RU2542260C2 - Ion selective material for detecting ammonium ions and method for preparing it - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: hydrated ammonium vanadium oxide bronze of formula (NH₄)_0.5V₂O₅·0,5H₂O is used as an ion-selective material for the selective detection of the ammonium ion concentration in solutions. Preparing hydrated ammonium vanadium oxide bronze of the above formulation is ensured by ammonium metavanadate NH₄VO₃ and anaqueous solution of citric acid is added drop by drop with constant stirring to set solution acidity within the range of 2.0≤pH≤6.0. The mixture is processed at temperature 140-180°C for 24-48 hours in a pressure steriliser. The prepared product is filtered, washed and dried.

EFFECT: invention enables preparing the ion-selective material for simple and reliable detection of the NH₄ ⁺ concentration in the solutions.

2 cl, 5 dwg, 1 tbl, 4 ex

Description

The invention relates to materials based on oxide vanadium compounds and can be used as an ion-selective material for the determination of ammonium ions in solutions.

в аналитической химии используют формальдегидный метод анализа, являющийся обязательным при анализе арбитражных проб (Л.Д. Глузман, И.И. Эдельман. Лабораторный контроль коксохимического производства. Харьков: Металлургиздат. 1957. 635 с.). Согласно известному способу ионы аммония с помощью формальдегида переводят в гексаметилентетрамин по реакции:Currently for the quantification of ions $$N{H}_{\mathrm{four}}^{+}$$

in analytical chemistry, the formaldehyde analysis method is used, which is mandatory in the analysis of arbitration samples (L.D. Gluzman, I.I. Edelman. Laboratory control of coke production. Kharkov: Metallurgizdat. 1957. 635 p.). According to a known method, ammonium ions with formaldehyde are converted into hexamethylenetetramine by the reaction:

проводят по следующей схеме: навеску исследуемого вещества растворяют в воде, прибавляют 25%-ный формалин, предварительно нейтрализованный 0.1 N раствором щелочи в присутствии фенолфталеина. Выделившуюся кислоту титруют 0.5 N раствором NaOH в присутствии фенолфталеина. Содержание азота в пересчете на сухое вещество (х, %) определяют по формуле:In this case, mineral acid is released in an amount equivalent to the ammonium salts in the sample. Next, by titration with a solution of sodium hydroxide NaOH, the amount of acid liberated in this case and the equivalent amount of nitrogen are determined. Definition $$N{H}_{\mathrm{four}}^{+}$$

carried out according to the following scheme: a sample of the test substance is dissolved in water, 25% formalin is added, previously neutralized with 0.1 N alkali solution in the presence of phenolphthalein. The liberated acid is titrated with a 0.5 N NaOH solution in the presence of phenolphthalein. The nitrogen content in terms of dry matter (x,%) is determined by the formula:

where V is the amount of sodium hydroxide NaOH solution used for titration, ml;

T is the titer of sodium hydroxide solution pre-installed according to the standard sample;

m - sample of the test substance, g.

The disadvantage of this method is the need to observe the neutrality of the solution, because the content of ammonium ions is determined titrimetrically by the amount of acid released according to reaction (1). As a result, it is difficult to determine ammonium ions in samples that are weakly and / or practically insoluble in water, but soluble in an acidic or alkaline medium. In addition, before each determination of ammonium ions, it is necessary to check the titer of the sodium hydroxide solution by phenolphthalein.

To date, the most common method for determining ammonium ions is the method of photometric determination using the Nessler reagent, based on the formation of an orange solution during the interaction of ammonium salts with the Nessler reagent (Korostelev P.P. Photometric and complexometric analysis in metallurgy. M .: Metallurgy. 1984. 179 p.). By the optical density of the solution, measured by the photocolorimetric method, proportional to the color intensity of the analyzed solution, the quantitative content of ammonium ions is judged.

