Mixer for liquid chromatograph

A mixer for a liquid chromatograph mixes plural kinds of liquids. It has a first mixer 45 for forcibly agitating the liquids and a second mixer 58 for agitating the liquids in accordance with a flow rate. Liquid passages of the first and second mixers 45, 58 are in communication with each other, and the first and second mixers 45, 58 are integrally mounted.

FIELD OF THE INVENTION 
This invention relates to a mixer for a liquid chromatograph, and more 
particularly to a gradient mixer, for example, suited to be used a liquid 
chromatograph, which is capable of correctly following a gradient program, 
in which a sufficient mixing effect, as well as an enhancement of the 
mixing efficiency, can be obtained, and in addition the liquid 
chromatograph to be designed small in size and light in weight. 
DESCRIPTION OF THE PRIOR ART 
A gradient elution method according to a liquid chromatograph is a method 
for analysis of a sample containing a plurality of ingredients, in which 
elution is performed by linearly, exponentially or stepwise gradually 
changing characteristics such as the kinds of mobile phase solvents, 
condensation of salt, pH, and the like from a weak solvent strength to a 
stronger solvent strength. 
Use of this method makes it possible to obtain suitable separation elution 
conditions even when a large number of ingredients are to be analyzed. 
Also, while ensuring separation of the peak of ingredients which are 
eluted rapidly, spread of the peak of ingredients which elute slowly is 
suppressed, thereby enhancing the sensitivity of detection. 
Gradient mixers are used for mixing mobile phase solvents. With respect to 
the gradient mixers, there is known a type in which beads are filled in a 
coil or a mixing chamber. There are also known a static mixer and a 
dynamic mixer, as disclosed in Japanese Laid-Open Utility Model 
Publication No. 6759/1996, the former being designed such that dead volume 
is disposed in a mixing chamber and a plurality of solvents are almost 
forcibly agitated, while the latter is designed such that a plurality of 
solvents are forcibly agitated. 
Among those conventional gradient mixers, the coil-like static mixer 
requires a predetermined length dimension sufficient to obtain a 
sufficient mixing result and is, therefore, readily subject to external 
conditions such as the installation space, the arrangement, etc. On the 
other hand, the dynamic mixer has problems such that concentration of 
ingredients in a direction of flow of the solvents is lessened to zero and 
therefore, the ingredients are degraded in accuracy and also in 
reproduction. In addition, no satisfactory result of analysis can be 
obtained because the replacement reaction is slow. 
Although the conventional liquid chromatograph mixers are easy to perform a 
mixing operation because the dead volume is generally large, it has a 
problem is being unable to correctly follow the gradient program because 
mixing ratios of the solvents, which vary with the passage of time are 
made uniform. This problem is particularly serious when the flow rate is 
slow. 
Moreover, a long time is required for the solvent to return to its initial 
composition and for the column to return to its initial state, and a 
reproduction of analysis is inferior. 
On the other hand, if the dead volume is small, there are problems such 
that no sufficient mixing effect can be obtained, and noise is increased 
so as to make a reproduction of analysis extremely bad. Especially, in 
case the mixing ratio is abruptly changed, an imperfect mixing results and 
the physical property of the mobile phase is non-uniform in a vertical 
section in a direction of movement, thus resulting in an adverse effect on 
the separation of the ingredients to be analyzed and the result of 
analysis. 
Therefore, it is demanded that gradient mixers can correctly follow the 
gradient program and that a sufficient mixing effect can be obtained. 
On the other hand, the conventional mixers are encumbered with problems 
such that they are readily adversely affected by pulsation of a liquid 
feed pump, and noises are likely to occur. As a consequence, the accuracy 
of analysis is sacrificed. 
In this case, if any buffer means such as a coil suitable for absorbing the 
pulsation should be provided, followability to the gradient program would 
be degraded because a flow passage of the solvent is increased in volume 
to that extent. Moreover, the form of the peak of the chromatograph would 
be spread and a large sized design and heavy weight of the liquid 
chromatograph result. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide a mixer for 
liquid chromatograph in which a sufficient mixing effect, as well as 
enhancement of the mixing efficiency, can be obtained. 
