Measuring and testing – Gas analysis – Gas chromatography
Reexamination Certificate
1999-12-24
2001-10-16
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Gas analysis
Gas chromatography
C073S023420, C073S023390, C073S864870, C210S656000
Reexamination Certificate
active
06301952
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a gas chromatographic device comprising an inlet system, a column and a pressure reducing means. More particularly, the present invention relates to a column for a gas chromatographic device with a pressure reducing means, being capable of operating under vacuum conditions.
BACKGROUND OF THE INVENTION
The market for routine analysis of complex samples requires columns which have a long life time, reduced column bleeding, and sufficient capacity. These columns must also allow for the analysis in a short period of time. In particular, the demand for systems comprising a gas chromatographic device coupled to a mass spectrometer (GC/MS) which are used for various analyses is continuously growing, because these systems get more user friendly, their dimensions get smaller and their purchasing costs keep decreasing. For GC/MS systems the separation capacity of the column is no longer that important. Although for sample analysis some separation capacity is required, in general it is not necessary to utilize long columns. However, in the GC/MS system the inlet pressure of the column is above atmospheric and the outlet pressure of the column is essentially vacuum because the column ends in the ionization chamber of the mass spectrometer. That is why the columns in GC/MS systems are often very long to provide the necessary pressure drop between the inlet and the outlet of the column. Consequently, long periods of time are often required to perform the sample analyses. Smaller bore columns having a reduced length could be used to provide the pressure drop, but these columns have a disadvantage such as a limited sample capability as well as practical problems with regard to installation, operation and elute peaks which are too fast to quantify using mass spectrometry systems.
SUMMARY OF THE INVENTION
The present invention intends to provide a solution for the problems described above. A gas chromatographic device comprises at least an inlet system, a column and a pressure reducing means. The pressure reducing means according to one embodiment of the present invention is disposed between the inlet system and the column. In this embodiment the column outlet is operated under vacuum conditions.
The pressure reducing means according to another embodiment is connected to the outlet of the column. In this embodiment the column outlet pressure is approximately equal to the pressure of the inlet system and the pressure reducing means outlet is operated under vacuum conditions.
In both embodiments the pressure reducing means can be an integral part of the column.
The columns to be used in the gas chromatographic device according to the present invention are relatively reduced in length which enables short analysis times of the samples. The eluting peaks have sufficient peak width (in seconds) to be properly integrated by contemporary mass spectrometry systems. Moreover, the proposed embodiments offer the further benefit that under vacuum the optimal linear gas velocity increases about tenfold and that components elute from the column at lower temperatures, especially important for thermolabile and high boiling components. Additionally, the life time of the column is generally longer than that of conventional columns due to reduced column bleeding. It is also not necessary to couple the column via a restriction to the ionization chamber of the mass spectrometer so that no leaks occur. An additional advantage is that a fixed or standard inlet pressure can be used which is preferably 10 kPa to 1000 kPa, and more preferably 10 kPa to 250 kPa.
According to the present invention the pressure reducing means is such that the pressure prevailing at the outlet of said pressure reducing means is 0.00001 kPa to 50 kPa (absolute pressure), preferably 0.01 kPa to 20 kPa (absolute pressure).
REFERENCES:
patent: 2920478 (1960-01-01), Golay
patent: 3049909 (1962-08-01), Thomas
patent: 3077766 (1963-02-01), Reinecke
patent: 3119252 (1964-01-01), Nerheim
patent: 3400514 (1968-09-01), Noda
patent: 3421292 (1969-01-01), Llewellyn
patent: 3455092 (1969-07-01), Llewellyn
patent: 3471692 (1969-10-01), Llewellyn et al.
patent: 3483731 (1969-12-01), Sanford et al.
patent: 3537297 (1970-11-01), Loyd et al.
patent: 3589171 (1971-06-01), Haley et al.
patent: 3772909 (1973-11-01), Anderson
patent: 3798973 (1974-03-01), Estey
patent: 3926561 (1975-12-01), Lucero
patent: 4215563 (1980-08-01), Clardy et al.
patent: 4479380 (1984-10-01), Novotny et al.
patent: 5236668 (1993-08-01), Higdon
patent: 5340543 (1994-08-01), Annino et al.
patent: 5719322 (1998-02-01), Lansbarkis et al.
de Nijs Rene Cornelis Maria
De Zeeuw Jaap
Peene Jan Adriaan
Bella Fishman
Berkowitz Edward H.
Larkin Daniel S.
Varian Inc.
Wiggins David J.
LandOfFree
Gas chromatographic device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas chromatographic device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas chromatographic device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2554745