The disadvantage of this method of determination is the use of highly toxic Nessler's reagent, which is an alkaline aqueous solution of potassium tetraiodomercurate (II) dihydrate of the composition K ₂ Hg _l4 (H ₂ O) ₂ . Nessler's reagent contains mercury, so it is toxic. In addition, certain storage conditions should be observed (dark bottle with a ground stopper, cold place). The known method does not allow determination of ammonium ions with high accuracy at an increased content of Mg, Ca, Fe and a number of others in the test solution, since the color colloidal complex formed with ammonia becomes unstable. Interfering ions cause its coagulation, as a result of which the solution becomes cloudy, its optical density changes. The determination of ammonium ions with the Nessler reagent is impeded by the presence of amines, chloramines, acetone, aldehydes, sulfides reacting with the Nessler reagent in the test solution.

через мембраны). Известный способ определения основан на изменении емкости монослоя ионофора в зависимости от концентрации $$N{H}_4^{+}$$

ионов, включающий определение изменения электропроводности или емкости монослоя ионофора, сформированного на подложке из золота, методом импедансной спектроскопии в зависимости от концентрации ионов аммония $$N{H}_4^{+}$$

в растворе.The closest to the intended application is a method for determining ammonium ions using an ion-selective electrode (patent US 2010/0290951, IPC C07 K / 54, C07D 273/00, 2010), manufactured using an ionophore 11-mercapto-N- (9.15 , 18-triisopropyl-6,12-dimethyl-2,5,8,11,14,17-hexaoxo-1,7,13-trioxa-4,10,16-triazacyclooctadecan-3-yl) butyl) undecanamide in polyvinyl chloride matrix (ionophore is an organic substance carrying out the transfer of cations $$N{H}_{\mathrm{four}}^{+}$$

through membranes). The known method of determination is based on a change in the capacitance of the ionophore monolayer depending on the concentration $$N{H}_{\mathrm{four}}^{+}$$

ions, including determining the change in electrical conductivity or capacitance of an ionophore monolayer formed on a gold substrate by impedance spectroscopy depending on the concentration of ammonium ions $$N{H}_{\mathrm{four}}^{+}$$

in solution.

The disadvantage of this method is the narrow working range for determining the concentration of ammonium ions 10 ^-2 -10 ^-1 M. In addition, the known ion-selective material is moderately selective with respect to ions Na ⁺ (K = 5.9 · 10 ^-2 ) and K ⁺ (K = 6.8 · 10 ^-3 ). Data on selectivity for other cations is not known. The principle of operation of the known ionophore as an ion-selective material is based on the complexation process with an ammonium ion. To ensure a sufficient speed of the complexation process, tetrabutylammonium bromide or tetraethylammonium chloride is used as the electrolyte, which affects the accuracy of determination of the indicated ion, since the ammonium group is part of these electrolytes. In addition, an electrode with a known ion-selective material can mainly be used only in the neutral region of acidity (pH 6).

Known hydrated oxide vanadium ammonium bronze composition (NH ₄ ) _0.5 V ₂ O _{5 ·} 0.9H ₂ O (PN Trikalitis, V. Petkov, MG Kanatzidis, Chem. Mater. 2003. V. 15. P. 3337-3342). To obtain the well-known vanadium bronze, 6.67 mM xerogel V ₂ O ₅ · nH ₂ O (1 g) dissolved in 50 ml of acetonitrile is mixed under nitrogen atmosphere for 4 hours with a stoichiometric amount of ammonium iodide NH ₄ I. Then, the precipitate is washed with acetonitrile and dried in a vacuum. As a result, a dark blue product of the composition (NH ₄ ) _0.5 V ₂ O ₅ · 0.9H ₂ O is formed, crystallizing in monoclinic syngony with unit cell parameters a = 11.845 Å, b, b = 3.677 (1) Å, s = 9.058 Å, β = 88.635 °. Particles (NH ₄ ) _0.5 V ₂ O ₅ · 0.9 H ₂ O have a morphology of nanoribbons 10 nm wide and several microns long. No use of hydrated ammonium vanadium oxide bronze is currently known.

