SU1644003A1 - Method of determination of 2,2ъ-dipyridyl - Google Patents

Abstract

The invention relates to analytical chemistry, in particular to the definition of 2,2-dipyridyl, which is used for dyeing fabrics. The goal is to increase the selectivity of the determination and simplify the method. The determination is carried out by treating the analyzed sample with a mixture of cobalt nitrate (+2) with complexone III at a molar ratio of 1: 3-5 and a solution of ferrocyanide (+2) potassium in the presence of acetic acid buffer solution at pH 3.3-3 , 4 followed by measuring the optical density of the solution. 4 tab.

Description

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WITH

The invention relates to analytical chemistry, namely to methods for the determination of 2,2-dipyridyl, and can be used for sewage analysis of textile industry, where 2,2-dipyridyl is used for dyeing fabrics, as well as in the chemical industry.

The purpose of the invention is to increase the selectivity of the determination and simplify the method.

Example 1. A test solution containing a mixture of 0.35 mg of 2,2-dipyridyl and 7.6 mg of 2-aminopyridine was placed into a 50 ml volumetric flask, and the required amount of glacial acetic acid was added (until the amines dissolved), 10 ml of M solution of cobalt (II) nitrate with complexone III, complex S-ethylene diamine tetraacetate sodium. To prepare a solution of cobalt (II) nitrate with complexone III (M for cobalt (II), 2.91 g of Co (Mo3) 2-6H2O are added to a 1000 ml volumetric flask, add

300 ml of a 10 M solution of complexone III, diluted to the mark with water and stirred. The molar ratio of cobalt (II) and complexone III in the resulting solution is 1: 3, a 2 M solution of potassium hydroxide to a pH of 3.3.10 ml of a solution of potassium ferrocyanide (II) potassium is diluted with water, stirred, and after 10 min the light absorption is measured colored solution at nm. The content of 2,2-dipyridyl is found by the method of standard additives. 0.37 mg of 2,2-dipyridyl was detected.

Example 2. A test solution containing a mixture of 0.49 mg of 2,2-dipyridyl, 8.2 mg of aniline, 6.7 mg of benzylamine and 3.2 mg of triethanolamine is placed in a 50 ml volumetric flask, and the required amount of glacial acetic acid is added. acid, 10 ml of M solution of cobalt (II) nitrate with complexone (III), 2M solution of KOH to pH 3.8; 10 ml of M solution of potassium ferrocyanide (II), diluted with water, stirred and measured after 10 minutes

but

Ј 4C With SL

light absorption solution. Found 0,52 mg 2,2-dipyridil.

Example 3. An analyte solution containing 1.12 mg of 2,2-dipyridyl, 4.2 mg of pyridine, 9.4 mg of quinoline, 10.2 mg of a-picolinic acid is placed in a 50 ml volumetric flask, and the necessary the amount of glacial acetic acid, 10 ml of M solution of cobalt (II) nitrate with complexone III, 2M KOH solution was adjusted to pH 4.4, 10 ml of M solution of potassium ferrocyanide (II) was added, diluted with water, stirred and after 10 min. measure the light absorption of the solution. Found 1,09 mg 2,2-dipyridil.

The physicochemical analysis of the resulting complex allows its composition to be expressed by the formula Co dip 2 4 Fe (CN) e З- The complex compound is formed in a buffer acetic acid solution with a pH of 3.3-4.4 and is colored intensely blue: the maximum light absorption is at A, 620 nm, the sensitivity of the determination of 2,2-dipyridyl is 6.2 µg in 1 ml. The definition of 2,2-dipyridyl using this reaction is very selective: 50-fold molar excesses of heterocyclic, aromatic, and fatty-aromatic amines: pyridine, quinoline, 2-aminopyridine, a-picolinic acid, aniline, benzylamine do not interfere with the analysis.

The determination should be carried out in the pH range of 3.3-4.4, since at 3 the colored complex is destroyed; at, 4, the light absorption of the complex drops noticeably, i.e., the sensitivity of the reaction decreases. In the pH range of 3.3-4.4, the light absorption rate does not depend on pH.

In tab. 1 shows the dependence of zetoabsorption (A) of a cobalt (II) complex with 2,2-dipyridyl (dip) and ferrocyanide (II) Fe (CN) | r on the pH of the Qei + solution

Table 1

PH 3.1 3.2 3.3 3.5 3.7 3.9 4.2 4.4 4.5 4.9 5.1 A0.46 0.46 0.46 0.47 0.46 0 , 46 0.43 0.41 0.38

t min

0.50 0.56 0.61 0.60 0.61 0.61

 M, .1 (G4 M, M, pH-340, KFK-2, nm, cm; Table 2 shows the dependence of the light absorption of the Co2 + -dip- complex - Fe (CN) g-, on time (SF-16, 1 cm, A, 620 mm.

The molar ratio of complexone III to cobalt (II) salt should be at least 3x. Otherwise, the determination becomes impossible due to the formation of precipitates of poorly soluble salts.

In tab. Figure 3 shows the dependence of the light absorption (A) of the Co-dip-Fe (CN) e complex on the molar ratio of Co: complex III (Cfo 3, M, Ca, p 9.10-, Qe (tv) .1073 M:, 8 ; pH-340; KFK - 2, nm, cm).

Thus, in the proposed method, the determination is possible at the molar ratio of complex III: C62 + 3-5: 1.

In tab. 4 shows the characteristic of the Vos t S

productivity () and accuracy of rep.

5 results of determination of 2,2-dipyridil (item 4,, 95).

Claims (1)

Invention Formula The method of determining 2,2-dipyridyl, 0 including the processing of an analyzed sample with a chemical reagent and measuring the optical density of a solution, characterized in that, in order to increase the selectivity of the determination and simplification of the method, the treatment is carried out with a mixture of cobalt nitrate 5 (II) with complexone III at a molar ratio 1: (3-5) and potassium ferrocyanide (II) solution in. in the presence of acetic acid buffer solution at pH 3.3-4.4. table 2 101520 25 Table 3 The ratio is 1: 1 1: 2 1: 2.5 1: 3 1: 4 Co: complex III Aoza- {Osa- Sediment 0.46 0.46 doc i doc Table 4 When- Enter- Found Relatively dip, dip, mg 10,350.37 + 0.03 5.6 20,490.52 + 0.03 6.1 31,121.09 + 3.07 .2.7