JPS6110770A - On column gas chromatograph using injector for splitting method - Google Patents

Abstract

PURPOSE:To enable measurement for capillary on column gas chromatogram, by operation of an injector and a sample injection for on column injection of a sample when measurement is done for capillary gas chromatogram by splitting method. CONSTITUTION:A carrier gas reaches a detector 7 passing through a metal tubulet 5 and a capillary column 6 from a sample introduction section 4 with a septum rubber 3 via a flowrate adjusting valve 1 and a carrier gas feed tube 2. Moreover, the tubulet 5 is covered with an Empire tube 8 and enters a tank piercing an insulation wall 10 of the heating tank 9 housed in the column 6 and connected to the column 6 at a connection 11. On the other hand, lead wires 13 and 14 successive to a transformer 12 are mounted to the tubulet 5 for heating by energization and either thereof is selected with a changeover switch 16. Then, this sample is injected with an injector into the tubulet 5, which is heated. Then, upon the end of solvent peaking, the heating tank 9 is raised in the temperature to obtain a chromatograph.

Description

[Detailed description of the invention]

The present invention relates to a method for measuring capillary on-column gas chromatograms. More specifically, the present invention relates to a method for measuring a gas chromatogram which is extremely useful in practice, in which a sample is injected on-column using a syringe and a sample injection operation when measuring a gas chromatogram using the split method. The capillary on-column gas chromatographic method has superior precision and
Excellent accuracy. However, in order to implement the capillary on-column method, the outer diameter is 0.27 tax
and 80. When using a syringe with a longer length, for example, the sample may not be aspirated into the syringe easily.The syringe needle cannot directly penetrate the septum rubber as it is, so a special sample introduction part is required. Some innovation is needed. There are drawbacks such as carrier gas being released outside the system during the sample introduction operation. The present inventor has diligently pursued a capillary on-column gas chromatogram measurement method that overcomes these drawbacks, and has devised the method of the present invention. That is, according to the method of the present invention, the sample is injected on-column using the syringe used in the split method into a thin tube connected to the head of the capillary column and, in principle, not coated with a liquid phase. The advantage of the method of the present invention is that it not only overcomes the above-mentioned drawbacks associated with conventional on-column methods, but also overcomes the influence on the chromatogram due to the presence of evaporation residues in the sample. Next, the idea that led to the devising of the method of the present invention will be described. At the head of a capillary column with an internal diameter of 0.25 m to 0.35 mm, a so-called aerodynamic ram made of silicic acid and having an internal diameter of 0.32 m to 0.35 m and not coated with liquid phase is provided. On-column injection using a syringe with a needle is known. In this case, once the sample injected into the aerodynamic ram is vaporized and reaches the capillary column coated with a liquid phase, the solvent in the sample is absorbed by the liquid phase, which temporarily increases the thickness of the liquid phase. The advance of the solute that first reaches it is extremely slow. The sample towards the end of the injection in the aerodynamic ram then catches up with the sample reaching the capillary column previously coated with the liquid phase, so that during the presence of the sample at the entrance of the capillary column, the sample band becomes narrower to some extent. Furthermore, at the 5th edge of the sample zone, the solvent dissolves into the carrier gas until it becomes saturated and advances, and at the tip of the sample zone it is absorbed by the liquid phase, temporarily increasing the thickness of the liquid phase film. , the solute after the solvent leaves moves forward and combines with the solute before it. The main principle of the on-column method is that by repeating this process and concentrating the sample through the solvent effect, it becomes as if the sample was injected into the head of a wide capillary column, creating a well-known on-column gas chromatogram. Inner diameter 0
．． 28 + ma length 50. An untreated glass aerodynamic ram with an inner diameter of 0.36 mm was attached to the head of a 0v-1 coated capillary column, and its length was varied from 1 m to 10 m, and the sample injection amount was varied from 10 to 100 μt. The number of separations between n-paraffins C29 and C30 (Trsnzhal
Number, a numerical value indicating how many triangles with an intermediate peak width can exist between C2g and C3o)
It was found that as long as the amount of sample injected shows a normal peak shape, the number of separations is determined by the length of the aerodynamic ram regardless of the amount of sample injected, and the longer the length, the lower the value becomes. Moreover, the number of separations did not change even if the sample was injected for a short time or the roots were hidden for 1 minute. From these facts, although there is a solvent effect in a capillary column coated with a liquid phase, if the aerodynamic ram is long, it takes time for the sample attached to the inner wall to desorb and reach the capillary column. During this time, the solute advances through the capillary column, increasing the length of the sample band, and before the solvent effect is fully exerted, the solvent moves forward, leaving the solute behind, and as a result, it is estimated that the number of separations decreases. Furthermore, when the inner wall of the aerodynamic ram was inactivated by so-called D4 (octamethyltetracyclosiloxane) treatment, the separation number was further reduced compared to when an untreated aerodynamic ram was used. This was thought to be because the n-paraffin dissolved in the extremely thin film of siloxane present on the inner wall of the aerodynamic ram and took time to pass through the aerodynamic ram. Therefore, in order to obtain a good chromatogram using the on-column method, it is sufficient to (1) slow the movement of the solute in the sample in the aerodynamic ram <L, and (2) slow down the movement of the initial sample band in the capillary column. I came to the conclusion that as long as the sample vapor does not become turbulent inside the person, there is no need to use it in the dead space of the aerodynamic ram. The method of the present invention was devised through specific experiments. The capillary column used in the method of the present invention is not particularly different from columns used in ordinary split methods or on-column methods, and usually has an inner diameter of 0.2 m to 0.3511111 mm. The number of separation stages in a capillary column is theoretically inversely proportional to its internal diameter, so if you use a capillary column with a small internal diameter of 0" to 0.05 mm to increase the number of separation stages, the tail behind the peak will tend to widen. However, they are often tolerable. The thickness of the liquid phase to be applied is preferably 0.3 μm or more in order to achieve the above [2] as much as possible. If it is too thick, the retention time of the high boiling point solute will become excessive, so from that point of view The most common film thickness is 0.6 μm or less. In the case of a low boiling point sample, the film thickness may even increase to about 3 μm. As with the usual on-column method, it is also preferable to crosslink the liquid phase membrane to increase the shape stability of the membrane. The material of the capillary column may be glass, fused silica, low adsorption stainless steel (for example, RAS manufactured by Nippon Chromato Industries), or untreated stainless steel depending on the target sample. However, glass is inferior to other flexible materials when it comes to the ease of manipulation of connecting an aerodynamic ram to the head of a capillary column. In that case, a known method such as using a heat-shrinkable Teflon pipe with a short flexible capillary as an intermediate auxiliary capillary at the end of a glass capillary column (K, Grob+Jr, and R-M'uller)
, J, Chromatogr, e244(i98
2) 185. ) to connect

