A convenient and efficient protocol for the synthesis of 4(1H)-cinnolones, 1,4-dihydrocinnolines, and cinnolines in aqueous medium: application for detection of nitrite ions

3-Aryl/alkyl-4(1H)-cinnolones are obtained in one step from 2-aryl/alkylethynyl aniline by reaction with sodium nitrite and dilute hydrochloric acid via Richter cyclization. The alkyl cinnolones on reduction with Sn/HCl furnish 1,4-dihydro-3-alkylcinnolines, which are converted to 3-alkylcinnolines by treatment with NaNO₂/HCl/KI. The whole process is carried out in aqueous medium at ambient temperature within a short reaction period. The reaction of 2-phenylethynyl aniline exhibits yellow color with UV absorbance at 391 nm and has been successfully tested for the detection of nitrite ions in water at parts per million concentration.     

Electrochemical Detection of Nitrite Based on Reaction with 2,3‐Diaminonaphthalene

Abstract

A voltammetric method for the determination of trace amounts of nitrite is proposed. In acidic solution, 2,3‐diaminonaphtalene (DAN) reacts with nitrite to form the 1‐N‐naphtotriazole. At the end of this reaction, the unreacted DAN was measured at a carbon paste electrode by using differential pulse voltammetry. Different parameters, such as pH of the medium, effect of the reaction time, and the effect of DAN concentration on the percentage of signal decrease, have been optimised. Detection limit of 0.2 µmol L^?1 was achieved. Results were improved by using bath injection analysis technique which permit 120 analysis per hour. Nitrites were determined in the real samples. The results have been compared with those obtained by spectrophotometric method based on the Griess reaction, and they are satisfactory. The method developed can be applied for rapid detection and monitoring trace of nitrite for field measurements because the instrumentation required is portable.     

High Performance Liquid Chromato-Graphy Separations of Nitrosamines. II. Acyclic Nitrosamines

Abstract

The separation of acyclic nitrosamines by HPLC using a β-cyclodextrin bonded silien gel column and a C₁₈ reversed phase column was evaluated. Four groups of nitrosamines were used to evaluate the utility of both columns: (1.) methylmethyl-, methylethyl-, methylpropyl and methylbutyl-; (2.) ethylmethyl-, ethylethyl-, and ethylpropyl-; (3.) propylmethyl-, propylpropyl-, and propylbutyl-; and (4.) butylmethyl-, butylethyl-, butylpropyl-, and butylbutyl nitrosamines.

The results show that both columns performed well in separating the nitrosamines in each group, with the C₁₈ column requiring a higher percentage of organic modifier (methanol) than the β-cyclodextrin column. The β-cyclodextrin column was superior in separating all the E to Z isomers of short chain alkyl nitrosamines, while the C₁₈ column was superior in separating long alkyl chain nitrosamines and their E and Z isomers.

It, was also found that, the longer the alkyl chain the longer the retention time, while nitrosamines having the same number of carbons, for example ethylbutyl-and propylpropyleluted at virtually the same time, using both columns.     

Flow Injection Biamperometric Determination of Nitrite and Nitrate

Abstract

A simple and efficient FIA method was used with good results to determine nitrite in residual waters and nitrate in natural waters. Nitrite determination is based on the reaction with iodide occurring in acidic medium and biamperometric detection of the formed iodine at two platinum electrodes polarised at a potential of 100 mV. Nitrate is similarly determined after its previous reduction to nitrite in a cadmium column. The method does not need the solution deaeration. However, the calibration graphs present two regions of linearity owing to the catalytic effect of the dissolved oxygen on the iodide oxidation by nitrite.     

The Determination of Nitrite and Nitrate Ions by Differential Pulse Polarography

Abstract

A previously reported method for the determination of nitrite ion has been extended to include nitrate ion. Nitrate is reduced to nitrite by a cadmium column and the nitrite ion determined as diphenylnitrosamine. Cadmium interference is removed by pH adjustment and the use of KDTA.     

Determination of Volatile N-Nitrosamines as Pesticide Contaminants by Gas Chromatography-Mass Fragmentography

Abstract

Pesticides have been checked for the presence of N-dimethylnitrosamine, N-diethylnitrosamine, N-dipropylnitrosamine, N-diisopropylnitrosamine and N-dibutylnitrosamine. Quantitation was accomplished by GC-MS operated in the E.I. mode with selected ion monitoring of the nitrosamines. Trifluralin was found to contain 34 ppm of N-dipropylnitrosamine. No nitrosamines were detected in the other pesticides analyzed.     

