Sample Holding Device for Electrophoresis Apparatus and Sample Injection Method

The present invention relates to the gel electrophoresis separation apparatus to analyze DNA, RNA or protein, and particularly to the sample holding device for fluorescence detection type DNA sequencer or the like, and to the sample injection method thereof.

DNA analysis uses gel electrophoresis. In recent years, there has been a widespread use of the apparatus which determines DNA sequences by fluorescence labeling of DNA and analyzing the DNA fragment length in real time. According to this apparatus, 0.1 mm to 0.3 mm thick polyacrylamide gel is formed in the gap between two sheets of glass, and is used as separation medium. Part of the gel top is made undulating to form sample injection wells. The sample is injected by the microsyringe into concave wells formed between sheets of glass.

In recent years, on the other hand, attention has been drawn to the method of using as separation medium the capillary gel, i.e. the gel formed in the capillary, in place of the slab gel. This is because high speed migration is enabled by providing high electric field since the capillary gel does not produce large joule's heat. Furthermore, electrophoresis systems provided with a great number of capillary gels have been developed. Such systems are disclosed, for example, in i) Kambara et al; Nature, vol. 361 (1993), pp. 565-566, ii) Mathies et al; Nature, vol. 359 (1992), pp. 167-169, iii) Takahashi et al; Japanese Patent Laid-Open 6-138037 (May 20, 1994) and iv) Takahashi et al; U.S. patent application Ser. No. 08/337,412 (Pending). According to this method, one end of the capillary is placed into the sample container, and voltage is applied between that end and another end of the capillary, thereby injecting DNA into the capillary by employing an electric field. Furthermore, v) Kambara; Japanese Patent Laid-Open-5-72177 (1991), vi) Kambara; U.S. Pat. No. 5,277,780 (Jan. 11, 1994) and vii) Kambara; U.S. Pat. No. 5,366,608 (Nov. 22, 1994) disclose an electrophoresis system wherein the capillary gels are connected to the sample injection holes at the side opposite to the sample injection side of the sample injection holes with which there is provided the sample injection plate having a great number of sample injection holes through which a great number of samples are injected.

Furthermore, viii) Kambara et. al; Bio/Technology, vol. 6 (1988), pp. 816-821 and ix) Kambara et. al; U.S. Pat. No. 4,971,677 (Nov. 20, 1990) show how the DNA fragments migrate in the gel.

The progress of genome analysis has come to require a great deal of the DNA base sequence determinations. This has resulted in the development of a DNA sequencer using the slab gel provided with a great number of migration lanes in the slab, and devices having many migration lanes with a great many capillaries arrayed. Despite increasing quantity of analysis, however, there has been a disadvantage of requiring much time and labor for the analysis, since the sample injection method has not been improved. Namely, in the slab gel apparatus, a great number of samples are injected one after another into the well by means of a microsyringe, requiring much time and labor.

According to the method using the capillary apparatus, on the other hand, the quantity of injected samples is about one hundredth of the samples stored in the sample container, with a great majority remaining unused. When the titer plate having holes exhibiting two-dimensional distribution for adjustment of the samples, it has not been possible to utilize the simplified method of controlling the temperature by pressing the capillary against the temperature controlled plate; this has disadvantageously been very inconvenient. Furthermore, electrophoretic injection of samples into the capillary gel to allow them to migrate has disadvantageously resulted in the tip end being damaged, which cannot be re-used.

In face of said problems, an object of the present invention is to solve the problems of said prior arts, and to provide a sample holding device and method thereof which permit easy injection of the samples into the gel or slab gel in particular in the electrophoresis system.

To attain the above object according to the present invention, sample holding capillaries (a capillary is represented by a capillary tube in the present Specification) are laid out in one or two dimensional array and are made into cartridge, which is used as sample holding device. Samples are held in the capillaries of said sample holding device, and the sample holding capillaries and electrophoresis separation gels are each connected with each other; then electric field is applied thereto and samples are injected.

