution mode, using an artificial serum sample with 50 μM NO 2 − and 50 μM NO 3 −, the limits of detection ( S/ N = 3) of 41 μM for NO 2 − and 26 μM for NO 3 − were obtained. The method was applied to human serum and saliva. We obtained peaks due to nitrite and nitrate in 10-fold diluted saliva.

Simultaneous determination of inorganic nitrogen species by microcolumn ion chromatography

Inorganic nitrogen species (nitrate, nitrite and ammonium ions) were simultaneously determined by microcolumn ion chromatography. Nitrate and nitrite were determined by UV detection at 206 nm, whereas ammonium ion was determined by fluorescence detection at excitation 410 nm and emission 470 nm. The latter fluorescence detection is based on the postcolumn reaction of ammonium ion with o-phthalaldehyde in the presence of 2-mercaptoethanol. Effects of the reagent concentration, pH, and other reaction conditions on the signal intensity were examined, and the optimum condition was explored. The present method allowed simultaneous determination of nitrate, nitrite and ammonium ions in river water.

Flow-injection analysis of nitrate by reduction to nitrite and gas-phase molecular absorption spectrometry.

Two flow-injection manifolds have been investigated for the determination of nitrate. These manifolds are based on the reduction of nitrate to nitrite and determination of nitrite by gas-phase molecular absorption spectrophotometry. Nitrate sample solution (300 microL) which is injected to the flow line, is reduced to nitrite by reaction with hydrazine or passage through the on-line copperized cadmium (Cd-Cu) reduction column. The nitrite produced reacts with a stream of hydrochloric acid and the evolved gases are purged into the stream of O2 carrier gas. The gaseous phase is separated from the liquid phase using a gas-liquid separator and then swept into a flow-through cell which has been positioned in the cell compartment of an UV-visible spectrophotometer. The absorbance of the gaseous phase is measured at 204.7 nm. A linear relationship was obtained between the intensity of absorption signals and concentration of nitrate when Cd-Cu reduction method was used, but a logarithmic relationship was obtained when the hydrazine reduction method was used. By use of the Cd-Cu reduction method, up to 330 microg of nitrate was determined. The limit of detection was 2.97 microg nitrate and the relative standard deviations for the determination of 12.0, 30.0 and 150 microg nitrate were 3.32, 3.87 and 3.6%, respectively. Maximum sampling rate was approximately 30 samples per hour. The Cd-Cu reduction method was applied to the determination of nitrate and the simultaneous determination of nitrate and nitrite in meat products, vegetables, urine, and a water sample.

Simultaneous determination of nitrate and nitrite in saliva and foodstuffs by non-suppressed ion chromatography with bulk acoustic wave detector.

In the present paper, nitrate and nitrite in foodstuffs and saliva were simultaneously determined using a non-suppressed ion chromatography (IC) method with a bulk acoustic wave sensor (BAW) as detector, and 1.5 mmol/L potassium hydrogenphthalate (KHP) as mobile phase. The IC-BAW method is simple, rapid and accurate. The determination limits for nitrite and nitrate are 0.20 and 0.30 mg/L, respectively. The IC-BAW is comparable and agrees with the conventional spectrophotometric method for nitrite and nitrate determination.

Bulk Acoustic Wave Sensor for Non-suppressed Ion Chromatographic Determination of Nitrate and Other Inorganic Anions in Vegetables

A new type of bulk acoustic wave sensing device based on a conductivity-bulk acoustic wave frequency response is applied in ion chromatography to determine nitrate and other inorganic ions in vegetables. The present method has the advantages in its rapidity, simplicity, sensitivity and accuracy. Detection limits (peak=3[sgrave]) are obtained for NO3 −, Cl−, NO2 −, H2PO4 − and SO4 2− at concentrations of 1, 0.6, 1, 7 and 3 ng (on column), respectively. Neither derivatization nor a clean-up step is necessary besides filtration. For the IC analysis, the analytical column is a Shim-pack IC AI column, and the eluent is 2.0 mM phthalic acid solution with pH 4.0. A comparison of IC-SBAW with conventional IC is made. The method allows the simultaneous determination of nitrate and other inorganic ion levels in vegetables.

Nitrate and nitrite determination in complex matrices by gradient ion chromatography

Simultaneous determination of nitrate and nitrite in human serum has been accomplished using gradient ion chromatography and direct UV detection, with centrifugal ultrafiltration as the only pretreatment. The method has advantages over previous techniques in both ease of use and cost per assay. The sensitivity is adequate for use as a monitor of nitric oxide induced changes in serum nitrate and nitrite levels.

