SU1704043A1 - Method for determination flotation agents on alkylinaphtaline base in air - Google Patents

Abstract

The invention relates to analytical chemistry, in particular the determination of a flotation agent based on alkyl naphthalenes in the air. The purpose of the invention is to increase the sensitivity of the analysis. It is conducted by passing an air sample through an absorber, acetic acid, followed by treating the resulting solution with ninhydrin in the presence of sulfuric acid when heated in a boiling water bath and photometrized. Under these conditions, the sensitivity increases from 10 to 2.5 µg (4 times). 3 tab.

Description

The invention relates to a technique for the analytical determination of toxic substances in air, in particular, to a method for determining the flotation reagent AAP-2 (an aromatic apolar reagent) based on alkyl naphthalenes.

AAP-2 flotation reagent is widely used in coal preparation plants as a 1.6% aqueous emulsion to speed up flotation. Approximate safe level of exposure (AELS) of AAP-2 flotation reagent in air 5, mg / m3 (TU 38.101765-78).

The method for determining the vapors of the AAP-2 flotation reagent in the air is not known, however, for its main part, alkylnaphthalenes, methods are described for determination in air.

A known method for the photometric determination of methylnaphthalenes, based on their absorption from air into acetic acid, nitration with a mixture of dilute

nitric and acetic acids and subsequent photometric determination. The disadvantage of it is the low detection sensitivity (40 µg in the analyzed volume).

The closest in technical essence and the result to the proposed is a method of determining additives based on potassium naphthenate in the air, which consists in dissolving potassium naphthenate in acetic acid, interacting with alloxanthin solution in sulfuric acid solution when heated in a boiling water bath followed by photometry of the resulting solution. The disadvantage of the method is also the low sensitivity of the determination - 10 µg in the analyzed volume.

The purpose of the invention is to create a method for determining the flotation reagent AAP-2 based on alkyl naphthalenes in the air.

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This goal is achieved by alkylating the AAP-2 flotation reagent on the core of naphthalene derivatives in the air by absorbing it from air into acetic acid, treating it with a solution of nine hydrin in acetic acid and sulfuric acid, heating on a boiling water bath for 20-30 min. subsequent photometry of the solution obtained.

To prepare a standard solution, weigh a 25 ml volumetric flask containing 10-15 ml of concentrated acetic acid on an analytical balance. Then, 1 drop of AAP-2 flotation reagent was added to the flask and repeated again, and the volume was made up to 25 ml with acetic acid. From the difference between the second and the first weighings, the content of flotation reagent in 1 ml is calculated. Working standard solutions 1 and 2 with a content of 100 µg / ml and 10 µg / ml of flotation reagent are prepared by appropriate dilution in concentrated acetic acid.

To construct the calibration graph, 0.25 working standard solution 2 and 0.1-0.25-0.5-1 ml of working standard solution 1, corresponding to 2.5-10-25-50-100 µg, are introduced into a series of tubes. flotation reagent AAP-2, the volume was made up to 1 ml with acetic acid, 1 ml of 1.2% of the yogonhydride was added, 2.5 mp of sulfuric acid sulfuric acid was added and the sweets were placed in a boiling water bath of 20 min. . After cooling, the solution measures their optical density in a cuver with a layer thickness of 1 cm and a length of 350-4 Oe. According to the result -: - 1, a graph is constructed in the coordinates: op- - peschg- density - the number of photoparagraphs of LLR-2, µg.

An example. 0.5 l of the test air containing AAP-2 flotation reagent vapors is passed through two absorption devices containing L ml of acetic acid at a rate of 0.25 l / min. For the analysis, 1 ml of the sample is taken, 1 ml of the 1.2% ninhydrine solution and 2.5 ml of concentrated sulfuric acid are added, the tubes are placed in boiling water Oanu for 20 minutes. After cooling, the optical density of the obtained solutions in a cell with a thickness of 1.0 cm at a wavelength of 380-400 is measured and the flotation reagent is found in the analyzed volume of the sample according to the calibration curve, and the concentration of flotation agent AAP-2 in air is mg / m are according to the formula

ga -V1

U V0 -V

where a is the amount of substance found in the analyzed sample volume according to the calibration curve, µg;

Vi is the total volume of the sample, ml;

V is the sample volume taken for analysis, ml;

V0 is the volume of air sampled, taken for analysis and reduced to normal conditions, l.

A comparison of the optical densities of the solutions at different concentrations of ninhydrin and the boiling time of the solutions is presented in Table. 1 and 2.

As can be seen from the table. 1 and 2, the optimum concentration range of ninhydrin in determining the flotation reagent AAP-2 is 0.5-0.75% solutions1 in acetic acid, the boiling time of the solutions in a separate bath is 20-30 minutes. Smaller amounts of ninhydrin and shortening of the heating time of the solutions underestimate the results of the AAP-2 flotation reagent, while higher quantities reduce the accuracy of the analysis results (due to intense staining of the blank).

In tab. Figure 3 presents experimental data comparing the results of the determination of the flotation reagent AAP-2 according to known (by reaction with alloxanthin) and known (by reaction with ninhydrin) methods. (P - 0.95. P 6).

As can be seen from the table. 3, the proposed method provides a 4-fold increase in detection sensitivity (the lower limit of measurement is reduced from 10 µg for the analyzed volume to 2.5 µg in the analyzed volume).

Thus, the method according to the invention will make it possible to determine the AAP-2 flotation reagent pairs in the air of the working area.

Claims (1)

The invention of the method for determining the flotation reagents based on alkyl naphthalenes in air by passing the analyzed air through an acetic acid scavenger, treating the solution obtained with a reagent in the presence of sulfuric acid while heating in a boiling water bath, followed by photometry of the solution obtained, about t and h and with the fact that, in order to increase the sensitivity of the determination, a solution of ninhydrin in acetic acid is used as a reagent. Table 1 table 2 Table 3