To be more specific, the sample holding device for electrophoresis apparatus according to the present invention has the functions of (1) holding respective samples (respectively different samples in normal cases) by means of a plurality of capillaries placed in parallel, and of (2) injecting samples into the respectively different migration lanes of the electrophoresis separation part of the electrophoresis apparatus.

The supporting block provided with a plurality of the through holes placed according to a specified layout holds said capillaries in the respective through holes, and the lower ends of the capillaries are allowed to contact the sample injection positions of the electrophoresis separation part of the electrophoresis apparatus. Alternatively, a plurality of plates having a specified thickness with said capillaries held in the through holes may be arranged in the longitudinal direction of the slender flexible film to ensure that the longitudinal direction of the capillary will perpendicularly cross that of the flexible film, and may be immobilized at specified intervals.

The sample holding capillaries can be freely attached or detached from the through holes of the supporting block by friction coupling. Alternatively, a plurality of the through holes may be arranged in a straight line, and the supporting block may be composed of two block pieces which are segmented at the position where each through hole is separated into two.

The said capillaries may be open capillaries or gel filled capillaries. When the open capillaries are used, samples are preferred to be injected into the electrophoresis part through gel filled capillaries.

Sample injection using said sample holding device can be implemented by electrophoretic sample injection as follows: The sample is held in each capillary of the sample holding device by capillarity, and the sample holding device for electrophoresis apparatus is installed on the electrophoresis apparatus so that the lower ends of the capillaries are allowed to contact the sample infection positions of the electrophoresis separation part of the electrophoresis apparatus; then voltage is applied to carry out electrophoretic sample injection.

This method is applicable to the capillary array electrophoresis apparatus, slab gel electrophoresis separation apparatus, electrophoresis apparatus with the gel formed in a plurality of grooves formed on the plate surface, and all other electrophoresis apparatuses.

The inner diameter of the sample holding capillary is preferred to be from 0.03 to 0.4 mm inclusive. Furthermore, the tube thickness is generally ranges from 0.05 to 0.2 mm inclusive, though there is no restriction whatever. The length of the sample holding capillary is normally 3 to 20 mm inclusive, and that of the gel filled capillary must be 5 to 30 mm inclusive. The block supporting the sample holding capillaries should normally have a thickness of 3 to 20 mm inclusive in the direction of the through holes. The sample holding capillaries arranged in an array are normally located at intervals of 0.4 to 9 mm inclusive.

The sample holding capillaries are composed of glass, quartz, polymer and the like, for example. Said supporting block is made up of Teflon, polymer, resin, mica and the like, for example.

The field intensity of the voltage applied for electrophoretic sample injection is 50 to 300 V/cm inclusive.

The sample holding cartridge can be installed or removed from the electrophoresis apparatus. It is easy to handle for its compact size and allows the samples to be injected automatically by means of an automatic pipetter. Combination of the cartridge with the migration part allows the samples to be injected into all migration lanes simultaneously in a short time. Injection of the sample solution into the sample holding capillaries can also be provided by suction from the lower ends of the capillaries by capillarity.

Furthermore, the capillary array cartridge can be composed of gel filled capillaries, or composition may be configured to allow the samples to be injected from the open capillary via the gel filled capillary, thereby making it possible to restrict within the capillary gel cartridge the gel portion destroyed in electrophoretic sample injection, not in electrophoresis separation part; this permits repeated use of the electrophoresis separation part.

Use of hydrophobic material to make the capillary supporting block prevents the sample solution from entering the gap formed by the supporting blocks placed on top of one another.

If the sample holding capillaries of the capillary array cartridge are composed of open capillaries alone, the reaction inside the capillary can be carried out or a specified amount of samples can be picked up and loaded into the capillary array, merely by dipping the capillary into the sample adjusted by the titer plate.

