JPS60102558A - Sample modulating cell for gas chromatography - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates generally to methods for improving response in chromatographic analyses, and more particularly to methods for detecting synchronization using improved signal-to-noise ratios. Regarding sample modulation cells.

[Background of the invention]

Two problems that limit the use of the detector in the gas chromatograph 2 fee are drift and noise.

Examples of detectors that are subject to drift include thermal conductivity detectors (TODs) and thermionic specific detectors (mHTsD).

Drift in TOD is caused by small changes in cell wall temperature. Drift in T0n is caused by small changes occurring on the surface of the bead.

These changes are both thermal and chemical changes. As an example of a detector where the dominant noise source is within the detector cell,
Flame photometric detector (FPD), hydrogen flame ionization detector (FPD)
ID) and TSD. Noise in FP'D is caused by random low frequency fluctuations in the visibility of the background flame. Similarly, TSD generates noise from variations in the properties of the bead surface.

When drift and noise sources are inherent in the detector and not in the electronics that control the detector or amplify the 1g signal from the detector, these problems are minimized or eliminated by AC techniques. It is known that you can. For example, Jeannie Green (J, A,
U.S. Patent No. 3,740,15 issued to
No. 4 discloses a flame photometer, by which the gas to be analyzed is modulated with a modulator comprising a flexible, sinusoidally vibrating R4 membrane. Since the sample gas is in direct contact with this thin film, this modulator cannot be used with some samples, such as corrosive samples and very hot samples. Fluid control devices that do not require flexible membranes of the type described above are available, for example, from L.B.

U.S. Patent No. a, a5 issued to B. Roof)
No. 7,233 and R. L. Horton (R.L.
U.S. Patent No. 4.309.
It is disclosed in No. 898b. However, two of these devices are fluid in nature and require flows that are orders of magnitude larger in order to operate properly.

Teenie Woodruff ('1', A, Wo
U.S. Patent No. 4.316.3 issued to
No. 81 and U.S. Pat. No. 4,316. :1B2 discloses a modulated detector that is provided with a cumulative quantity for modulation in the flow path. With the detector, measurements are taken only when the flow has stopped. This measurement is a static measurement and not a continuous dynamic process, which allows for shorter response times.

[Summary of the invention]

It is therefore an object of the present invention to provide a sample modulator for improving the signal-to-noise ratio of chromatography detectors by synchronous detection.

It is another object of the present invention to provide a sample modulating means for alternately supplying a fluid sample to two input channels, which is capable of operating effectively at flow rates substantially below that required for a fluid flow control device. Another object of the present invention is to provide a sample modulator that allows continuous dynamic measurements.

Another object of the invention is to provide a sample modulator with valve means for alternately supplying a fluid sample to two input channels without direct contact with the fluid sample.

Another object of the invention is to provide a sample modulator that allows the entire sample from a gas chromatography column to be utilized at the detector.

〔Example〕

A horizontal view of a sample modulation cell for a gas chromatography detector embodying the invention is illustrated in FIG. Gas for controlling the direction of sample flow enters the flow diverter valve 15, flow controlled by the combined operation of a pressure regulator 11 and a flow restrictor 12 of all known types. The gas to be controlled may hereinafter be referred to as a diversion gas.The diversion valve 15 may be an analogous mechanical device whose operation is to alternately divert the incoming flow into an upper passage 16 and a lower passage 17. good. The upper route 16 and the lower route 17 are
At positions 21 and 22, respectively, they enter the vertical conduit 20. Position 1ii21 is above position 22.0 The sample to be analyzed enters the cell through the entry path 2B. Entrance 25
A 1-shaped portion 26 is formed at a position between the lower and lower tits 21 and 22 and communicates with the conduit 20. When the sample from the inlet passage 25 reaches the character 1 portion 26, the sample is alternately discharged from the upper opening 31 and the lower opening 3z by the gas distribution means which flow through the lower axial passage 17 and the upper passage 16, respectively. That is, during the alternating phases of operation of the diverter valve 15, as the diverted gas is diverted to the upper passage 16, the sample from the inlet passage 25 will be trapped within the conduit 20 as the gas movement is indicated by the dashed arrows. It is allowed to flow downwardly through the lower aperture 32. - On the other hand, during the other phases of alternating operation of the diverter valve 15, when the carrier gas is diverted to the lower path 17, the sample from the inlet path 25 is removed from the conduit as the movement of the gas is indicated by the solid arrow. 20 and is allowed to flow upwardly through an upper aperture 31. The duty cycle of the diverter valve 15 need not be s o /s o, or
It is not necessary that the gas containing the sample should pass through the upper aperture 31 and the lower aperture 32 each 50% of the time during each cycle. In the case of high frequency operation, it may prove advantageous to reduce this ratio due to peak broadening. In one mode of operation, for example, the upper aperture 31 may be It may be inserted into a silica detector insert (not shown). The net gas flow through each aperture 31 and 32 is the same because the counterbalance 35 above the lower aperture 32 is aligned to balance the load downstream of the upper aperture 31 for the detector. Additionally, a substantially constant gas flow, either sample-containing gas or pure split gas, is flowing through both apertures 31 and 32 at all times during operation. The modulated sample flow into the detector is converted into an electrical signal by a suitable transducer (not shown) and detected synchronously by any method known to those skilled in the art.

