Method of determining benzoic acid in water

FIELD: chemistry.

SUBSTANCE: invention relates to analytical chemistry, particularly to methods of determining benzoic acid, and describes a method for quantitative determination of benzoic acid from a methyl derivative thereof - methyl ether in aqueous matrices with determination sensitivity of 5.0·10-5 mg/cm3 with determination error of not more than 25%. The method is characterised by that quantitative determination of benzoic acid is carried out using a chromatographic method with flame-ionisation detection and includes the following steps: extraction concentration of an analyte with benzene in water samples acidified with 25% sulphuric acid solution to pH 1-3 while adding sodium chloride until a saturated solution is obtained, conducting a benzoic acid methylation reaction with diazomethane to obtain a derivative - methyl ether of benzoic acid and determining the formed methyl ether of benzoic acid by a chromatographic method with flame-ionisation detection.

EFFECT: method provides high sensitivity, selectivity and easy implementation during quantitative determination of benzoic acid in aqueous media and enables use thereof in practice in factory analytical laboratories, central laboratories of chemical companies and chemical-toxicology laboratories.

1 ex, 3 tbl

 

The invention relates to the field of analytical chemistry, and in particular to methods for the determination of benzoic acid in aqueous samples, and can be used in the practice of factory control and analytical laboratories, Central factory laboratory of chemical plants, chemical and Toxicological laboratories.

There is a method to separate the determination of phenol and benzoic acid in aqueous solution, the essence of which is the concentration of the analyzed substances acetone in the presence of vicariates - ammonium sulfate and subsequent potentiometric titration of the resulting extract in acetone ethanol solution of potassium hydroxide. The limit of detection of benzoic acid is 0.4 mg/l [1].

The disadvantages of this method are the duration of the analysis and low sensitivity.

The known method of determination of sorbic and benzoic acids, based on their extraction from the sample buffer solution of ammonium acetate containing acetonitrile, with subsequent quantification in the extract using high-performance liquid chromatography using reversed-phase column and a spectrophotometric detector in the ultraviolet region of the spectrum [2].

The disadvantages of this method include that it does not have high sensitivity. The range is ons of the measured mass fractions of sorbic and benzoic acids are 50-1500 million -1.

The closest technical solution and the results achieved is the method of determination of benzoic acid in the products of processing fruits and vegetables, which is that the analyzed sample mass 50 g is quantitatively transferred into a separating funnel, poured from 0.5 to 1.0 cm3solution Caprylic acid, from 10 to 20 cm3a saturated solution of sodium chloride and from 1 to 2 cm3ethyl alcohol. Acidifying the solution to pH 2. The extraction was performed with chloroform three times with portions of 50 cm3while stirring , in a separating funnel for 5 minutes, each time selecting the lower chloroform layer. The combined extract is dewatered by filtering through a funnel filled with anhydrous sodium sulfate. The extract is evaporated on the extraction evaporator at 45°C is almost dry. The balance in pasture flask is dissolved in 1 cm3ethyl alcohol. The resulting solution was used for chromatographic analysis [3].

The method is characterized by a large number of steps, duration of implementation and low sensitivity.

An object of the invention is to reduce the duration, increase the sensitivity and selectivity of the determination of benzoic acid in water samples.

The problem is solved using the proposed method, which zaklyuche the Xia is to analyze the water sample add benzene, sodium chloride and adjusted with sulfuric acid to pH 1-3. The test tube is placed in an orbital shaker for 10-12 minutes After removal of the tubes from the shaker and the separation of benzene and aqueous layers are selected organic phase, which is subjected to methylation with diazomethane. The resulting solution was used for analysis. The quantitative content of benzoic acid in the sample is calculated according to the method of absolute calibration using a calibration solution of the methyl ester of benzoic acid (MAPK) in terms of benzoic acid with regard to its concentration.

Comparative analysis of the proposed solutions with the prototype shows that the inventive method differs from the known fact that as extractant benzoic acid from water used benzene. To increase the degree of extraction of benzoic acid from water in the aqueous phase of the extraction system is added to sodium chloride, but not its solution. Excluded procedures associated with dehydration of the extract and evaporation of the extract in a rotary evaporator. In addition, to increase the intensity of the response of the flame ionization detector is used, the process of derivatization of benzoic acid to its methyl ester, i.e. the proposed solution meets the criterion of "novelty".