When the present invention uses for adjusting the sample the titer plate having holes exhibiting 2-dimensional distribution, sample injection is performed by allowing the capillaries to be held by the supporting block having the through holes formed in a linear array, after the sample in the titer plate has been put into each capillary. This results in the samples being injected into the electrophoresis separation slab gel or electrophoresis separation gel capillaries having the tube end of the one-dimensional arrangement (linear arrangement); then the separation gel contacts with the temperature controlled plate, thereby ensuring temperature control of electrophoresis separation gel. It is apparent that, when the temperature controlled plate is not used for temperature control, the titer plate having holes exhibiting 2-dimensional distribution is used, samples can be injected into the electrophoresis separation gel capillaries having the tube end of the 2-dimensional arrangement.

FIG. 1 is a perspective view representing a sample holding capillary cartridge in the first embodiment;

FIG. 2 is a schematic illustration representing the sample holding capillary cartridge in the first embodiment as installed in the electrophoresis apparatus;

FIG. 3 is a perspective view representing another sample holding capillary cartridge in the first embodiment;

FIG. 4a is a plan view representing still another sample holding capillary cartridge in the first embodiment;

FIG. 4b is a side view representing the sample holding capillary cartridge of FIG. 4a;

FIGS. 5a and 5b illustrate the method of using the sample holding capillary cartridge of FIGS. 4a and 4b;

FIG. 6 is a schematic illustration representing the capillary array using the sample holding capillary cartridge in the second embodiment;

FIG. 7 is a schematic perspective illustration representing the method of injecting the samples into the sample holding capillary cartridge in the second embodiment;

FIG. 8 is a schematic perspective illustration representing electrophoresis apparatus using the sample holding capillary cartridge in the fourth embodiment;

FIG. 9 is a schematic cross sectional view representing electrophoresis apparatus provided with another sample holding capillary cartridge in the fourth embodiment; and

FIG. 10 is a schematic cross sectional view representing the state in which the sample holding capillary cartridge in the third embodiment is installed on the migration capillary.

Application of the present invention can be broadly classified into two types; slab gel sample injection and capillary array sample injection. The following describes the details of both of them with reference to embodiments:

Embodiment 1

The present embodiment relates to the slab gel. In the conventional slab gel, samples have been injected into the wells enclosed by glass plate and gel formed on the top of the conventional slab gel. Each well is isolated by gel, however, insufficient gel strength has make it very difficult to decrease the space between wells. Another disadvantage is that the gel once used cannot be used again because the wells are deformed.

The present embodiment uses the sample holding capillary cartridge 1 illustrated in FIG. 1. In this example, capillary 3 is inserted in the holes on the glass or acryl resin block 2 (5 mm thick) and the surface 8 is ground; this is used as the sample holding capillary cartridge 1.

This embodiment uses the capillary 3 having an inner diameter of 0.1 mm and an outer diameter of 0.3 mm, and block 2 is provided with holes having a diameter of 0.3 mm are arranged at intervals of 1 mm. These holes may be circular or rectangular. The hole tops are tapered in the form somewhat similar to the funnel.

When the sample solution is mounted on the top of the capillary, it is sucked inside by capillarity, thereby filling the lowest end with sample solution. In this case, use of an automatic pipetter permits automatic injection of samples into each of the capillaries in the sample holding capillary cartridge.

Alternatively, the bottom of the capillary 3 is put into the sample container, and sample solution is sucked by capillarity, thereby injecting the sample. In this case, sample can be sucked with capillary 3 removed from the block 2, and capillary 3 after sample injection can be inserted into the holes of block 2.

FIG. 2 illustrates the connection between the sample holding capillary cartridge and slab gel. The cartridge 1 is installed on the slab gel 4, and the bottom of each capillary 3 injected with samples is made to contact the top of the slab gel 4. Then the top of the cartridge is filled with buffer solution 5, to which electric field is applied. The cartridge top can be filled with the buffer solution, for example, by attaching onto the block 2 of the cartridge 1 under water tight condition the casing 7 provided with opening on the bottom thereof via the O-ring, or by providing the top of the block 2 with a dent to store buffer solution 5. Voltage of 1.4 kV is applied to both ends of the slab plate, and 100-volt voltage is applied to the upper and lower ends of the capillary cartridge for about five seconds to inject the sample into the gel. After injecting the sample into the gel, the cartridge may be removed so that buffer solution 5 is brought in direct contact with the slab gel 4.