Another object of the present invention is to provide a mixer for a liquid 
chromatograph capable of correctly following a gradient program. 
A further object of the present invention is to provide a mixer for liquid 
chromatograph in which the number of parts can be reduced and the 
chromatograph can be made small in size and light in weight. 
A still further object of the present invention is to provide a mixer for a 
liquid chromatograph suited to be used as a gradient mixer for a liquid 
chromatograph. 
A yet further object of the present invention is to provide a mixer for a 
liquid chromatograph which can be used not only as a dynamic mixer but 
also as a static mixer. 
A mixer for a liquid chromatograph for mixing plural kinds of liquids 
comprises a first mixer for forcibly agitating liquid, a second mixer for 
agitating liquid in accordance with a flow rate, and a liquid passage for 
the first mixer and a liquid passage for the second mixer in communication 
with each other, the first and second mixers being integrally mounted. 
Owing to the above construction, a sufficient mixing effect, as well as 
enhancement of mixing efficiency, can be obtained, and in addition, the 
number of parts can be reduced and a small-sized design and a light weight 
can be obtained.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention will now be described in a form of one preferred 
embodiment as illustrated, in which the present invention is applied to a 
gradient mixer for a liquid chromatograph. FIG. 1 shows an analytical 
system for aldehydes contained in exhaust gas from automobiles. In the 
Figure, reference numeral 1 denotes a column oven of a liquid 
chromatograph. A rotary control type six port valve 2 for column switching 
is disposed within the oven 1. The six port valve 2 includes six ports P1 
through P6 which are in communication with the outside. One end of a 
dilution tube 3 is connected to the port P1, opposite ends of a 
condensation tube 4 are connected to the ports P2, P5, one end of an 
analytical tube 5 is connected to the port P3, one end of a mixing tube 6 
is connected to the port P4, and one end of a discharge tube 7 is 
connected to the Port P6. 
The other end of the dilution tube 3 is in communication with a dilution 
liquid 9 such as water contained in a dilution liquid container 8. A 
liquid feed tank 10 for the dilution liquid 9 is connected to the tube 3 
on its upstream side. A switch valve 11 is interposed between the dilution 
liquid container 8 and the liquid feed pump 10. One end of a cleaning tube 
12 is connected to the switch valve 11, and the other end of the cleaning 
tube 12 is in communication with a cleaning fluid 14 received in a 
cleaning fluid container 13. 
A three port valve 15 is connected to the dilution tube 3 on the downstream 
side of the liquid feed pump 10, an injector 16 for injecting a sample 
containing DNPH (2,4-dinitrophenyhydrazine) aldehydes is connected to the 
three port valve 15 on its downstream side, and a mixer 18 is connected to 
the injector 16 on its downstream side through a three port valve 17. The 
mixer 18 used in this embodiment is a second mixer as later described. 
A bypass tube 19 is connected between the three port valves 15 and 17. A 
resistor setter 20 is connected to the bypass tube 19 on its upstream side 
and first ends of a plurality of resistor tubes 21 having various passage 
resistance values are connected to the resistor setter 20 so that the 
resistor tubes 21 can selectively be switched. 
[The other end of each resistor tube 21 is connected to a joint 22 which is 
provided with seven ports, and the bypass tube 19 is connected to the 
joint 22. 
A condensation column 23 is connected to the condensation tube 4, the other 
end of the analytical tube 5 is in communication with a drain, an 
analytical column 24 is connected to the analytical tube 5, and a detector 
25 is disposed in the analytical column on its downstream side. 
A mixer 26 is connected to the other end of the mixing tube 6, and 
downstream side end portions of a plurality of elute conduits 27, 28 are 
connected to the mixer 26. Upstream side end portions of the elute 
conduits 27, 28 are in communication with various kinds of elutes 31, 32 
contained in elute containers 29, 30. 
[In this embodiment, 10% of THF (tetrahydrofuran) is used as the elute 31, 
and CH3CN (acetonitrile) is used as the elute 32. They can be supplied to 
the mixer 26 through the liquid feed pumps 33, 34. 
