RU2555775C1 - Method for rapid evaluation of safety of articles made of phenol-formaldehyde plastic - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: safety of articles made of phenol-formaldehyde plastic is evaluated using a multichannel gas analyser (MAG-8) with 8 piezo-quartz resonators, the electrodes of which are modified by applying solutions of polydiethylene glycol succinate, polyethylene glycol sebacate, polyethylene glycol phthalate, polyphenyl ether, trioctylphosphine oxide, bee glue, beeswax and a composite sorbent - bee glue with iron (III) chloride. The mass of the sorbent film is 15-20 mcg after removing the solvent at 40-50°C for 15-20 min. The modified piezo-quartz resonators are then placed in the closed detection cell of the MAG-8 and held for 5 min to establish a stable zero signal. Further, 5.00 g of a ground sample of phenol-formaldehyde plastic is placed in a sampler which is then tightly closed with a polyurethane plug and held at 20±1°C for 15 min to saturate the gas phase with phenol vapour. Further, 3 cm³ of the equilibrium gas phase is collected through the polyurethane plug and injected into the closed cell of the MAG-8, followed by measuring the change in the oscillation frequency of the piezo-sensors for 120 s and calculating the area of the "visual print" S_v.p., Hz·s, using the formula S_v.p.=f(C_ph), S=1959·C_ph+35. For the calculation, a calibration curve of S_v.p., Hz·s versus phenol concentration C_ph, mg/dm³ is plotted first. If the area S_v.p.≥130±10 Hz·s, the concentration of free phenol in the equilibrium gas phase over the phenol-formaldehyde plastic C_ph>0.05 mg/dm³ exceeds the recommended level for food plastics, and if S_v.p.>260 Hz·s or higher, high content of phenol and formaldehyde is recorded.

EFFECT: invention provides fast evaluation of safety of articles made of phenol-formaldehyde plastic.

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Description

The invention relates to analytical chemistry of gas and air environments and can be used to assess the safety of products from phenol-formaldehyde plastics.

An object of the invention is to develop an express method for assessing the safety of products made of phenol-formaldehyde plastics, which allows to determine the microconcentrations of phenol and formaldehyde without prior concentration and other multi-stage sample preparation using piezoelectric quartz resonators with thin-film coatings, characterized by high sensitivity, low detection limits of phenol, accuracy, expressivity and selectivity of analysis , objectivity of measurement and adoption resolved i.

To solve the technical problem of the invention, an express method for assessing the safety of products made of phenol-formaldehyde plastics is proposed, characterized in that an array of 8 piezoelectric crystals with a natural oscillation frequency of 10 MHz is used as a test device, the electrodes of which are modified by applying polydiethylene glycol succinate to them from individual solutions, polyethylene glycol sebacinate, polyethylene glycol phthalate, polyphenyl ether, trioctyl phosphine oxide, bee glue, beeswax and a combination sorbent - bee glue with iron (III) chloride, and the modifier is applied so that the mass of the sorbent film after removal of the solvent by drying in an oven at a temperature of 40-50 ° C for 15-20 minutes was 15-20 μg, modified piezoelectric crystals placed in a closed cell for detecting a multi-channel gas analyzer MAG-8 and kept there for 5 min to establish a stable zero signal, then a finely ground sample of phenol-formaldehyde plastic weighing 5.00 g is taken into a sampler, flat it is closed with a polyurethane plug, kept at a temperature of 20 ± 1 ° C for 15 min to saturate the gas phase with phenol vapor, then 3 cm ^{3 of the} equilibrium gas phase is taken with a syringe through a polyurethane plug and injected into the closed cell of the MAG-8 multichannel gas analyzer, fixed for a frequency change of 120 pezosensorov oscillation analytical signal is calculated - the area "visual fingerprint» S _VO , Hz · s, and according to the calibration graph constructed in the coordinates, the area of the “visual imprint” S _v. , Hz · s, from the concentration of phenol C _f , mg / dm ³ , S _v.o. = f (C _f ), S = 1959 · C _f +35, the content of free phenol is determined, and the calibration curve is built using standard phenol solutions if the area of the “visual imprint” is greater than or equal to 130 ± 10 Hz · s, S _{v.o .} ≥130 ± 10 Hz · s, the concentration of free phenol in the equilibrium gas phase over phenol-formaldehyde plastics is higher than that recommended for food plastics, With _f > 0.05 mg / dm ³ , and if the area of the “visual imprint” is greater than 260 Hz · s and above, _s.o. > 260 Hz · s, the content of phenol and formaldehyde is simultaneously recorded and indicate a significant emission of them into the air from the products.

The technical result of the invention is to assess the safety of products made of phenol-formaldehyde plastics, in express measurements, high sensitivity, low detection limits of phenol, accuracy, selectivity of analysis, objectivity of measurement and decision making.

