SU1396054A1 - Method of analysis of organic thiophosphates - Google Patents

Abstract

The invention relates to analytical chemistry, in particular the determination of organic amidothiophosphates. Samples are analyzed by dissolving in ethanol, followed by potentiometric titration of AgNO, in an environment of 38-95% ethanol in water in the presence of a buffer solution with pH 9 and using an ion-selective electrode. These conditions increase the selectivity of the process and its sensitivity to 1.5 mg in the presence of organophosphorus substances that do not have a thiophosphoryl moiety. 1 tab. (L with so O5

Description

ate

four

This invention relates to analytical chemistry, and specifically to methods for the quantitative determination of amidothiophosphates.

NH

R in the presence of organophosphorus compounds that do not have thiophosphoryl

 grouping.

The aim of the invention is to improve: -

: Seenie selectivity of the method.

Example 1. A sample of 25 mg (can be 25-75 mg) was added to a 25 ml flask and made up to the mark with ethyl alcohol.

An aliquot containing 0.01–0.03 mmol of the substance is added to a 50 ml beaker, 4 ml of borate buffer solution (pH 9) and distilled water and ethyl alcohol are added to a volume of 20 ml so that the concentration of alcohol in the titratable solution was 50% by volume. Titrate with a 0.01 M aqueous solution of silver nitrate (I) with a sulfide-silver indicator electrode and a calomel reference electrode. The calomel electrode is connected to the test solution by a bridge filled with 0.1; M

potassium nitrate solution. 35 titrant portions are poured with magnetic stirring. The potential is measured after each addition of titrant. Construct the titration curve in the coordinates: mV-mp. The content of 40 substances was found along the curve or the second derivative.

The table shows the results of determination of amidothiophosphates, DZ

The use of a water-alcohol environment is due to the fact that: 1) most of the samples are insoluble in water; 2) large amounts of water can promote hydrolysis of organophosphorus compounds

The use of 95% alcohol as a solvent without the addition of water leads to the same results, 55 as with the use of 50% alcohol. However, pr-l of snitch concentration below 40% increases the error

ness Therefore, to standardize the conditions, the analysis is carried out in 50% (by volume) alcohol.

Example 2. For the amidothiophosphate under the conditions of Example I in a 95% alcohol, 4.02 mg, found 4.00 mg; in 38% alcohol 3.65 mg found mg.

The determination is carried out in an alkaline medium. If the amount of alkali is not enough to completely neutralize the liberated acid, the results are underestimated. For weights of the analyzed substances, 01 - 0.03 mmol (-1.5-4 mg), it is sufficient to add 4 ml of borate buffer. It is impractical to determine in a more acidic environment, since it is necessary to guarantee the presence of an excess of alkali. An increase in the excess of alkali is possible, however, co-oxidation of silver oxide may occur, which leads to excessive results of the analysis, i

For example, at pH 8 taken amidothiophosphate 3.46, found 2.84; at pH 10 taken 3.85 mg, found 3.92 mg.

In the analysis of 0,0-dimethyl-K-acetyl-amidothiophosphate, 2 ml of an alcohol solution with an analyte content of 3.243 mg were taken for analysis. 1.77 ml of a 0.01 N silver nitrate solution was used for titration.

% substance

V - N M

100,

V is the volume of titrant, ml;

N is the normality of the titrant;

M is the molecular mass of the sample to be analyzed;

a - sample weight of the analyzed sample, mg.

, 01 -183

3.243 99.88

or found, mg:

3.243 99.88 100

 3.236

Thus, 3.243 mg given, 3.236 mg found.

No precipitation was observed during the titration. The turbidity of the solution occurs after the equivalence point when free silver ions enter the alkaline solution.

Results of the determination of 0,0-dimesh1amidothiophosphate

CHjO

/

(I)

NH

in the presence of 0,8-dimethylamidophosphate (II) CHjO S P

CHjO

/

h

NH,

following mg: taken up (l) 3.85; (ll) 3.72; found (l) 3.86.

Results of determination of 0,0-dimethylamvdothiophosphate (l) in the presence of 0,5-dimethyl-K-acetylamide thiophosphate

(t)

54

h

following mg: taken up (l) 3.64; (ill)

3.02; found (l) 3.63.

The sensitivity of the method is 1.5 mg, the method makes it possible to determine the amidothiophosphates in the presence of phosphorus-organic compounds that do not have a thiophosphoryl group.

Claims (1)

Invention Formula The method of determining organic amidothiophosphates, which, in order to increase the selectivity of the determination, the analyzed sample is dissolved in ethyl alcohol and subjected to potentiometric titration with a solution of silver nitrate in a medium of 38-95% by volume nooh CHjO1DN2 2 g p CHjO T "HCOCH5 3 fS  . .2,93 2,95 O-NHC / iHg but 2 Note. The confidence interval Y is 99.69% + 0.63% (p 10, “0.95). Relative standard deviation 0.72%. Compiled by S. Khovanska Editor M. Bandura Tehred M. Khodanych Proofreader M. Demchik Order 2490/46 Circulation 847 Subscription VIIIPI State Committee of the USSR for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 3.21 3.20 3.04 3.03