[It's a good idea to keep it. In this case, there may or may not be a liquid phase on the inner wall of the short piece of the flexible capillary.
(It means the head of something that has an intermediate auxiliary capillary attached.) The aerodynamic ram requires an internal diameter that allows insertion of a conventional split method syringe needle. Since the outer diameter of the smallest split method injection needle is 0.4 cage, the inner diameter of the aerodynamic ram must be at least 0.5 m. However, an aerodynamic ram with an inner diameter Im is usually preferred for ease of needle insertion. Even if the inner diameter of the aerodynamic ram is made larger than that, no advantage can be found, and after two days or more, depending on the operating conditions such as the inner diameter of the capillary connected to it and the linear velocity of the carrier gas, the tail of the peak may become smaller. There are times when the deterioration of the shape is noticeable,
It is also unattractive because it is thick and difficult to handle. Immediately after injecting the sample on-column, this aerodynamic ram rapidly heats it to about 100 to 300°C. Realize [1]. For this purpose, the aerodynamic ram must be a thin metal tube that can be heated with electricity. The length depends on the amount of sample injected and the inner diameter of the aerodynamic ram, but if the amount of injection is less than 5μ, it can be approximately 1 m. The inner wall of the metal capillary is required to be inert. In addition to commercially available low-adsorption stainless steel capillaries (for example, RAS manufactured by Nippon Chromato Industries), glass-lined stainless steel capillaries can also be used without significantly low adsorption if the inner diameter is treated in the same way as the deactivation treatment of ordinary glass capillaries. In some cases, there may be 5. The bending process must be carried out before the deactivation process, and it is difficult to wind it into a circle, so it is difficult to use it in lengths of about 503 or more. In addition to these methods, there is also a method of using a metal capillary in which a fused silica capillary with an inner diameter of 0.5 yen or more is inserted (hereinafter, "metal capillary" is not particularly specified, but also includes glass-lined and fused silica capillaries inserted). ). Although having a liquid phase exist on the inner wall of the metal capillary tube has an advantage in terms of reducing the activity of the untreated active inner wall, it is disadvantageous in realizing the above-mentioned [1]. Therefore, in such a case, it is necessary to reduce the amount of the liquid phase as much as possible and to raise the temperature particularly rapidly. The shape of a metal capillary tube is usually constant in thickness. However, only the part where the injection needle is inserted has an inner diameter of 0.5. It is conceivable to do nothing above and then make it thinner as appropriate, but there is no particular advantage to doing so. The head of the capillary column and the tail of the metal capillary can be connected by a known method such as using a heat-shrinkable tear run pipe, or by using a connection tool known as a method for connecting metal capillaries or fused silica capillaries with a cap nut or push-in screw. I do. For the purpose of heat retention, the metal tube is
After the sample injection point, cover the tube with a glass employer tube up to the point where it connects to the capillary column. Then connect the head of the metal capillary to the sample introduction part. The structure of the sample introduction section is the same as the sample injection evaporation section of the split method without the evaporation section, and the sample passes through the septum rubber and is injected on-column. The capillary column is installed in the heating tank of the gas chromatograph, and its end is connected to the detector, and the other end is connected to a metal capillary tube covered with a glass employer tube, but the metal capillary column is not necessarily entirely inside the heating tank. 20 to 60cm from head
The rn position is passed through the heat insulating wall of the heating tank and taken out to the outside.
It may be connected to a sample introduction part provided completely separately from the heating tank as appropriate. Rather, this method has the advantage that cold on-column injection is easier to implement. The initial temperature of the capillary column is the same as in the case of the normal on-column method, which is about ±20℃ of the boiling point of the solvent in the sample, but in order to strengthen [2] above and improve the shape of the peak tail, the initial temperature should be A boiling point of around -20'C is good. In the cold-on-column method, the initial temperature of the metal capillary at that time may be approximately the initial temperature of the column from the point where the injection needle reaches. In the hot on-column method, the pressure is increased to 20'C above the boiling point of the solvent. The flow rate of the carrier gas is adjusted to a linear velocity of 20 to 60 ω/sec, which is the same as in the conventional on-column method or split method. The sample is injected on-column through the septum rubber just as in the split method. Immediately after that, the metal capillary rapidly changes its size from 100 to 300.
