SU828038A1 - Method of formaldehyde quantitative determination - Google Patents

Description

The invention relates to the field of analytical chemistry, namely, to methods for the quantitative determination of formaldehyde.

It is known to determine formaldehyde by treating an analyzed sample with phenylhydrazine hydrochloride in isopropyl alcohol in the presence of potassium ferriciannd and alkali to form a compound colored red.

The disadvantage of this method is the low detection sensitivity (0.1 µg / ml) and the low accuracy of the determination, since the introduction of potassium ferricyanide leads to a colored zero sample.

The closest to the described invention by technical sush.nost and the achieved result is a method of quantitative determination of formaldehyde by treating the sample being analyzed with 1-benzyl-2-hydrazinobenzimidazole hydrochloride in an organic solvent when heated in the presence of pyridine as a catalyst, followed by treatment of the mixture with cyclohexanol and spectrophotometry of the extract 2.

The disadvantage of this method is its complexity, since as an organic

solvent and catalyst use highly toxic organic pyridine base.

In addition, the use of pyridine as

a strong nucleophilic catalyst, in the auto-oxidation reaction leads to a constant development of color over time, which requires extraction into the organic solvent layer to stabilize

cyclohexanol.

The aim of the invention is to simplify the determination of formaldehyde.

The goal is achieved by the described method of quantitative determination of formaldehyde by treating the sample being analyzed with 1-benzyl-2-hydrazinobenzimidazole hydrochloride in an organic solvent medium under heating in the presence of 0.15-0.30% aqueous sodium acetate solution, followed by spectrophotometry of the resulting colored solution.

Sodium acetate is used as a catalyst for the nucleophilic reaction of formaldehyde with 1-benzyl-2-hydrazinobenzimidazole hydrochloride, which results in the formation of a colored compound 1,5-dibenzylbenzimidazolylformazan.

The reagent is used in the form of an alcohol solution. Ethyl alcohol is an organic solvent of the reaction product, since the resulting colored "compound - heterocyclic formazan" dissolves only in the medium of an organic solvent.

The method consists of stages of sample processing and photometry.

A solution of sodium acetate and an alcohol solution of 1-benzyl-2-hydrazinobeynmidazole chlorhydrate are added to an aliquot of the sample. The mixture was kept in a water bath when heated and after cooling it was photometrized at a wavelength of 540 nm (for a spectrophotometer) or with a No. 6 optical filter (for a photoelectric colorimeter) with an absorbing layer thickness of 10 mm.

Under these conditions, the formaldehyde solutions are subject to the belief in the coicitration range of 0.001-0.015 mg in 2 ml of the sample (1-15 μg in 2 ml of the sample).

The concentration of pho) small) Dehyd in air is determined by the following trace — the formula:

a b 1000, 0 ,,.

(MG / M, (1)

with vo

where a - o6ntee amount of the investigated

solution, ml;

L is the amount of fordehyde found in the analyzed volume, mg; C - the number of samples to togo the solution,

taken for analysis, ml; Vo is the volume of air under investigation, reduced to normal conditions, l.

Example. Construction of graduation-rafika.

Prepared a standard solution of formaldehyde in water with a content of 10 µg / ml. In 8 tubes take 0.1; 0.3; 0.5; 0.7; 0.9; ,one; 1.3; 1.5 ml of standard size

alignment. The resulting data is tabulated.

Determination of formaldehyde content in air. The test air is drawn through two absorption devices with a porous plate No. 1 containing 5 ml of water at a rate of 1 l / min.

2 ml of the absorbing solution from each absorber are added to the colorimetric tubes, 2 ml of a 0.3% alcohol solution of 1-benzyl-2-hydrochloride hydrochloride 1-benzyl-2-hydroxydrazino-benzimidazole are added and 30 ml of a water bath is maintained at a VOC C. After cooling, the optical

The density of the solution and the graduation schedule determine the formaldehyde content in 2 ml of the sample.

The optical density of the sample at 540 nm is 0.22. According to the calibration schedule

The formaldehyde content in the sample is 0.11 mg. Sample volume (C) 2 ml; total sample volume (A) 5 ml.

An air sample is taken within 20 minutes at a rate of 1 l / min.

The volume of air drawn to normal conditions.

Vo V. k,

where V is the volume of drawn air; k is the coefficient for adjusting the air volume to normal conditions at 25 ° C, 740 mm Hg. (k 0.8919).

5-0,011,100

 1.54 mg / m.

2-0,8919-20

The preferred method for the determination of formaldehyde based on heterocyclic hydrazine 1-benzyl-2-hydrazinobenzimidazole compared with the known, not inferior to it in accuracy, is less toxic and difficult to perform by eliminating the extraction step with cycloheteranol.

Indicators

formaldehyde and bring the volume to 2 ml with water. Then, 2 ml of a 0.6% aqueous solution of sodium acetate and 2 ml of a 0.1% aqueous solution of 1-benzyl-2-hydrazinobenzimidazole hydrochloride are added to each tube. The tubes are placed in a water bath (70 ° С) for 30 minutes. After 30 minutes, the tubes are removed from the bath, cooled to room temperature, and the optical density of each formula is measured.

The method of quantitative determination of formaldehyde by processing analyzing my sample with 1-benzyl-2-hydrazino-benzimidazole hydrochloride in an organic solvent medium when heated in the presence of a catalyst, followed by spectrophotometry of the obtained colored solution, which differs

56

in order to simplify the definition of free formaldehyde, - Hygiene

as a catalyst, 0.15 is used ((anitari, 1968, No. 6, p. 100-103,

0.30% sodium acetate aqueous solution .2. USSR author's certificate

Sources of information, according to application number 2403563 / 23-04, cl. C 07 C

taken into account at ec-epe; l-ise5 47/04, 1976 (prototype). 1. Petrol G. I. Method of determination

828038

Claims (1)

Claim A method for the quantitative determination of formaldehyde by processing the analyzed sample with hydrochloride-1-benzyl-2hydrazinobenzimidazole in an organic solvent under heating in the presence of a catalyst, followed by spectrophotometry of the obtained colored solution, characterized in that, to simplify the determination, 0.15-0 is used as a catalyst , 30% aqueous solution of sodium acetate.