JP4492245B2 - Autosampler - Google Patents

Description

  The present invention relates to an autosampler that automatically collects a sample solution for an analyzer such as a liquid chromatograph and analyzes the sample and introduces it into the analyzer.

  In a liquid chromatograph, an autosampler is used to automatically select a large number of samples and introduce them into a column. FIG. 3 is a schematic diagram illustrating an example of a flow path configuration of an autosampler in a conventional liquid chromatograph disclosed in Patent Document 1 and the like.

  In the autosampler 3, an injection valve (high pressure valve) 4 is a rotary 6-port 2-position flow path switching valve having six ports 4a to 4f, and two adjacent ports are selectively connected by a switching operation. Is done. That is, the combination of the two connections of solid line or dotted line in FIG. 3 can be switched. On the other hand, the low-pressure valve 5 is a rotary 7-port 6-position valve having seven ports 5a to 5g, and the common port 5g to which the metering pump 6 is connected is one of the other six ports 5a to 5f. The two adjacent ports among the ports 5a to 5f are connected in conjunction with each other. For example, as shown by the solid line in FIG. 3, when the common port 5g and the port 5b are connected, the ports 5a and 5f are connected.

  A column flow path leading to the column 2 is connected to the port 4b of the injection valve 4, and a mobile phase flow path to which a mobile phase (solvent) is supplied by the liquid feeding unit 1 is connected to the port 4c. The sample loop 7 is connected to the port 4d, and further connected to the port 4a via the needle 10 and the injection port 9. The port 4e and the port 4f are connected to the port 5b and the port 5c of the low pressure valve 5, respectively. A cleaning port 8 is connected to the port 5a of the low-pressure valve 5, the port 5e is connected to the metering pump 6, and a cleaning liquid is supplied to the port 5d. A small vial 11 in which a sample solution is stored is accommodated in a sample rack 12. The needle 10 can be moved in the horizontal direction and the vertical direction by the moving mechanism 13, can move onto the vial 11 and the washing port 8, and can be inserted into each liquid.

  A basic operation sequence at the time of sample introduction in the above apparatus will be described. At the time of sample collection, the injection valve 4 and the low pressure valve 5 are switched to the connected state shown by the solid line in FIG. 3, and the needle 10 is moved onto the vial 11 and inserted into the sample liquid (position 10 ′). . In this state, when the plunger of the metering pump 6 is pulled, the sample solution is sucked from the vial 11 through the mobile phase (or the cleaning solution having the same component) filled in the flow path from the metering pump 6 to the needle 10. The sample liquid is held in the sample loop 7. The amount of sample liquid collected is equal to the amount of suction by the metering pump 6.

  After sampling, the needle 10 is returned to a position on the injection port 9 and connected to the injection port 9. Further, the injection valve 4 is switched to a connection state indicated by a dotted line in FIG. Then, the mobile phase supplied from the liquid feeding unit 1 is sent to the column 2 through the sample loop 7, the needle 10, and the injection port 9. At this time, the sample liquid previously held in the sample loop 7 is sent to the column 2 together with the mobile phase, and the components are separated when passing through the column 2 and sequentially detected by a detector (not shown). .

  Cleaning of the needle 10 to which the sample liquid has adhered by sample suction is performed as follows. That is, the injection valve 4 and the low pressure valve 5 are switched to the connection state indicated by the solid line in FIG. Then, the plunger of the metering pump 6 is pulled and the cleaning liquid is sucked into the syringe. Thereafter, both the injection valve 4 and the low pressure valve 5 are switched to the connection state indicated by the dotted line in FIG. 3, and when the plunger is pushed and the cleaning liquid is discharged from the metering pump 6, the cleaning liquid is introduced into the cleaning port 8 and filled. Then, excess cleaning liquid is discharged from the drain port of the cleaning port 8. Next, as shown in FIG. 4, the needle 10 is moved onto the cleaning port 8 and immersed in the cleaning liquid stored in the cleaning port 8. After the needle 10 is cleaned for a predetermined time, the needle 10 is returned to the injection port 9.

  In the autosampler 3 described above, since the cleaning operation of the needle 10 as described above is always performed between the introduction operation of one sample and the introduction operation of the next sample, the previous sample becomes the next sample. Cross contamination mixed in is reduced. However, such cleaning does not completely eliminate cross contamination. One of the reasons is as follows.

  FIG. 5 is a schematic longitudinal sectional view showing an enlarged connection portion between the needle 10 and the injection port 9. In the needle 10, the range indicated by A in FIG. 5 has a straight shape, and the range indicated by B at the distal end has a tapered shape in which the outer diameter continuously decreases toward the distal end. On the other hand, the sealing member 90 provided in the injection port 9 is formed with an insertion hole 90b whose upper part (reference numeral 90a) is opened in a funnel shape. When connecting the needle 10 to the injection port 9, the needle 10 is lowered and the tip of the needle 10 is inserted into the insertion hole 90 b of the seal member 90.