Alternatively, electrophoresis may be carried out with the cartridge remaining in position. The bottom of the gel 4 is in contact with the buffer solution 6 to serve as a bottom end for application of electric field. The sample injected into the gel is made to migrate and is separated by the voltage applied across the gel. The position a specified distance away from the migration starting position is irradiated by laser beam to detect the fluorescence emitted from the sample passing thereby.

FIG. 3 shows a variation of the sample holding capillary cartridge shown in FIG. 1. This cartridge comprises the blocks 2a and 2b split into two segments and capillaries 3. The split surface of the blocks 2a, 2b of the cartridge are provided with the grooves 3a, 3b to accommodate the capillaries 3. Each capillary 3 is put into the sample solution to suck sample by capillarity, and is then placed on the groove 3a on the block 2a split into two. After that, blocks 2a and 2b are integrated to form a cartridge.

FIGS. 4a and 4b illustrates another example of the sample holding capillary cartridge; FIG. 4a is a plan view while FIG. 4b is a side view. This cartridge is made up, for example, of a plurality of the plates 32 having a thickness of 0.5 mm made of the acryl resin or Teflon (registered trade name) bonded onto the flexible film 31 having a thickness of about 0.02 mm, and capillaries 3 inserted in holes provided in parallel on the surface of the plate 32.

FIGS. 5a and 5b illustrate the sample holding capillary cartridge given in FIGS. 4a and 5b. This cartridge can be folded at the portion of the flexible film between the plates 32 adjacent to this cartridge, and the distance between adjacent capillaries 3 can be changed freely, depending on the degree of this folding. Accordingly, when a plurality of sample solutions placed on the titer plate are injected in respective capillaries 3, for example, it is possible to carry out simultaneous injection of a plurality of sample solutions by folding so that the spacing between capillaries 3 will be equal to that of sample wells in the titer plate, as illustrated in FIG. 5a. After sample injection into capillaries 3, adjacent plates 32 are made to contact with one another, as illustrated in FIG. 5b; then the spacing between the capillaries 3 holding the sample solutions becomes about 1 mm, and samples can be injected into the slab gel, as in the case of the sample holding capillary cartridge shown in FIG. 1.

At the time of electrophoretic sample injection into the gel using the sample holding capillary cartridge illustrated in FIGS. 3, 4a, 4b, 5a and 5b, the voltage can be applied by inserting the needle electrodes into capillaries 3.

Embodiment 2

The present embodiment relates to the capillary array type electrophoresis apparatus.

FIG. 6 shows an example of the capillary array device equipped with the sample injection part according to the present invention. The tip 10 of the gel capillary array 15 of the electrophoresis separation part on the sample injection side is distributed in two dimensions and, and is supported by the supporting plate 11 made of hydrophobic plastic material such as Teflon (tradename registered), as illustrated in FIG. 6. Use of hydrophobic plastic material to manufacture the supporting plate 11 is intended to ensure that the sample will not be held on the surface of the supporting plate. The supporting plate 11 is provided with holes having a diameter corresponding to the outer diameter of the capillaries of the electrophoresis separation part. Each capillary of the gel capillary array 15 is inserted into each of these holes and is held by friction to ensure that the tip of the capillary will be level with the top of the supporting plate 11.

The sample injection capillary cartridge 12 is composed of the sample holding capillary 13 and the supporter 14 comprising hydrophobic material such as Teflon, and serves to ensure that the sample holding capillary 13 will be arranged in the same layout as the tip 10 on the sample injection side of the gel capillary array 15. After filling the sample holding capillary 13 with the gel and injecting the sample therein, the capillary 13 is placed on top of the supporting plate 11, and is connected with the separation gel capillary 15. Positioning of the supporting plate 11 and the supporter 14 is performed by inserting the pins 61 and 62 of the supporter 14 into the holes 63 and 64 provided on the supporting plate 11. The thickness of the supporter 14, that is the length of the sample holding capillary 13 is 0.5 to 2 cm inclusive. The sample holding capillary 13, is inserted into the holes provided on the supporter 14, and is held in that position by friction. Numeral 16 denotes the measurement part of the capillary array.

