RU1774236C - Method of estimating naphthalene disulfonates - Google Patents

Abstract

Use in analytical chemistry SUMMARY OF THE INVENTION Naphthalene disulfonates are extracted from a sample in an alkaline medium with 2,4-dinitrophenol methylpentadecyl ethylenediammonium, the aqueous phase is separated, followed by photometry 1 syl, 4 tab.

Description

The invention relates to analytical chemistry, in particular, to methods for the determination of naphthalene disulfonates of anionic surfactants and can be used to quantify naphthalene disulfonates in solutions and technological electrolytes.

There is a known method for determining anionic surfactants by treating the analyzed solution with dye - methylene blue in an acidic medium, extracting the resulting colored complex with chloroform, followed by photometric analysis of the extract. The disadvantage of this method is the low selectivity of anionic surfactants even in the presence of anion

A weighted method for determining anionic surfactants, including naphthalene disulfonates, is also known, based on dissolving the analyzed object in alcohol by evaporating it and weighing the dry residue. The disadvantage of this method is the low selectivity, high complexity

A number of anion-exchange extraction methods for determining anionic surfactants are also known. based on the extraction of organic anions with salts of higher quaternary ammonium bases The disadvantage of this method for the determination of naphthalene disulfonates is the low selectivity of the determination and the insufficient sensitivity of the Naftzlindisulfonate anions, which are hydro 4

4 Yu SO O

fmlic and extremely weakly extracted with salts of higher quaternary ammonium bases.

Closest to the invention in technical essence and the achieved result is the method for determination of fatty carboxylic acids described in (5). The method involves processing an aliquot of the test substance about an alkaline medium with a 2,4-dinitrophenolate salt of a higher quaternary ammonium base containing 32-45 carbon atoms.

However, this method is not selective when used to determine naphthalene disulfoates. Most inorganic and organic anions interfere with its determination (Tables 1 and 2),

The aim of the invention is to increase the selectivity for the determination of naphthalene disulfonates.

This goal is achieved by the fact that in the method for determining naphthalenedisulfonates by treating the analyzed sample with an extractant in an alkaline medium, separating the aqueous phase and then photometric measuring it, the bis-quaternary ammonium salt - 2,4-dinitrophenol methylpenta-decylethylenediammonium is used as an extractant MPDDL (DNF) 2 having the formula

CH3 (CloH2l) 2N + (CH2) 2N + (CloH2ll3 x

(M02) 20 2

When shaking an aqueous solution containing naphthaleidisulfonate anions with a toluene solution of 2.4-dinitrophenol and MPDDA, an anion exchange reaction occurs:

MPDDA 2 (DNF)) z + Naff2 - MPDDA + 2 Naff2 + 2 DNF.

As can be seen from the reaction equation, the naphthalene disulfonate anions are extracted by an ion exchanger, the colored dinitrophenol t anions are separated into the aqueous phase. By measuring the optical density of the aqueous phase depending on the initial content of naphthalene disulfates, a calibration graph can be constructed and used to quantify naphthalene disulfonates .

EXAMPLE 1. Construction of a calibration graph.

0.5-1-2-3-4-5 ml of a standard solution of sodium naphthalene disulfonate are added successively into 5 tubes with ground stoppers with a capacity of 25 ml

with a concentration of 30.9 g / l, 1 ml of 0.01 M NaOH solution and adjusted to a volume of 10 ml with distilled water. Then, 10 ml of a toluene solution of a reagent, 2,4-dinitrophenol methylpentadecyletylethylenediammonium with a concentration of 2.5 M, are added to each tube. The contents of the tubes are shaken for 23-3 minutes. After settling the phases, the lower aqueous

phase, filtered through a paper filter and photometer at a wavelength of 410 nm in a 1 cm cuvette.

Based on the data obtained, a calibration graph is constructed in the coordinates:

5 A (optical density) - C (concentration of naphthylindisulfonate, mg / L).

The calibration graph is shown in the drawing.

Example 2 Determination of Sodium Naphthalenedi 0 Sulfonate

, 9 ml of the analyzed solution containing sodium naphthalene disulfonate are added to a tube with a ground stopper, 1 ml of 0.01 M NaOH and 10 ml of a toluene solution of 2,4-dinitrophenol MPDDA with a concentration of 2.5 M are added, the contents of the tube are shaken 2- 3 minutes. After settling of the phases, the lower aqueous phase is selected, filtered through paper

0 filter and absorbance is measured at a wavelength of 410 nm in a 1 cm cuvette. The concentration of naphthalene disulfonate is determined from a pre-constructed calibration curve.

5 In the table. Figure 1 shows the results of the determination of naphthalene disulfonate over a wide concentration range.

A study of the selectivity of the determination of naphthalene disulfonate

0 sodium using 2,4-dinitrophenol trinonyloctadecylammonium (prototype) and the claimed method. The results of the study of the selectivity of the methods are expressed in terms of selectivity factors — that is, the limiting 5 mass ratio of make up: basic substance, at which a 10% error in the determination of the basic substance is observed.

0 As can be seen from the table. 2 when using

According to the claimed method of analysis, the selectivity for the determination of sodium naphthalene disulfonate increases 13-116 times depending on the type of interfering anion.

5 A similar picture is observed when anions of alkyl sulfates and alkylaryl sulfonates, which are often in the same mixture with sodium naphthalene disulfonate, act as interfering anions (Table 3).

As can be seen from Table 3. and in the case of the presence of organic interfering anionopes, when using the claimed method, a significant increase in selectivity factors occurs.

Since 2,4-dinitrophenol is a weak acid (), the acidity of the aqueous phase has a significant effect on the results of the analysis (Table 4).

As can be seen from the table. 4, in a neutral and acidic environment, the results of the analysis are systematically underestimated due to the transition of 2,4-dinitrophenol t-anionop to the acid form and its extraction into the organic phase. Therefore, the determination of sodium naphthalene disulfonate must be carried out in an alkaline environment.

Using the proposed method allows to sharply increase the selectivity of the determination of naphthalene disulfonates relative to inorganic and organic anions, which can be used in the analytical chemistry of this surfactant

Claims (1)

SUMMARY OF THE INVENTION A method for determining naphthalene disulfonates by treating an analyzed sample with an extractant in an alkaline medium for separating the aqueous phase and then photometric it, characterized in that in that in order to increase the selectivity of determination, 2,4-dinitrophenolate methylpenta-decylethylenediammonium is used as an extractant. Table 1 Sodium Naphthalene Disulfonate Results (,, 95). Solution volume 10 ml table 2 Selectivity factors for the determination of sodium naphthalindisphonate in the presence of inorganic acid anions. Reagent concentration - 2 ,, Toluene solvent Zkstragent Mesh anions cwj | SCH I i JNOj f Vg j CL TablesZ Selective factors for the determinations of sodium naphthalenedisulfonate on the presence of interfering anions: benzene sulfonate (BS), naphthalene sulfonate (HC), ethyl sulfate (Cg), butyl sulfate (C) hexyl sulfate (Ctf), and ohtyl sulfate (Cd). Reagent concentration 2, I. Solvent - G G p and c 4 The effect of pH of aqueous fa-sh on the results of determination of sodium naphthalene disulfonate (p T P 0 95) H 12 10 8 7 4 2 Introduced NaMaft μg 795 79 5 79 5 7Q5 795 795 795 795 Found NaNaft mcg 79 1 t 2 O 79 5 ± 1 9 780 + 20 75 2 ± 2.2 60 5 ± 2 5 49.8 ± 22 82 ± 30 B..covered -g V and C At, f 4- / yu,