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.     

Biparametric potentiometric analytical microsystem for nitrate and potassium monitoring in water recycling processes for manned space missions

The construction and evaluation of a Low Temperature Co-fired Ceramics (LTCC)-based continuous flow potentiometric microanalyzer prototype to simultaneously monitor the presence of two ions (potassium and nitrate) in samples from the water recycling process for future manned space missions is presented. The microsystem integrates microfluidics and the detection system in a single substrate and it is smaller than a credit card. The detection system is based on two ion-selective electrodes (ISEs), which are built using all-solid state nitrate and potassium polymeric membranes, and a screen-printed Ag/AgCl reference electrode. The obtained analytical features after the optimization of the microfluidic design and hydrodynamics are a linear range from 10 to 1000 mg L⁻¹ and from 1.9 to 155 mg L⁻¹ and a detection limit of 9.56 mg L⁻¹ and 0.81 mg L⁻¹ for nitrate and potassium ions respectively.     

Back titration with mercuric nitrate in alkaline medium analysis of tertiary mixtures of mercury(II) with some other metals

Summary Tertiary mixtures each containing mercury(II) were analysed by simple procedures involving combination between the recent method of back titration with mercuric nitrate in alkaline medium, and the volumetric methods which make use of masking agents as cyanide. The content of mercury(II) in most mixtures is determined potentiometrically with potassium iodide using the silver amalgam as indicator electrode. End points are attended with fair accuracy within 0.02 ml titrant and with reasonable jumps from 60 to 90 mv per 0.1 ml of mercuric nitrate solution or from 170 to 200 mv per 0.1 ml of potassium iodide solution.     

Determination of amorphous silica and total silica in plant materials

Amorphous silica in plant material was dissolved with potassium carbonate solution, after nitric acid/hydrogen peroxide digestion. Total silica in plant material and some minerals was obtained after ashing and fusing in nickel crucibles with potassium hydroxide containing potassium tetraborate/nitrate. The relative standard deviation for determinations of silicon by these methods in plant material was <2% for plant material containing 2–2100 μmol Si g^?1 (dry weight).     

Titrimetric determination of fluoride in some pharmaceutical products used for fluoridation

Two titrimetric methods were developed for the determination of fluoride contents in some pharmaceutical preparations used for fluoridation. One of the methods is catalytic controlled-current potentiometry involving two identical platinum indicator electrodes and thorium nitrate as titrant. The reaction between hydrogen peroxide and potassium iodide in the presence of acetate buffer (pH 3.6), which is catalysed by the excess of thorium nitrate, served for the end-point indication. The other method is the automatic potentiometric titration involving a fluoride-selective electrode and lanthanum nitrate as titrating agent. In both procedures, special attention was paid to sample pretreatment and to determination of optimal experimental conditions. Fluoride contents in the range 16-32 microg/ml are determined with a relative standard deviation less than 1.34%. The results are compared to those obtained by standard methods described in the United States Pharmacopeia XXI and recommended by the manufacturer of the preparations.     

Membrane separation of potassium nitrate from mixed brines

Liquid membranes made of chlorinated hydrocarbons and containing the macrocyclic polyether dibenzo-18-crown-6 can separate potassium nitrate from aqueous solutions of mixed sodium nitrate, potassium chloride and other salts. Experiments with the Schulman bridge show that this separation occurs because the membrane facilitates transport of complexed potassium nitrate ion pairs. Experiments with emulsion liquid membranes show that this separation has commercial potential.     

Microdetermination of nitrates and nitrites-III Gasometric and gravimetric methods based on reduction with formic acid

Simple microgasometric and gravimetric methods for the determination of the nitrate and nitrite groups are described. These are based on reduction with formic acid whereby one mole of nitrous oxide and four moles of carbon dioxide are simultaneously liberated per two moles of nitrate; two moles of nitrous oxide and six moles of carbon dioxide are liberated per seven moles of nitrite. Nitrous oxide is measured gasometrically and carbon dioxide gravimetrically. Results accurate to +/- 0.2% absolute are obtained for both nitrate and nitrite.     

