Method For Determination Of Nitrate Research Articles

Development of an Analytical Method for Determination of Nitrate in Leafy Vegetables Using Ion Chromatography

The presence of nitrate in food in general may indicate a threat to human health. Nitrate can be converted to nitrite, a toxic species, in saliva and in the gastrointestinal tract. This work describes a precise and sensitive method using ion chromatography to determine nitrate (NO-3) in hardwood vegetables. In the proposed method the extraction of the nitrate of the vegetal matrix was carried out in an aqueous medium at a temperature of 70°C. The limit of detection (LOD) for the determined ion was 0.06 μg·L-1. The accuracy of the method was evaluated as the relative standard deviation (DPR) of the analytical signal area and the retention time, with values of 0.63% and 0.41%, respectively, for a solution of NO-3 5.0 mg·L-1. The detector presented linearity between 0.22 and 10 mg·L-1 with a correlation coefficient of 0.9999. The accuracy of the procedure was evaluated by addition/recovery test using real samples in which values greater than 95% were obtained. The validation of the proposed method was also performed by comparing the NO-3 concentrations obtained using the selective ion electrode method (EIS). The paired Student t test and the F test showed that both methods provide equivalent results concerning accuracy and precision.

A Simple Electrochemical Method for Nitrate Determination in Leafy Vegetables

A fast and easy electrochemical method for nitrate determination in leafy vegetables was developed. It is a much cheaper method compared to the HPLC method or chemiluminescence detection, the most sensitive method in determination of nitrate, which requires expensive instrumentation. A nitrate ion selective electrode was employed and the electric potentials were measured before and after a series of standard nitrate solutions added to the vegetable sample solution without any pre-treatment.

A VALIDATED ULTRA-PERFORMANCE LIQUID CHROMATOGRAPHY METHOD FOR NITRATE AND NITRITE MEASUREMENT

Objective: The objective of this study was to develop a simple and sensitive ultra-performance liquid chromatography (UPLC) method for determination of nitrate and nitrite in plant extracts and biological samples.Methods: Nitrate was analyzed directly by injecting the filtered sample into UPLC and monitoring the chromatogram at 222 nm whereas, for nitrite analysis, the samples were derivatized using Griess reagent, and chromatogram was monitored at 520 nm. The method was validated for accuracy and precision.Results: The calibration curve was obtained in the range of 0.05–500 μg/ml for nitrate and 5–3200 ng/ml for nitrite which were extremely linear, where both correlation coefficients were >0.9990. Accuracy of the method was found as 99.87% and 100.24% for nitrate and nitrite, respectively. High degree of precision and repeatability was obtained since coefficient of variation values were <2.1%. Among the three commonly used anticoagulants, i.e., K2EDTA, Li-Heparin, and sodium citrate, Li-Heparin did not show any interference with nitrate or nitrite analysis.Conclusion: Results clearly indicate the sensitivity and suitability of the developed method for estimation of nitrate and nitrite in plant extracts and biological samples. Our findings also indicate that Li-Heparin does not interfere with analysis and thus can be used as anticoagulant while collecting blood.

Method for Nitrate Determination in Water in the Presence of Nitrite

Method for Nitrate Determination in Water in the Presence of Nitrite

Development and validation of a sub-minute capillary zone electrophoresis method for determination of nitrate and nitrite in baby foods

This paper proposes an innovative sub-minute capillary zone electrophoresis method and a simple sample preparation procedure for simultaneous nitrate and nitrite determination. The novelty of the method is the simplicity of execution and the capacity to separate the analytes in less than 0.5 min. The BGE is composed of 10 mmol L(-1) perchloric acid and 40 mmol L(-1) β-alanine at pH 3.96. Thiocyanate was used as an internal standard. The method was validated following the Eurachem guidelines and applied to the analysis of 14 baby food samples. Of these samples, one had nitrate levels above that permitted by Brazilian legislation (250 mg kg(-1)) and for all samples the nitrite concentrations were under the limit of quantification. The good analytical performance verified for this method indicates that it is suitable for implementation in food laboratories for the routine determination of nitrate and nitrite as an alternative to the official method provided by the AOAC.