Simultaneous Determination of Nitrate and Nitrite in Biological Samples by Multichannel Flow Injection Analysis

An automated method for the simultaneous determination of nitrite and nitrate in biological samples by using a multichannel flow injection analyzer has been developed. The method was based on the reaction of nitrite with Greiss reagent. The sample solution was injected and equally divided into two channels; channel one (1) represented total nitrite obtained by cadmium reduction of nitrate to nitrite while channel two (2) represented only nitrite. The absorbance of the color product was measured by photometric detectors with 540-nm filters. This method combines high reproducibility of sample introduction via flow injection and sensitivity of spectrophotometric detection. The detection limit is 25 nMfor both nitrite and nitrate. The chemistry manifolds are constructed of Teflon tubing which, along with a low-pressure Flowfit connector system, provides for low maintenance, ease of use, and high sample throughput. We demonstrated that the system can be used for the determination of both nitrate and nitrite in a variety of biological samples as well as a comparison of the results from this system and the HPLC system.

Determination of Nitrate and Nitrite in Tap Water and Vegetables by High Performance Liquid Chromatography

A method is presented for the simultaneous determination of nitrate and nitrite by high performance liquid chromatography (HPLC) with an anion exchange (Partisil SAX) column, a 0.030 M potassium dihydrogen orthophosphate/phosphoric acid buffer of pH 3.5 mobile phase and UV detector. Without using a preconcentration system the detection limits are 0.2 ng for nitrate and 1 ng for nitrite. A suitable extraction procedure has been established for its application to the analysis of tap water, lettuce and apple tree leaves. The reproducibility of the method, calculated as the relative standard deviations in the optimum range, is always less than 2% for nitrates and 5% for nitrites.

Simultaneous high‐performance liquid chromatographic determination of nitrate, nitrite, and organic pesticides in soil solution using a multidimensional column with ultraviolet detection

Abstract In many fertilizer trials, the amount of nitrate‐nitrogen in soil solution must be quantified frequently because nitrate is easily leached. Because pesticides are generally applied to cropland with fertilizers, quantitative information is needed on the concentration of these chemicals still available in the soil. Information on nitrite, nitrate and pesticide concentrations in food, water and environmental samples is essential because of their toxicity and potential for groundwater and surface water contamination. Most of the methods currently used for nitrate determination also account for nitrite, because nitrite and some organics act as interferences. Some of the existing analytical methods require sample reduction or derivatization, complex solvent mixtures or large sample volumes which make analysis times long. A High‐Performance Liquid Chromatography (HPLC) method has been developed for the simultaneous determination of nitrate, nitrite and organic pesticides in soil solution samples and ext...

Simultaneous determination of nitrate, chloride, sulfate, and phosphate in plant materials by ion chromatography

Abstract Simultaneous determination of anions in plant materials is needed. A simple and precise ion‐chromatographic (IC) method for ‐ O2‐ 4 simultaneous determination of NO3, Cl‐ , S. , and PO3‐ 4. in plant samples was developed. It involves extraction of these anions with deionized water and their simultaneous determination by IC. The averages of 10 plant samples by the IC method agreed closely with those obtained by the steam‐distillation method for NO‐ 3 (0.158 vs 0.164%), titrimetric method using AgNO3 and K2CrO4 for Cl‐ (1.22 vs 1.19%), and colorimetric heteropoly blue method for PO3‐ 4 (0.335 vs 0.330%). The average SO2‐ 4 S value of 10 plant samples by the IC method (0.067%) was somewhat lower than the corresponding value (0.075%) obtained by the reduction and colorimetric determination of methylene blue. The IC method is based on separation of the anions by a separator column containing Dionex low‐capacity anion‐exchange resin in the HCO‐ 3 form and on converting the various anions to their corresponding acids by a suppressor column containing a strong cation‐exchange resin in the H+ form. A solution of 3.0 mM Na2CO3 + 1.8 mM Na2CO3 was used as the eluent, and electrical conductivity is used as the mode of detection. The method is precise and accurate and can detect as little as 0.1 mg/L of NO‐ 3‐N, Cl‐, SO2‐ 4‐S, or PO4‐3‐P in plant extracts. In addition to those anions, malic acid was separated and determined. With the IC method, the four anions indicated and malic acid can be determined simultaneously in 2 mL of plant extract in approximately 20 min.