The synthesis of a known compound occurs as a result of a topotactic (topotactic reaction is a solid-phase reaction in which the packing of atoms in the reagent crystal remains largely unchanged during the course of the reaction) of a heterogeneous redox reaction in which the reduction of V ⁵⁺ to V ⁴⁺ ions occurs due to the oxidation of ions I ^- to I ⁰ . A disadvantage of the known production method is the use of a very weak reducing agent of ammonium iodide NH ₄ I, which leads to a significant increase in reaction time and requires additional mixing, grinding the reaction mass during synthesis to obtain a product with 100% yield.

в растворе. Причем предлагаемый материал должен быть селективен в отношении других одно- и двухвалентных ионов в присутствии ионов аммония.Thus, the authors were faced with the task of obtaining ion-selective material for the determination of ammonium ions in solution, which allows simple and reliable determination of the concentration

in solution. Moreover, the proposed material should be selective for other mono- and divalent ions in the presence of ammonium ions.

в качестве ионоселективного материала для селективного определения концентрации ионов аммония в интервале концентраций

и кислотности среды

The problem is solved by the use of hydrated oxide vanadium ammonium bronze composition

as an ion-selective material for the selective determination of the concentration of ammonium ions in the concentration range

and acidity

включающем растворение метаванадата аммония

в воде, добавление при постоянном перемешивании по каплям водного раствора лимонной кислоты

до установления кислотности раствора

с последующей обработкой смеси при температуре 140 - 180°С в течение 24-48 часов в автоклаве, фильтрацию, промывание и сушку.The problem is also solved in the method of obtaining hydrated oxide of vanadium ammonium bronze composition

including dissolution of ammonium metavanadate

in water, adding with constant stirring dropwise an aqueous solution of citric acid

until the acidity of the solution is established

followed by processing the mixture at a temperature of 140 - 180 ° C for 24-48 hours in an autoclave, filtering, washing and drying.

а также не известен способ получения этой бронзы путем гидротермальной обработки в предлагаемых условиях.Currently, the patent and scientific and technical literature do not know the use as an ion-selective material for determining ammonium ions in a solution of hydrated vanadium oxide bronze ammonium composition

and also not known is the method of producing this bronze by hydrothermal treatment under the proposed conditions.

обладает свойством катионной функции, которое позволяет использовать ее в качестве ионоселективного материала для определения ионов аммония в растворе. Предпосылками возникновения катионной функции являются наличие в соединении ионов ванадия в двух степенях окисления

а также слоистая структура, обеспечивающая легкость процесса интеркаляции/деинтеркаляции катиона аммония по отношению к ванадий-кислородной матрице.Studies conducted by the authors led to the conclusion that hydrated ammonium oxide vanadium bronze composition

It has the property of a cationic function, which allows its use as an ion-selective material for the determination of ammonium ions in solution. The prerequisites for the emergence of the cationic function are the presence of vanadium ions in two oxidation states in the compound

as well as a layered structure, which ensures the ease of intercalation / deintercalation of the ammonium cation with respect to the vanadium-oxygen matrix.

, или

или

или

или

или

или

или

Экспериментальным путем было установлено, что существенным фактором, определяющим состав, структуру и морфологию конечного продукта, является величина кислотности исходного раствора

(значение рН), создаваемая лимонной кислотой. В процессе получения в присутствии лимонной кислоты пятивалентный ванадий частично восстанавливается до четырехвалентного состояния, образуя продукт с низкоразмерной морфологией. Необходимо соблюдать точное значение рН среды

для получения бронзы требуемого состава. Проведение процесса в указанном интервале кислотности позволяет получать однофазный продукт, исключить процессы гидролиза исходного метаванадата аммония

