JP3775008B2 - Sampling device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for sampling by heating and keeping a sample at a predetermined temperature in an analyzer such as a gas chromatograph.
[0002]
[Prior art]
One of the gas chromatograph analysis methods is a headspace gas analysis method. In this method, a liquid or solid sample is sealed in a sample bottle with a septum lid, leaving some space at the top, and kept at a predetermined temperature for a predetermined time. By collecting and analyzing with a syringe, the volatile components in the sample are qualitatively or quantitatively determined. What is important in the headspace analysis method is temperature control during the pretreatment heat retention, and if the temperature varies, sufficient reproducibility of the analysis results cannot be obtained.
[0003]
Conventionally, what is often used as a means for heating and keeping the sample bottle is called dry bath (or block bath). In this case, a plurality of holes having an inner diameter slightly larger than the diameter of the sample bottle are formed in a metal heat insulating block heated by an electric heater, and the sample bottle is inserted into the hole for heat insulation. If an appropriate temperature controller is used, the temperature can be automatically adjusted to any temperature. Since a metal block with good heat conduction is used, there is little temperature unevenness, and the overall structure is simple and easy to handle. It is also relatively easy to construct the block itself so as to move mechanically.
[0004]
As another means, a wet bath system (liquid bath system) may be used. In this method, the sample bottle is kept warm by immersing the sample bottle in a heated liquid bath. Since the heat transfer is good, the sample is heated quickly and uniformly.
[0005]
[Problems to be solved by the invention]
The conventional dry bath method that heats and heats the sample bottle requires some clearance between the heat retaining block and the bottle in view of the variation in the outer diameter of the sample bottle and the ease of inserting and removing the bottle. As a result, the adhesion is poor, and heat can be transmitted only by a small amount of conduction from the contact portion and radiation from the inner wall of the block, so that the heat transfer efficiency is low and it is difficult to adjust the temperature effectively. In other words, even if the heat insulation block is uniformly heated to a predetermined temperature, not all the inserted bins are maintained at the predetermined temperature, and this is a big problem in the analysis that emphasizes reproducibility. Become.
[0006]
On the other hand, the wet bath method that heats and keeps heat has no problem in terms of heat transfer, but in order to improve the temperature control accuracy, a device that circulates or stirs the liquid, and a liquid volume management that copes with liquid evaporation loss. An accompanying device and a structure for guarding surrounding mechanical devices from liquid leakage and scattering are required, and the overall structure becomes complicated, so it is not suitable for obtaining an automated device in a compact manner.
[0007]
As described above, the present invention provides a sampling device including a sample bottle heat retaining device that has two features of good heat transfer and a simple structure excellent in operability, which cannot be achieved by the conventional method. It is intended.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention fills a hole of a metal heat insulation block in which a hole for inserting a sample bottle is formed and controlled to a predetermined temperature with a heat transfer medium having a good thermal conductivity , The hole mouth is provided with a mechanism for wiping the heat transfer liquid from the sample bottle . When the sample bottle is inserted with the heat medium liquid filled, the heat medium liquid fills the gap between the inner wall of the hole, the heat transfer efficiency is improved, and the temperature of the sample is accurately controlled.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which the present invention is applied to a gas chromatograph automatic headspace sampling apparatus will be described with reference to FIGS.
[0010]
FIG. 1 shows an automatic headspace sampling apparatus 10, which is fixed so that a syringe 11 is positioned directly above a sample inlet 21 of a gas chromatograph 20, and is generally controlled by a program control apparatus (not shown). The A syringe drive mechanism 15 that moves the syringe 11 up and down and a plunger drive mechanism 16 that moves the plunger 13 of the syringe 11 up and down are provided. Both of these drive mechanisms use a motor or an air cylinder as a prime mover, but the detailed configuration is not directly related to the present invention, so it is simplified in FIG.
[0011]
The sample bottle 19 containing the analysis sample is mounted on a metal heat insulating block 18 that functions as a sample holder. The sample bottle 19 has a structure in which the mouth is sealed with a septum made of rubber or soft plastic, and an internal gas or liquid can be taken in and out by penetrating a syringe needle 11S described later into the septum.
[0012]
As shown in the schematic shape of FIG. 2, the heat retaining block 18 has a “C” shape having a notch 18K in a part of the ring, and is ± 180 degrees around the center of the ring. In range, it is rotated by the sample drive mechanism 17. Since the configuration of the sample driving mechanism 17 is not directly related to the present invention, it is simplified in FIG. The heat retaining block 18 is heated by a planar heater 24 fixed in close contact with the outer periphery thereof, and is controlled to a predetermined temperature set according to the analysis purpose by a temperature controller (not shown). The syringe 11 is also heated to substantially the same temperature as the heat retaining block 18 by the heater jacket 12.
[0013]