Raise the temperature to about ℃ and make sure that the above [1] is carried out reliably. The temperature may then be lowered after a few minutes. As can be seen from this description, even if there is evaporation residue in the sample and it adheres to the inner wall of the metal capillary, rapid heating will separate the volatile components from the evaporation residue and leave it in the capillary column for a short time. It is sent in. Since the inner diameter of the metal capillary is 0.5 or more, it is difficult for the pressure of the carrier gas in the sample introduction part to increase abnormally IC even when evaporation residue accumulates, and the method of the present invention also reduces evaporation residue. This method is superior to Korai's on-column method as an on-column method for samples containing . The temperature of the capillary column after sample injection may be maintained at the initial temperature of the column, depending on the sample, by a constant temperature method, but usually the temperature is increased at a rate of 1 to 10° C./min. The temperature may be started immediately after the sample is injected, but it is better to start the temperature increase when the solvent peak is almost over so that the solvent effect can be sufficiently exerted. There is no particular difference in this point from the conventional on-column method. From the perspective of the conventional on-column method, if the diameter of the aerodynamic ram is simply increased, the surface area of the inner wall of the aerodynamic ram will increase, and its residual activation effect will also increase, and the above [1] will not be achieved satisfactorily. . As a result, especially for high boiling point solutes and solutes that are easily adsorbed, the width of the peak becomes wider or the tail of the peak becomes tailed, and the peak does not have a good shape. Furthermore, similar disadvantages are observed for samples containing evaporation residues that have an affinity for solutes, and furthermore, the reproducibility of coomadograms is also poor. Rapid heating immediately after sample injection is necessary to achieve the above-mentioned [1]. This rapid heating is preferably carried out from room temperature to 300° C. within 10 to 30 seconds. Any method may be used as long as it can achieve this, but since electrical heating was considered to be a simple method, the method of the present invention was limited to that method. Electrical isolation from other parts of the gas chromatograph when electricity is applied can be achieved with simple knowledge, and if a transformer with independent primary and secondary sides is used as the power source for electricity heating, electrical insulation is especially important. There is no need to devise a method. The setting of the rapid heating section of the metal tube can be freely changed depending on the position of the terminal connected to the tube, and the small heat capacity makes it easy to carry out on-column heating under coal, and immediately raise and cool the temperature over the entire length of the metal tube. It is possible to In order to further facilitate the understanding of the present invention, the present invention will be specifically explained with reference to the following examples. Example 1 FIG. 1 is a diagram showing the configuration of a capillary on-column gas chromatograph that is convenient for carrying out the method of the present invention. The carrier gas passes through the flow rate control valve (1), the carrier gas supply pipe (2), and the septum rubber (3).
The sample passes from the sample introduction part (4) marked with a metal tube (5) and capillary column (6) to the detector (7). The metal capillary tube (5) K is covered with a glass fiber envelope tube (8), which penetrates the heat insulating wall (LO) of the heating tank (9) containing the capillary column (6) and enters the tank. (6) is connected to the connecting part set 1. Also, the metal thin tube is connected to the transformer a2 for heating with electricity.
Lead wires 0, 4 and 1 are attached,
The lead wire (14, tEl can be selected by the switch e) and the temperature is 5°C. This example was conducted under the following conditions. The metal tube (5) is RASloo (manufactured by Nippon Taromato Industries, Low adsorption stainless steel capillary inner diameter 11!j11 outer diameter 2m) 60a++,
The capillary column (6) has an inner diameter of 0.25 rran,