и образование в качестве примесей различных ванадатов.Essential are the conditions for observing the parameters of the production process, as claimed in the proposed technical solution. Only the use of citric acid, which is a mild reducing agent, to create the required acidity (pH) of the solution allows one to obtain hydrated bronze of the required composition in 100% yield, without possible impurities in the form of compounds

, or

or

or

or

or

or

or

It was established experimentally that the essential factor determining the composition, structure and morphology of the final product is the acidity of the initial solution

(pH value) created by citric acid. In the process of preparation in the presence of citric acid, pentavalent vanadium is partially restored to the tetravalent state, forming a product with a low-dimensional morphology. The exact pH of the medium must be observed.

to obtain bronze of the required composition. Carrying out the process in the specified range of acidity allows to obtain a single-phase product, to exclude the hydrolysis of the initial ammonium metavanadate

and the formation of various vanadates as impurities.

, образуется продукт с морфологией частиц, подобной шарам. При значении кислотности раствора в интервале

образуется продукт с морфологией частиц, подобной цветку. Экспериментально были определены температура и время гидротермальной обработки реакционной смеси, только при соблюдении которых может быть получена гидратированная ванадиевая бронза аммония состава

Так, при снижении температуры гидротермальной обработки менее 140°С или при повышении ее выше 180°С и при выходе за заявленные значения временного интервала, в конечном продукте появляются в качестве примеси непрореагировавший метаванадат аммония

оксид ванадия(V) V₂O₅ или оксид ванадия(IV) V₂O₄. Совокупность предлагаемых условий проведения процесса позволяет получать гидротермальной обработкой реакционной смеси низкоразмерную гидратированную оксидную ванадиевую бронзу аммония состава

In addition, when the acidity of the solution is equal to

, a product is formed with particle morphology similar to spheres. When the acidity of the solution is in the range

a product with a flower-like morphology is formed. The temperature and time of hydrothermal treatment of the reaction mixture were determined experimentally, only if they are observed, hydrated vanadium ammonium bronze of the composition can be obtained

So, when the temperature of the hydrothermal treatment decreases below 140 ° C or if it rises above 180 ° C and when the stated time interval is exceeded, unreacted ammonium metavanadate appears as an impurity in the final product

vanadium (V) oxide V ₂ O ₅ or vanadium (IV) oxide V ₂ O ₄ . The combination of the proposed process conditions allows to obtain a hydrothermal treatment of the reaction mixture low-dimensional hydrated ammonium oxide vanadium bronze composition

может быть получена следующим образом. Берут метаванадат аммония

и растворяют его в воде, добавляют при постоянном перемешивании по каплям водный раствор лимонной кислоты

до установления кислотности раствора

затем помещают в автоклав и обрабатывают при температуре 140-180°С в течение 24-48 часов. Полученный продукт фильтруют, промывают и сушат.Hydrated Oxide Vanadium Ammonium Bronze Composition

can be obtained as follows. Ammonium metavanadate taken

and it is dissolved in water, an aqueous solution of citric acid is added dropwise with constant stirring

until the acidity of the solution is established

then placed in an autoclave and processed at a temperature of 140-180 ° C for 24-48 hours. The resulting product is filtered, washed and dried.

Phase uniformity and morphology of the obtained product are controlled by X-ray phase analysis (XRD) and scanning electron microscopy (SEM), respectively. When carrying out the process by adjusting the pH of the reaction medium, it becomes possible to obtain a product of different morphology and, therefore, different particle size distribution.

соответственно. При этом поливинилхлорид добавляют в виде 5%-ного раствора в тетрагидрофуране. Полученную смесь наносят на графитовый стержень, а затем сушат при комнатной температуре до полного испарения тетрагидрофурана.To study the ion-selective function of the obtained material, a mixture is prepared containing polyvinyl chloride, dibutyl phthalate and the obtained powder of hydrated ammonium vanadium bronze in the following ratio of components: polyvinyl chloride: dibutyl phthalate: hydrated vanadium ammonium bronze

respectively. In this case, polyvinyl chloride is added in the form of a 5% solution in tetrahydrofuran. The resulting mixture was applied to a graphite rod, and then dried at room temperature until the tetrahydrofuran was completely evaporated.