Against which of the proposed solutions with prototype and other technical solutions in this field made it possible to identify the signs, significantly distinguish the claimed solution to the prototype, namely the presence of a set of actions that affect the ability to obtain a technical result.

The technical solution was implemented based on the results of optimization of sample preparation steps of the analysis in the following areas:

- substantiation of the method of extraction of benzoic acid from aqueous media;

- determination of distribution coefficients of benzoic acid in a biphasic aqueous-organic systems (aqueous solution of benzoic acid is an organic extractant);

- choose the method derivatization benzoic acid;

- establishing the limit of detection of benzoic acid (derived) using the method of gas chromatography;

- study the possibility of using "vasilevousa" inorganic electrolytes, the influence of the pH of the aqueous solution on the extraction rates of the analyte during the extraction.

When the extraction of benzoic acid from aqueous media using water-immiscible solvents (diethyl ether, methylene chloride, chloroform, benzene and hexane), it was established that:

- diethyl ether, methylene chloride and chloroform, when used to extract a significant amount of undesirable impurities salt;

from a hydrophobic, non-polar solvents (benzene and hexane), the most high is some extraction capacity of benzene.

In the analysis of extracts of benzoic acid using gas chromatography in combination with capillary columns with polar stationary phases were identified strong blur peak corresponding benzoic acid. This fact is probably due to the influence of carboxyl groups, which is especially pronounced in the analysis of the concentrations below 1.0·10-2mg/cm3.

The elimination of the influence of carboxyl groups on the parameters of the chromatographic peak is carried out by conducting preliminary methylation (derivatization) benzoic acid in the medium of organic solvent by diazomethane with the quantitative formation of its methyl ester.

Setting the lower limit of detection MAPK by gas chromatography was performed using solutions in benzene at concentrations of 5.0·10-1, 1,0·10-1, 5,0·10-2, 1,0·10-2, 5,0·10-3, 1,0·10-3, 5,0·10-4mg/cm3(in terms of benzoic acid) on the instrument the complex firm "Agilent Technologies", including gas chromatograph 6890N equipped with a flame ionization detector. Experimental conditions:

the injector temperature is 270°C;

the detector temperature is 270°C;

the volume of injected sample - 3 µl;

time Besobrasova operation of the injector is 0.1 min;

the separation of samples was performed on a capillary is alance HP-5 length 30 m, the inner diameter of 0.32 mm, a thickness of the stationary phase 0.25 μm in the temperature programming mode:

the initial temperature of thermostat to 50°C;

lift speed thermostat temperature - 15°C;

the final temperature of thermostat - 270°C.

Time output methyl ester benzoic acid - 5,88 minutes

The results of the experimental evaluation of the range of definitions methyl ester of benzoic acid in benzene chromatographic method with flame ionization detection are presented in table 1.

Table 1
The results of determining the response of a flame ionization detector on the number of input MAPK (P=0.95, and n=4)
Concentration MAPK in terms of benzoic acid, mg/cm3The area of the chromatographic peak, oted
5,0·10-16017,0±127,0
1,0·10-11749,2±46,0
5,0·10-2865,3±30,6
1,0·10-2178,7±7,3
5,0·10-392,±4,2
1,0·10-323,6±1,2
5,0·10-413,7±0,8

Analysis of the data presented in table 1, revealed a concentration range determination of methyl ester of benzoic acid in benzene using this detector, which in terms of benzoic acid and 1.0·10-1-5,0·10-4mg/cm3.

The next stage of the research was to determine the distribution coefficients of benzoic acid in a biphasic aqueous-organic systems, depending on the pH of the medium and having vasilevousa" inorganic electrolytes.

The experiment was carried out as follows. Prepared water matrix with a pH in the range from 3.0 to neutral. Adjustment of pH was carried out by 25% solution of sulfuric acid. Next was preparing working aqueous solutions of benzoic acid with a concentration of 5.0·10-3mg/cm3. Transferred to 1.5 ml of the prepared solution in a test tube with a glass stopper was added 1.5 ml of benzene and placed in an orbital shaker for 10-12 min (V=300 rpm), selected organic phase and metilirovanie. After methylation, the sample was kept for 2-5 min, were selected aliquot part and moved into vials for chromatographic analysis. The results of the quantitative determi the population methyl ester of benzoic acid in the organic phase (benzene) after extraction are presented in table 2.

