SU968753A1 - Method of determining ternary amine in amine oxide - Google Patents

Description

The invention relates to analytical chemistry, in particular to a method for determining a tertiary amine in an amine oxide, and is intended to control the production process.

Soyin oxide, obtained by oxidation of a tertiary amine (apkildimethylamine) with hydrogen peroxide, is used as a surfactant as a component of synthetic detergents, as well as additives in a mixture for alkaline degreasing of metal parts before electroplating;

A known method for determining the tertiary amine 3 amine oxide, based on its extraction four times with petroleum ether. The extracts are combined and evaporated to a volume of 1-2 t / ai, 25 ml of glacial acetic acid is added and titrated with 0.1% hydrochloride hydrochloride on a crystal violet indicator. The total content of amine oxide and, tertiary amine in the extract is determined. Next, 50 ml of water, 3 ml of 18N of sulfuric acid, 10 ml of 0.2 n-solution of titanium sulfate are added and allowed to stand for 10 minutes under an inert gas atmosphere. Add - / s 3 ml 0.1 n. thiocyanate

ammonium and titrated with a 0.1N solution of iron-ammonium alum to an orange-red color at the end point. The content of the amine oxide in the extract is determined by reaction with the titanium solution. From the difference in the total content of the amine oxide, the content of the tertiary steppe Cl is determined.

However, this method is very long, it allows to determine the tertiary amine when its content is higher than 3-4%. The incomplete extraction, oxidation of titanium with air oxygen or other possible oxidizing agents leads to

15 major errors and poorly reproducible results.

Closest to the proposed technical essence and the achieved result is a method for determining a tertiary amine in an amine oxide, which consists in dissolving two samples in isopropyl alcohol. One of them is titrated potentiometrically with 0.2 N, alcohol, hydrochloric acid solution. The cyiviMapHoe content of amine oxide and tertiary amine is determined. To another sample, add 3 ml of methyl iodide and hold for 15 minutes at 30–50 ° C to convert the tertiary amine to a quaternary ammonium compound, followed by potentiometric titration with 0.2 and an alcoholic solution of hydrochloric acid. The content of amine oxide is determined. The difference between these two titrations gives the tertiary amine content in the f2 amine oxide. The disadvantage of this method is its low sensitivity, since the content of the tertiary amine is determined indirectly by the difference in two titrations. When the content of the tertiary amine is less than 4-5%, the results of the analysis are not very reliable, since the determination error is 0.51.5% (absolute). This method of determining the tertiary amine is indiscriminate. The aim of the invention is to increase the sensitivity, accuracy and selectivity of the method. This goal is achieved in that according to the method for determining a tertiary amine in an amine oxide by treating an analyte solution with alkyl iodide in the presence of alcohol with heating followed by potentiometric titration of the resulting solution with titrant, silver nitrate solution is used and titration is carried out in the presence of acetic acid . Example. A 100 ml chemical beaker is placed in a portion of amine oxide in the order of 1 g, distilled water is added to a total volume of 3 m, 2 ml of methyl iodide is added with a pipette, 1 ml of ethanol is mixed, mixed, placed in a water bath at 50 ° C and incubated for 10 minutes. Then cooled to room temperature, 1 ml of concentrated acetic acid is added with a pipette, and 40 ml of ethanol is measured using a measuring cylinder. Place the beaker on the touchscreen mixer and conduct potentiometric titration with 0.01 N silver nitrate solution. In the blank run, a sample of amine oxide in the order of 0.2 g is placed in a 100 ml beaker, distilled water is added to a total volume of 3 ml, 2 ml of methyl iodide and 6 ml of ethyl alcohol are added with a pipette and then continue, as in working experience. For potentiometric titration, a pH-meter pH-millimeter voltmeter is used (silver and chlorine silver electrodes). According to the results of the titration, the titration curve in the potential – temperature coordinates of the titrant solution was plotted and an equivalence point was found. The content of the tertiary amine in the amine oxide (X,%) is calculated by the formula 1.1 1 ° g / 1 1 {go (c:) where the molecular weight of the tertiary amine; Y is the volume of 0.01 n. Of silver nitrate solution consumed. For titration in working experience, ml; У „- volume of 0.01 n. Of silver nitrate solution consumed for titration in the idle Experiment, ml; K - correction factor 0.01 n. Silver nitrate solution; G, is the weight of amine oxide, taken for analysis in working experience, g; G.- A portion of amine oxide, taken on analysis in the blank experiment, in the table. Figure 1 shows the results of the determination of the tertiary amine in the presence of various alkali and acid additions of chlorides and bromides. Table 1 /

62.40 30.20 3.4 64.10 28.5 5.0

4.01

4.0 -.7.2 1.45 1.40 5.5

As can be seen from the table. 1, the proposed method is very selective. Even in the presence of various alkaline and acid additives, as well as chlorides and bro: MIDA, the tertiary formula is determined

with good ACCURACY. ,

According to the known acid-base method, the tertiary amine cannot be determined with reliable accuracy, since the presence of alkali and

. 30.3 30.0 30.5

Continuation of table 1

acid additives overestimate the results.

In tab. Figure 2 shows the results of the analysis of model mixtures of amine oxide, tertiary amine and hydroiodic acid, which is a permanent impurity in alkyl iodide, and the same weights of model mixtures were taken for analysis.

table 2

hl

As can be seen from the table. 2, the proposed method is selective, since the presence of hydroiodic acid does not interfere with the determination of the tertiary amine. The high sensitivity of the method makes it possible to determine up to a hundredth percent of the tertiary amine impurity with good accuracy.

According to a known method, reliable results are obtained only with co-continuation of the table. 2

holding tertiary amine above 4%.

when impurities of hydroiodic acid are present, the total content of the tertiary amine and hydroiodic acid is determined.

in tab. Figure 3 shows the reproducibility of the results of quantifying the tertiary amine in several technical samples of amine oxide in this method.

Table 3

The data table. 3 show good reproducibility of the results of the analysis of the proposed method.

In this method, a tertiary amine with a content of up to 0.5% is determined with an accuracy of 0.04%, with a content of up to 1% with an accuracy of 0.08%, 69.4V 30.4 0.12 0.11 0, 11b8, -4 31.0 0.55 0.52 0.58 68.8 30.1 1.10 1.12 1.17

The data table. 4 shows the applicability of various iodide alkyls.

Claims (2)

1.Brooks R.T. Sternglanz T) Tanomet De Determination of the N-OXide in Pyrid Ine-N-Oxide and Related Compounds.-Ana 1. Chem. 1959, 31, 4, p. 561. 2.Metcalfe L.D. Potentiometry with Alkye Halter-to-E Termiary interference.-Ana 1. Chem. l962, 34, 13, p. 1849 (prototype). 0.12 0.13 0.11 0.50 0.57 0.52 1.03 1.09 1.14