The study of the ion-selective function of the material was carried out by measuring the EMF of a galvanic cell of the type

electrode | test solution || KCl us., AgCl | Ag

using the ionomer I-130.2M.

To determine the potentiometric selectivity coefficients, the continuous solution method was used (Okunev M.S., Khitrova N.V., Kornienko O.I. Estimation of the selectivity of ion-selective electrodes // Journal of Analytical Chemistry. 1982. V. 37. No. 1. P. 5-13). The obtained value of the selectivity coefficients of ammonium selective material are presented in the table.

Table

Selectivity factors (K _{NH / M} ) of ammonium material

The methods for producing and using hydrated ammonium vanadium bronze are illustrated by the following examples.

кристаллизуется в моноклинной сингонии с параметрами кристаллической решетки

и

и состоит из слабо агломерированных наночастиц шарообразной формы диаметром 150-250 нм. 2 мг полученного порошка смешивают с 0,5 мл 5%-ного поливинилхлорида в тетрагидрофуране и 0,05 мл дибулилфталата, что соответствует соотношению поливинилхлорид:дибутилфталат:гидратированная ванадиевая бронза аммония

Полученную смесь наносят на графитовый стержень и сушат при комнатной температуре до полного испарения тетрагидрофурана.Example 1. Take 0.2 g of powder of ammonium metavanadate NH ₄ VO ₃ and dissolve it in 12 ml of distilled water. An aqueous solution of citric acid is added dropwise to the resulting solution, with stirring, until a pH of 2.0 is established. The resulting mixture was placed in an autoclave, heated to 140 ° C and maintained at this temperature for 48 hours. After that, the autoclave is cooled to room temperature, the resulting product is filtered, washed with water and dried in air at room temperature. According to x-ray phase and electron microscopy analyzes, the resulting product is single-phase, has the composition

crystallizes in monoclinic syngony with crystal lattice parameters

and

and consists of weakly agglomerated spherical nanoparticles with a diameter of 150-250 nm. 2 mg of the obtained powder is mixed with 0.5 ml of 5% polyvinyl chloride in tetrahydrofuran and 0.05 ml of dibulyl phthalate, which corresponds to the ratio of polyvinyl chloride: dibutyl phthalate: hydrated ammonium vanadium bronze

The resulting mixture was applied to a graphite rod and dried at room temperature until the tetrahydrofuran was completely evaporated.

На фиг. 2 приведено изображение наночастиц

синтезированных при рН = 2.0, полученное на сканирующем электронном микроскопе. На фиг. 3 представлен ИК-спектр соединения. Полосы поглощения при 3215 см^-1 и 1395 см^-1, при 3413 см^-1 и 1631 см^-1 подтверждают наличие в полученном соединении аммонийных группировок и адсорбционной воды, соответственно. На фиг. 4 представлена зависимость потенциала электрода от концентрации катионов аммония в растворе при рН 4. При рН 4 в интервале концентраций

угловой коэффициент электродной функции близок к теоретическому значению и равен

In FIG. 1 presents a radiograph

In FIG. 2 shows an image of nanoparticles

synthesized at pH = 2.0, obtained using a scanning electron microscope. In FIG. 3 shows the IR spectrum of the compound. Absorption bands at 3215 cm ^-1 and 1395 cm ^-1 , at 3413 cm ^-1 and 1631 cm ^-1 confirm the presence of ammonium groups and adsorption water in the resulting compound, respectively. In FIG. Figure 4 shows the dependence of the electrode potential on the concentration of ammonium cations in solution at pH 4. At pH 4 in the concentration range

the angular coefficient of the electrode function is close to the theoretical value and is equal to