A commercially available stainless steel capillary with an outer diameter of i, o mm and a length of 15 m was coated with 5E-so (polymethylsiloxane) as a liquid phase by a dynamic method. For connection part 0, a heat-shrinkable Teflon pipe was used. The carrier gas nitrogen is adjusted with the flow control valve (1) to set the linear velocity to 60 cm/sec, the initial temperature of the heating tank (9) is set to 60°C, and the metal capillary tube (5) is connected to the lead wire ta and (14). Pass a current between 7
The temperature was adjusted to 0°C. The sample is n-paraffin C121C14
1C169C1B and C9 are almost equally matched, and it is n
- A solution diluted 50,000 times with hexane was used. Inject 3 μl of this sample into the metal capillary tube (5) through the septum rubber using a syringe with a needle with an outer diameter of o and 155 m+, and immediately switch the switch 0 to the lead wire (from 14 to 10) and insert the metal capillary tube (5). was heated to 250° C. for 15 seconds, and when the solvent peak had almost ended, the temperature of the heating tank (9) was raised at a rate of 4° C./min. The resulting chromatograph is shown in FIG. In the figure, peak kB is a peak based on the solvent, and peaks (8, Koshiki'), 90.ea and (2) are 121 due to CCCC and C2o, respectively.
14' 161 18 peak. The shape of the tail of the peak was in good condition as seen in FIG. Example 2 FIG. 3 is a diagram showing the configuration of a capillary on-column gas chromatograph for carrying out the method of the present invention. Figure 3 shows that the glass capillary column (6) K intermediate auxiliary capillary (to) is connected with the connection part (material), the metal capillary tube (5) is housed in the heating tank (9), and the lead wire number. It is the same as in Figure 1, except that j is connected to the intermediate auxiliary capillary (2). This example was conducted under the following conditions. The metal tube (5) is a stainless steel tube with an inner wall of glass lining and an inner diameter of 0.5 was and an outer diameter of 1.5 m, which has been subjected to acid washing and -silylation treatment to reduce adsorption properties, and has a length of 15 mm. . The capillary column (6) has an inner diameter of 0.1 and an outer diameter of 0.8.
It is a glass capillary column with a length of 15 m and coated with 0V-1 to a thickness of 0.3-μm. The intermediate auxiliary capillary (2) is RAS25 (low adsorption stainless steel capillary manufactured by Nippon Chromato Industries, inner diameter 0.2511II)
+1. The outer diameter is 0.6 pieces) and the length is 10 pieces. One end is connected to the capillary column (6) using a heat-shrinkable Teflon pipe to form a connection part @, and the other end is connected to a metal capillary tube (5) using a pipe connection tool with cap nuts at both ends to form a connection part ■. . The linear velocity of the carrier gas nitrogen was set to 30.7 seconds, the initial temperature of the heating tank (9) was set to 60°C, and a current was applied to the metal tube (5) from the transformer connection between lead wires 0 and 1!3. I prepared for the flow. Samples are 2.6 xylidine, 2,6 xylenol, n-decanol, n-paraffin C131C
14 and C17 are diluted approximately 50,000 times with n-hexane solvent. This sample was passed through the septum rubber (3) using a syringe with an outer diameter of 0.4 m and a length of 25I needle attached to the metal capillary tube (
5) Inject 0°3μ from behind the sample introduction part (4) on the inner wall at point 113, and immediately after that, apply a current between the lead wire tel and ℃
I did it. 3.5 minutes after the sample was injected, the solvent peak had almost finished appearing, so the temperature of the heating tank (9) was increased at a rate of 4° C./min, and heating of the metal capillary tube (5) was stopped. The obtained chromatogram is shown in Figure 4, where the peaks (
C), Kan, 1. @, @, @, cm, and c3n are the solvent n-hexane, the solute 2,6-xylidine, and 2, respectively.
．． These are peaks based on 6-xylenol, n-decanol, n-paraffins C131C14 and C17. In FIG. 4, trailing can be seen at the tail of each peak. The peaks due to n-paraffins (29, 30°31) also have tails like the peaks due to n-decanol (to), so these tails are caused by metal tubes (5), capillary columns (6), etc. It is assumed that this is not due to chemical adsorption in the sample flow path, but is due to a physical cause that may occur at the connection point (11, u) between the metal tube (5) and the capillary column (6). Ru. But a sufficiently useful - madogram was obtained. As explained above from the pupil side, the method of the present invention uses a commonly used syringe for the split method, injects the sample on-column through the septum rubber in the same way as the split method, and provides a method to obtain a chromatogram. It is something. In addition to the above-mentioned pupil side, various changes and improvements can be made within the scope of the spirit of the present invention, but all of them are included in the present invention.