In FIG. 1 shows the kinetic “visual imprints” of the responses of sensors in phenol vapor and in the equilibrium gas phase above the samples;

in FIG. 2 is a calibration graph for an array of sensors in the detection of phenol vapor (S _v.o. = f (C _f )).

The express method for assessing the safety of products made of phenol-formaldehyde plastics is as follows.

Polyethylene diethylene glycol succinate, polyethylene glycol sebacinate, polyethylene glycol phthalate, polyphenyl ether, trioctyl phosphine oxide, bee glue, beeswax and combined sorbent - bees glue (for example, beeswax glue) are applied to the electrodes of 8 piezoelectric crystals used as test devices from individual solutions the mass of the sorbent film after removal of the solvent by drying in an oven at a temperature of 40-50 ° C for 15-20 minutes was 15-20 μg. Modified piezoelectric quartz resonators with a film are placed in a closed cell for detecting the MAG-8 multi-channel gas analyzer and the initial (“zero”) response of the sensors — the oscillation frequency — is recorded. Then a finely ground sample of phenol formaldehyde plastic weighing 5.00 g is taken into the sampler, tightly closed with a polyurethane stopper and kept at a temperature of 20 ± 1 ° C for 15 min to saturate the gas phase with phenol vapor. Then, a 3 cm equilibrium gas phase is taken with a syringe through a polyurethane plug and injected into a closed detection cell of the MAG-8 multi-channel gas analyzer. Register using a computer with a program the change in the frequency of the oscillation of the piezoelectric crystal with a film in phenol vapor for 120 s. The analytical signal is calculated — the area of the “visual imprint” of the responses of the piezosensors in phenol vapors S _v. , Hz · s (Fig. 1). The content of free phenol is determined by the calibration graph, plotted in the coordinates of the area of the "visual imprint", S _VO , Hz · s, on the concentration of phenol C _f , mg / DM ³ , S _VO = f (C _f ), and the calibration graph is built on standard phenol solutions (Fig. 2). If the area of the “visual imprint” is greater than or equal to 130 ± 10 Hz · s, S _v.o. ≥130 ± 10 Hz · s, the concentration of free phenol in the equilibrium gas phase over phenol-formaldehyde plastics is higher than recommended for food plastics, With _f > 0.05 mg / dm ³ . When the area of the "visual imprint" is more than 260 Hz · s and above, S _century > 260 Hz · s, the content of phenol and formaldehyde is simultaneously recorded and indicate a significant emission of them into the air from the products.

All measurements are carried out in a closed detection cell of a multichannel gas analyzer with injection injection of samples in static conditions.

The method is illustrated by the following example.

Example 1

Polyethylene ethylene glycol succinate, polyethylene glycol thalate, polyphenyl ether, trioctylphosphine oxide, beeswax and iron gum mixed with beeswax and iron gum mixed with beeswax and gum are mixed with beeswax and gum mixed with beeswax and gum mixed with beeswax and gum mixed with beeswax and gum mixed with beeswax and gum mixed with beeswax in an oven for 20 minutes at a temperature of 45 ° C, placing the resonators strictly horizontally in the holder. The mass of the films after drying and cooling is about 20 μg. The prepared piezoelectric quartz resonators with a film are placed in a closed cell for detecting the MAG-8 multi-channel gas analyzer and the initial (“zero”) response of the sensors — the vibration frequency — is recorded. The drift of the "zero" line after drying is ± 2 Hz / min. With a larger deviation, the film resonator is re-dried. Prepare standard phenol solutions with a phenol concentration of 0.10 to 1.00 mg / dm ³ , tightly close with a polyurethane stopper and incubate at a temperature of 20 ± 1 ° C for 15 min to saturate the gas phase with phenol vapor. Then, an equilibrium gas phase containing phenol vapor is injected into the cell with a syringe. Register using a computer with a program the change in the frequency of the oscillation of the piezoelectric crystal with a film in phenol vapor for 120 s. The areas of “visual imprints” of the responses of the piezosensors in phenol vapors S _v. , Hz · s (Fig. 1) and build a calibration graph in the coordinates of the area of the "visual imprint" on the concentration of phenol, S _VO = f (C _f ) (Fig. 2). For research, take 2 samples of finely ground phenol-formaldehyde plastics (1 - a part from a vacuum cleaner, 2 - a box from under the disk). The equilibrium gas phase is injected into the detector with a syringe over phenol-formaldehyde plastic samples containing phenol. They are fixed with a frequency meter or using a computer with a program for changing the sensor response (oscillation frequency) for 120 s. The area of the “visual imprint” of the responses of the piezosensors in phenol vapors S _{v.o. is} calculated in the software _. , Hz · s (analytical signal) (Fig. 1) and according to the calibration graph (Fig. 2) find its content in the analyzed plastics. For the first sample S _VO = 258.9 Hz · s, therefore, the concentration of free phenol in the equilibrium gas phase over this sample is higher than recommended for food plastics. For the second specimen S _VO = 583.7 Hz · s - in the equilibrium gas phase, the presence of phenol and formaldehyde is recorded. Both samples of phenol-formaldehyde plastics do not meet the recommended phenol concentration for food grade plastics.