Since the inner diameter of the insertion hole 90b is slightly larger than the outer diameter of the end of the tip of the needle 10, the tip of the needle 10 initially enters the insertion hole 90b, but the tip of the needle 10 is tapered. Therefore, when the needle 10 is lowered to a certain position, the outer peripheral surface of the needle 10 comes into contact with the inner peripheral surface of the insertion hole 90b. When lowering the needle 10 at a predetermined pushing force, but its pushing force is up to overcome the frictional force of the contact surface (including the repulsive force of the seal member 90) the needle 10 is pressed, the frictional force exceeds the pushing force When this happens, the lowering of the needle 10 stops. That is, at this time, the outer peripheral surface of the needle 10 and the inner peripheral surface of the insertion hole 90b are in close contact with each other, thereby ensuring liquid tightness.

  When the sample liquid is aspirated from the vial 11, a part of the sample liquid adheres to the outer periphery of the tip of the needle 10. After that, as described above, the needle 10 is inserted into the seal member 90 of the injection port 9, so that the sample is located on the inner periphery of the insertion hole 90 b of the seal member 90 and in contact with the outer periphery of the tip of the needle 10. Liquid adheres. Even when the mobile phase flows from the needle 10 to the injection port 9, the sample liquid adhering to the contact surface is not carried away by the mobile phase, so that the sample liquid remains even after the needle 10 is removed. Then, when the needle 10 is inserted again into the insertion hole 90b of the seal member 90 in order to introduce the next sample liquid, the previous sample liquid adhering to the inner peripheral surface of the insertion hole 90b is pushed to the needle 10. May be mixed in the flow path.

  In particular, when analyzing a sample having a property that is easily adsorbed on the surface of the metal needle 10, for example, a basic compound or a fat-soluble substance, the above-mentioned cross contamination often becomes a problem.

  Conventionally, in the autosampler described in Patent Document 2, for example, noble metal is deposited or coated on the outer peripheral surface of the needle in order to make it difficult for chemical adsorption of the sample to the outer periphery of the tip of the needle. It has been broken. These measures are effective for samples adhering to the needle surface mainly due to chemical adsorption phenomena such as basic compounds, but for those that adhere due to factors other than chemical adsorption phenomena, such as fat-soluble substances. Is ineffective.

JP 2002-277450 A JP 2002-228668 A

  In recent years, with the increase in sensitivity and accuracy of analysis, a small amount of cross-contamination as described above has a great influence on analysis results. Furthermore, the samples to be analyzed are diversified more and more, and it is required to reduce cross contamination regardless of the type of sample.

  The present invention has been made in order to solve such problems. The object of the present invention is to further reduce the cross-contamination further than before without depending on the type of the sample, thereby achieving high sensitivity and high sensitivity. The object is to provide an autosampler that enables analysis of accuracy.

  The conventional measures as described above are designed to prevent the sample liquid from adhering to the outer peripheral surface of the needle tip by adding a device to the surface state of the needle. Focusing on the fact that it greatly depends on the contact area between the outer peripheral surface of the needle tip and the inner peripheral surface of the insertion hole of the seal member of the injection port, the idea is to reduce cross contamination by reducing the contact area. did.

That is, the present invention made to solve the above problems includes a needle having a tip formed in a tapered shape for sucking and discharging a liquid, and a moving mechanism for moving the needle in a horizontal direction and a vertical direction. And an injection port having an insertion hole into which the tip of the needle is inserted. The tip of the needle is immersed in the sample solution stored in the container, and the sample solution is sucked into the holding channel through the needle. And holding the sample solution collected previously by inserting the outer periphery of the tip of the needle into the insertion hole of the injection port so as to be in close contact with the inner periphery of the insertion hole . In an autosampler for a liquid chromatograph that introduces the sample solution into an analysis flow path including a column by discharging the solution, the outer diameter of the end of the tip of the needle is 0.6 m. Hereinafter and 0.1mm or more, and the pressing force when inserting the tip of the needle into the insertion hole of the injection port and wherein the set below 3 kg f.

  Conventionally, the outer diameter of the end of the tip of the needle is 0.65 mm or more, whereas in the autosampler according to the present invention, the outer diameter of the tip of the needle is 0.6 mm or less and 0.1 mm or more. Therefore, when the needle is inserted into the insertion hole of the injection port, the contact area between the outer peripheral surface of the tip of the needle and the inner peripheral surface of the insertion hole of the injection port is reduced. Therefore, when introducing the sample liquid through the injection port, the absolute amount of the sample liquid that moves from the outer peripheral surface of the needle to the inner peripheral surface of the insertion hole of the injection port, that is, adheres, is reduced. Thereby, the cross contamination can be reduced more than before.