[The liquid feed pumps 33, 34 are controllable in discharge quantity based 
on various conditions for analysis and in accordance with a gradient 
program, thereby enabling the formation of a predetermined mixing ratio 
for the elutes 31, 32. 
The elute conduits 27, 28 are preferably provided on their downstream side 
end portions or connection ports 35a, 35b with a check valve for 
preventing a back-flow of the elutes 31, 32. 
As shown in FIG. 2, the mixer 26 includes a three-way joint 35 into which 
end portions of the elute tubes 27, 28 can be screwed, and a sleeve-like 
cap 36 into which a downstream side end portion of the mixing tube 6 can 
be screwed. They are integrally joined by screwing an outlet tube 37 of 
the three-way joint 35 into a joint hole 38 of the cap 36. 
In the illustration, reference numeral 37a denotes a threaded portion 
formed in a peripheral surface of the end of the outlet tube 37, and 38a, 
a threaded portion formed in an inner surface of the joint hole 38. 
Within the three-way joint 35, an inlet port 39 is provided. The inlet port 
39 is in communication with connection ports 35a, 35b of the elute 
conduits 27, 28. Within the outlet tube 37, a concave chamber 40 having an 
enlarged diameter is defined. An outlet port 41 in communication with the 
inlet port 39 is opened at a bottom portion of the concave chamber 40. 
A spacer 42 is received in the bottom portion of the concave chamber 40, a 
recess 43 is formed in an axial direction of the spacer 42, and a passage 
44 in communication with the outlet port 41 is formed in a bottom portion 
of the recess 43. A first mixer 45 of a dynamic type is received in the 
recess 43. 
The first mixer 45 includes a housing 46 for dividing outside. A mixing 
chamber 47 having a small volume is defined within the housing 46. An 
inlet/outlet port of the mixing chamber 47 is tapered so that a dead space 
of the inlet/outlet port is reduced. 
Through-holes 48, 49 in communication with the mixing chamber 47 are 
disposed at opposing locations of the housing 46. The through-hole 49 is 
in communication with the recess 43. 
In this case, the housing 46 may be eliminated and an agitator as later 
described may be received directly in the recess 43. By doing so, a dead 
volume caused by the housing 46 is reduced and the number of parts is 
reduced, too. At that time, the recess 43 is preferably made as compact in 
volume as the mixing chamber 47 and slightly reduced in diameter on both 
its upstream and downstream sides so that the dead volume may be reduced. 
An agitator 50 made of a magnet coated with Teflon (merchandise name 
manufactured by Du Pont) is rotatably received in the mixing chamber 47. 
The agitator 50 is formed in the shape of a stone as is used in a Go game 
(Japanese chess), as shown in FIG. 3, or in the shape of a ball as used in 
rugby football, or in the shape of a circular sleeve. The agitator 50 is 
normally located on an inner opening portion of the through-hole 48. 
In the illustration, reference numeral 51 denotes an agitation motor 
installed immediately under the three-way joint 35. The motor 51 is 
variable in speed of rotation within a range of from 0 to 500 rpm. An 
output shaft of the motor 51 is provided with a rotor 52 made of a magnet 
and having a generally U-shaped configuration. Owing to this arrangement, 
the agitator 50 is drawn by magnetic force of the rotor 52 such that the 
agitator 50 can be rotated in synchronism with the rotor 52. 
A mixer base 53 is received on the spacer 42. The mixer base 53 is provided 
at axially opposite end portions thereof with recesses 54, 55. They are in 
communication with each other through an introduction hole 56. 
The recess 54 is disposed opposite the recess 43, and a filter 57 is 
attached to the recess 54. The recess 55 is in communication with the 
joint hole 38. One end of a second mixer 58 of a static mixer type is 
received in the recess 55 and the other end is inserted into a fitting 
hole formed in an inner part of the joint hole 38. 