[Brief explanation of the drawing]

FIGS. 1 and 3 are diagrams of a capillary on-column gas chromatograph prepared to facilitate the implementation of the method of the present invention. FIGS. 2 and 4 are examples of p-madograms obtained by carrying out the method of the present invention. 1...Flow control valve, 2...Carrier gas supply pipe,
3... Septum rubber, 4... Sample introduction part, 5°metal thin tube, 6... Capillary column, 7... Detector, 8... Empire tube, 9... Heating tank, 1σ
...insulation wall, 11.24...connection section, 12...transformer, 13, 14, 15...lead wire, 16.
...Switch, 17, 25...Peak due to solvent, 18, 19, 20, 21, 22, 26
,27,. 28, 29.31...Peak due to solute.

Claims (1)

[Claims] 1. A thin metal tube with an inner diameter of 0.5 mm or more that can be heated by electricity is attached to a sample introduction part having a septum rubber, and a capillary column coated with a liquid phase is connected to the capillary column, and the other end of the column is connected to a detector. After maintaining the initial temperature of the capillary column, the sample is injected on-column into the metal capillary tube through the septum rubber using a syringe equipped with a needle with an outer diameter of 0.4 mm or more. A method for measuring a capillary on-column gas chromatogram, which is characterized in that the temperature of a capillary column is increased by rapidly increasing the temperature of a capillary column by energizing a capillary tube. 2. The method for measuring a capillary on-column gas chromatogram according to claim 1, wherein the metal capillary has an inner diameter of 0.5 mm or more and 2.0 mm or less. 3. The method for measuring a capillary on-column gas chromatogram according to claim 1, wherein the outer diameter of the injection needle is 0.4 mm or more and 0.7 mm. 4. The inner diameter of the capillary column coated with the liquid phase is 0.2 m.
The method for measuring a capillary on-column gas chromatogram according to claim 1, wherein the capillary on-column gas chromatogram is from m to 0.35 mm. 5. The method for measuring a capillary on-column gas chromatogram according to claim 1, wherein no liquid phase exists on the inner wall of the metal capillary.