Optimization of Zinc-Cadmium Reduction Method for Determination of Nitrate in Seawater

The linear of nitrate standard curve and blank values were ​​affected by many factors such as blank water quality, temperature, etc. The seawater determination of nitrate optimization methods in this paper based on the GB "marine monitoring specification (seawater analysis)"GB12763.4-2007. It indicated that doubly distilled water with excellent pure sodium chloride for preparation of artificial seawater produce a good linear of standard curve and lowest blank value at 20 °C -25 °C.

Determination of Nitrate in Water by HPLC

We established a method fordetermination of nitrate in water by High Performance Liquid Chromatography(HPLC). The sample was analysed by HPLC-ADA and was quantitated by externalstandard method after being simply processed. This methd has the advantages ofhigh separation efficiency and fast analysis. The experiment result showed thatthe linearly dependent coefficient was0.994, the recovery rate was between 98.7%～105.7%,the relative standard deviation（RSD）wasless than 2.1 %, and the lowest detectable limit is 0.01ng (S/N=1.6).

Evaluation of an HPIC Method for Determination of Nitrates in Vegetables

The aim of the work was to verify the reliability of an HPIC method for determination of nitrates in vegetables using statistical analysis to evaluate validation parameters according the ISO/IEC 17025:2005. Standard solutions were used for the construction of a calibration curve, which was supported by Varian Star Workstation software. All calculated validation characteristics were summarized in an Excel table with final evaluation of the method. Repeatability was characterized by the selected variation coefficient sR, calculated from the standard deviation sd and arithmetic mean from a series of measurements under repeat conditions, accuracy by the variation coefficient sR, and recovery. The repeatability of the method of 3.62% is under the set limit of 5%. The calculated uncertainty was 4.22% with a recovery of 99.2%. Determination of nitrate was linear over the whole range of the calibration graph. The LOQ was 0.60 mg L−1, which is fully acceptable within the requirements for nitrate determination in plant materials. Standard uncertainty of these methods was calculated as an expanded uncertainty according to Eurachem documents in the PC program Metro2003, version 2.30.

Nitrite as undesirable substances in animal feed ‐ Scientific Opinion of the Panel on Contaminants in the Food Chain

Nitrite as undesirable substances in animal feed ‐ Scientific Opinion of the Panel on Contaminants in the Food Chain

A diagnostic tool for determining the quality of accuracy validation. Assessing the method for determination of nitrate in drinking water

Realistic internal validation of a method implies the performance validation experiments under intermediate precision conditions. The validation results can be organized in an X (NrxNs) (replicates x runs) data matrix, analysis of which enables assessment of the accuracy of the method. By means of Monte Carlo simulation, uncertainty in the estimates of bias and precision can be assessed. A bivariate plot is presented for assessing whether the uncertainty intervals for the bias (E +/- U(E)) and intermediate precision (RSDi +/- U(RSDi) are included in prefixed limits (requirements for the method). As a case study, a method for determining the concentration of nitrate in drinking water at the official level set by 98/83/EC Directive is assessed by use of the proposed plot.

Determination of nitrate by suppressed ion chromatography after copperised-cadmium column reduction

The nitrate-selective copperised-cadmium (Cu-Cd) reduction reaction coupled directly to the highly sensitive nitrite ion chromatographic detection, produced a more precise method for determination of nitrate than any one of the two conventional methods. A borate buffer solution used in the reduction reaction, in place of the conventional ammonium–EDTA buffer solution, eliminated interferences from co-eluting ions in the subsequent ion chromatographic detection of nitrite. Optimised experimental conditions included using a packed-bed Cu-Cd reductor column length of 12.5 cm, a solution flow rate of 3.0 ml/min, and using 10.0 ml of borate buffer solution for each 20.0 ml of nitrate-containing solution. Precision was high for results obtained within a greatly extended linear dynamic range of 0.006–1.20 mg/l NO 3 −, with a much lower limit of detection of 0.40 μg/l NO 3 −. Cu-Cd reductor column efficiency was 98.20 ± 6.03%. Validation of the method was undertaken using certified reference materials. The method was successfully applied to analysis of dam water, river water and storm water samples, producing more precise results than either the conventional colorimetric method or the conventional ion chromatographic method.