Table 2
The results of quantitative determination of methyl ester of benzoic acid in terms of benzoic acid (Bq) (P=0.95, n=4)
SamplepH"Wasalive" inorganic electrolyteConcentration MAPK in benzene in terms of BK, mg/cm3The average distribution coefficient benzene-water
Control (benzene solution of benzoic acid after methylation)-no5,0·10-3-
An aqueous solution of benzoic acid, acidified with sulfuric acid1,0no(2,5±0,1)·10-30,50
An aqueous solution of benzoic acid, acidified with sulfuric acid3,0no(2,3±0,1)·10-30,46
An aqueous solution of benzoic KIS is the notes (distilled water) 5,8no(8,7±0,4)·10-40,17
An aqueous solution of benzoic acid, acidified with sulfuric acid7,0no(5,1±0,2)·10-40,10
An aqueous solution of benzoic acid, acidified with sulfuric acid1,0NaCl to saturation(4,8±0,2)·10-30,97
An aqueous solution of benzoic acid, acidified with sulfuric acid3,0NaCl to saturation(4,2±0,2)·10-30,84
An aqueous solution of benzoic acid, acidified with sulfuric acid5,8NaCl to saturation(3,5±0,2)·10-30,71

Given the above, to ensure the highest coefficients of extraction of benzoic acid when carrying out sample preparation water samples as extraction systems was selected by two-phase system benzene-p is kislany saturated aqueous solution of sodium chloride.

In addition to identifying the optimal conditions of extraction, derivatization of benzoic acid and conditions for gas chromatographic determination of methyl ester benzoic acid, we investigated the possibility of concentration of the analyte by changing the volume ratio of the aqueous phase and the extractant. To study the possibility of extraction concentration of benzoic acid without significant changes in the coefficients of its distribution within the range of ratios of volumes of the aqueous phase extractant from 1 to 11.5.

Example

Sample preparation

In a test tube with a glass stopper with a capacity of 10 ml were placed to 4.5 ml of an aqueous solution of benzoic acid and 0.5 ml of benzene, was added 1.5 to 2.1 g of sodium chloride and 0.6 ml of 25% sulfuric acid solution. The tube was closed with a glass stopper and placed in an orbital shaker for 10-12 min (V=300 rpm). After removal from the shaker tube was left to stand for 2-3 minutes before separation of the benzene and aqueous layers, and then selected the organic phase was subjected to methylation. The presence of an excess of the formed diazomethane controlled by a straw-yellow colour benzene solution. After methylation, the sample was kept for 2-3 min, were selected aliquot part and moved into vials for chromatographic analysis.

Analysis

The quantitative content of what antinoi acid was calculated by the method of absolute calibration using a calibration solution of the methyl ester of benzoic acid with subsequent conversion to benzoic acid. The determination results are presented in table 3.

Table 3
The results of the quantitative chemical analysis of aqueous solutions of benzoic acid (P=0.95, n=4)
Entered, mg/cm3The peak area of the derivative, the river. unitsFound, mg/cm3
1,0·10-21721,3±126,5(1,0±0,1)·10-2
5,0·10-3864,2±66,1(5,0±0,4)·10-3
1,0·10-3176,9±16,3(9,9±0,9)·10-4
5,0·10-4a 94.6±9,6(5,1±0,5)·10-4
1,0·10-426,0±3,1(1,1±0,1)·10-5
5,0÷10-512,9±1,6(4,7±0,6)·10-5

Thus, the developed method allows quantitative determination of benzoic acid and its methyl derivatives of the one - methyl ether in aqueous matrices with detection sensitivity of 5.0·10-5mg/cm3with a measurement error of not more than 25%.

Literary sources

1. Pat. 2021594 Russian Federation, IPC G01N 31/16/ Way separate determination of phenol and benzoic acid in aqueous solution [Text] / Korenman YA: applicant and patentee Voronezh technological Institute, No. 4950458/04; Appl. 26.06.91; publ. 15.10.94.