The second mixer 58 is of a circular sleeve-like configuration. The second 
mixer 58 comprises, as shown in FIGS. 4 and 5, an outer sleeve 60 made of 
metal, and an inner sleeve 61 made of metal or ceramic. A mixer tube 62 
made of ceramic is integrally attached to inside the outer sleeve 60. A 
lead groove 63 is axially spirally formed in an inner surface of the mixer 
tube 62. The groove 63 is of a generally arcuate configuration in section. 
An arrangement pitch P of the spirally formed groove 63 is axially 
slightly reduced or increased. 
In this case, the mixer tube 62 is preferably made of other hard synthetic 
resin, Teflon, or ceramic than metal because if an outer sleeve 19, an 
inner sleeve 61 and a mixer tube 62 made of metal should be used for 
analyzing a biological sample, the sample would be deposited on an inner 
surface of the mixer tube 62 and denatured. 
The inner sleeve 61 is of a circular sleeve-like configuration. An outside 
diameter d of the inner sleeve 61 is smaller than an inside diameter D of 
the mixer tube 62. A small gap e to serve as a flow passage for an elute 
is formed between the inner sleeve 61 and the mixer tube 62. A lead groove 
64 is axially spirally formed in a peripheral surface of the inner sleeve 
61. The groove 64 is of a generally arcuate configuration in section. A 
width of the groove 64 is almost the same as that of the lead groove 63 
and an arrangement pitch P of the spirally formed groove 64 is larger than 
the afore-mentioned arrangement pitch p. The spiral groove 64 is axially 
formed at generally equal pitches. 
In this case, the arrangement pitch p of the lead groove 63 may be equally 
formed and the arrangement pitch P of the lead groove 64 may be axially 
slightly increased or reduced. By doing so, the lead groove 63 can more 
easily be formed compared with an irregular arrangement pitch. 
Moreover, both the pitches p and P may be axially slightly increased or 
reduced. By doing so, a passage 65 for elute formed by the confronting 
lead grooves 63, 64 can be varied in sectional configuration and sectional 
area to enhance the mixing effect and efficiency. 
In the above embodiment, the filter 57 and mixer 53 are spacedly interposed 
between the first mixer base 45 and the second mixer 58. However, it is 
preferred that they are arranged in as much proximal a relation as 
possible. By doing so, the mixer 26 can be designed small in size and 
light in weight, and in addition, the elutes 31, 32 mixed by the first 
mixer 45 can rapidly be fed to the second mixer 58. 
The mixer for liquid chromatograph thus constructed comprises the first 
mixer 45 of a dynamic type and the second mixer 58 of a static type 
integral with the first mixer. Accordingly, the number of parts is reduced 
compared with a case where those mixers 45, 58 are separately situated. 
Moreover, the time and labor required for the mounting thereof are reduced 
and a mounting space is easily obtained, thus enabling them to be 
installed on the column oven. 
The first mixer 45 includes a single mixing chamber 47 and its volume is 
designed to be as compact as possible. Accordingly, the mixer 45 can be 
designed small in size compared with as case where the mixer includes a 
plurality of mixing chambers. Moreover, a mixing of the liquid in a 
vertical direction to the flowing direction of the liquid as later 
described is enhanced to enhance followability to the gradient program. 
A method for analyzing aldehydes contained in exhaust gas from automobiles 
in the analytical system of FIG. 1 and an operation thereof will now be 
described. 
First, the switch valve 11 is operated have the dilution tube 3 
communicated with the dilution liquid 9, and the cleaning tube 12 is 
closed. 
Then, the three port valves 15, 17 are operated to have the liquid feed 
pump 10, the injector 16 and the mixer 18 communicated with one another. 
On the other hand, opposite ends of the bypass tube 19 are closed. 
Then, the six port switch valve 2 is operated to have the port P1 
communicated with the port P2, the port P3 with the port P4, and the port 
P5 with the port P6, respectively. 
By doing so, the dilution tube 3 is communicated with the condensation tube 
4 through the ports P1, P2, and the downstream side end portion of the 
condensation tube 4 is communicated with the discharge tube 7 through the 
ports P5, P6. 
Further, the elution liquid conduits 27, 28 are communicated with the 
analytical tube 5 through the ports P4, P5, and further communicated with 
the drain through the detector 25. 