Determination of Nitrate,Nitrite, and Phosphate at 214 NM by Reverse PhaseHPLC

Abstract

Nitrate and nitrite can be determined by reverse phase HPLC, using 1:1 methanol-water at pH 3.0 as the mobile phase and UV detection at 214 nm. Phosphate can be determined using 1:1:1 methanol-water-isopropyl alcohol at pH 3.0. At a flow rate of 1.0 mL/min, these anions elute within 5 min. A comparison of the mobile phases 1:1 methanol-water and Low UV PIC A reagent, indicates that 1:1 methanol-water yields 10 fold greater sensitivity to nitrate and 2 fold less to nitrite. The use of 1:1 methanol-water for the extraction of nitrate and nitrite from soil results in 19% higher recovery than in the case of water alone.     

An Extractive Spectrophotometric Method for the Determination of Nitrite Using Fluorescein Amine Isomer I

ABSTRACT

A sensitive spectrophotometric method for the determination of nitrite using fluorescein amine isomer I is described. The method is based on the formation of azido derivative of fluorescein amine isomer I, which is selectively extracted into 20% iso amyl alcohol in toluene and is stripped to aqueous phase using NaOH. Formation of the azido derivative depends on nitrite concentration and the system obeys Beer's law in the range 0-0.4 ppm of nitrite at 495 nm. The molar absorptivity of the colour system is 6.67 × 10⁴ L mol^-1 cm^-1 with a relative standard deviation of 3% for 10 determinations at 1 μg of nitrite. The proposed method is successfully applied for the determination of nitrite and nitrate in soil, water and radiator coolant sample, NO₂ gas in a laboratory fume cupboard is determined after fixing it as nitrite in sodium arsenite absorber solution.     

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.     

Spectrophotometer Determination of Nitrite Using Salbutamol sulphate as a Reagent

Abstract

A simple spectrophotometric method for the trace determination of nitrite (NO^? ₂) is described. Nitrite is reacted with Salbutamal sulphate in acidic medium which gives a yellow colour in alkaline medium (?pH 7) and can be determined in the presence of several cations and anions. Beer's law is obeyed in the range of 1.8 to 27.6 ppm of nitrite with the molar absorptivity 1.8 × 10³ 1 × mole^?1 × cm^?1 at 4l0 nm. The proposed method can also be utilized for the determination of nitrate (NO^? ₃) after its reduction to nitrite. The method has been applied for the determination of various samples containing traces of nitrite.     

Determination of Nitrate and Nitrite Ions in Human Plasma by Ion Exchange-High Performance Liquid Chromatography

Abstract

Acetonitrile precipitation of plasma samples followed by injection of supernatant onto a reverse phase precolumn coupled to an anion exchange column allowed ultraviolet detection (214 nm) of eluting nitrate and nitrite ions. Sensitivity in plasma is about 0.01 mM for both ions and linearity is excellent from 0.02 to 1.0 mM. Nitrite accuracy assessed by diazotization coupling was good. Reproducibility studies demonstrated withinrun coefficients of variation of < 4%. Interferences were few. Random endogenous serum nitrate concentrations (0.03–0.12 mM) were determined. Serum nitrite and nitrate concentrations were measured in a patient following an overdosage of isobutyl nitrite. The method is applicable for nitrite/nitrate studies in plasma at these concentrations.     

Electrolysis at the Interface between Two Immiscible Electrolyte Solutions: Determination of Acetylcholine by Differential Pulse Stripping Voltammetry

Abstract

A three-electrode system with the hanging electrolyte drop electrode (HEDE) was developed for the analytical exploitation of electrolysis at the interface between two immiscible electrolyte solutions (ITIES). The use of the differential pulse stripping voltammetry (DPSV) for the quantitative determination of the species which participates in a charge transfer reaction at ITIES was demonstrated with acetylcholine cation transfer across the water/nitrobenzene interface. Trace concentration of acetylcholine in water in the part per million level (ppm) can be determined. It was concluded that the electrolysis at ITIES represents the perspective method of chemical analysis.     

