RU2618530C1 - Reagent for aliphatic amines and their polyaminoplicarbone derivatives (complexes) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: reagent consists of two components: a complexing ion based on polyvalent elements in lower oxidation states, such as Co²⁺, Mn²⁺, Ce³⁺, Forming stable complexes with nitrogen-containing ligands, and an oxidizer based on 18-tungsten, molybdo-2-phosphates of composition M₆[P₂W_18-nMo_nO₆₂]⋅xH₂O, where M=Li, Na, K, NH₄; n=0-18; x=10-12.

EFFECT: invention allows to determine the polyaminopolycarboxylic amines and their derivatives in the presence of compounds that absorb light in the medium and short-wave part of the spectrum.

3 ex

Description

The invention relates to the field of chemical analysis of water-soluble primary, secondary and tertiary aliphatic amines and their polyaminopolycarboxylic derivatives (complexones) [Dyatlova N.M., Temkina V.Ya., Popov K.I. Complexones and complexonates of metals. - M .: Chemistry, 1988. - 544 p.]. The proposed reagent can be used to identify and quantify amines and their polycarboxylic derivatives in various objects: in industrial products and in intermediate products of complexon production, in natural objects and artificial mixtures containing aliphatic amines and their polycarboxylic derivatives.

The prior art method for determining organic nitrogen, including aliphatic amines and their derivatives, according to the Kjeldahl method, which consists in the decomposition of a sample with sulfuric acid with the restoration of organic nitrogen to ammonia, followed by distillation of NH ₃ in a titrated acid solution and its titrimetric determination of the residue [ Volynets V.F., Volynets M.P. Analytical chemistry of nitrogen / Series: Analytical chemistry of elements. - M .: Nauka, 1977. - 307 p.].

However, this method is lengthy and time-consuming and includes a series of sequential operations requiring a highly skilled operator, and is also limited by the ammonia content to 10 ^-2 mol / l with a relative error of about 1%.

There is also a method of determining amines by converting them to NH ₃ and further spectrophotometric determination using Nessler reagent [Volynets V.F., Volynets M.P. Analytical chemistry of nitrogen / Series: Analytical chemistry of elements. - M .: Nauka, 1977. - 307 p.].

However, this method is only suitable for determining low ammonia contents, and its main drawback is the use of toxic mercury compounds.

The determination of polyaminopolycarboxylic compounds (complexones) is also possible by the method of complexometric titration [Schwarzenbach G., Flashka G. Complexometric titration. - M .: Chemistry, 1970. - 360 p.], For example, with solutions of Cu, Mg, etc. or also according to GOST 10652-73 [Reagents. Sodium disodium ethylenediamine-Ν, Ν, Ν ', Ν'-tetraacetic acid 2-water (Trilon B). Technical conditions M.: Standardinformation, 2007, 14 p. Official publication] titrated metal solutions (Zn, Pb).

When titrating complexones, the analyst’s individual ability to distinguish between close colorations is necessary and is largely a subjective factor, depending on his qualifications. The disadvantage of this method is that the minimally determined complexon content in titrimetry is related to the values of permissible determination errors, the stability constants of the resulting complexes, and the degree of proximity of the equivalence point to the indicator RT and does not allow determining complexons with a concentration below 10 ^-2 -10 ^-3 mol / l

The closest method for determining amines, taken as a prototype of the present invention, is spectrophotometric determination of nitrogen-containing compounds according to the Griss-Ilosvay method, which consists in converting them into a nitrite form with subsequent diazotization and the formation of an azo dye (λ = 525 nm) [Volynets V.F., Volynets M.P. Analytical chemistry of nitrogen / Series: Analytical chemistry of elements. - M .: Nauka, 1977 .-- 307 p .; Guidance on the chemical analysis of seawater. Guiding document 52.10.243-92 - S.-Pb .: 1993. - 246 p.].

The disadvantages of this method are the need to convert the nitrogen of amines and polyaminopolycarboxylic derivatives into a nitrite form, which requires the creation of special conditions for each individual amine and the selection of the most suitable region in the absorption spectrum of the resulting product; the duration of the process (up to 2-6 hours) and the need to maintain a low temperature for the diazotization reaction; low accuracy (relative error of the method 4-12%).