When the liquid feed pump 10 is activated under such circumstances, the 
dilution liquid 9 in the dilution liquid container 8 is sucked up, then 
passed through the dilution tube 3 and fed to the injector 16. When a 
sample containing DNPH (2,4-dinitrophenyhydrazine) aldehydes contained in 
the exhaust gas is injected to it through the injector 16, the sample is 
mixed with the dilution liquid 9 and moved to the mixer 18 where the 
sample and the dilution liquid 9 are mixed. This liquid mixture flows into 
the six port valve 2. 
The liquid mixture is moved to the condensation tube 4 via the port P1, 
port P2 of the six port valve 2 to condense specific gradients in the 
sample at the condensation column 23 and is accumulated. Thereafter, the 
liquid mixture is returned to the six port valve 2, moved to the discharge 
tube from the port P6 via the port P6, and then discharged. 
On the other hand, on or about the condensation of the sample, the 
agitation motor 51, the liquid feed motor 51 and the liquid feed pumps 33, 
34 are activated. 
When the agitator 51 is activated, the rotor 52 is rotated to draw the 
agitator 50 within the mixing chamber 47 by its magnetic force so that the 
agitator 50 is drawn to the bottom portion of the mixing chamber 47 for 
synchronous rotation. 
When the liquid feed pumps 33, 34 are activated, the elutes 31, 32 in the 
elute containers 29, 30 are sucked up and introduced into the elute tubes 
27, 28. Then, the elutes 31, 32 are moved to the three-way joint 35 and 
converged from the inner inlet port 39 via the outlet port 41. Thereafter, 
they are moved from the passage 44 through the through-hole 48 and 
introduced into the mixing chamber 47 of the first mixer 45. 
The elutes 31, 32 are forcibly agitated for mixture by the agitator 50, 
which is rotating in the mixing chamber 47, and then flow from the outlet 
port 49 to the recess 43. 
In this case, because the mixing chamber 47 is small in volume and of a low 
dead volume, the elutes 31, 32 are rapidly mixed, thereby enhancing a 
vertical mixture to the flowing direction thereof, i.e., a mixture in 
which the mixing ratios of the two kinds of liquids are gradually varied. 
Thereafter, a liquid mixture of the elutes 31, 32 is moved through the 
filter 57 so that foreign matter is removed therefrom. The liquid mixture 
is then moved through the introduction hole 56 and introduced to the 
second mixer 58. 
In this case, because the introduction hole 56 is extremely reduced in 
diameter and small in size, the volume of the introduction hole 56 is 
suppressed to be as small as possible, thereby maintaining the mixing 
state of the liquid mixture moving therethrough so that the mixture will 
not be denatured. 
In the second mixer 58, the liquid mixture of the elutes 31 and 32 is moved 
spirally around the inner periphery 61 along the passage 65 defined by the 
peripheral surface of the inner sleeve 61 or the lead groove 64. During 
the flowing process, the liquid mixture is caused to mix with a secondary 
stream i.e., a vertical flow to the flowing direction thereof, and thus 
the condensation gradient is maintained. 
In this case, a plurality of passages 65 are formed in the periphery of the 
inner sleeve 61 as shown in FIG. 6 and have various sectional areas and 
sectional configurations as shown. The passages 65 are strictly changed in 
radius of curvature so that various actions of the secondary stream are 
set. 
Accordingly, the liquid mixture of the elutes 31 and 32 are subjected to 
the mixing action for mixture over a long passage and moved while varying 
in flow rate, and the maintenance of the afore-mentioned condensation 
gradient is enhanced under the various effects of the secondary stream. 
Moreover, a part of the elutes 31, 32 moving through the passage 65 slip 
through the gap e and flowed into an adjacent or separated other passage 
65 where the flow rate of the elutes 31, 32 are uniformed to reduce the 
effect of pulsation. 
The liquid mixture of the elutes 31, 32 is passed through the second mixer 
58 with the condensation gradient maintained. After movement in the second 
mixer 26, the liquid mixture is introduced by the mixing tube 6 into the 
six port valve 2 and flows into the analytical tube 5 from the port P4 via 
the port P3. Then, it is discharged through the analytical column 5 and 
the detector 25. 
