Functionalization of platinum nanoparticles for electrochemical detection of nitrite

In this work, a novel electrochemical method for nitrite detection by using functionalized platinum nanoparticles (PtNPs) is proposed. Firstly, a gold electrode is immobilized with 4-(2-aminoethyl)benzenamine. Then, PtNPs are modified with 5-[1, 2]dithiolan-3-yl-pentanoic acid [2-(naphthalene-1-ylamino)-ethyl]amide (DPAN). Consequently, in the presence of nitrite ions, Griess reaction occurs between 4-(2-aminoethyl)benzenamine on the electrode and DPAN on PtNPs, thus PtNPs are localized onto the electrode surface. So, PtNPs-electrocatalyzed reduction of H₂O₂ can be achieved to correlate the electrochemical signal with the concentration of nitrite ions. The linear concentration range can be as wide as 10–1,000 μM, while the detection limit is as low as 5 μM. The proposed method has been also successfully applied to the detection of nitrite with the local lake water, and the result is well consistent with that obtained by UV-visible spectrophotometric method. So, this method has potential use for monitoring nitrite in drinking water supplies in the future.     

A simple and rapid spectrophotometric method for the determination of nitrite by its decolorizing effect on peroxovanadate complex

A rapid, simple, and most economical spectrophotometric method was proposed for the determination of nitrite in various water samples, soil samples, and roots of leguminous plants. The method is based on decolorizing effect of nitrite on complex formed between hydrogen peroxide and vanadate in acidic medium. The decolorization of that complex by nitrite was exploited to monitor the reaction spectrophotometrically at 470 nm.The method was optimized for effect of concentrations of ammonium metavanadate, hydrogen peroxide, various acids, concentrations of sulphuric acid, order of reagents addition and color stability. The color of the complex was found to be stable for about 2 days, and the stability constant of the complex was also calculated by modified Job's method. The linearity range of the calibration graph was over 6.67-66.7 microg ml(-1) of nitrite with molar absorptivity, 0.276 x 10(3) mol(-1) l cm(-1) and Sandell's sensitivity, 0.1667 microg cm(-2). The method was applied successfully for the determination of nitrite in soil samples, various wastewater samples and roots of leguminous plants.     

溴酸钾氧化吡口罗红G催化动力学光度法测定痕量NO-2

研究了在磷酸介质中亚硝酸根催化溴酸钾氧化吡口罗红Ｇ而使其褪色，建立了催化动力学光度法测定痕量亚硝酸根的新方法，测定范围为０．２～２０μｇ／ｍＬ，检出限为０．２ｎｇ／ｍＬ，用于食品和水样中的亚硝酸根测定获得满意结果     

溴酸钾氧化亮绿SF催化光度法测定痕量亚硝酸根

本文基于亚硝酸根对溴酸钾氧化亮绿ＳＦ而使其褪色所起的催化作用，建立了高灵敏度催化吸光光度法测定痕量亚硝酸根的新方法，测定范围为０．０５－２０ｎｇ／ｍｌ，用于不同水样中亚硝酸根的测定，获得了满意结果。     

2-Amino-5,7-dimethyl-1,8-naphthyridine as a fluorescent reagent for the determination of nitrite

A new fluorescent reagent 2-amino-5,7-dimethyl-1,8-naphthyridine (ADMND) was proposed for the determination of trace nitrite. The reaction is based on the diazotization of naphthyridine amine with nitrite to form a diazonium salt that hydrolyzed when boiling to give hydroxyl group substituted naphthyridine. Fluorescence quenching degree of ADMND by nitrite ion is linear in the nitrite concentration range of 1 x 10(-7) to 2.5 x 10(-6)mol l(-1) with a detection limit of 4.06 x 10(-8)mol l(-1). Reaction and determination acidity for nitrite is the same which made the method much simpler compared with the widely accepted fluorescence method with DAN as a fluorescence reagent.     