2. GOST P 52052-2003. The products of processing fruits and vegetables. The method of determining the mass fraction of sorbic and benzoic acids using liquid chromatography. [Text]. - An introd. 2004-07 - 1. - Minsk: Migos. Council on standardization, Metrology and certification; - M.: Institute Publishing house of standards, 2003. - 10 S.

3. GOST 30669-2000. The products of processing fruits and vegetables. Gas chromatographic method for the determination of benzoic acid. [Text]. - An introd. 2002-01-01. - Minsk: Migos. Council on standardization, Metrology and certification; - M.: Institute Publishing house of standards, 2001. - 7 S.

The method of determination of benzoic acid in water, characterized in that sequentially carry out extraction concentration of the analyte from acidified with 25%solution of sulfuric acid (pH 1-3) water samples benzene adding sodium chloride to obtain a saturated solution, methylation of benzoic acid with diazomethane and determination of the resulting derivative - metrolog the ester of benzoic acid by gas chromatography with flame ionization detection with a sensitivity of 5.0·10 -5mg/cm3.



 

Same patents:

FIELD: engines and pumps.

SUBSTANCE: proposed method is based on application of simplified model of intake of admixtures into cabin which allows for only oil decomposition products in gas turbine engine. Major portion of air samples, 95-97%, required for identification and quantitative determination of oil decomposition products, is sampled on surface from device simulating oil decomposition conditions including air temperature and pressure at point of sampling from engine compressor, and oil stay time in hot zone.

EFFECT: decreased time of in-flight experiments and that of surface analysis of samples.

1 cl, 1 ex, 1 tbl, 1 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to laboratory methods of analysis and deals with method of quantitative determination of manganese, lead and nickel in bile by method of atomic-absorption analysis with atomisation in flame. Essence of method lies in the following: sampling of bile is carried out during duodenal probing, after that it is frozen, and unfrozen at room temperature, homogenisation of bile by mixing being performed already at partial soft unfreezing. After that, sampling of homogenised bile is carried out for preparation for analysis, concentrated nitric acid is introduced into it with volume ratio 1:1, mixture is kept at room temperature, then heated and further mixture is kept for not less than 2.5 hours at room temperature. In order to obtain analyte, to obtained mixture added is concentrated hydrogen peroxide in volume ratio 1:1 to volume of bile sample volume, analyte is heated, after that cooled to room temperature. After that by method of atomic-absorption spectrometry, using graduated diagram, quantitative content of particular type of metal: manganese, lead and nickel is determined in analyte.

EFFECT: invention allows increasing accuracy of quantitative determination of manganese, lead and nickel in bile.

6 tb

FIELD: physics.

SUBSTANCE: vapour-gas mixture source has a mixer which has connecting pieces for inlet and outlet of the vapour-gas mixture. The vapour-gas mixture source also has a diffusion pipe filled with working fluid and an auxiliary pipe designed for filling the diffusion pipe with working fluid. Part of the diffusion pipe is filled with substance which retains the working fluid. The level of working fluid in the auxiliary pipe is lower than the level of substance in the diffusion pipe. The substance which retains the working fluid used can be sand, granular material with particle size between 10 and 10000 mcm, porous substances, e.g. ceramic metal etc.

EFFECT: more accurate measurement and maintenance of concentration of the vapour-gas mixture coming out of the source, provision for constant diffusion flow of vapour of working fluid into the mixer.

11 cl, 2 dwg

FIELD: instrument engineering.

SUBSTANCE: invention is designed for calibrating gas analyser detectors, according to which there prepared is calibration substance solution with concentration A=By/k (%) as per Henry constant value k (mg/m %) at calibration temperature and as per the specified value of calibration substance mass concentration in calibration steam/gas mixture By (mg/m). After the solution has been introduced into the vessel in quantity enough for fully saturated equilibrium calibration steam/gas mixture to appear above the solution surface, the sensor calibration is carried out by means of mixture; at that, mixture concentration is changed by means of direct proportional change of solution concentration by diluting concentrated reference solution of calibration substance with analytical accuracy up to the specified concentration value A (%). There also proposed is the device for realising this method, which includes a solution point for preparing calibration solution with analytical accuracy, vessel with thermostatic device for obtaining steam/gas mixture with constant concentration corresponding to Henry law; at that, solution point includes graduated dose metre, graduated diluter, mixer with a reducer, capacity with solvent, and reference container with reference solution, which is stabilised with a gate valve meant for multiple use of container, and vessel with thermostatic device consists of thermometre and heat-insulating cover plate with an inlet branch pipe containing a normally closed return valve and a pusher for valve opening.