The upper part of the sample holding capillary cartridge 14 is filled with the buffer solution as in the case of Embodiment 1, and electric field (150V/cm) is applied to cause electrophoresis. Since fragments migrate from the sample holding capillary 13 to the separation part capillary 15 sequentially starting from the shortest fragment, ensuring electrophoresis for a proper length of time prevents the long fragments in the sample or template DNA from being injected into the capillaries of the separation part. In several minutes, the sample holding capillary cartridge 12 is removed, and electric field is applied to the separation part capillaries to continue electrophoresis separation; then the template DNA and long DNA fragments obtained in complementary chain extending reaction (sequence reaction) remain in the sample injection capillary 13; thus, the signals appearing in the measured DNA fragment spectra can be reduced to zero at a specified fragment length or more. This ensures the repeated measurements without being mixed with the signals of the previous samples, despite repeated injection of the samples into the same gel capillaries.

Furthermore, the sample contains almost no salt. Compared with the gel containing a lot of salt, the electric resistance is high. This provides a high electric resistance in the area where the sample is present in the initial phase of electrophoresis, and high voltage is applied to the shorter part; as a result, the gel close to the sample injection site may be damaged by heat generation, making it impossible to make a repeated use of the same gel. According to the present embodiment, the damaged site is located inside the sample holding capillary, without the possibility of the gel of the electrophoresis part being damaged. This allows repeated use of electrophoresis separation part gel.

The gel used in the sample holding capillary may be agarose, N-isopropylacrylamide gel or the similar material which is turned into liquid with the reticular structure changed by heat generation. In this case, if the solution containing DNA is made to migrate through the capillary filled with this gel, the DNA is trapped in the gel because of its larger molecular size, and salts can be removed there; this makes it possible to concentrate the DNA in this gel. Then it is connected with the separation capillary and is made to migrate by raising the temperature; this allows the DNA to be concentrated to enter the separation part with high efficiency.

The sample migrating inside the gel capillary array 15 is measured by the capillary array measuring part 16. As disclosed in said U.S. Pat. Nos. 5,277,780 and 5,336,608 and Japanese Patents Laid-open No.6-138037 (1994) and No.5-72177 (1993), simultaneous measurement of all capillaries may be made using one or more immobilized laser beams, or each capillary may be measured in sequence through scanning by laser beam.

The behavior of the DNA fragments in the gel has been examined in details using the slab gel [e.g. said Kambara et al; Bio/Technology, vol. 6, pp. 816-821 (1988)]. Electrophoresis by 22 cm in the 6% polyacrylamide at the field intensity of 50 V/cm requires About 4 hours in the case of the 400 bases long DNA. Electrophoresis time is inversely proportional to the electric field and is proportional to the gel length. Thus, when electric field (150V/cm) is applied to a 1 cm sample holding capillary, the 400 bases long DNA enters the separation gel capillaries at the rate of 4 min. or less. Assume that the length of the separation gel capillary is l, the length of the sample holding gel capillary is .DELTA.t, and the time required to remove the sample holding gel capillary is t.sub.0 min. The field intensity and gel concentration is assumed to be the same at both of separation and sample holding gel capillaries; then the last long DNA having entered the separation gel capillary reaches the measuring part in t=(l.t.sub.0 /.DELTA.l) minutes.

This allows the next sample to be injected after "t" minutes. When "l" is 25 cm and gel concentration is 6%, "t" is about 90 minutes. That is, this allows sample injection and measurement to be repeated every 90 minutes. Reduction in gel concentration leads to shorter electrophoresis time. This allows one and the same gel to be used for ten times or more. A robot used for installation and removal of the sample injection part will provide a base sequencing capacity of 4K bases per day per capillary, namely, a total of 400K bases per day in terms of 100 bundled capillary arrays.

