RU2253106C1 - Universal multi-sensor detecting cell - Google Patents

Abstract

FIELD: gas phase analysis technologies.

SUBSTANCE: device consists of thermostat-processed reaction tank, branch pipes for input and output of carrier gas and sample, reaction tank has two hermetically interconnected cylindrical portions; into upper portion detachable holder is built for 25 piezoquartz sensors and electronic control device, into lower portion perforated case for sample is built as well as air ventilator for removal of concentration gradient of flying compositions along whole volume of cell.

EFFECT: higher precision, higher efficiency, broader functional capabilities.

1 tbl, 1 dwg

Description

The invention relates to techniques for analyzing the gas phase and can be used in the analysis of qualitative and quantitative indicators of gaseous, liquid and powdery substances (for example, tea, coffee, tobacco, tobacco products).

Known thermostatic detection cell with a volume of 200 cm ³ with injection injection of a sample of the analyte with a volume of 10 μl using a microsyringe directly into the cell [Selective piezoelectric odor sensor using molecularly imprinted polymers. Ji HS., McNiven S., Ikebukuro K., Karube I. // Anal. Chim. Acta. 1999. V.300. P.93-100]. The sensor before measurements is kept in a stream of nitrogen at a flow rate of 0.2 DM ³ / min until the analytical signal is stabilized. Then the nitrogen supply is stopped, 10 μl of the solution of the analyte is introduced into the cell and evaporated. Measurement of the analytical signal is terminated when the change in the oscillation frequency of the sensor does not exceed 1 Hz / min.

The drawback of the cell is the introduction of a small sample volume into the cell, at which the sensor signal will be at the level of “noise” or so large that it will increase the error when the sample is introduced with a microsyringe, in addition, the inability to analyze solid and powder products is impossible.

The closest in technical essence and the achieved effect is a detection cell with a volume of 500 cm ³ made of stainless steel, equipped with a thermostatic jacket, the outer side of which is covered with heat-insulating material, consisting of a reaction vessel, inlet pipes, air and sample outlets, a piezoelectric crystal, and the lid with an integrated holder for the piezoelectric crystal made of the same material, and the nozzle for direct injection of the sample into the reaction vessel of the cell is equipped with silicone howl gasket (Patent 2207539, G 01 N 5/02, 27/12. Declared 06/20/2002)

The disadvantages of this cell are the inability to determine several volatile substances that make up the analyzed object, because there is only one piezoelectric crystal sensor, the duration of equilibrium due to the presence of a concentration gradient, the impossibility of determining the partial pressures of substances, the inability to analyze solid and powder substances.

The objective of the invention is the creation of a universal multisensor detection cell, which allows to identify gaseous, liquid and powder products containing volatile components, to obtain an accurate quantitative assessment of the interaction of several analytes (up to 25) with selective sorbents deposited on the electrodes of the piezoelectric crystal, to eliminate the concentration gradient inside the cell , increase the volatility of the determined components, i.e. to increase the accuracy of the analysis by creating a vacuum inside the cell and the ability to measure the partial pressures of the components.

The problem is achieved in that in a universal multi-sensor detection cell, consisting of a thermostatically controlled reaction vessel, inlet and outlet pipes of the carrier gas and sample, the new fact is that the reaction vessel consists of two cylindrical parts hermetically connected to each other; a removable holder for 25 piezoelectric quartz sensors and an electronic control device are mounted in the upper part; a perforated sample cassette and an air fan are mounted in the lower part.

The scheme of a universal multisensor detection cell is shown in the drawing.

The technical result consists in the creation of a universal multisensor detection cell, which allows to identify gaseous, liquid and powder products containing volatile components, to obtain an accurate quantitative assessment of the interaction of several analytes (up to 25) with selective sorbents deposited on the electrodes of piezoelectric quartz sensors, to eliminate the concentration gradient inside cells, increase the volatility of the determined components (i.e., increase the accuracy of the analysis) by creating a vacuum inside the cell and the ability to measure partial pressures of the components.

A universal multisensor detection cell with a volume of 500 cm ³ consists of two cylindrical parts 1, 2, hermetically connected to each other through a vacuum connection 3, equipped with a jacket for temperature control 4 with nozzles for input 5, air outlet (carrier gas, for example, nitrogen) 6, regeneration sensors, or for pumping air, an air fan 7, which allows to accelerate the output of the sensor cell to the operating mode and increase the accuracy of measurements, cassette 8 for sample 9, a removable holder 10 for 25 piezosensors 11, connected to an electronic the second control device 12 located in the upper part of the cell from the outside.

Universal multi-sensor cell detection works as follows. A pre-prepared holder with an appropriate set of piezoelectric quartz sensors is placed in the upper part of the cell, which is preliminarily held in the flow of dried laboratory air for several minutes until a stable analytical signal is obtained, and the sensor readings are measured (for each type of the analyzed sample, a different set of sorbents applied to the sensor is selected). A sample of the substance to be determined is placed in the sample cassette; both parts of the cell are hermetically connected to each other, which allows creating a vacuum in it; include an air fan to remove the concentration gradient of volatile substances throughout the cell volume and thermostating, and also, if necessary, air is pumped out of the cell. The stopwatch counts the time after which the signal of the piezoelectric sensors does not change. The difference between the signals of the piezosensors before and after contact with a carrier gas enriched in the components of the sample or by the components themselves, if the analysis takes place in a vacuum, is a characteristic of qualitative and quantitative determinations. The detachable parts of the cell make it easy to maintain (prepare for a new analysis). After the analysis is complete, the parts are disconnected, a removable holder with sensors is removed, the cell is washed and dried to remove residual volatile compounds, a new sensor holder with an appropriate set of sorbents is inserted. After that, the cell is ready for analysis again.

The results of comparing the characteristics of the proposed sensor cell with the prototype are presented in the table.

Table. Comparison of the characteristics of the proposed cell and prototype.

Options Suggested cell Prototype Identification of multiple sample components maybe Impossible Partial pressure measurement capability maybe Impossible The presence of a concentration gradient Is absent Occurs Sample entry The sample is inside the reaction vessel Microsyringe The accuracy of the analysis (the limit of detection of mol / m ³ according to Triton X-100) * 2.85 × 10 ^-6 3.55 × 10 ^-6 * The detection limit is calculated as the ratio of a signal three times higher than the “noise signal” to the sensitivity of the sensor.

Thus, the proposed universal multisensor detection cell allows you to:

- carry out analyzes of gaseous, liquid and powder products containing volatile components (target);

- measure the partial pressure of volatile components;

- conduct quantitative and qualitative analyzes of volatile components of solid samples;

- increase the accuracy of measurements due to the continuous mixing of the gas phase with a fan in the cell (“ideal mixing reactor”);

- prevent the loss of the analyte, since a pre-weighed sample of the solid substance is placed directly in the cell.

Claims (1)

Universal multi-sensor detection cell, consisting of a thermostatically controlled reaction vessel, carrier gas inlet and outlet nozzles and samples, characterized in that the reaction vessel consists of two cylindrical parts hermetically connected to each other, a removable holder for 25 piezoelectric sensors and an electronic control unit are mounted in the upper part device, a perforated sample cassette and an air fan are mounted in the lower part.