EFFECT: decrease of calibration substance losses; accuracy and reproducibility of metrological performance, and meeting requirements of industrial and ecological safety.

6 cl, 2 dwg

FIELD: instrument engineering.

SUBSTANCE: device for generating flow of vapor-gas mixture with preset concentration of vapor has vessel partially filled with fluid, second vessel provided with branch pipes for supply and removal of gas, and vapors of fluid pipeline-leak. One of vessels is connected with gas discharge forcer; fluid vapors pipeline-leak connects both vessels. Vessel, partially filled with fluid, is mounted inside second vessel. Pipeline-line, connecting both vessels, is totally placed inside second vessel. Device is also provided with additional discharge forcer for adjusting concentration of fluid vapor in second vessel. Granulated filler is introduced into vessel partially filled with fluid. Device is also provided with gas analyzer for providing gas concentration in space of second vessel.

EFFECT: higher precision of keeping of preset concentration of vapor; improved efficiency of vapor concentration control and adjustment.

FIELD: chemical technology.

SUBSTANCE: invention relates to a method for synthesis of ester perfluorinated derivative by using a chemical reaction. This reaction represents the fluorination reaction of the parent compound as a raw, the reaction of chemical conversion of fragment of ester perfluorinated derivative to yield another ester perfluorinated derivative or the interaction reaction of carboxylic acid with alcohol under condition that at least one or reagent, i. e. carboxylic acid or alcohol, represents a perfluorinated compound wherein indicated perfluorinated derivative of ester represents a compound comprising a fragment of the formula (1):

with a boiling point 400°C, not above. The reaction time for carrying out abovementioned chemical reaction is sufficient to provide the required yield of ester perfluorinated derivative and wherein this yield of ester perfluorinated compound is determined by the gas chromatography method by using a nonpolar column. Also, invention relates to a method for pyrolysis of ester perfluorinated derivative with a boiling point 400°C, not above, to yield the dissociation product wherein this product represents a derivative of acyl fluoride or ketone and wherein pyrolysis time is sufficient to provide the required degree of conversion of ester perfluorinated derivative and wherein the indicated conversion degree of ester perfluorinated derivative is determined by gas chromatography method by using a nonpolar column. Also, invention relates to a method for analysis of ester perfluorinated derivative with a boiling point 400°C, not above, that involves analysis of ester perfluorinated derivative in a sample containing ester perfluorinated derivative by gas chromatography method by using a nonpolar column wherein ester perfluorinated derivative represents compound comprising a fragment of above given formula (1).

EFFECT: improved method of synthesis.

8 cl, 1 dwg, 2 ex

The invention relates to the field of analytical chemistry of organic compounds, namely, the field determination of organic compounds in their joint presence using gas-liquid column chromatography, and can be used for the separate determination of phenols in liquid environments, mainly in industrial effluents, as well as the analysis of natural waters

The invention relates to the field of gas analysis and can be used for calibration of gas analysis equipment

The invention relates to the field of analytical instrumentation, in particular, to devices for preparation of calibration gas mixtures used in the calibration and verification of gas analyzers

The invention relates to the field of analytical instrumentation and can be used in the calibration and verification of gas analyzers

FIELD: chemistry.

SUBSTANCE: group of inventions relates to analytical chemistry and can be used to indicate the end of the service life of a filter cartridge. The chemical sensor has a film which includes a film body which reacts to the presence of a chemical by changing colour, wherein the film body comprises: a detection layer; a barrier layer; a reflecting layer between the barrier layer and the detection layer, and a semi-reflecting layer on the side of the detection layer opposite to the reflecting layer. The barrier layer has a main surface attached to the film body in given regions of the sensor, but inert to the detection layer to prevent change of colour in the film body in the region lying in a direction which is perpendicular to the main surface of the barrier layer. The group of inventions also relates to a filter cartridge having said sensor, and a respirator having one or more of said filter cartridges.