  For example, if the autosampler according to the present invention is applied to a liquid chromatograph, even if a peak derived from a component contained in a previous sample does not appear or appears in a chromatogram when performing analysis of a certain sample. The peak intensity is reduced. Thereby, the calculation accuracy of the peak height and area of the component originally desired to be analyzed is improved, and the analysis accuracy can be improved. In addition, trace amounts of components that have been difficult to detect due to the influence of cross-contamination can be detected, and the analysis sensitivity can be improved.

However, when the outer diameter of the tip of the needle is reduced, the mechanical strength is reduced, so that buckling or the like during needle insertion is likely to occur. Therefore, in order to prevent these things, in the autosampler according to the present invention, the pressing force when inserting the tip of the needle into the insertion hole of the injection port than conventional 4 kg f set small, below 3 kg f It is preferable.

The frictional force when pressing the needle in the contact area is reduced between the outer peripheral surface and the inner peripheral surface of the insertion hole of the needle tip as described above also decreases, liquid-tight even lowered pushing force as described above It is possible to push the needle to such an extent that the properties can be sufficiently secured, thereby preventing buckling deformation of the needle.

  Even when the outer diameter of the end of the needle tip is reduced compared to the conventional case, the taper angle itself of the tip is kept at the same level as the conventional one, so that the resistance force when penetrating the needle into the septum is also improved. Since the outer diameter of the needle tip is small, the resistance force at the initial stage of penetration can be suppressed to be smaller than the conventional one.

  An embodiment of an autosampler according to the present invention will be described below with reference to FIG. FIG. 1 is a longitudinal sectional view showing a state in which a needle 10 is inserted into an insertion hole 90b of a seal member 90 of an injection port 9, wherein (a) is a conventional autosampler, and (b) is an autosampler of this embodiment. It is. In FIG. 1, the unit of dimension is omitted, but the unit is all mm.

First, a conventionally used needle 10 and seal member 90 will be described with reference to FIG. The needle 10 has an outer diameter of 1.2 mmφ and an inner diameter of 0.4 mmφ at the straight portion indicated by A in FIG. 1, and an outer diameter of 0.65 mmφ and an inner diameter of 0.26 mmφ at the tip of the tapered portion indicated by B. is there. However, the outer diameter of the tapered portion gradually decreases toward the tip, but the inner diameter is straight. On the other hand, the inner diameter of the insertion hole 90b of the seal member 90 is 0.79 mmφ. When inserting the needle 10 into the insertion hole 90b of the seal member 90, it lowers the needle 10 vertically from above, multiplying the pressing force of about 4 kg f. At that time, on average, the depth (length) of the contact portion between the outer peripheral surface of the tip of the needle 10 and the inner peripheral surface of the insertion hole 90b is 0.4 mm on the short side and 0.63 mm on the long side. Become.

  The needle 10 is made of stainless steel, and the seal member 90 is made of polyetheretherketone resin represented by PEEK (registered trademark). This point is the same in the following embodiment.

  In contrast, the needle 10 in the autosampler of the present embodiment has an outer diameter of 1.2 mmφ and an inner diameter of 0.4 mmφ in the straight portion in the range indicated by A in FIG. 1, and at the tip of the tapered portion indicated by B. The outer diameter is 0.4 mmφ and the inner diameter is 0.2 mmφ. Since the taper angle of the taper portion is set to be the same as that of the prior art, the length of the taper portion itself is longer than that of the prior art, as is apparent from a comparison between FIGS.

The inner diameter of the insertion hole 90b of the seal member 90 is set to 0.5 mmφ in accordance with the reduction in the outer diameter of the needle 10 tip. Since the tip of the needle 10 is thus narrow, the mechanical strength is lower than the conventional one. Therefore, when inserting the needle 10 into the insertion hole 90b of the seal member 90, which sets the pushing force of the drop conventional about 1/2 to about 2 kg f. Pushing the outer diameter of the needle 10 tip lowers the pushing force if they are identical when the needle 10 although insufficient, in this embodiment, the insertion of the sealing member 90 by the outer diameter of the tip portion of the needle 10 is small due to the reduced friction force between the hole 90b, it is possible to push the needle 10 to the extent that liquid-tightness of the contact surfaces of both even lower the pressing force as described above can be sufficiently secured. At that time, on average, the length of the contact portion between the outer peripheral surface of the tip of the needle 10 and the inner peripheral surface of the insertion hole 90b is 0.31 mm on the short side and 0.45 mm on the long side.

