Radiant energy – Fluent material containment – support or transfer means
Reexamination Certificate
2001-01-17
2003-10-21
Wells, Nikita (Department: 2881)
Radiant energy
Fluent material containment, support or transfer means
C250S430000, C250S435000, C250S281000, C250S282000, C250S288000
Reexamination Certificate
active
06635885
ABSTRACT:
BRIEF DESCRIPTION OF THE INVENTION
This invention relates generally to an apparatus for delivering gaseous calibration compounds to mass spectrometers, and more particularly to an apparatus in which metered volumes of different calibrants can be delivered to the ionization region of a mass spectrometer system.
BACKGROUND OF THE INVENTION
Traditional methods of introducing calibration compounds e.g. perfluorotributylamine to the ionization region of mass spectrometers involve the use of ball valves or needle valves. Instrument designs which feed the calibrant directly to the ionization region of the mass spectrometer typically utilize the needle valves due to the extremely small quantity (<4 ng/s) of calibrant required. Also, it is desirable to meter in a different amount of calibrant based on whether the instrument is operating in the EI or CI mode. Due to the close machining tolerances involved in the production of valves for this purpose, they tend to be costly. Other difficulties arising from these prior art metering methods include poor regulation due to variations in headspace pressure, poor regulation due to self-contamination (outgassing of calibrant from o-rings, valve seats and packings), lack of reproducibility when returning a valve to a previous setting, unknown volume delivery and poor equilibrium time.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus for delivering calibrant gas to the ionization region of a mass spectrometer at selected flow rates.
It is another object of the present invention to provide a delivery apparatus which uses calibrated restrictors and continuously pumped valves.
The foregoing and other objects of the invention are achieved by an assembly which employs calibrated restrictors connected between a calibrant gas source and the ionization region of a mass spectrometer through valves which can selectively connect the calibrant sources to the ionization chamber or to a vacuum pump.
REFERENCES:
patent: 5237175 (1993-08-01), Wells
patent: 6460401 (2002-10-01), Hoshino et al.
Guckenberger George B.
McCauley Edward B.
Dorsey & Whitney LLP
Thermo Finnigan LLC
Wells Nikita
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