Flow-injection analysis-spectrophotometric determination of nitrite and nitrate in water samples by reaction with proflavin

A flow-injection manifold is proposed for determination of nitrite based on the reaction with 3,6-diamino acridine (proflavin sulfate) in hydrochloride acid medium. The assembly is adapted for nitrate determination by including a reductive column filled with copperized cadmium. The influence of foreign substances is also studied. The method gives a linear calibration graph over the range 0.06-4 mg 1(-1) nitrite, with an RSD <0.5%. The method was applied to nitrite and nitrate determinations in either waste water or coastal marine water samples.     

Determination of nitrite in food samples by second-order calibration of kinetic spectrophotometric data

A method for the determination of nitrite in soil and vegetable samples by UV-Vis spectroscopy was proposed. The kinetic UV-Vis data were collected during the reaction between nitrite and 4-amino-3-hydroxynaphthalene-1-sulfonic acid with concentration of 0.001 M and pH 1.6. Data were collected by standard addition method. Multivariate curve resolution-alternating least squares was employed to analyze data with non-negativity and three-way data structure constraints. The method can be used to solve matrix effect and unknown interferents in the determination of nitrite in complex samples. The proposed method was used to determine nitrite at low mg/L levels with satisfactory results in soil, lettuce, cabbage and cucumber samples.     

A Fluorescence Quenching Method for the Determination of Nitrite with Indole

A new fluorescence quenching method has been developed to determine nitrite in water and food samples. The method is based on the reaction between nitrite and the fluorescent indole to form a compound which has no fluorescence in acidic medium. The fluorescence intensity was measured in 1 cm quartz cell with excitation and emission wavelengths of 285 and 350 nm, respectively. The relationship was obtained between the fluorescence intensity and nitrite concentration in the range 0.01–0.6 μg ml⁻¹. The detection limit was 2.5 ng ml⁻¹. The proposed method was applied to determine nitrite in water and food samples. The mechanism involved in the reaction was studied.     

Sensitive flow injection colorimetry of nitrite by catalytic coupling of N-phenyl-p-phenylenediamine with N,N-dimethylaniline

A rapid, sensitive and selective flow-injection colorimetry method is proposed for the determination of trace amounts of nitrite. It is based on the nitrite's catalytic effect on the oxidative coupling of N-phenyl-p-phenylenediamine with N,N-dimethylaniline to produce a green dye (lambda(max)=735 nm) in the presence of bromate. The change in absorbances of the dye were monitored in continuos flow mode. Linear calibration curves were obtained for the nitrite concentration range 2.0-100 ng ml(-1). The proposed method had a low detection limit (0.6 ng ml(-1)) and high sample throughput (approximately 30 samples h(-1)). The RSD for 10 and 50 ng ml(-1) nitrite were 2.4 and 1.3% (n=10), respectively. The method has been successfully applied to the determination of nitrite in river water samples.     

Flow-Injection Catalytic Spectrophotometric Determination of Trace Amounts of Nitrite

ABSTRACT

A flow-injection catalytic spectrophotometric method is proposed for the determination of nitrite based on its catalytic effect on potassium bromate oxidation of acridine orange in phosphoric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of acridine orange at 491.5 nm coupling with the stopped-flow technique. The calibration curve was linear between 3.4 and 65 ng/mL, and the detection limit was 2.2 ng/mL. Up to 30 samples can be analyzed per hour with a relative precision of ca. 1.9%. The proposed method was successfully applied to the determination of nitrite in waters and food samples with satisfactory results.     

Kinetic Spectrophotometric Determination of Nitrite with Tropaeolin 00-Bromate System

A simple accurate kinetic spectrophotometric method was developed for the determination of nitrite based on its catalytic effect on the redox reaction between tropaeolin 00 and bromate in acid medium. Nitrite was determined by measuring the decrease in the absorbance of tropaeolin 00 at 530 nm by a fixed time method, after 30 s from the initiation of the reaction. The calibration graph was linear in the range 6–500 ng mL^?1 of nitrite and the detection limit was 2 ng mL^?1. The proposed method is selective and is useful for the determination of nitrite in drinking water samples.     