Electrophoretic sample injection is used to introduce samples into the sample holding capillaries. As illustrated in FIG. 7, the sample is held in the open capillary 19 and is connected to the top of the sample holding capillary 13 inside the cartridge; then voltage is applied to perform electrophoretic sample injection. As discussed previously, electric field may be applied via the buffer solution. Alternatively, the needle electrode may be inserted into the open capillary 19. The open capillary 19 is held by the cartridge 17 having the same structure as that of the sample holding capillary cartridge 12, and is bonded placed on top of the sample holding capillary cartridge 12. To inject the sample into the open capillary 19, the sample is placed on the top and is filled into the capillary by capillarity. It is apparent that capillaries may be dipped into the sample solution stored in the sample container to suck the sample by capillarity, thereby storing it into the cartridge. It is also possible to connect it directly to the tip of the separation capillary. Numerals 14 and 18 in FIG. 7 denote supporters.

Embodiment 3

The sample holding part disposed 2-dimensionally was used in Embodiment 2 to inject the sample into the electrophoresis separation gel capillary. It is also possible to use the sample holding part disposed linearly as in the present Embodiment. FIG. 10 illustrates the present Embodiment as one example. The electrophoresis separation capillaries 15 are bundled in a sheet and are held by the supporting plate 11. The sample injection parts are arranged linearly at intervals of about 1.5 mm. The polyimide coated tube produced by Polymicrotechnology Inc. in the United States was used as capillary 15. Capillary 15 has an inner diameter of 0.1 mm and outer diameter of 0.2 mm. The sample holding cartridge 51 is designed in such a way that the acryl plate having a thickness of 11 to 14 mm inclusive (the plate made of other resin or metallic material may be used) is provided with the holes comprising the sample holding part 53 having a diameter of 0.1 to 0.2 mm inclusive and a length of 2 to 5 mm inclusive, and the capillary guide 52 having a diameter of 0.2 to 0.3 mm inclusive and a length of about 5 mm. To ensure easy sample injection and insertion of the capillary 15, both ends of each hole are tapered, as the diameter being greater at the position closer to the end. The sample is injected into the hole as the sample holding part 53, and the sample holding cartridge 51 is fixed to a cartridge holder (not illustrated). The end of the array of the electrophoresis separation capillary 15 is located on the lower side of the sample holding cartridge 51. Furthermore, a group of the electrodes 54 lined at the same pitch as that of the holes of the sample holding part 52 and the capillary guide 52 are supported by the electrode holder 55 on the upper sides of the sample holding cartridge 51. The sample holding cartridge 51 and the electrode holder 55 are slide so that the electrophoresis separation capillary 15 and the electrode 54 contact the sample in the sample holding part 53; then electric field is applied on the capillaries to inject the sample electrophoretically into the gel in the electrophoresis separation capillary 15.

It is obvious that the inner diameter of the sample holding capillary may be made greater than the outer diameter of the separation gel capillary, and the end of the gel capillary may be partially inserted into the sample holding capillary, thereby injecting the sample.

The sample holding capillaries are not used in the present embodiment, but the similar effects as those obtained by sample holding capillaries are obtained by utilizing the sample holding cartridge 51 having unique holes, as stated above.

The inner diameter of the hole of the sample holding part 53 of the sample holding cartridge 51 shown in the present embodiment should normally be within the range of the outer or inner diameter of the electrophoresis separation capillary 15. The inner diameter of the capillary guide 52 is normally about the outer diameter of the capillary 15 to 0.1 mm larger than that so that the capillary 15 can be inserted and held therein. The taper on both ends of the hole is only required to ensure easy sample injection and capillary insertion; there is no restriction whatever. The length of the sample holding part 53 is 2 to 5 mm inclusive. The length of the capillary guide 52 is about 5 mm, but is not restricted thereto so long as the capillary 15 is held easily.