и растворяют его в 12 мл дистиллированной воды. К полученному раствору при перемешивании по каплям добавляют водный раствор лимонной кислоты до установления рН раствора 3.0. Полученную смесь помещают в автоклав, нагревают до 150°С и при этой температуре выдерживают 48 часов. После этого автоклав охлаждают до комнатной температуры, полученный продукт фильтруют, промывают водой и сушат на воздухе при комнатной температуре. 2 мг полученного порошка смешивают с 0,5 мл 5%-ного поливинилхлорида в тетрагидрофуране и 0,05 мл дибулилфталата, что соответствует соотношению поливинилхлорид:дибутилфталат:гидратированная ванадиевая бронза аммония

Полученную смесь наносят на графитовый стержень и сушат при комнатной температуре до полного испарения тетрагидрофурана.Example 2. Take 0.2 g of powder of ammonium metavanadate

and dissolved in 12 ml of distilled water. An aqueous citric acid solution is added dropwise to the resulting solution with stirring until the pH of the solution reaches 3.0. The resulting mixture was placed in an autoclave, heated to 150 ° C and maintained at this temperature for 48 hours. After that, the autoclave is cooled to room temperature, the resulting product is filtered, washed with water and dried in air at room temperature. 2 mg of the obtained powder is mixed with 0.5 ml of 5% polyvinyl chloride in tetrahydrofuran and 0.05 ml of dibulyl phthalate, which corresponds to the ratio of polyvinyl chloride: dibutyl phthalate: hydrated ammonium vanadium bronze

The resulting mixture was applied to a graphite rod and dried at room temperature until the tetrahydrofuran was completely evaporated.

кристаллизуется в моноклинной сингонии с параметрами кристаллической решетки

и состоит из слабо агломерированных наночастиц шарообразной формы диаметром 150-250 нм. При рН 5 в интервале концентраций

угловой коэффициент электродной функции близок к теоретическому значению и равен 54±2 мВ/pC_NH.According to x-ray phase and electron microscopy analyzes, the resulting product is single-phase, has the composition

crystallizes in monoclinic syngony with crystal lattice parameters

and consists of weakly agglomerated spherical nanoparticles with a diameter of 150-250 nm. At pH 5 in the range of concentrations

the angular coefficient of the electrode function is close to the theoretical value and is equal to 54 ± 2 mV / pC _NH .

Полученную смесь наносят на графитовый стержень и сушат при комнатной температуре до полного испарения тетрагидрофурана.Example 3. Take 0.2 g of powder of ammonium metavanadate NH ₄ VO ₃ and dissolve it in 12 ml of distilled water. An aqueous citric acid solution is added dropwise to the resulting solution with stirring until the pH of the solution reaches 4.0. The resulting mixture was placed in an autoclave, heated to 180 ° C and maintained at this temperature for 24 hours. After that, the autoclave is cooled to room temperature, the resulting product is filtered, washed with water and dried in air at room temperature. 40 mg of the obtained powder is mixed with 3.0 ml of 5% polyvinyl chloride in tetrahydrofuran and 0.4 ml of dibulyl phthalate, which corresponds to the ratio of polyvinyl chloride: dibutyl phthalate: hydrated ammonium vanadium bronze

The resulting mixture was applied to a graphite rod and dried at room temperature until the tetrahydrofuran was completely evaporated.

