초록 ▼

The invention relates to a method for determining the non-volatile component of aerosol particles in a gas sample, especially in the exhaust gas of internal combustion engines, where the aerosol particles are deposited on an oscillating sensor (2) of at least one crystal microbalance (3), and the ch

The invention relates to a method for determining the non-volatile component of aerosol particles in a gas sample, especially in the exhaust gas of internal combustion engines, where the aerosol particles are deposited on an oscillating sensor (2) of at least one crystal microbalance (3), and the change in at least one oscillation parameter of the oscillating sensor is employed as measurement variable. According to the invention the oscillating sensor (2) of at least one crystal microbalance (3) is maintained at a temperature of more than 200° C. during deposition of the aerosol particles, and preferably between 250° C. and 350° C.

대표청구항 ▼

1. Method for determining non-volatile components of aerosol particles in a gas sample, comprising the steps of:depositing said aerosol particles of said gas sample on a piezoelectric resonator of at least one crystal microbalance, said piezoelectric resonator being temperature stable up to at least

1. Method for determining non-volatile components of aerosol particles in a gas sample, comprising the steps of:depositing said aerosol particles of said gas sample on a piezoelectric resonator of at least one crystal microbalance, said piezoelectric resonator being temperature stable up to at least 600° C.,maintaining said piezoelectric resonator of said at least one crystal microbalance at a temperature of more than 200° C. during deposition of said aerosol particles, anddetermining a change in at least one oscillation parameter of said piezoelectric resonator as measurement variable of said non-volatile components.2. Method according to claim 1, wherein said piezoelectric resonator is maintained at a temperature between 250° C. and 350° C.3. Method according to claim 1, wherein said gas sample is an exhaust gas sample of an internal combustion engine.4. Method according to claim 1, wherein said gas sample is thermostabilized at a temperature of more than 200° C. prior to deposition on said piezoelectric resonator of said at least one microbalance.5. Method according to claim 4, wherein said gas sample is thermostabilized at a temperature between 250° C. and 350° C.6. Method according to claim 1, wherein said piezoelectric resonator is heated to more than 600° C. in order to pyrolytically remove deposited graphitic component of said aerosol particles from said piezoelectric resonator.7. Method according to claim 6, wherein a change in resonance frequency of said piezoelectric resonator is monitored during pyrolytic removal of said graphitic component for controlling removal status.8. Method according to claim 6, wherein said piezoelectric resonator is subjected to an oxidizing atmosphere before or during said pyrolytic removal of said graphitic component.9. Method according to claim 8, wherein said piezoelectric resonator is subjected to clean air.10. Method according to claim 1, wherein two or more crystal microbalances are used whose piezoelectric resonators are maintained at different temperature levels.11. Method according to claim 10, wherein for separate measurement of non-volatile graphitic particles and mineral particles of said gas sample, said piezoelectric resonator of a first of said crystal microbalances is maintained at a temperature of more than 200° C., while said piezoelectric resonator of a second of said crystal microbalances is maintained at a temperature of more than 500° C.12. Method according to claim 11, wherein for measurement of total particle content of said gas sample, said piezoelectric resonator of a third of said crystal microbalances is maintained at a low temperature.13. Method according to claim 1, wherein deposition of said aerosol particles on a sensitive area of said piezoelectric resonator is effected by low-pressure impaction.14. Method according to claim 1, wherein at least two oscillator parameters of said piezoelectric resonator are used for determination of said measurement variable, thereby compensating for a non-mass-proportional change in resonance frequency caused by viscoelastic properties of said particles deposited.15. Method according to claim 14, wherein said oscillator parameters are resonance frequency and attenuation.16. Apparatus for determining non-volatile components of aerosol particles in a gas sample, having at least one measuring cell provided with gas inlet and containing an piezoelectric resonator of a crystal microbalance subjected to said gas sample, wherein said piezoelectric resonator is temperature stable up to at least 600° C. and is provided with a thermostat device maintaining a temperature of more than 200° C.17. Apparatus according to claim 16, wherein the temperature is maintained at between 250° C. and 350° C.18. Apparatus according to claim 16, wherein said thermostat device is provided with a heating chamber placed upstream of said measuring cell, including a nozzle plate for directing said gas sample into said measuring cell.19. Apparatus according to claim 18, wherein in order to generate a partial vacuum in said measuring cell, an outlet of said measuring cell is connected to a vacuum pump and said heating chamber is provided with an entrance orifice for said gas sample.20. Apparatus according to claim 18, wherein a plurality of measuring cells are connected in parallel, having thermostat devices to subject said individual piezoelectric resonators to different temperatures.21. Apparatus according to claim 16, wherein said piezoelectric resonator is provided with a resistance- or radiation-type heating element for heating said oscillating sensor to a temperature of more than 600° C.22. Apparatus according to claim 16, wherein said piezoelectric resonator is a BAW-resonator made from temperature-stable material of a group consisting of GaPO4, La3Ga5SiO14, Sr3Ga2Ge4O14, Ca3Ga2Ge4O14, Ln3Nb0.5Ga5.5O14 and Ln3Ta0.5Ga5.5O14 with Ln=La, Pr, Nd.