In this embodiment, seven holes 18H for mounting the sample bottle 19 are provided at intervals of 45 degrees. In general, since the pretreatment heat retention time is longer than the analysis time, in order to perform analysis continuously, a plurality of samples are kept warm in parallel. For this reason, a plurality of holes are required. The inner diameter of the hole 18H is slightly larger than the outer diameter of the sample bottle 19, and the gap is filled with oil A having good thermal conductivity. A plastic funnel-shaped collar 14 having appropriate elasticity and heat resistance is fixed to the mouth of each hole.
[0014]
The automatic headspace sampling apparatus 10 configured as described above operates as follows in accordance with a program that is set in advance.
[0015]
First, a liquid sample to be analyzed (a sample may be a solid, but in the following description, it is a liquid) is sealed in a sample bottle 19 and inserted into a hole in a heat retaining block 18. Since the bottom of the hole is filled with a small amount of oil A as a heating medium liquid in advance, when the sample bottle 19 is inserted, the liquid level of the oil A rises and fills the gap between the sample bottle 19 and the inner wall of the hole. Excess oil A flows down through the overflow pipe 23 and is recovered by the oil receiver 22. After the time until the sample in the sample bottle 19 reaches gas-liquid equilibrium, the heat retaining block 18 is rotationally driven by the sample driving mechanism 17 and moves until the sample bottle 19 is positioned directly below the syringe 11. Until this time, the syringe 11 has been lifted up to the uppermost position immediately after the previous sampling. Here, the syringe 11 is lowered by the syringe drive mechanism 15, and the needle 11S penetrates the septum of the sample bottle 19 to the tip. Stops in the upper space in the sample bottle 19 and does not reach the liquid level. Next, the plunger 13 is pulled up by the plunger driving mechanism 16 and the gas in the upper space in the sample bottle 19 is sucked into the syringe 11. Since the syringe 11 is heated to substantially the same temperature as the heat retaining block 18, the inhaled gas does not cause a phase change in the syringe 11.
[0016]
Subsequently, the syringe 11 is pulled up by the syringe drive mechanism 15, the heat retaining block 18 is moved by the sample drive mechanism 17, and the notch 18 </ b> K is positioned directly below the syringe 11. When the syringe 11 is lowered to the lowest position by the syringe drive mechanism 15, the needle 11 </ b> S of the syringe 11 passes through the notch 18 </ b> K and penetrates the septum provided at the upper portion of the sample injection port 21. Immediately thereafter, the plunger 13 is pushed down by the plunger drive mechanism 16, and the collected gas is discharged into the sample injection port 21.
[0017]
Thereafter, the syringe 11 is returned to the uppermost position by the syringe drive mechanism 15 to complete one cycle of the operation of the automatic headspace sampling apparatus 10. The sample bin 19 after sampling is taken out from the heat retaining block 18 manually by an operator or by a robot device provided separately, and another sample bin 19 is newly inserted.
[0018]
The oil A adhering to the outer periphery when the sample bottle 19 is extracted is wiped by the collar 14 and returns to the same hole 18H, so that the loss of the oil A is small, but the oil A still needs to be replenished. The replenishment may be performed manually by the operator, or may be performed automatically using an oil pump (not shown) that is operated by a program. In this case, it is naturally considered to recycle the oil A collected in the oil receiver 22.
[0019]
In order to wipe the oil A, instead of the collar 14, a brush-like material or a material made of another material such as a metal may be used. In addition to this, the collar 14 keeps the sample bottle 19 at the center of the hole 18H, and prevents the sample bottle 19 from being lifted by the buoyancy received from the oil A when the sample bottle 19 is pressed by the frictional force and the sample amount is small. It also has a role to play.
[0020]
The oil A as the heat transfer liquid is selected and used with appropriate heat conductivity and viscosity, and heat resistance according to the heating temperature. If the heating temperature is about 60 degrees Celsius or less, water is used. It can also be used and is not limited to oil A.
[0021]
The present invention can be applied not only to the head space sampling in the above embodiment, but also to the case where the sample is sampled at a constant temperature for the purpose of preventing the phase change of the sample. The analyzer is not limited to the gas chromatograph but can be widely applied to analyzers based on other principles, and the effect can be obtained.
[0022]
【The invention's effect】
As described above in detail, according to the sampling device of the present invention, heat conduction from the heat insulation block to the sample bottle is improved, and the accuracy of heat insulation can be improved. Therefore, it is effective particularly in the case where the temperature accuracy at the time of the pretreatment heat retention of the sample directly affects the composition of the sampled gas as in the head space analysis method.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a sampling apparatus according to the present invention.
FIG. 2 is a diagram showing the shape of a heat insulation block in the sampling device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Syringe 11S ... Needle 12 ... Heater jacket 13 ... Plunger 14 ... Collar 15 ... Syringe drive mechanism 16 ... Plunger drive mechanism 17 ... Sample drive mechanism 18 ... Thermal insulation block 18H ... Hole 18K ... Notch Part 19: Sample bottle 20 ... Gas chromatograph 21 ... Sample inlet A ... Oil

Claims (1)

  In a device for keeping a sample warm by inserting a sample bottle containing a sample to be analyzed into a hole made in a metal heat insulation block controlled at a predetermined temperature, the hole of this block is filled with a heat transfer liquid, A sampling apparatus comprising a mechanism for wiping the heat transfer liquid from the sample bottle at the mouth of the hole.

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