2N illustrates one way of operating a modulation cell of the type shown in FIG. This scheme is intended to improve the operating disadvantage mentioned above, namely that one-half of the sample leaving the gas chromatography column is diverted away from the detector; . Two passages 116 and 117 from a flow divider valve (not shown) as well as the sample input are used to utilize all of the sample to achieve further conversion and increase the peak response obtained by the modulation cell. Channels 125 open into annular conduit 140 at locations 121, 122 and 126, respectively. Furthermore, the exit passage 145
opens into the annular conduit 140 at location 14B and connects the annular conduit 140 to the exit boat 15G. For the convenience of explanation, we assume that the clockwise and counterclockwise rotation [t
The left-hand and right-hand portions of conduit 140 from x2s to position [148 will be referred to as channels A and B, respectively.

The position fl (14B) is placed such that flow path B is twice as long as flow path A. This means that the modulated sample passing through paths A and B will be 180 in flow
This is to create a phase difference of .

To operate the modulation cell of FIG.
and 122 alternately enter the isotube 140.

If a sample is introduced at position 126 using appropriate pressure, the sample will move through the flow path A by movement of the carrier gas.
The flow will be alternately shunted into B and B. The contours of the modulated sample flow in channels A and B indicate the mode of operation? To explain the low frequency state, we will use the song 1W in Figure 3 (
bl and ←). As mentioned above, the lengths of paths A and B are determined by the introduction of a 180 degree phase difference there, and the mass flow rate of the sample measured at position 14B is either curved (fb) or (cl). The curve in FIG. 3 with a peak twice the height of the peak (which would be indicated by dl).

This desired result is obtained because half of the sample leaving the cell through the lower aperture (32 in Figure 1) is not wasted and is further utilized by the detector. Alternatively, a periodic flow of gas, such as a compressed pulse of either a control gas or a caustic gas, is applied at location 148 as shown in FIG. 2, or alternatively between locations 14B and 150. Somewhere Muro Boat 1
49, the mass flow rate measured at location 150 will increase due to the increased gas flow rate. Of course, the phase of such a compression pulse may be such that the sample portion of the waveform (Figure 3(d)) is inside the exit passage or between positions [148 and 150] when the pulse is applied. Must be in phase. For example, if the flow at location 148 is doubled when a compression pulse is applied, the same mass will be moved to exit boat 150 in half the time.
The peak mass flow rate will double and the flow profile will become as shown in Figure 3(e).

FIG. 4 shows a modulated sample profile for butane eluted from a capillary column at a frequency of 5 Hz without the use of the compression pulses described above through inlet boat 149. - The dashed curve is the sample 711 modulated from the FID -
・It is the old age of . The iL7-multiplied peak response obtained by the second phase shift modulation cell is not shown.

Although the invention is disclosed based only on the example of 2.3,
These examples are meant to be illustrative rather than limiting. Accordingly, the disclosure should be interpreted broadly.

