Chemistry: analytical and immunological testing – Including chromatography
Patent
1990-04-23
1992-11-24
Housel, James C.
Chemistry: analytical and immunological testing
Including chromatography
422 88, 422 89, 73 1902, 73 2324, 73 2327, G01N 3020
Patent
active
051660768
DESCRIPTION:
BRIEF SUMMARY
The invention relates to devices and methods for sample dosing in gas chromatography.
PRIOR ART
The efficiency of gas-chromatographic analysis depends to a large extent on the charging of the sample [dosing] into the separation column. "Slugs" of sample gas that are delimited as sharply as possible are required in the stream of carrier gas, which flows with a flow velocity that is ideal for the respective separation column. Since in practice, the pressure in the sample gas source often lies at a level that is lower than the required operating pressure for the carrier gas, pressure surges occur during sample dosing, which adversely affect the analysis results. Therefore, pumps must be provided to bring the pressure in the sample supply line (leading) to the dosing mechanism up to the required level. When capillary separation columns are used, a flow divider is provided, which makes it possible to dose [quantitatively regulate] a very small sample quantity. Such a configuration is described, for example, in the U.S. Pat. No. 4,442,217.
In the case of this known configuration, dosing into a separation column is accomplished by switching a carrier gas stream at a junction, from which a sample injection limb leads out on one side and a vent limb on the other side. With the help of restrictions to flow, flow rate ratios are adjusted so that the flow rate in an inlet line is greater than the flow rate in the sample injection limb, but smaller than that in the vent limb. This achieves that in a first switch position of a changeover switch, the carrier gas flows via a supply injection limb through the separation column, and the sample flows off through the vent limb, while in a second switch position, a small portion of the sample is conveyed through a flow divider into the separation column, and the remaining sample quantity is discharged. The flow divider consists of a conduit, having an inlet connectable to the carrier gas source and having an outlet which is connected to the supply injection limb leading to the separation column. This conduit is surrounded by a cylindrical chamber and is provided with a centrical opening. On its upper end, the cylindrical chamber is provided with a connection for the inlet limb. On its lower end with a connection for the carrier gas and with a connection for the vent limb. The junction is formed through an opening in the conduit within the chamber. In the case of this known configuration as well, subject to function, the pressure in the sample supply line must be the same or higher than the carrier gas pressure.
Thus the task consists in creating a device for sample dosing, which will enable the samples to be charged independently of the pressure existing in the sample gas source.
DESCRIPTION OF THE INVENTION
The task is able to be solved with a device that has a carrier gas source of a constant and adjustable pressure, a two-way reversing valve, whose inlet is connected via a conduit to the carrier gas source, and a branch line connected to an outlet of the reversing valve. Additionally, the present invention has a flow divider including a tubing connected to the branch line, with an opening and a chamber surrounding the tubing and extending upstream and downstream from the opening. The present invention also has a conduit section connected to the output of the tubing and leading to the separation column. A branch line is connected to the second outlet of the reversing valve and discharges into the downstream part of the chamber. An outgoing line has an adjustable resistance to flow and emanates from the downstream part of the chamber. A supply line is provided for the sample that has an adjustable resistance to flow and which discharges into the upper, upstream end section of the chamber. The flow resistances are dimensioned so that the volumetric flow rate (Q11) in the supply line is less than the flow rate (Q10) through the outgoing line, but is greater than the flow rate (Q4) into the separation column. The present invention also includes a dosing valve with six conn
REFERENCES:
patent: 3077766 (1963-02-01), Reinecke
patent: 4442217 (1984-04-01), Deans
Clauss Fernand
Muller Friedhelm
Housel James C.
Redding David
Siemens Aktiengesellschaft
LandOfFree
Device and method for sample dosing in gas chromatography does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device and method for sample dosing in gas chromatography, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device and method for sample dosing in gas chromatography will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-921330