Method of determining aniline, o-nitroaniline, and o- tolidine in air

FIELD: analytical methods.

SUBSTANCE: electrodes of piezoelectric resonator are modified with menthol phenyl salicylate vaseline oil, recommended solvent being toluene, modifier film weight 5-20 μg, drying temperature 20-35°C, and drying time 40-48 h. The following gains in aromatic amine determination sensitivity are thus obtained: for aniline, from 282 to 368 Hz-m3/g; for o-tolidine, from 68 to 78 Hz-m3/g; for 9-nitroaniline, from 136 to 125 Hz-m3/g. Reductions in relative deviation are, respectively, 6.0 to 3.2%, 7.0 to 3.6%, and 6.0 to 4.3%, sensor response time is decreased by 5 times, regeneration time is decreased by 24 times, and aniline detection threshold is lowered from 0.84 to 0.11 Δ, g/m3.

EFFECT: increased sensitivity and accuracy of determination.

1 dwg, 2 tbl, 11 ex

 

The invention relates to gas analysis, in particular to the modifiers electrodes piezoquartz resonator, and can be used in analytical chemistry to activate the surface of the resonator in the manufacture of a sensor for the determination of aromatic amines in the air.

Known sensor on the basis of polystyrene, trialkylamines and trialkylphosphines for determination of aniline in the gas phase /Korenman YA, Trachylina POSTGRADUATE, Lisitskaya R.P., Shlyk J.K., Rakovich L., A. D. "a Method for determining the concentration of aniline vapors in the air of working zone. Pat. 2155333, Russia, Yugoslavia, IPC 7 G 01 N 30/00./ - 99125524/04; publ. 27.08.2000, bull. No. 24 // the Invention. 2000. No. 24 (part II)/S 324/.

A disadvantage of the known sensor is a long response time, low sensitivity, the duration of stage of regeneration.

An object of the invention is to develop a sensitive and affordable coverage electrodes piezoquartz resonator (CRP) gas sensor that is selective to the pairs of aromatic amines, as well as the expansion of the Bank's existing modifiers used for the selective and sensitive determination of amines in the air.

The technical problem of the invention is achieved in that in the method of determination of aniline, o-nitroaniline and o-toluidine, comprising preparing a solution of a modifier, Nanase what s it to the electrodes, drying, exposure to vapor analytes and the analytic signal, what is new is that as a modifier applied metaphenylenediamine oil, the recommended solvent is toluene, the weight of the film modifier 5-10 mcg, temperature drying 20-25°C, the drying time 40-48 h

The technical result of the invention consists in the intensification of the process of regeneration of the sorbent, the expansion of existing modifiers when determining concentrations of aromatic amines in the air, reducing the overall time of analysis, lower detection limits and relative error of determination.

Sensor-based metaphenylenediamine oil is characterized by low latency, fast regeneration of the surface of the sorbent, availability, and security applications.

Metaphenylenediamine oil (MFSM, medical name - Mentholum phenylii saicylas oleum vasellin) is a complex mixture of organic compounds. The mass ratio of the components: menthol (C10H19OH) - 1.0 g, fenilsalitsilat (NOSE6H4(CO)OS6H5) - 3.0 g, liquid paraffin (a mixture of saturated hydrocarbons, resistant to oxidants) - 96,0,

The method of determination of aniline, o-nitroaniline and o-toluidine in the air using MFSM as follows.

Prepare rastvortsev (solvent - toluene), then the solution of the sorbent is applied to the electrodes CRP (AT - cut) with microspace so that the mass of the film after drying was 5-10 mcg. The finished sensor is dried in a desiccator at a temperature of 20-25°C for 40-48 hours Drift zero line sensor prepared by the present method, is not more than ±3 Hz/min Temperature drying film sorbent is selected in accordance with thermal instability MFSM, at temperatures above 30°With the decomposition of the modifier. Optimum drying time 40-48 hours Due to the high viscosity of the inventive sorbent is not recommended to form a large mass of the film, the optimal weight of 5-10 mcg, the optimal solvent MSVM - toluene (fully dissolves sorbent).