The technical result of the present invention is to develop a reagent for the simple determination of amines and their polyaminopolycarboxylic derivatives (complexones) in the concentration range up to 10 ^-6 mol / L by the value of the optical density of the solution in the long-wave part (λ = 600-900 nm) in the presence of absorbing compounds light in the middle and shortwave spectra.

The specified technical result is achieved by the fact that a substance consisting of two components is used as a reagent: cationic (CT) and anionic (An) part. Ions of polyvalent transition elements in lower oxidation states (Co ²⁺ , Mn ²⁺ , Ce ³⁺ ) are used as the cationic part of the reagent, which form complexes with nitrogen-containing ligands having free electron pairs. The same elements with a higher oxidation state (Co ³⁺ , Mn ³⁺ , Ce ⁴⁺ ) form similar, but several orders of magnitude more stable complexes with the same nitrogen-containing ligands [Lurie, Yu. Yu. Handbook of Analytical Chemistry - 6th ed. - M .: Chemistry, 1989. - 488 p.]. In this case, as a result of complexation reactions, the ions initially taken as the cationic part of the reagent become sufficiently strong reducing agents (the redox potential of these ions, depending on the nature of the nitrogen-containing ligands, decreases by 0.5-1.0 or more) [Turyan Y.I. Redox reactions and potentials in analytical chemistry. - M .: Chemistry, 1989. - 248 p.]. As the anionic part of the reagent (An), potassium, sodium, lithium or ammonium derivatives of 18-tungsten, molybdo-2-phosphates of the following composition are used: M ₆ [P ₂ W _18-n Mo _n O ₆₂ ] ⋅xH ₂ O, where Μ = Li, Na, K, NH ₄ ; n is 0-18; x = 10-12 [Maslov L.P. Synthesis of 18-tungsten, molybdo-2-phosphates / Journal of Inorganic Chemistry, 1986, T. 31, No. 5, S. 1169-1173]. The anionic part of the reagent, stable under ordinary conditions, with a decrease in the redox potential of the cationic part of the reagent below 0.7 V, is restored with the appearance of an intensely blue staining of the solution in the region of 600-900 nm in proportion to the concentration of the nitrogen-containing ligand.

The action of the proposed reagent for objects containing amines and their polyaminopolycarboxylic derivatives (complexones) is based on differences in the stability constants of transition element complexes (Co, Μn, Ce), which are in different oxidation states (as a rule, the complex stability constants are in a higher oxidation state many orders of magnitude higher compared to a similar complex of the same element, which is in a lower degree of oxidation) [Turyan Ya.I. Redox reactions and potentials in analytical chemistry - M .: Chemistry, 1989. - 248 p.]. For example, the logarithms of the stability constants of complexes (logβ) of cobalt (II and III) with ethylene diamine tetraacetate (EDTA) are 16.31 and 40.6, respectively, and the stability constants of similar complexes of manganese (II and III) are 14.04 and 24.9, respectively [Lurie Y. Yu. Handbook of Analytical Chemistry - 6th ed. - M .: Chemistry, 1989. - 448 p.]. These differences lead to the fact that the redox potential of the system (E ° _{Ox / Red} ) changes dramatically, and the ion, which is in a lower oxidation state, becomes a strong reducing agent, for example, E ° _{Ox / Red} in the Co-EDTA system reaches 0 , 38 V, and Mn-EDTA up to 0.5 V. As part of the proposed reagent, the anion contains a tungsten-molybdenum phosphorus complex obtained in the form of ammonium salt according to the procedure [Maslov L.P. Synthesis of 18-wolfram-, molybdo-2-phosphates / Journal of Inorganic Chemistry, 1986, T. 31, No. 5, P. 1169-1173] or by means of exchange reactions in the form of sodium, potassium or lithium salts. Solutions of these compounds are readily reduced at a potential of E <0.75 V and in the reduced form have strong light absorption in the region of 600–900 nm, in which most organic impurity compounds practically do not absorb light and do not interfere optically with the determination of the desired substance.

