Techniques for active passivation
In one embodiment, active (continuous or intermittent) passivation may be employed to prevent interaction of sticky molecules with interfaces inside of an instrument (e.g., an infrared absorption spectrometer) and thereby improve response time. A passivation species may be continuously or intermittently applied to an inlet of the instrument while a sample gas stream is being applied. The passivation species may have a highly polar functional group that strongly binds to either water or polar groups of the interfaces, and once bound presents a non-polar group to the gas phase in order to prevent further binding of polar molecules. The instrument may be actively used to detect the sticky molecules while the passivation species is being applied.
1. A method for preventing interaction of sticky molecules with interfaces inside of an instrument, comprising:
applying a sample gas stream including the sticky molecules to an inlet of the instrument;
while the sample gas stream is being applied, continuously applying a passivation species to the inlet, the passivation species being a species that includes a polar functional group that binds to either water or polar groups of the interfaces, and once bound presents a non-polar group to prevent further binding of polar molecules; and
using the instrument to detect the sticky molecules while the passivation species is being applied to the inlet.
2. The method of claim 1 , wherein the sticky molecules comprise nitric acid (HNO 3 ) and the passivation species comprises at least one of perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) or perfluorobutane sulfonic acid (PFBSA).
3. The method of claim 1 , wherein the sticky molecules comprise ammonia (NH 3 ) and the passivation species comprises 1H,1H-perfluorooctylamine (PFOAm).
4. The method of claim 1 , wherein the inlet is a particle separation inlet that comprises a virtual impactor, a cyclone particle separator, or a PolyTetraFluoroEthylene (PTFE) membrane particle filter.
5. The method of claim 1 , the method wherein the continuously applying comprises:
introducing the passivation species into a stream of air; and
entraining the stream of air now including the passivation species into the sample gas stream.
6. The method of claim 5 , wherein the introducing comprises:
bubbling or passing the stream of air through a bubbler that contains the passivation species.
7. The method of claim 1 , the method wherein the continuously applying comprises:
injecting the passivation species through a calibration port of the inlet.
8. The method of claim 1 , the method wherein the continuously applying comprises:
bubbling or passing the sample gas stream through a gas bubbler that contains the passivation species.
9. The method of claim 1 , wherein the instrument is an infrared absorption spectrometer.
10. A method for preventing interaction of sticky molecules with interfaces inside of an instrument, comprising:
applying a sample gas stream including the sticky molecules to an inlet of the instrument;
while the sample gas stream is being applied, intermittently applying a passivation species to the inlet, the passivation species being a species that includes a polar functional group that binds to either water or polar groups of the interfaces, and once bound presents a non-polar group to prevent further binding of polar molecules, the passivation species applied for a first period of time to build a protective coating on the interfaces, and withheld during a second period of time during which the built protective coating continues to prevent interaction of sticky molecules with the interfaces; and
using the instrument to detect the sticky molecules during the first period of time while the passivation species is being applied to the inlet and during the second period of time when the passivation species is withheld.
11. The method of claim 10 , wherein the protective coating is a perfluoroheptanoic acid ammonium salt (NH 4 + /PFHpA − ) salt.
12. The method of claim 10 , wherein the protective coating is a perfluorobutane sulfonic acid ammonium salt (NH 4 + /PFBSA − ).
13. The method of claim 10 , wherein the instrument is an infrared absorption spectrometer and the inlet is a particle separation inlet.
14. The method of claim 10 , the method wherein the intermittently applying comprises:
introducing the passivation species into a stream of air; and
entraining the stream of air now including the passivation species into the sample gas stream.
15. An instrument configured to prevent interaction of sticky molecules with interfaces inside of the instrument, comprising: an inlet of the instrument configured to receive a sample gas stream including the sticky molecules; a passivation species delivery system coupled to the inlet and configured to apply a passivation species to the inlet while the inlet is receiving the sample gas stream, the passivation species being a species that includes a polar functional group configured to bind to either water or polar groups of the interfaces, and once bound presents a non-polar group to prevent further binding of polar molecules; and a detection system configured to receive a gas stream from the inlet and detect the sticky molecules while the passivation species is being applied to the inlet.
16. The instrument of claim 15 , wherein the passivation delivery system is configured to apply the passivation species continuously to the inlet.
17. The instrument of claim 15 , wherein the passivation delivery system is configured to apply the passivation species intermittently to the inlet such that the passivation species is applied for a first period of time to build a protective coating on the interfaces, and withheld during a second period of time during which the built protective coating continues to prevent interaction of sticky molecules with the interfaces.
18. The instrument of claim 15 , wherein the sticky molecules comprise nitric acid (HNO 3 ) and the passivation species comprises at least one of perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) or perfluorobutane sulfonic acid (PFBSA).
19. The instrument of claim 15 , wherein the sticky molecules comprise ammonia (NH 3 ) and the passivation species comprises 1H,1H-perfluorooctylamine (PFOAm).
20. The instrument of claim 15 , the wherein the passivation species delivery system comprises:
a gas bubbler that contains the passivation species through which a stream of air is bubbled or passed,
wherein the passivation species delivery system is configured to entrain the stream of air now including the passivation species into the sample gas stream.
21. The instrument of claim 15 , wherein the instrument is an infrared absorption spectrometer and the inlet is a particle separation inlet.
22. The instrument of claim 15 , the wherein the passivation species delivery system is configured to inject the passivation species through a calibration port of the inlet.
23. The instrument of claim 15 , the wherein the passivation species delivery system includes a gas bubbler that contains the passivation species through which the sample gas is bubbled or passed.