To assess the sensitivity MFSM the organic compounds of different classes ready sensor (solvent MSVM - toluene) were exposed in pairs of test compounds (see drawing). It is established that MSWM exhibits high sorption affinity and sensitivity to aromatic amines and can be used as an effective modifier piezosensor with the definitions in the gas phase.

All the measurements were carried out in nanosensors cell detection with injection sample introduction in static conditions. The volume of injected sample - 3 cm3. The method is illustrated by the following examples.

Example 1 (FR what type)

Piezoquartz resonator at-cut with aluminum electrodes (diameter 5 mm, the area of 0.2 cm2and own 10 MHz modify toluene solution of polystyrene according to the method "static evaporation of the droplets. Then the sensor is dried at 60°C for 30 min (weight of film 8 μg). The drift of the zero signal of the sensor prepared in accordance with the prototype, not more ±4 Hz/min Ready sensor exhibited in pairs of aniline, o-toluidine and o-nitroaniline. The results of the survey of the sensor shown in table 1, the method is implemented.

Example 2 (the proposed method)

Prepare a solution MSWM in toluene (fully dissolves sorbent), then the solution of the sorbent is applied to the electrodes CRP (AT-cut) with microspace so that the mass of the film after drying was 5-10 mcg. The finished sensor is dried in the desiccator at 20-25°C for 40-48 hours Temperature drying film sorbent is selected in accordance with thermal instability MFSM, at temperatures above 30°With its decomposition. Optimum drying time 40-48 hours Due to the high viscosity of the inventive sorbent is not recommended to form a large mass of the film, the optimal weight of 5-10 mcg.

The mass of the formed film was 8.1 μg, the drift of the zero signal of the sensor is not more than ±3 Hz/min Then the sensor exhibited in pairs of aniline, o-toluidine and o-neath aniline, the results of the survey of the sensor shown in table 1, the detection error does not exceed 5%, way feasible.

Example 3

The electrodes CRP modify, as shown in example 2, reducing the drying time of the sensor up to 40 hours Weight film of 7.9 µg, the sensor is stable, the results of the survey are shown in table 1, the method is implemented.

Example 4

The electrodes CRP modify, as shown in example 2, reducing drying time up to 24 hours a sensor Signal is unstable, is the breakdown of self-oscillations of the resonator, the method is not feasible.

Example 5

The electrodes CRP modify, as shown in example 2, increasing the drying time up to 50 hours Weight film of 6.1 µg, the sensor signal is stable, however, increasing the drying time reduces expressnet determine if the constancy of the main characteristics of the definition. The results of the survey of the sensor shown in table 1, the method is implemented.

Example 6

The electrodes CRP modify, as shown in example 2, by increasing the drying temperature to 25°C. After cooling, the sensor signal is stable, the weight of the film 8 mcg, the drift of the zero signal of the sensor ±3 Hz/min, the results of the survey of the sensor shown in table 1, the method is implemented.

Example 7

The electrodes CRP modify, as shown in example 2, by increasing the drying temperature to 30-35°C. After cooling, the sensor signal is unstable, the drift of the "zero" signal ± 30 Hz/min, is spreading film sorbent beyond the boundaries of the sensitive element, the method is not feasible.

Example 8

The electrodes CRP modify, as shown in example 2, reducing the temperature of drying up to 10-15°C. the weight of the film of 5.8 µg, the sensor is unstable, the method is not feasible.

Example 9

The electrodes CRP modify MFSM dissolved in hexane according to the method of "static evaporation of the droplets. Sorbent partially soluble in hexane. The finished sensor is dried in a desiccator at 20°C for 40-48 hours Weight film of 5.3 µg, the drift of the zero signal of the sensor prepared by the present method, ±15 Hz/min Sensor exhibited in pairs aromatic amines, the results of the survey of the sensor shown in table 1. The response of the sensor based on MSWM prepared in toluene and hexane, equal, however, the most preferred solvent for the proposed modifier is toluene due to lower drift of the zero signal, the best reproducibility and less time desorption. Way feasible.