The advantages of using the proposed reagent are:

- ease of use and objectivity of the results;

- the ability to conduct analysis under ordinary (normal) conditions (without prolonged exposure to cooling or heating;

- stability of the reagent during prolonged storage;

- analysis in the presence of substances that absorb in the UV and visible spectral regions (up to 600 nm), in the presence of substances that do not form strong compounds with Co, Μn, and Ce (acetates, benzoates, chlorides, sulfates, aromatic compounds, inorganic anions and cations);

- the range of determined concentrations is up to 10 ^-4 -10 ^-6 mol / l with a relative mean square error of 1-3%.

The objects of analysis can be natural, waste water, technological solutions, industrial samples of products.

The essence of the proposed method is illustrated by the following examples.

Example 1

To determine ethylenediaminetetraacetate (EDTA), a reagent of the following composition was prepared: 1 g of cobalt chloride CoCl ₂ ⋅ 2H ₂ O was triturated in an agate mortar with 16.7 g (NH ₄ ) ₆ [P ₂ W ₁₂ Mo ₆ O ₆₂ ] ⋅11Н ₂ O.

Method of determination: 5.0 g of reagent was dissolved in a 100.0 ml volumetric flask in water with gentle heating in a water bath at 40-60 ° C. Calibration solutions were prepared in 50.0 ml volumetric flasks, adding from 1.0 to 10.0 ml of a 10 ^-3 Μ EDTA solution, then 5.0 ml of the reagent solution was added to all solutions, the volume of the solution was adjusted to the mark, and after 10 minutes measured the optical density of the solution at λ = 650-750 nm.

Example 2

To determine diethyleneamine (DEA), a reagent of the following composition was prepared: 1 g of manganese sulfate MnSO ₄ ⋅ 7H ₂ O was triturated in an agate mortar with 10.7 g of K ₆ [P ₂ W ₁₄ Mo ₄ O ₆₂ ] ⋅11H ₂ O.

Method of determination: 5.0 g of reagent was dissolved in a 100.0 ml volumetric flask in water with gentle heating in a water bath at 40-60 ° C. Calibration solutions were prepared in 50.0 ml volumetric flasks, adding from 1.0 to 10.0 ml of 10 ^-3 Д DEA solution, then 5.0 ml of reagent solution was added to all solutions, 2.5 ml of 10 ^{-2 -2 was} added NaHCO ₃ solution, the volume of the solution was adjusted to the mark, and after 10 minutes the optical density of the solution was measured at λ = 650-750 nm.

Example 3

To determine diethylene triamine pentaacetate (DTPA), a reagent of the following composition was prepared: 1 g of cerium nitrate Ce (NO ₃ ) ₃ ⋅ 6Н ₂ O was triturated in an agate mortar with 6.8 g Νa ₆ [Ρ ₂ W ₆ Μo ₁₂ O ₆₂ ] ⋅11Η ₂ O .

Method of determination: 5.0 g of reagent was dissolved in a 100.0 ml volumetric flask in water with gentle heating in a water bath at 40-60 ° C. Calibration solutions were prepared in 50.0 ml volumetric flasks, adding from 1.0 to 10.0 ml of 10 ^-3 Д DTPA solution, then 5.0 ml of reagent solution was added to all solutions, the volume of the solution was adjusted to the mark, and after 10 minutes measured the optical density of the solution at λ = 650-750 nm.

Claims (1)

A reagent for spectrophotometric determination of amines and their polyaminopolycarboxylic derivatives (complexones), consisting of two components: a complexing ion based on polyvalent elements in lower oxidation states, such as Co ²⁺ , Mn ²⁺ , Ce ³⁺ , which form stable complexes with nitrogen-containing ligands and an oxidizing agent based on 18-tungsten, molybdo-2-phosphates of the composition M ₆ [P ₂ W _18-n Mo _n O ₆₂ ] ⋅xH ₂ O, where M = Li, Na, K, NH ₄ ; n is 0-18; x = 10-12.