In the present embodiment, the sample holding part is disposed linearly, but it may be disposed 2-dimensionally if the capillary guide and electrophoresis separation gel capillary group are aligned.

Embodiment 4

FIG. 8 illustrates an embodiment of applying the present invention to the grooved gel where the finer groove provided on the glass surface is used as electrophoresis capillary. The cross section of the slender groove 20 provided on the quartz plate 21 as the glass plate is 0.5 mm wide and 0.2 mm deep with a pitch of 1 mm. The quartz plate 21 equipped with the slender groove 20 and flat quartz plate 22 are put together to form the capillary migration lane, which is filled with gel 50. The quartz plate is held horizontal and the sample injection window 23 is provided on the sample injection side of the flat quartz plate 22. The downstream side of the groove is connected to a gap space 26 of 0.1 to 0.2 mm width filled with buffer solution. The space is sandwiched with two quartz plates 24 and 25 having flat surfaces. The sample being eluted from the gel end migrates into the gap space 26, where the buffer solution injected from the buffer solution injection port 27 flows in a laminar flow, which prevent the DNA band to diffuse. Furthermore, laser beam is irradiated in the flow channel to allow fluorescent measurement. Laser beam is irradiated on the gap space 26 along the quartz plane as in the case of Embodiment 1, or the laser beam from the position perpendicular to the plane is scanned.

The sample is held inside the capillary 29 of the gel capillary cartridge 28 as in Embodiment 2, and the capillary 29 is inserted into the sample injection window 23. Voltage is applied between the capillary and the downstream end for electrophoresis to inject the sample into the separation gel 50. The present embodiment uses the open capillary or gel capillary as the sample holding capillary 29. The gel capillary also serves to prevent the gel in the separation gel capillary from being damaged. In FIG. 8, the reference numeral 30 denotes a supporter for capillary 29.

When the sample is held by the open capillary and is injected, the gel in the separation part is likely to be damaged, so gel cartridge 40 is placed between open capillary cartridge 43 and the separation gel part, as illustrated in FIG. 9. Where, detachable capillaries 41 are put in the cartridge 40. This is effective in preventing the gel of the analysis part from damage. In this case, supporters 42 and 45 are preferably made of hydrophobic materials such as Teflon. The cartridge 40 comprises the gel capillaries 41 inserted into the holes provided on the supporter 42, while the open cartridge 43 is composed of the open capillaries 44 inserted into the holes provided on the supporter 45. Each capillary is held in each hole by friction. When the composition is as shown in FIG. 9, the gel inside the gel cartridge 40 is damaged by high voltage applied in the initial stage of electrophoresis, without separation gel 50 being damaged. This allows repeated use of electrophoresis separation gel 50.

In another example, this gel can be composed of gel soluble by heating. First, the capillary cartridge holding the sample is put on the gel filled capillary cartridge. Then a high electric field is applied on the capillaries for connecting sample in the gel through electrophoresis. Then the sample holding gel cartridge is put on the top of the separation capillaries, and temperature is raised to make the sample holding gel dissoluble, causing the sample to migrate rapidly to the separation capillary to be injected. In this case, the gel in the gel cartridge constitutes a fine reticular form at low temperature; this does not easily allow the DNA sample to pass by. When temperature is raised, it becomes liquid, allowing the DNA to pass by easily.

Reference numerals 21, 22 and 23 in FIG. 9 denote the quartz plate provided with slender grooves, flat quartz plate, and sample injection window, respectively, as in FIG. 8.

In the above figures, the same numerals denote virtually the same parts unless otherwise specified.

As discussed above, the sample holding capillary cartridge is connected to the electrophoresis separation part to carry out electrophoretic sample injection, according to the present invention. This ensures very easy sample injection. Furthermore, in capillary electrophoresis, gel breakdown is likely to occur around the sample injection end, preventing re-use of the gel separation plate. The analysis gel is protected and repeated use is possible by filling the sample holding capillaries with gel or installing the detachable gel capillaries between the gel and analysis gel capillaries, resulting in considerable improvement in operability.