Simplified version of the sodium salicylate method for analysis of nitrate in drinking waters

The salicylate method for determination of nitrate in drinking waters has been simplified by using the calibration solutions for 54 days, and therefore, reducing the work time. The results obtained can be considered satisfactory with regard to limit of determination (0.10 mg l −1 nitrate as nitrogen (NO 3 −-N)), precision (relative standard deviations <4% for five determinations were found) and accuracy (recoveries from 88 to 106% for nitrate in spiked drinking water were obtained).

COMPARISON OF METHODOLOGIES FOR NITRATE DETERMINATION IN PLANTS AND SOILS

ABSTRACT Several procedures have been described for the determination of nitrate by biological reduction, cadmium reduction, and salicylic acid electrophilic substitution. However, all are subject to interference by constituents of soil and plants. The aim of this work is to compare the results obtained using these methods with those obtained by ion chromatography. Because most of the interferences to which these methods are subject are due to organic matter, three pretreatments to reduce the presence of organic matter in the sample extracts were compared: 1 – adding activated charcoal; 2 – filtering through a 0.45 μm filter; and 3 – ultra-filtering through a 10 kDa membrane. A method and respective pretreatment were considered acceptable for measurement of nitrate in a particular soil or plant extract if: (i) nitrate added to the extraction medium used (without the soil or the plant material) was quantitatively recovered, and an acceptable reference curve could be established; (ii) between 95% and 105% of the nitrate added to the sample was recovered; and (iii) replicates agreed within 10%. Method recommendation for future analysis was based on: 1 – simplicity; 2 – accuracy; 3 – interferences; 4 – equipment needed; and 5 – cost of analysis. Application of these criteria to the results indicated that the biological reduction of nitrate with nitrate reductase (NR) from E. coli is the most suitable method for nitrate determination in laboratories that are not equipped with an ion chromatograph.

Improved ultraviolet spectrophotometric method for determination of nitrate in natural waters

An improved UV spectrophotometric method for determination of nitrate in natural waters was proposed and the determination accuracy of the method was discussed in this study. As a result of estimation of the proposed method, adoption of 215 and 220 nm for detection of nitrate and interfering substances resulted in decreasing standard error to about a half of that of a conventional spectrophotometric method. One of the reasons was thought that the coefficient of variation of relative absorbance of interfering substances (rs) at 215 nm was smaller and more stable than that at 275 nm, which was used in the conventional method. The other reason inferred was that most of the interfering substances absorbed UV light at wavelengths of 215 and 220 nm. Although rs has to be renewed when targeted water quality is under extreme conditions, the procedure of the proposed method is very simple, namely only measuring two UV absorbances of a filtrated sample, and more accurate than the conventional spectrophotometric method. Consequently, the proposed method is available for rapid determination of nitrate in natural waters.

Evaluation of a second derivative UV/visible spectroscopy technique for nitrate and total nitrogen analysis of wastewater samples

A method for nitrate analysis based on second derivative UV/Visible spectroscopy was developed by Simal et al. (1985: Simal J., Lage M. A., and Iglesias I. (1985) Second derivative ultraviolet spectroscopy and sulfamic acid method for determination of nitrates in water. J. Assoc. Analyt. Chem. 68, 962–964) and Suzuki and Kuroda (1987: Suzuki, N. and Kuroda R. (1987) Direct simultaneous determination of nitrate and nitrite by ultraviolet second-derivative spectrophotometry. Analyst 112, 1077–1079), and later modified for the analysis of total nitrogen in aqueous samples of varying nitrate:organic nitrogen ratios ( Crumpton et al., 1992 : Crumpton W. G., Isenhart T. M. and Mitchell P. D. (1992) Nitrate and organic N analyses with second-derivative spectroscopy. Limnol. Oceanogr. 37, 907–913). The procedure uses the second derivative of the absorption spectrum for nitrate (NO − 3), which has a peak at ∼224 nm that is proportional to the NO − 3 concentration. Samples for total N analysis are first oxidized to NO − 3 by persulfate digestion. The objectives of this study were to: (1) test the accuracy and precision of the second derivative method through the use of NIST-traceable wastewater check samples; (2) determine whether the second derivative method for nitrate analysis can be used for wastewater samples and whether the method compares favorably with other currently used nitrate analysis methods; and (3) use the method to analyze wastewater samples containing a range of nitrate and total nitrogen concentrations. Our results indicated that the method needed to be modified to include a longer digestion time (60 min) and dilution of samples prior to digestion (if needed). With the modified method, nitrogen recoveries were not significantly different ( P≥0.05) from samples with known N concentrations. In addition, nitrate concentrations in constructed wetland and wastewater samples analyzed by both second derivative spectroscopy and ion chromatography were not significantly different. Total nitrogen concentrations in wastewater samples also compared favorably to the same samples analyzed by Kjeldahl digestion. The method is faster, simpler, requires smaller sample volumes, and generates less waste than many EPA-approved methods of N analysis, and may offer a suitable alternative to current methods for analysis of nitrate and total N in wastewater samples.