乙醇胺类原料形成亚硝胺的比较

为了探究目前表面活性剂生产和应用中用脂肪酸甲基单乙醇酰胺或脂肪酸单乙醇酰胺替代脂肪酸二乙醇酰胺的趋势的可行性,本文首先采用亚硝酸叔丁酯法合成3种乙醇胺的亚硝胺化合物作为基准物,通过鉴定产物结构研究亚硝胺的形成历程,然后以亚硝酸法合成亚硝胺化合物,通过生成率比较3种乙醇胺形成亚硝胺化合物的难易程度。 亚硝化历程分析结果表明,二乙醇胺或甲基单乙醇胺均直接形成相应的亚硝胺,而单乙醇胺通过歧化反应生成二乙醇胺继而形成少量N-亚硝基二乙醇胺。 与二乙醇胺相比,甲基单乙醇胺或单乙醇胺更不易生成亚硝胺,因此用脂肪酸甲基单乙醇酰胺或脂肪酸单乙醇酰胺替代脂肪酸二乙醇酰胺是合理可行的。 本研究结果对保障人类生命健康安全具有理论和实践意义。     

Enhanced Electrochemical Detection of Nitrite and Nitrite at a Cu-30Ni Alloy Electrode

ABSTRACT

Significant catalytic activity towards the reduction of nitrite at unmodified Cu - 30% Ni alloy electrodes was found within the concentration ranges 16 – 200 μM nitrite. The reduction of nitrite was found to occur at potentials significantly less negative than the reduction of nitrate thereby providing clear resolution and the possibility of reliable nitrite / nitrate speciation. The results are contrasted with those found at a bare copper electrode where the spatial resolution of the nitrate and nitrite reduction processes is severely limited with significant overlap of the reduction processes. The procedure represents an inexpensive and facile method for nitrite determination in a number of applications.     

A Sensitive Analysis for Nitrosamines

Abstract

A number of nitrosamines have been reduced to hydrazines and condensed with 9-anthraldehyde and 9-phenanthraldehyde to give highly fluorescent hydrazones which can be separated by thin layer chromatography and identified using R_f, ultroviolet and mass spectra.     

Kinetic Determination Of Nitrite Based On The Griess Reaction And The Stopped Flow Technique

Abstract

A kinetic method for nitrite determination in solution is described. The method is based on the Griess reaction and the stopped-flow technique. The time between two preset levels of the output signal is used as a measure of the nitrite concentration. The determination involves only one step and is independet on the background absorption of the reagents. The working curve can be made with only 2 or 3 points. No blank value is shown. The method can be applied to dilute or(more) concentrated nitrite solutions by appropriate change of their pH. Concentrations as low as 1.10^?6M NO₂ ^? can be determined.     

The Estimation of Total Non-Volatile Nitrosamines and Nitrosamides in Microgram Amounts

Abstract

Nitrosamines and nitrosamides are denitrosated by thionyl chloride to form nitrosyl chloride, which can be volatilized in a stream of nitrogen, trapped in alkali and determined as inorganic nitrite. Other compounds containing a N-O bond such as nitramines and nitramides do not react similarly under the conditions used.     

Automated flow-injection spectrophotometric determination of nitrosamines in solid food samples

A spectrophotometric method using a flow-injection system is proposed for the determination of nitrosamines in foods (cured-meats). The method is based on the photochemical cleavage of the N-NO bond of the nitrosamine to yield the corresponding amine and nitrite. The nitrite is then detected spectrophotometrically, at 542 nm, by use of its reaction with a modified Griess reagent. Different linear ranges between 0.8 and 2000 ng mL(-1) are obtained for the method, depending on the time of exposure of the sample to the UV radiation. The relative standard deviation varies between 2.0 and 3.9% and the sample throughput is between three and seven samples per hour, depending on the experimental conditions. The proposed method was successfully applied to the analysis of N-nitrosodimethylamine in cured ham and loin, bacon, and sausages.     

A Sensitive Gas Chromatograph Detector for Nitrosamines

Abstract

A GC method using a flame thermionic detector (FTD) with a RbSO₄ source to determine nitrosamines is described. The method is sensitive enough to be used for a preliminary screening of foodstuffs for the presence of volatile nitrosamines. The lowest detection limit is 0.1 ng for DMNA, DENA, or DPNA, with a linear range of 0.1 ? 100 ng determinable. The method has a favorable stability; the factors affecting its sensitivity, e.g. the H₂ flow rate, column temperature and the solvent used, have been studied.     

Reagent‐free and pH‐independent degradation of N‐nitrosamines using electrons generated via corona discharge at ambient pressure

Traditional degradation methods for N‐nitrosamines are either confined with acid solution or required for additional chemical reagents to guarantee high reaction efficiency. Herein, we demonstrate a facile and effective way for reagent‐free and pH‐independent degradation of N‐nitrosamines, which was induced by free electrons generated via corona discharge at ambient pressure. The highly reactive free electron is produced in situ and responsible for degradation of three N‐nitrosamines, which was also theoretically confirmed. N‐nitrosamines were believed to be reduced by electrons and to form the radical anion, which underwent a selectively heterolytic cleavage of the N–NO bonds to form the corresponding secondary amines as the degradation products.