Method of determining methylphenylcarbinol in the air

 

(57) Abstract:

The invention relates to methods of analytical chemistry and can be used in laboratories performing environmental monitoring. A method for determining methylphenylcarbinol in the air by its concentration using solid absorber, subsequent elution and analysis of the eluate by gas chromatography. The method allows a simple way to determine the concentration methylphenylcarbinol in the air. table 1.

The invention relates to the field of analytical chemistry, in particular to a method of determining methylphenylcarbinol ( - methylbenzylamino alcohol) in the air and can find application in laboratories performing environmental monitoring.

Known group method for the determination of higher alcohols by reaction with p-dimethylaminobenzaldehyde in the presence of sulfuric acid (guidelines for the definition of harmful substances in the air, Novokuibyshevsk, 1971, pp. 331 - 334).

The disadvantage of this method is nespecificnomu and labor costs associated with the preparation of a standard scale, validity of which is limited, and the use of concentrated sulfuric acid as p is d definition of alcohols by the reaction of interaction with andyoshinobu complex. (Guidelines for the definition of harmful substances in the air, Novokuibyshevsk, 1971, pp. 347 - 348).

The disadvantage of this method is nespecificnomu and complexity associated with a limited shelf life standard scale.

The closest in technical essence and the achieved result is the method of determination of benzyl alcohol in the air chromatographic method (which could be used to determine its homolog - - methylbenzylamino alcohol), according to which the air sample in the amount of 30 DM3aspiritual at the rate of 1 DM3/min through the adsorption unit containing a 10 cm3ethanol, while cooling. The obtained concentrate chromatographic on the instrument with a flame ionization detector using a sorbent of apiezon-L on the W chromo-sorbitol-treated clear. (Collection of guidelines on methods for the determination of harmful substances in the air, issue 15, guidelines N 1986-79, Ministry of health, USSR, M. 1979).

The disadvantages of this method are the low sensitivity and the relative duration of sampling (30 min at a rate of 1 DM3/min), and as a result, high accuracy resultativity samples associated with the need for cooling of the absorber.

The essence of the invention is a method of determining methylphenylcarbinol in the air, by which methylphenylcarbinol cocentric by passing the investigated air through the adsorption unit containing silica gel or alumel adsorbed methylphenylcarbinol elute water-acetone or water-alcohol mixture at a volume ratio of water: acetone or alcohol= (70 - 80) : (30 - 20), the eluate determine methylphenylcarbinol known by gas chromatography.

The essential features of the present invention, which differs from the known technical solutions are used as absorber silica gel or alumina and as an eluent of methylphenylcarbinol - water-acetone or water-alcohol mixture at a volume ratio(70 - 80):(30 - 20).

The use of these essential features allows to obtain a concentrate of methylphenylcarbinol from the air of the working zone with the concentration sufficient for subsequent chromatographic determination with a sensitivity of 5 mg/cm3the liquid, which corresponds to a detection sensitivity of methylphenylcarbinol in air 2.0 mg/m min, the amount of alumina (silica gel) 3 cm3the volume of eluent 7 cm3.

Availability and expressnet way, as well as the accuracy of the results obtained according to the invention provide the ability to implement operational sanitary control of the air of the working zone on the content of methylphenylcarbinol that indicates compliance with the criterion "industrial applicability".

The invention is carried out as follows: aluminum oxide (alumel) TU 38-101190-75 or silica gel according to GOST 3956-75 crushed and sieved with a sampling fraction from 0.5 to 1.0 mm Filtered-out particles are washed several times with distilled water to remove residue dust) and dried at a temperature of 200 - 250oC for 4 - 5 hours

In the absorber jaworowski placed 3 cm3prepared alumina (silica gel), is connected to the trap and the suction device, set the air speed of 3 to 4 DM3/min and miss analyzed air within (5 to 10) minutes

At the end of the selection, in the adsorption unit with absorber contribute 7 cm3water-acetone or water-alcohol mixtures containing the internal standard, which is used as benzyl alcohol according to GOST 8751 - 72, usbat is to dust until the disappearance of turbidity (6 - 7 min at a rotation speed of 4000 rpm).

Using microspace injected into the chromatograph evaporator prepared sample and write the chromatogram on the scale of sensitivity, providing the maximum height of the peaks.