EFFECT: group of inventions increases accuracy and reliability of analysis by providing clear contrast between original and signalling colours of the sensor.

17 cl, 3 dwg, 1 tbl, 3 ex

FIELD: medicine.

SUBSTANCE: group of inventions refers to medicine and may be used for detecting biological pathogens in a sample. A clinical indicator unit for detecting biological pathogens comprises a carrier foldable to form two opposite sheets. The inner side of the first sheet of the carrier comprises a contact surface of the sample and an absorbent pad, while on the inner side of the second sheet, there is an indicator surface opposite the contact surface; the indicator surface contains a solvatochromic stain discolouring if a bacterial pathogen is found in the test sample. The unit also comprises a results windows on the outer surface of the second sheet with the absorbent pad engaging a stained reaction zone if the first sheet is folded with the second one. The group of inventions also refers to a version of the above unit wherein the first and opposite second carriers are the two sheets or parts of the same first carrier folded to face each other, and to a method for using the above unit for bacterial infection analysis.

EFFECT: group of inventions enables fast and easy bacteria detection in the sample, and also provides differentiating between bacterial and viral pathogens.

16 cl, 6 dwg, 1 tbl, 9 ex

FIELD: chemistry.

SUBSTANCE: invention can be used to determine content of iron (II) in solutions of pure salts containing iron (II) in very low concentrations. The method involves converting iron (III) into a complex compound with an organic reagent in a weakly acidic medium. The iron (II) solution with pH 2-5 is mixed with 200-300 times the amount of the organic reagent which is Congo red, 0.2-0.4 ml surfactant solution in form of a 0.2% solution of monoalkyphenyl ester of polyethylene glycol based on a polymer distillate and 10 ml water, followed by heating on a water bath at temperature of 80-98°C for 10-15 minutes.

EFFECT: high sensitivity of analysis.

5 dwg, 1 ex

FIELD: chemistry.

SUBSTANCE: method involves using sulphonazo as a colour reagent and photometering, wherein a sulphonazo ion-associate with an azo dye is formed in the solution, which is then concentrated on a foamed polyurethane sorbent, followed by photometering of the ion-associate directly on the solid phase at pH=8 and wavelength 538 nm.

EFFECT: high sensitivity and selectivity of analysis.

1 ex, 2 tbl, 3 dwg

FIELD: chemistry.

SUBSTANCE: present invention relates to a chemical marker for concealed marking of substances, materials and articles, which contains a mechanical mixture of phthaleins, silca gel, carboxylic acid and weakly oxidised atactic polypropylene, characterised by that it further contains 3-(3'-methyl-4'-hydroxyphenyl)-3-(4"-hydroxyphenyl) phthalide of structural formula , with the following ratio of components, wt %: phenolphthalein- 0.5-28.0; o-cresol phthalein - 14.1-56.5; silica gel - 15.0-25.0; citric acid or oxalic acid- 2.0-4.0; weakly oxidised atactic polypropylene - 10.0-16.0; 3-(3'-methyl-4'-hydroxyphenyl)-3-(4"-hydroxyphenyl) phthalide - 8.0-39.3. The present invention also relates to a method of preparing a mixture of phenolphthalein homologues.

EFFECT: high output of 3-(3'-methyl-4'-hydroxyphenyl)-3-(4"-hydroxyphenyl) phthalide, which increases reliability of marking substances, materials and articles, reduces the probability of falsification of the marker and simplifies composition thereof.

2 cl, 5 ex, 1 tbl

FIELD: chemistry.

SUBSTANCE: method involves dissolving the analysed sample in purified water; holding on a water bath while stirring and at temperature of 30-40°C until complete dissolution; bringing the volume of the solution to the mark using the same solvent; successive treatment of an aliquot part of the obtained solution with 1% alkaline solution of sodium nitroprusside, 3% hydrogen peroxide solution and 0.1 M KOH solution and photoelectric colorimetry of the coloured solution.

EFFECT: high sensitivity, selectivity and accuracy of analysis.

1 ex, 9 dwg

FIELD: chemistry.