  Thus, in the autosampler of the present embodiment, the outer diameter of the tip of the needle 10 is reduced as compared with the conventional one, and the inner diameter of the insertion hole 90b of the seal member 90 of the injection port 9 is also reduced accordingly. The contact area between the two becomes smaller. Specifically, the contact area is about ½. Therefore, the amount of the sample liquid adhering to the contact surface is reduced, and as a result, cross contamination can be reduced.

  Next, an actual measurement example of the effect of reducing the cross contamination will be described. In this experiment, a solution obtained by diluting strongly basic chlorohexidine hydrochloride (12 mg / 10 mL) in the same liquid as the mobile phase was used as a sample, and the area α of the obtained peak was obtained. Subsequently, only the mobile phase liquid (blank sample) was obtained. Similarly, the area β of the peak appearing at the same holding time is calculated, and the amount of cross contamination is expressed by the ratio of β to α.

  FIG. 2A is a chromatogram which is an analysis result of the chlorohexidine hydrochloride solution, and FIG. 2B is a chromatogram which is an analysis result of the blank sample. Both chromatograms have the same scale on the horizontal axis, which is the time axis, but the scale on the vertical axis, which is the intensity axis, is much smaller in FIG. 2B than in FIG. From FIG. 2 (a), the peak area α corresponding to chlorohexidine hydrochloride detected at the time of analysis of the chlorohexidine hydrochloride solution is obtained as 41055552. On the other hand, the peak area β corresponding to chlorohexidine hydrochloride detected at the time of blank sample analysis is 74712 for the conventional autosampler and 14728 for the autosampler of this embodiment. When the amount of cross contamination is calculated from this, it is 0.182% for the conventional autosampler and 0.036% for the autosampler of this embodiment. That is, it can be seen that the cross-contamination amount is reduced to about 1/5 in the auto sampler of this embodiment as compared with the conventional auto sampler.

In addition, the said Example is only an example of this invention, and especially the outer diameter size of the front-end | tip of a needle and the inner diameter of the insertion hole of a sealing member which are the characteristics of this invention are not restricted to the thing as described in the said Example. The outer diameter of the tip of the needle is 0.6 mm or less, and it is desirable that the outer diameter is as small as possible from the viewpoint of reducing the contact area, but the mechanical strength decreases as the outer diameter decreases. In addition, a flow path is formed inside thereof, and it is difficult to secure a necessary flow rate if the inner diameter of the flow path is too small. Therefore, if these are judged comprehensively, it is necessary that the outer diameter of the tip of the needle be 0.1 mm or more. On the other hand, the inner diameter of the insertion hole of the seal member will not be able to secure sufficient liquid tightness too is shallow insertion length of the tip portion of the small over-Gill and needle 10, while the insertion length of the too large needle 10 is long Thus, the contact area with the inner periphery of the insertion hole is increased. Therefore, it is necessary to set an appropriate inner diameter in accordance with the outer diameter of the needle tip to be used.

The longitudinal cross-sectional view which showed the connection part of the needle and injection port in the auto sampler which is one Example of this invention with contrast with the conventional auto sampler. The figure for demonstrating the cross-contamination reduction effect in the autosampler of a present Example. Schematic which shows an example of the flow-path structure of the autosampler in the conventional liquid chromatograph. The flow-path block diagram for demonstrating operation | movement of the autosampler in the conventional liquid chromatograph. The schematic longitudinal cross-sectional view which expanded and showed the connection part of a needle and an injection port.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid feeding unit 2 ... Column 3 ... Autosampler 4 ... Injection valve 4a-4f ... Port 5 ... Low pressure valve 5a-5g ... Port 6 ... Metering pump 7 ... Sample loop 8 ... Washing port 9 ... Injection port 90 ... Sealing member 90b ... insertion hole 10 ... needle 11 ... vial 12 ... sample rack 13 ... moving mechanism

Claims (1)

An injection port having a needle having a tapered tip for sucking and discharging liquid, a moving mechanism for moving the needle horizontally and vertically, and an insertion hole into which the tip of the needle is inserted The tip of the needle is immersed in the sample liquid stored in the container, and the sample liquid is sucked and held in the holding channel through the needle, and then the needle is inserted into the insertion port of the injection port. By inserting the outer periphery of the distal end portion so as to be in close contact with the inner periphery of the insertion hole and discharging the sample liquid previously collected by liquid feeding from the liquid feeding unit, the sample is supplied to the analysis flow path including the column. In an autosampler for liquid chromatography that introduces liquid,
That the outer diameter of the end portion of the tip of the needle and 0.6mm or less 0.1mm or more, and the pressing force when inserting the tip of the needle into the insertion hole of the injection port is set lower than 3 kg f A featured autosampler.

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