A fluorescence quenching method for the determination of nitrite with Rhodamine 110

A simple and sensitive fluorescence quenching method for the determination of trace nitrite has been developed. The method is based on the reaction of Rhodamine 110 with nitrite in acidic medium to form a new compound, which has much lower fluorescence. The optimum experimental conditions were studied. The linear range was obtained at a nitrite concentration of 1.0 x 10(-8)-3.0 x 10(-7)mol l(-1) with a detection limit of 7.0 x 10(-10) mol l(-1) (S/N=3). The proposed method has been successfully applied to the determination of nitrite in tap water and lake water without extraction.     

Flow-injection catalytic spectrophotometric determination of nitrite using the redox reaction between naphthol green B and potassium bromate

A flow injection catalytic spectrophotometric method is proposed for the determination of nitrite based on its catalytic effect on the redox reaction between naphthol green B and potassium bromate in phosphoric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of naphthol green B at the maximum absorption wavelength of 722 nm. The detection limit is 0.5 ng cm(-3) in a sample volume of 90 mm(3). Up to 50 samples can be analyzed per hour with a relative precision of ca. 2%. The method is free from most interferences, especially from large amounts of nitrate. The procedure was successfully applied to the determination of trace nitrite in natural waters.     

浊点萃取光度法测定水样中亚硝酸根

A new method for the determination of trace nitrite by spectrophotometric after cloud point extraction was proposed.The effects of experimental conditions such as acidity,concentration of chromogenic reagent and surfactant,equilibration temperature and time on cloud point extraction were discussed.Under the optimum conditions,a good linear relationship was obtained in the range of 4.0～200 μg/L of the nitrite(r=0.9998),the detection limits of 0.43 μg/L.The recoveries fell in the range from 97.7% to 102.4% an...     

A Novel Flow-Injection System for Simultaneous Determination of Nitrate and Nitrite Based on the Use of a Zinc Reductor and a Bulk Acoustic Wave Impedance Detector

A novel flow-injection system has been developed for the simultaneous determination of nitrate and nitrite present in water, foodstuffs, and human saliva. The system is based on the use of a zinc-filled reduction column and a bulk acoustic wave impedance sensor (BAWIS) as detector. With water as carrier stream, both nitrate and nitrite are converted on-line to ammonia, whereas with sulfamic acid, only nitrate is converted to ammonia. The ammonia formed diffuses across a PTFE membrane and is trapped in an acid stream causing a change in the solution conductance, which is monitored by a BAWIS detector. At a throughput of about 60 h⁻¹, the proposed system exhibited a linear response to the concentration of nitrate and nitrite from 2.5 μM to 1.00 mM, with detection limits of 1.7 and 1.8 μM, respectively, and the relative standard deviation of the peak heights (n= 6) ranged between 0.83 and 1.75% for the entire working range. In analysis of real samples, the simultaneous determination of nitrate and nitrite was achieved by the proposed method with a simple change of the carrier stream between water and sulfamic acid, and the results agreed well with those of conventional colorimetry.     

荧光分析法测定痕量亚硝酸根

在硫酸介质中,亚硝酸根能还原吡咯红Y,使其荧光猝灭据此提出了一个测定痕量亚硝酸根的荧光分析法,方法的检出限为2.7ng/mL,线性范围为6.0-88ng/mL,可直接用于电厂废水、自来水、井水中亚硝酸根的测定。     

Flow injection catalytic spectrophotometric simultaneous determination of nitrite and nitrate