Sequential potentiometric determination of chloride and nitrate in meat products

The analytical control of chloride and nitrate in meat products is important. For this reason in this work a sequential method for their determination by using chloride- and nitrate-selective electrodes has been developed. The extraction of both ions was carried out by stirring the samples for 30 min in a hot 5.0 × 10 −2 mol litre −1 sulphuric acid solution. Direct potentiometry for chloride and multiple standard additions for nitrate were used as analytical techniques of measurement. The mean coefficient of variation and the average percentage of spike recoveries calculated for the chloride determination in five different meat products were 0.68% and 101%, respectively. For the nitrate determination these data were 0.84% and 101%, respectively. The limits of detection were 71.0 mg kg −1 and 23.2 mg kg −1 for chloride and nitrate, respectively. The mean chloride and nitrate concentrations determined by application of the developed method to 50 samples of meat products were found to be 21.1 g kg −1 and 133.5 mg kg −1, respectively. Throughout the study, the Volhard titration for determination of chloride and the brucine spectrophotometric method for determination of nitrate, adopted as reference methods, were used simultaneously. Comparison of variances and linear regression analysis of the results obtained were carried out to validate the proposed sequential potentiometric method.

A Rapid Method for Determination of Nitrate in Soil by Hydrazine Reduction Procedure

A Rapid Method for Determination of Nitrate in Soil by Hydrazine Reduction Procedure

Voltammetric determination of nitrate with a modified carbon paste electrode

AbstractA method for the voltammetric determination of nitrate in drinking water is presented. Nitrate exerts a catalytic effect on the reduction and reoxidation of thallium (1 ↔ 0) in cyclic and differential pulse voltammetry, leading to a peak enhancement. Nitrate can be preconcentrated together with tetrachlorothallate(III) from hydrochloric acid solutions onto a carbon paste electrode modified with a liquid anion exchanger. (Amberlite LA2) under open circuit conditions. After reduction of the Tl(III) to Tl(0) at the electrode surface at a potential of −1.2 V (vs. SCE), the increase of the reoxidation current of Tl(III) to TI(I) by nitrate is exploited for analytical purposes. Linearity between current and concentration exists for 0.5 to 60 μg · mL−1 nitrate when applying anodic differential pulse vokammetry. Mechanical regeneration of the electrode surface is necessary after each measurement. The interference of other anions and the influence of methodical parameters are invistigated. The applicability of this method for the determination of nitrate in drinking wat concise overview on the the electroanalytical techniques for the Quantitative determination of nitrate is also presented.

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.

A note of caution on reduction conditions when using the cadmium-copper column for nitrate determinations in aquatic environments of varying salinities

In a widely used method for nitrate determination in seawater, the reduction of nitrate occurs under acidic conditions because the sample is mixed with pure ammonium chloride. Under these conditions, about 40% of the nitrite formed is reduced further, leading to poor sensitivity and reproducibility. When the pH of ammonium chloride is adjusted to 8.5 with ammonia, the loss of nitrite is only about 5%, the sensitivity is improved by a factor of two, and the precision by a factor of five for seawater as well as freshwater. For samples of varying salinities ((0–30) S × 10 3), the use of buffered ammonium chloride obviates the need for salinity corrections.