Mercurous nitrate as a reductimetric reagent : The titration of various oxidising agents

It has been found that when excess of a solution containing ferrous ions is added to certain oxidising agents, the equivalent amount of ferric iron produced can be titrated accurately with mercurous nitrate, enabling the original oxidant to be assessed. Oxidising agents which have been determined in this way are potassium permanganate, potassium persulphate, ceric sulphate, sodium vanadate, potassium chlorate, hydrogen peroxide and potassium dichromate. The last substance provides a convenient primary standard for the standardisation of mercurous nitrate solutions.     

A thermogravimetric study of acidic and basic solutes in two molten alkali metal nitrate eutectics

The reaction of ten oxyanions and oxides, acting as Lux—Flood acids have been studied in both lithium nitrate—potassium nitrate and sodium nitrate—potassium nitrate eutectics and the stoichiometries of the reactions established. A series of acids arranged in order of decreasing strength has been drawn up, which is very similar for both eutetic solvents.Five Lux—Flood bases have also been studied in these two solvents. Sodium carbonate proved to be very stable to 500°C. Sodium peroxide revealed significant differences in stability and solubility in the two solvents, while lithium, sodium and potassium hydroxides showed differences in the two melts and also considerable differences between each other, suggesting that little cation exchange takes place in these solutions.     

Simultaneous determination of potassium nitrate and sodium monofluorophosphate in dentifrices by single column ion chromatography

The simultaneous determination of potassium nitrate and sodium monofluorophosphate in dentifrices by single column ion chromatography is described. Nitrate and monofluorophosphate are extracted from the dentifrice with deionized water and separated by a low capacity anion separator column with 0.2% sodium benzoate (adjusted to pH 5.8 +/- 0.1 with formic acid) as the mobile phase. A conductivity meter is used for concentration measurements. The method has been applied to commercial dentifrices containing both potassium nitrate and sodium monofluorophosphate. The mean recoveries for potassium nitrate and monofluorophosphate from spiked samples were 99.0% and 99.2%, respectively, with corresponding standard deviations of 1.73% and 2.55%. The minimum detectable concentration is 5 micrograms/ml for both nitrate and monofluorophosphate.     

Purification of potassium nitrate solutions by coprecipitation of impurities on hydrated aluminum oxide

Coprecipitation of 3d-element impurities from potassium nitrate solutions on hydrated aluminum oxide was studied. The efficiency of the process was examined in relation to the weight of the collector, the solution-collector contact time, pH of medium, concentration of microimpurities, and presence of oxidant. The parameters for efficient purification of potassium nitrate solutions were determined.     

Verfolgung der Verbrennungsreaktionen exothermer Massen auf Basis von Aluminium,Fluoriden und Kaliumnitrat mit Differentialthermoanalyse

DTA was applied to investigate the course of combustion of exothermic mixtures composed of aluminium, fluorides and potassium nitrate, and the results obtained were compared with the simultaneous results of X-ray investigations. The combustion of exothermic mixtures composed of aluminium, fluorides and potassium nitrate is similar to the combustion of mixtures where the potassium nitrate is substituted by sodium nitrate. Two exothermic reactions occur: between 400 and 520?, and between 800 and 1130?, in mixtures with sodium fluoride and between 450? and 650? and 850 and 1130? in mixtures with calcium fluoride. The reaction in the lower temperature range initiates the combustion of the mixture. In sodium fluoride mixtures this reaction takes place at lower temperature and seems to be more intense, since these mixtures inflame earlier than those with calcium fluoride. The reaction in the higher temperature range, which occurs at approximately the same temperature in the two cases, liberates the main part of the useful heat of the exothermic mixtures.     