The concentration of methylphenylcarbinol in the analyzed air is calculated by the formula:

< / BR>
where C is the content of methylphenylcarbinol in the sample, mg/m3;

TOmcalibration coefficient;

Sm, Sb- the value of the peak areas of methylphenylcarbinol and benzyl alcohol, respectively;

7 - the amount of water-acetone or water-alcohol mixture, taken on the elution of methylphenylcarbinol, cm3;

0,008 - standard substances (benzyl alcohol) in the sample solution (mg/cm3;

VCR- volume of sample air passed through the absorber DM3(the product of the duration of sampling in minutes on speed selection in DM3/min), reduced to standard conditions (20oC and 760 mm RT.cent.), according to the formula:

< / BR>
where Vt- air volume taken for analysis of DM3;

P - barometric pressure, mm RT.article;

t is the air temperature at the place of sampling,oC.

Isoline of methylphenylcarbinol made known quantity, placed in a glass ampoule with a siphon and polysiphonia, air supplied with a speed of 3 DM3/min adsorption device jaworowski, containing 3 cm3alumina with a grain size from 0.5 to 1.0 mm

Using microspace introduced a 6-mm3solution IFC in water-acetone mixture containing methylphenylcarbinol 3.1 mg/cm3that corresponds to the

< / BR>
The speed of drawing air 3 DM3/min, duration broaching 40 min (specified duration broaching air is not associated with the conditions of the analysis, and adopted to ensure completeness blowing hanging methylphenylcarbinol). After blowing pegloticase disconnect from the sampling system, pour in 7 cm3water-acetone mixture with a volume ratio of water: acetone = (80 : 20), shake for 6 min, the eluate is poured into centifuge tube and centrifuged for 6 min with a speed of 4000 Rev/min 3 mm3transparent eluate injected into the chromatograph evaporator and discharged the chromatogram in terms of:

- sorbent: 5% politicalintelligence and 0,5% 1, 2, 3, 4, 5, 6 hexacis - canadacheck on inerton AW fraction of 0.16 - 0.20 mm

- the length of the column, m ... 1,0

- internal dies samplesoC ... 110 3

- temperature detector,oC ... 200 3

the flow of carrier gas (nitrogen), DM3/h 1,8 ...

- the speed of the ribbon diagram, mm/h 200 ...

- the volume of injected sample, mm3... 3

The result of the analysis presented in the table.

Example 2. Check the acceptability of silica gel as absorbent. The experience carried out in full accordance with example 1, except that as an absorber using silica gel with a grain size from 0.5 to 1.0 mm

The result of the analysis presented in the table.

Example 3.

To establish the optimal amount of acetone in water-acetone mixtures spend four experience using mixtures of water: acetone- (90: 10); (80:20); (70:30) and (60:40) in accordance with example 1.

The results are presented in the table.

Example 4. Check the acceptability of the use of water-alcohol mixture as eluent. Conduct two experiments in accordance with example 1 with the only difference that as eluent using a water-alcohol mixture with a ratio of 80:20 and 70:30.

The results are presented in the table.

Example 5. Perform two parallel analysis of workplace air. Within 3 minutes about what I fraction of 0.5 1.0 mm, with a speed of 3 DM3/min (volume of sample 3 5 = 15 DM3provides a detection sensitivity of methylphenylcarbinol in air 2.0 mg/m3that is enough to control the air of working zone with MPL = 10 mg/m3). At the end of the selection in the sinks pour in 7 cm3water-acetone mixture (80:20) and continue the analysis as described in example 1.

The result of the analysis presented in the table.

Examples 1 and 2 show that the deviation of the results of the analysis from the target value is within range.

Example 3 shows that when the volumetric ratio of acetone : water (10: 90) - a decrease of the frequency of occurrence and the underestimation of the results.

- (80: 20) and (70:30) - results close to the specified value (as in example 1).

- (60: 40) on the chromatogram a decrease in the sharpness of the separation of acetone and methylphenylcarbinol); because of the volatility of the mixture tends to overestimate the results of the analysis, as well as reducing the reproducibility of the results.

Example 4 shows that the deviation results from the target value is within range.

Example 5 shows that the repeatability of the determination of IU"ptx2">

The experiments were carried out using alumina fraction (0.5 to 1.0) mm Analysis is possible when using other factions alumina; however, the use of the above fraction is preferable when implementing the inventive method, because:

- use fractions less than 0.5 mm leads to the necessity of taking additional measures to prevent ash from the absorption flask with the sample (the complexity of the sampling flask).

- use fractions greater than 1 mm leads to the need to increase the amount of sorbent (to prevent leakage of methylphenylcarbinol), which in turn requires more water-acetone mixture for subsequent elution.

Method of determining methylphenylcarbinol in the air by its concentration using the absorber and analysis of the concentrate using gas-liquid chromatography, characterized in that the absorber is used alumel or silica gel, and the adsorbed methylphenylcarbinol elute water-acetone or water-alcohol mixture at a volume ratio of water : acetone or alcohol equal(80 - 70) : (20 - 30).

 

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