A new flow injection catalytic spectrophotometric method is proposed for the simultaneous determination of nitrite and nitrate based on the catalytic effect of nitrite on the redox reaction between crystal violet and potassium bromate in phosphoric acid medium and nitrate being on-line reduced to nitrite with a cadmium-coated zinc reduction column. The redox reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of crystal violet at the maximum absorption wavelength of 610 nm. A technique of inserting a reduction column into sampling loop is adopted and the flow injection system produces a signal with a shoulder. The height of shoulder in the ascending part of the peak corresponds to the nitrite concentration and the maximum of the peak corresponds to nitrate plus nitrite. The detection limits are 0.3 ng ml⁻¹ for nitrite and 1.0 ng ml⁻¹ for the nitrate. Up to 32 samples can be analyzed per hour with a relative standard deviation of less than 2%. The method has been successfully applied for the simultaneous determination of nitrite and nitrate in natural waters.     

A simple and accurate method to determine nitrite and nitrate in serum based on high‐performance liquid chromatography with fluorescence detection

A simple method for accurate determination of nitrite and nitrate in serum was proposed to avoid the variation of nitrate reduction. For nitrite determination, serum samples were directly precipitated with methanol pre‐nitrate conversion, and then the supernatant reacted with 2,3‐diaminonaphthalene (DAN) to form 2,3‐naphthotriazole (NAT), which was quantitatively analyzed by high‐performance liquid chromatography coupled with fluorescence detection (HPLC‐FL). For nitrate determination, samples were firstly heated at 70°C for 10 min to inactivate endogenous reductase‐inhibiting proteins, then nitrate in the samples was quantitatively reduced to nitrite by reductase added experimentally. The difference in total nitrite concentrations between pre‐ and post‐nitrate conversion was used to calculate the amount of nitrate in the samples. In addition to good specificity, high sensitivity, satisfactory accuracy and reproducibility, our method is simple and suitable for the quantitative determination of nanomolar level of nitrite and nitrate in a large number of serum samples. Copyright © 2013 John Wiley & Sons, Ltd.     

荧光探针8-(3’,4’-二氨基苯)-二氟化硼-二吡咯甲烷用于光度法 灵敏测定食品中亚硝酸根和硝酸根

新型荧光探针8-(3’,4’-二氨基苯)-二氟化硼-二吡咯甲烷本体荧光很弱, 在酸性条件下, 和亚硝酸盐于30 ℃下反应15min后生成强荧光的三氮唑产物. 硝酸根可通过锌粉和氯化镉还原成亚硝酸根. 由此建立了一种新的荧光光谱法灵敏测定食品中的亚硝酸根和硝酸根. 其线性范围为0.06～6 μmol&#8226;L－1. 当信噪比等于3时, 方法的检出限为2 nmol&#8226; L－1. 将该方法首次用于多种食品中亚硝酸盐和硝酸盐的测定, 加标回收率为98.16%～103.20%.     

A kinetic method for the determination of nitrite by its catalytic effect on the oxidation of chlorpromazine with nitric acid.

A catalytic spectrophotometric method for the determination of trace amounts of nitrite is proposed. In acidic solution, chlorpromazine (CP) is oxidized by nitric acid to form a red compound, which is further oxidized to a colorless compound. The reaction is accelerated by trace amounts of nitrite and can be followed by measuring the absorbance at 525 nm: nitrite ion is regenerated and multiplied by nitric acid. The absorbance of the reaction increased with an increase in the reaction time, reached a maximum and decreased rapidly. Since the time required for the absorbance to reach the maximum decreased with increasing nitrite concentration, this value was used as the measured parameter for the nitrite determination. Under the optimum experimental conditions (2.3 M nitric acid, 1.2 x 10(-5) M CP, 40 degrees C), nitrite can be determined in the range 0-100 microg l(-1). The relative standard deviations (n = 6) are 4.7 and 1.8% for 40 and 100 microg l(-1) nitrite, respectively. The detection limit of this method (3sigma) is 1.2 microg l(-1). This method was successfully applied to a determination of nitrite in natural water samples.