Determination of Surface Silanols of Silica Gels and HPLC Bonded Phases

Abstract

A rapid method determining the surface silanols of silica gels and HPLC bonded phases involves a titration of silica gel with sodium hydroxide, in a medium of any of the following 10% aqueous salts: sodium chloride, sodium nitrate, sodium sulfate, potassium chloride, potassium nitrate and potassium sulfate. The silanols are quantified as m eg/g. It is possible to determine cation exchange capacity of a cation-exchanger due to an acid as an end group and surface silanols separately.     

立方亚铁氰化锌钾颗粒的制备和抗菌性能研究

研究了以硝酸锌和亚铁氰化钾为原料制备立方状亚铁氰化锌钾抗菌材料的方法。通过比较不同产物的形貌、产率、化学组成、晶型和抗菌性能,确定了最佳的反应物配比。采用SEM、XRD、ICP等方法表征了样品的颗粒形貌、晶型和元素组成等信息;并检测了添加了立方状亚铁氰化锌钾颗粒的涂层的抗菌性能。研究发现当锌离子和亚铁氰化钾的物质的量比在1.5/1时,所得样品白度好、形貌稳定且对金色葡萄球和大肠杆菌都表现出了良好的抗菌性能。     

Determination of Nitric Oxide-Derived Nitrite and Nitrate in Biological Samples by HPLC Coupled to Nitrite Oxidation

Nitrite and nitrate are main stable products of nitric oxide, a pivotal cellular signaling molecule, in biological fluids. Therefore, accurate measurement of the two ions is profoundly important. Nitrite is difficult to be determined for a larger number of interferences and unstable in the presence of oxygen. In this paper, a simple, cost-effective and accurate HPLC method for the determination of nitrite and nitrate was developed. On the basis of the reaction that nitrite is oxidized rapidly to nitrate with the addition of acidic potassium permanganate, the determination of nitrite and nitrate was achieved by the following strategy: each sample was injected twice for HPLC analysis, i.e. the first injection was to measure nitrate, and the second injection was to measure total nitrate including initial nitrate and the nitrate from the conversion of nitrite with the addition of acid potassium permanganate in the sample. The amount of nitrite can be calculated as difference between injections 2 and 1. The HPLC separation was performed on a reversed phase C₁₈ column for 15 min. The mobile phase consisted of methanol–water (2:98 by volume); the water in the mobile phase contained 0.60 mM phosphate salt (potassium dihydrogen and disodium hydrogen phosphate) and 2.5 mM tetrabutylammonium perchlorate (TBAP). The UV wavelength was set at 210 nm. Additionally, we systemically investigated the effects of the concentration of phosphate salt and TBAP in the mobile phase, the pH of the mobile phase, and the amount of acidic potassium permanganate added to the sample on the separation efficacy. The results showed that the limits of detection (LOD) and the limit of quantitation (LOQ) were 0.075 and 0.25 μM for nitrate (containing the oxidized nitrite), respectively. The linear range was 1–800 μM. This developed approach was successfully applied to assay nitrite/nitrate levels in cell culture medium, cell lysate, rat plasma and urine.

     

Solubility in the diagonal sections of the 2KCl + Ca(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> ⇆ 2KNO<Subscript>3</Subscript> + CaCl<Subscript>2</Subscript>–H<Subscript>2</Subscript>O system

Solubility data in the diagonal sections of the quaternary reciprocal 2KCl + Ca(NO₃)₂ → 2KNO₃ + CaCl₂–H₂O system at 25 and 15°C are presented. It has been shown that the quaternary system has no stable diagonal at the studied temperatures, but contains a stable pair of salts, namely, potassium nitrate and calcium chloride. The obtained data can be used to optimize the thermal and concentrational parameters of the synthesis of potassium nitrate from calcium nitrate and potassium chloride.     