кристаллизуется в моноклинной сингонии с параметрами кристаллической решетки

и состоит из частиц с морфологией, подобной цветку, образованной пересекающимися пластинками толщиной 100-350 нм и шириной 0.8 - 1 мкм (фиг. 5). При рН 6 в интервале концентраций

угловой коэффициент электродной функции близок к теоретическому значению и равен

According to x-ray phase and electron microscopy analyzes, the resulting product is single-phase, has the composition

crystallizes in monoclinic syngony with crystal lattice parameters

and consists of particles with a flower-like morphology formed by intersecting plates with a thickness of 100-350 nm and a width of 0.8 - 1 μm (Fig. 5). At pH 6 in the range of concentrations

the angular coefficient of the electrode function is close to the theoretical value and is equal to

и растворяют его в 12 мл дистиллированной воды. К полученному раствору при перемешивании по каплям добавляют водный раствор лимонной кислоты до установления рН раствора 6.0. Полученную смесь помещают в автоклав, нагревают до 180°С и при этой температуре выдерживают 32 часа. После этого автоклав охлаждают до комнатной температуры, полученный продукт фильтруют, промывают водой и сушат на воздухе при комнатной температуре. 2 мг полученного порошка смешивают с 0,5 мл 5%-ного поливинилхлорида в тетрагидрофуране и 0,05 мл дибулилфталата, что соответствует соотношению поливинилхлорид:дибутилфталат:гидратированная ванадиевая бронза аммония

Полученную смесь наносят на графитовый стержень и сушат при комнатной температуре до полного испарения тетрагидрофурана.Example 4. Take 0.2 g of powder of ammonium metavanadate

and dissolved in 12 ml of distilled water. An aqueous solution of citric acid is added dropwise to the resulting solution with stirring until the pH of the solution is 6.0. The resulting mixture was placed in an autoclave, heated to 180 ° C and maintained at this temperature for 32 hours. After that, the autoclave is cooled to room temperature, the resulting product is filtered, washed with water and dried in air at room temperature. 2 mg of the obtained powder is mixed with 0.5 ml of 5% polyvinyl chloride in tetrahydrofuran and 0.05 ml of dibulyl phthalate, which corresponds to the ratio of polyvinyl chloride: dibutyl phthalate: hydrated ammonium vanadium bronze

The resulting mixture was applied to a graphite rod and dried at room temperature until the tetrahydrofuran was completely evaporated.

кристаллизуется в моноклинной сингонии с параметрами кристаллической решетки

и состоит из частиц с морфологией, подобной цветку, образованной пересекающимися пластинками толщиной 100-350 нм и шириной 0.8-1 мкм. При рН 5 в интервале концентраций

угловой коэффициент электродной функции близок к теоретическому значению и равен 54 ± 2 мВ/рС_NH·According to x-ray phase and electron microscopy analyzes, the resulting product is single-phase, has the composition

crystallizes in monoclinic syngony with crystal lattice parameters

and consists of particles with a flower-like morphology formed by intersecting plates 100-350 nm thick and 0.8-1 microns wide. At pH 5 in the range of concentrations

the angular coefficient of the electrode function is close to the theoretical value and is equal to 54 ± 2 mV / rC _NH ·

Предлагается также простой и надежный способ получения ванадиевой бронзы указанного состава.Thus, the authors proposed the use as an ion-selective material for determining ammonium ions in a solution of hydrated ammonium vanadium bronze composition

A simple and reliable method for producing vanadium bronze of the specified composition is also proposed.

Claims (2)

1. The use of hydrated ammonium vanadium bronze ammonium composition (NH ₄ ) _0.5 V ₂ O ₅ · 0,5H ₂ O as an ion-selective material for the selective determination of the concentration of ammonium ions. 2. A method of obtaining a hydrated ammonium vanadium oxide bronze of the composition (NH ₄ ) _0.5 V ₂ O ₅ · 0.5H ₂ O according to claim 1, comprising dissolving ammonium metavanadate NH ₄ VO ₃ in water, adding dropwise aqueous under continuous stirring a solution of citric acid C ₆ H ₈ O ₇ until the acidity of the solution is 2.0 p pH 6 6.0, followed by processing the mixture at a temperature of 140-180 ° C for 24-48 hours in an autoclave, filtering, washing and drying.

Images