Example 10

The electrodes CRP modify, as shown in example 2, increasing the weight of the film MSWM to 15 micrograms. The sensor is unstable within 24-30 h of spontaneous reduction of the mass of the film to 9.1 ág (assuming the evaporation of menthol with the film surface), the method is not feasible.

When is EP 11

The electrodes CRP modify, as shown in example 2, decreasing the mass of the film MSWM to 3 µg. The sensor is unstable, the feedback received during exposure of fumes of aniline and its derivatives can't be recreated, the method is not feasible.

From examples 1-11, table 1 and 2 of the drawing, it follows that the greatest effect with the use of the proposed modifier is achieved by the detection of aromatic amines on film MFSM weight film of 5-10 µg, drying time 40-48 h at 20-25°With recommended solvent sorbent - toluene. Increase (example 10) or decrease (example 11) the mass of the film results in unstable signal of the sensor, increasing the drift of the "zero" signal and error detection. Optimum drying time 40-48 h at 20°With (examples 2 and 6), increase (example 7) or decrease (example 8) temperature leads to the disruption of self-oscillations of the resonator; the increase of the drying time (example 5) is impractical due to the reduction of expressnet analysis. Reducing drying time (example 4) results in an unstable response of the sensor and a significant drift of the "zero" signal, applying a different solvent sorbent (example 9) is impractical due to incomplete dissolution of the sorbent, a significant drift of the "zero" signal and poor reproducibility of results.

Thus, the proposed Modific the tor for the detection of aromatic amines in comparison with the prototype allows you to:

to increase the sensitivity of the determination of aromatic amines (aniline from 282 to 368 Hz·m3/g, o-toluidine - from 68 to 78 Hz·m3/g o-nitroaniline from 136 to 125 Hz·m3/g);

to reduce the relative error of determination (aniline - from 6.0 to 3.2%, o-toluidine - from 7.0 to 3.6%, o-nitroaniline - from 6.0 to 4.3%);

to reduce the response time of the sensor 5 times;

to reduce the time of regeneration of the sorbent and the total analysis time 24 times;

to reduce the detection limits of aniline (from 0.84 to 0.11 Δ, g/m3).

In addition, MSWM is economically affordable and environmentally friendly sorbent.

The proposed modifier allows you to expand the data Bank of existing modifiers electrodes CRP applicable for the selective and sensitive determination of aromatic amines in the air.

-
Table 1
The results of the survey of the sensor during exposure of vapors on-toluidine (1), aniline (2) and o-nitroaniline (3); the volume of injected sample 3 cm3
Number exampleThe mass of the film, mcgResponse HzSensitivity, Hz·m3/gThe measurement error Δ, %The implementation of the method is
  123123123 
18,0134316682821367,06,06,0feasible
28,1155617783681453,63,24,3feasible
37,9155517783621453,23,24,1feasible
4*

-
--------impossible
56,1135017683281454,2the 3.8the 3.8feasible
68,0155517783621454,14,1the 3.8feasible
7*

-
---------impossible
85,8---------impossible
95,3 135112643357912,611,913,9feasible
1015,0-------- impossible
113,0---------impossible
-* - determination of the mass of the film is impossible due to the instability of the zero signal.
Table 2
Comparison of the characteristics of the sorption of aromatic amines (for example aniline) films of polystyrene (prototype) and claimed modifier - MSWM; solvent - toluene
MethodThe mass of the film mcgResponse time τSorb.withthe time of regeneration τ desorb.withThe measurement error Δ, %Sensitivity Hz·m3/gThe detection limit, g/m3
The placeholder8,0802406,02820,84
Declare8,115103,23680,11

The method of determination of aniline, o-nitroaniline and o-toluidine in the air, comprising preparing a solution of a modifier, marking the electrodes, drying, exposure to vapor analytes and the analytic signal, characterized in that as a modifier applied metaphenylenediamine oil, the recommended solvent is toluene, the weight of the film modifier 5-10 mcg, temperature drying 20-25°C, the drying time 40-48 h



 

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