When implementing the express method for assessing the safety of products made of phenol-formaldehyde plastics, the expressness of measurements, high sensitivity, low detection limits of phenol, accuracy, selectivity of analysis, objectivity of measurement and decision making are achieved.

The method is feasible.

As can be seen from the example and FIG. 1-2, the proposed method for assessing the safety of products made of phenol-formaldehyde plastics using piezosensors makes it possible to evaluate the safety of products made of phenol-formaldehyde plastics using piezoelectric quartz resonators modified from individual solutions of polyethylene glycol succinate, polyethylene glycol sebacinate, polyethylene glycol phthalate, polyphenyl phenyl ether, test solutions wax and combined sorbent - bee glue with iron (III) chloride by n applying them to the electrodes, followed by drying for 15-20 minutes at a temperature of 40-50 ° C so that the mass of the sorbent film is 15-20 μg, the phenol content is found according to the calibration graph for the area of the “visual imprint” of the sensor responses in phenol vapor.

The express method, characterized by the accuracy of determination, reliability, high sensitivity, the minimum number of stages and the cost of reagents, is easy to implement, highly selective, applicable for assessing the safety of phenol-formaldehyde plastics.

A change in the nature of the sorbent, the modifier film formation method, temperature and time during drying, and also its mass does not allow the formation of a homogeneous thin-film coating on the surface of the piezoelectric crystal and, as a result, leads to a decrease in the sensitivity and high error in the determination of phenol and formaldehyde content in phenol-formaldehyde plastics. The change in the time of registration of the analytical signal of the sensor during sorption leads to high errors in constructing the calibration graph and quantitative estimation of phenol vapor in the equilibrium gas phase.

The developed express method for assessing the safety of products made of phenol-formaldehyde plastics is characterized by:

- minimum number of stages;

- minimal reagent costs;

- high sensitivity;

- expressity;

- selectivity of analysis;

- accuracy (analysis error of 5%);

- objectivity of measurement and decision making.

Claims (1)

An express method for assessing the safety of products made of phenol-formaldehyde plastics, characterized in that an array of 8 piezoelectric quartz resonators with a natural oscillation frequency of 10 MHz is used as a test device, the electrodes of which are modified by applying to them from individual solutions of polyethylene glycol succinate, polyethylene glycol sebacinate, polyethylene glycol phthalate, , trioctylphosphine oxide, bee glue, beeswax and combined sorbent - bee glue with iron (III) chloride, p Therefore, the modifiers are applied so that the mass of the sorbent film after removal of the solvent by drying in an oven at a temperature of 40-50 ° C for 15-20 minutes is 15-20 μg, the modified piezoelectric crystals are placed in a closed cell for detecting the MAG-8 multichannel gas analyzer and kept in it for 5 min to establish a stable zero signal, then a finely ground sample of phenol-formaldehyde plastic weighing 5.00 g was taken into the sampler, tightly closed with a polyurethane stopper, kept at at a temperature of 20 ± 1 ° C for 15 min to saturate the gas phase with phenol vapor, then 3 cm ^{3 of the} equilibrium gas phase is taken with a syringe through a polyurethane plug and injected into the closed cell of the MAG-8 multichannel gas analyzer detection, the frequency change is recorded for 120 s oscillations of piezosensors, calculate the analytical signal - the area of the "visual imprint" S _VO , Hz · s, and according to the calibration graph constructed in the coordinates, the area of the “visual imprint” S _v. , Hz · s, from the concentration of phenol C _f , mg / dm ³ , S _v.o. = f (C _p), S = 1959 · C _f 35, determine the content of free phenol, the calibration graph constructed by standard phenol solutions if "visual footprint" area of greater than or equal to 130 ± 10 Hz · s, S _{VO .} ≥130 ± 10 Hz · s, the concentration of free phenol in the equilibrium gas phase over phenol-formaldehyde plastics is higher than that recommended for food plastics, With _f > 0.05 mg / dm ³ , and if the area of the “visual imprint” is greater than 260 Hz · s and above, _s.o. > 260 Hz · s, the content of phenol and formaldehyde is simultaneously recorded, which indicates their significant emission into the air from products.

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