SUBSTANCE: method is realised by treating a droplet of an oil sample with a solvent which consists of 50% toluene and 50% isopropanol in the presence of filter paper which is saturated with aqueous solution of bromthymol blue, followed by comparing its colour with the reference colour, wherein the droplet of the oil sample is added to a mixture which consists of 70% of a 20% ethyl alcohol aqueous solution and 30% solvent; 1% bromthymol blue solution is used; after holding in bromthymol blue, the filter paper is soaked with cotton fabric and dried in a horizontal position.

EFFECT: high accuracy of estimation.

FIELD: chemistry.

SUBSTANCE: groups of inventions is meant for rapid determination of high concentrations of hydrogen chloride, ammonia, chlorine and nitrogen dioxide in air, which are chemically hazardous substances, and can be used to monitor atmospheric contamination during industrial disasters associated with emission of chemically hazardous substances into the environment. The indicator plate consists of organic glass, indicator paper attached to the organic glass and insulated from the atmosphere by an adhesive tape, a cardboard strip and two guide marks on the organic glass. The adhesive tape has an incision to mark the tearing point of the cardboard strip. The group of inventions also relates to a method of determining high concentrations of chemically hazardous substances in air using said indicator plate, involving: opening the bottom part of the indicator plate by tearing the cardboard strip; recording the time of tearing the cardboard strip; monitoring colouring reaction of the indicator paper upon reaction with chemically hazardous substances and progression of the coloured layer upwards; determining concentration of the substance from the height of progression of the front of the dye relative the first or second guide mark.

EFFECT: simple and fast determination of high concentrations of chemically hazardous substances in air.

8 cl, 1 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to production of special chemical substances used for concealed marking of substances, materials and articles, and can be used when conducting different types of examination of trading and industrial enterprises. The chemical marker contains the following in wt %: 42.3-50.2 phenolphthalein, 5.3-12.5 o-cresol phthalein, 5.3-6.3 thymolphthalein, 0.1-1.0 fluorescein, 20.0-30.0 silica gel, 2.0-4.1 citric or oxalic acid, 5.0-15.9 low-oxidised atactic polypropylene. The chemical marker is obtained by depositing an adhesive polymer on the outer surface of powdered phthalein particles. The phthalein mixture is pre-suspended in 10-15% solution of low-oxidised atactic polypropylene in hexane or benzene. The solvent is distilled off by heating the suspension to boiling. The powder is dried in a thin layer of thickness 2-5 mm in air at 15-25°C. Silica gel and carboxylic acid are then fed, followed by homogenisation of dry components with intense mixing.

EFFECT: longer time for integrity of concealed marking on marked objects, high illegality of use of the markers and reliable identification thereof during examination.

2 cl, 1 tbl, 6 ex

FIELD: chemistry.

SUBSTANCE: method involves oxidation of reducing substances with copper (II) compounds in an alkaline medium while heating on a boiling water bath for 10 minutes, bringing the volume of the cooled solution to a defined value, determining optical density at wavelength 670 nm, making an adjustment to partial oxidation of non-reducing carbohydrates, which is subtracted from the optical density reading, and estimating concentration of reducing substances from a calibration curve.

EFFECT: high accuracy and reproducibility of analysis.

5 ex, 6 tbl, 4 dwg

FIELD: analytical methods.

SUBSTANCE: group of inventions is directed on detecting and quantitatively determining hydrogen radicals present in water or in aqueous solution and is characterized by adding sodium 3,5-dibromo-4-nitrosobenzenesulfonate to sample to detect hydrogen radicals from coloration appearing as a result of their absorption characteristics, and additionally characterized by blowing gaseous hydrogen through 1,1-diphenyl-2-picrylhydrazide solution absorbing near 517 nm and sodium 3,5-dibromo-4-nitrosobenzenesulfonate solution at constant velocity in presence of platinum black in order to quantitatively evaluate hydrogen radical concentration using calibration curve based on correlation between coefficient of absorption near 450 nm for azo compound of sodium 3,5-dibromo-4-nitrosobenzenesulfonate and concentration of hydrogen radicals appeared.

EFFECT: increased determination accuracy and enabled analysis of hydrogen radicals in various media.

6 cl, 15 dwg, 1 tbl, 5 ex

Up!