Determination of Nitric Oxide-Derived Nitrite and Nitrate in Biological Samples by HPLC Coupled to Nitrite Oxidation

Nitrite and nitrate are main stable products of nitric oxide, a pivotal cellular signaling molecule, in biological fluids. Therefore, accurate measurement of the two ions is profoundly important. Nitrite is difficult to be determined for a larger number of interferences and unstable in the presence of oxygen. In this paper, a simple, cost-effective and accurate HPLC method for the determination of nitrite and nitrate was developed. On the basis of the reaction that nitrite is oxidized rapidly to nitrate with the addition of acidic potassium permanganate, the determination of nitrite and nitrate was achieved by the following strategy: each sample was injected twice for HPLC analysis, i.e. the first injection was to measure nitrate, and the second injection was to measure total nitrate including initial nitrate and the nitrate from the conversion of nitrite with the addition of acid potassium permanganate in the sample. The amount of nitrite can be calculated as difference between injections 2 and 1. The HPLC separation was performed on a reversed phase C₁₈ column for 15 min. The mobile phase consisted of methanol–water (2:98 by volume); the water in the mobile phase contained 0.60 mM phosphate salt (potassium dihydrogen and disodium hydrogen phosphate) and 2.5 mM tetrabutylammonium perchlorate (TBAP). The UV wavelength was set at 210 nm. Additionally, we systemically investigated the effects of the concentration of phosphate salt and TBAP in the mobile phase, the pH of the mobile phase, and the amount of acidic potassium permanganate added to the sample on the separation efficacy. The results showed that the limits of detection (LOD) and the limit of quantitation (LOQ) were 0.075 and 0.25 μM for nitrate (containing the oxidized nitrite), respectively. The linear range was 1–800 μM. This developed approach was successfully applied to assay nitrite/nitrate levels in cell culture medium, cell lysate, rat plasma and urine.     

Study of the behavior of chromium(III) in potassium nitrate solutions at 25°C

Solubility in the KNO₃-Cr(NO₃)₃-H₂O system at 25°C was studied by an isothermal method. The existence of solid phases of potassium nitrate and chromium(III) nitrate nonahydrate was confirmed by constructing a phase diagram, chemical analysis, and IR spectroscopy. Crystallization of potassium nitrate from aqueous solutions was studied. Potassium nitrate does not interact with chromium(III) nitrate within the range of micro and macro concentrations. The capture of chromium(III) by KNO₃ crystals is due to adsorption and occlusion of a mother solution.     

Hydration of complexes of 18-crown-6 with potassium nitrate or potassium picrate in the polymer phase

Adsorption of water vapor by granular polymer based on dibenzo-18-crown-6 and containing potassium nitrate or potassium picrate in the polymer phase was studied by the isopiestic method at 298 K. The adsorption of water vapor is described by isotherms corresponding (according to BDDT classification) to polymolecular absorption with a high adsorptive potential. In terms of the Aranovich model of polymolecular absorption, the monolayer capacity and differential heat of adsorption were calculated, and the stoichiometry of hydration of the potassium nitrate and potassium picrate complexes with immobilized crown ether was estimated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1940–1942, October, 1998.     

Titration of cyanide and hexacyanoferrate(II) with silver nitrate-I Calculation of titration curves for potentiometric and conductometric titration

Stepwise potentiometric titration of cyanide and hexacyanoferrate(II) with silver nitrate is possible in the absence of potassium ions. At an initial concentration below 5.00 x 10(-4)M, cyanide can be titrated with silver nitrate (Ag:CN = 1:2) and the end-point indicated by precipitation of silver hexacyanoferrate(II); hexacyanoferrate(II) can be titrated with silver nitrate (Ag: Fe(CN)(6) = 4:1) and the end-point indicated by precipitation of silver dicyanoargentate. The hexacyanoferrate(II) reacts with silver to form two poorly soluble salts, Ag(4)Fe(CN)(6), KAg(3)Fe(CN)(6). The formation of these salts has been confirmed by conductometric titration of hexacyanoferrate(II) with silver nitrate in solutions containing varying concentrations of potassium nitrate.