For example, the first and second figures are merely schematic diagrams and do not represent preferred dimensional relationships. Accordingly, conduit 140 need not be precisely annular, and passages 116 and 117 as well as entry 1
The dimensions of 25 leading to conduit 140 need not necessarily be as depicted in FIG. Figure 1 need not necessarily be considered a horizontal view, and the apparatus may be oriented analogously to a vertical position, notwithstanding the use of the expressions "above", "below" and "vertical" in the foregoing. may be placed.

The split gas may or may not be the same as the carrier gas used in gas chromatography.

The scope of the present invention is 1. @Limited only by the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 illustrates a sample modulation cell according to the invention. FIG. 2 shows another embodiment of a sample modulation cell according to the invention. FIG. 3 shows examples of sample mass flow profiles at various positions of the cell of FIG. 2 and under different conditions of operation of the cell. FIG. 4 is a chromatogram obtained by the modulation cell of FIG. 2. [Main symbols] 11--one pressure regulator 12--one flow restrictor 15--one flow valve 16--one upper passage 17--lower passage 20--one vertical conduit 21, 22.121.122.126.148-one position I
t25, 125--Passway 26--'j'' portion 31--Upper opening 32--Lower opening 3 To-Equilibrium load 116.117-Through % 140-Annular conduit 145-
-Exit passage 149-One-person robot 150--Departure robot patent applicant Parian Associates Engraving of drawings (no change in content) FIG, 2 all FIG. November 1980 911 Mr. Manabu Shiga, Commissioner of the Patent Office ■, Indication of the case 1988 Patent Application No. 218731 3, Relationship with the person making the amendment φ Patent applicant address (residence) Name (name) Varian Associates Incorporated 4, agent residence + #i IJ! 1-6-211 Nishi-Shinbashi, Shato Minato-ku” 5
, 14a of the amendment order] Voluntary

Claims (1)

[Claims] 1. A sample modulator for gas chromatography, comprising: a conduit; and for causing gas to flow into the conduit through alternately a first boat and a second boat communicating with the conduit. and a sample entry port communicating with the conduit between the first boat and the second boat. 2. The modulator according to claim 1, wherein the conduit has a first open end and a second open end;
The modulator, wherein the open end is positioned above the second open end. 3. The modulator of claim 2, further comprising a balanced load at the second open end on the conduit. 4. The modulator as set forth in claim 1, wherein the conduit is of a closed configuration with an outlet boat to provide two channels between the sample entry boat and the outlet boat. The modulator that defines the area. 5. The modulator according to claim 4, wherein one of the two flow paths is longer than the other flow path. 6.% The modulator according to claim 5, wherein the longer channel is approximately twice as long as the shorter channel. 7. A modulator as claimed in claim 4, further comprising an exit passage connected to said conduit and communicating with said conduit through said exit boat. 8. The modulator according to claim fJx, further comprising means for adjusting the flow state of the gas. 9. A modulator according to claim 4, further comprising: introducing an additional periodic gas flow into the outlet passage to measure the sample at the downstream end of the outlet passage; a modulator comprising: means for increasing the mass flow rate of; 10. A method for obtaining an improved response-to-noise ratio in chromatographic analysis of a sample by means of a sample modulator, the method comprising: introducing the sample into a conduit through an entry port; 3. A method comprising: periodically alternating each of two flow paths to cause the diverted gas containing the sample and the diverted gas not containing the sample to flow from the entry boat to the exit boat. 11.% The method of claim 1θ, wherein the exit boat is connected to an exit passageway to transport the diverted gas and the sample to a detector. 12. The method according to claim 11, wherein all of the sample introduced into the conduit by the sample introduction step is utilized by the detector in the analysis. la, lpQ The method according to claim 10, further comprising:
A method comprising the step of introducing a phase shift of o. 14. The method according to claim 13, comprising the step of adjusting the flow rate of the diverted gas into the conduit at a process power of t1M to introduce the phase shift. 15. The method of claim 13, further comprising periodically applying an inverse additive gas flow into the outlet passageway to increase the peak response obtained by the modulator. A method consisting of a process. 16. In the chromatographic analysis of the sample in which a first type of flow that does not include the whole sample and a second type of flow that contains the sample are caused in a conduit alternately in six periods, A method for improving phase response comprising the step of applying an additional periodic flow of gas within the conduit, wherein the flow of the sample measured at a downstream location in the conduit is The method of increasing by an additional periodic flow.