Under such circumstances, when the intended gradients are all condensed by 
the condensation column 23, the six port switch is switched to have the 
port P1 communicated with the port P6, the port P2 with the Port P3, and 
the port P4 with the port P5, respectively. 
By doing so, the dilution tube 3 is communicated with the discharge tube 7 
through the ports P1, P6, while the mixing tube 6 is communicated with the 
condensation tube 4 through the ports P4, P5. The downstream side end 
portion of the condensation tube 4 is communicated with the analytical 
tube 5 through the ports P2, P3, and communicated with the drain by the 
detector 25. 
As a consequence, the dilution liquid 9 is discharged via the dilution tube 
3, the ports P1, P6 and the discharge tube 7. The liquid mixture of the 
elutes 31, 32 is introduced into the condensation tube 4 via the ports P4, 
P5 and, elutes the sample condensed and accumulated in the condensation 
column 23 so as to be sent out. The eluted sample is introduced from the 
condensation tube 4 into the analytical tube 24 via the ports P2, P3, and 
is separated by the analytical column 24 so that each ingredient is 
detected by the detector 25 one after another. 
In this case, the elutes 31, 32 are filly and accurately mixed by the mixer 
26 into a complete mixed state. 
Because the elutes 31, 32 have the sample move with the condensation 
gradient maintained in the vertical direction to the flowing direction, 
the present invention is advantageously applied to the gradient elution in 
which samples are eluted while gradually varying the mobile phase 
compositions, and particularly advantageously applied to elution of 
samples containing multiple components. 
In order to confirm the above, the inventor of the present invention used 
the mixer 26 of the present invention for mixing the elutes, and analysis 
experiments were repeated five times using the conventional static mixer, 
namely, a mixer formed of a coil spring like mixer tube with a plurality 
of beads filled therein under the same conditions. The results of FIGS. 7 
and 8 were obtained. 
In the illustrations, the results of the analysis are shown in an 
overlapped manner. 
When the results of analysis obtained by using the mixer 26 of the present 
invention and by using only the conventional static mixer were compared, 
the result of FIG. 9 was obtained. FIG. 9 shows the results of the two in 
offset relation in the direction of the vertical axis. 
FIG. 7 shows a result of experiment using the mixer 26 of the present 
invention. Five chromatographs of FIG. 7 are generally the same. It was 
confirmed that the gradient is performed very correctly and accurately. 
On the other hand, FIG. 8 shows the result of analysis using only the 
conventional static mixer. It was confirmed that the chromatograph of FIG. 
8 is large in irregularity and the gradient is low in correctness. 
Further, in FIG. 9, a distinctly clear difference appears in noise and base 
line at the ports a, b. It was confirmed that the mixing is insufficient, 
many noises are generated, and the base line is unstable in the 
conventional example, while the noise is less, the base line is stable, 
and mixing is fully performed in the present invention. 
Therefore, the mixing according to the present invention correctly and 
rapidly follows the gradient program for gradually increasing the solvent 
strength by varying the mobile phase compositions in the gradient elution, 
and enhance the elution of predetermined ingredients corresponding to the 
program, thereby smoothly separating them. 
For this reason, troubles are obviated such that the retention time of the 
peak of each ingredient is correct and stable in the chromatogram and a 
plurality of ingredients are not separated but eluted simultaneously. 
Actually, only a trace of the aldehydes as the samples is contained in the 
exhaust gas from automobiles, and there are many cases were no sample of a 
predetermined condensation can be obtained by the aforementioned 
condensation. 
[In view of the above, there is actually employed a method in which a large 
quantity of sample is injected and a required quantity of sample is 
condensed for analysis. 
In this case, the resistor setter 20 is operated to set the resistor tube 
21 corresponding to a separation ratio between the dilution tube 3 and the 
bypass tube 19. In the embodiment, the flow rate of the bypass tube 19 is 
set to about three to four times the dilution tube 3. 
When the liquid feed pump 10 is drive under such conditions, the dilution 
liquid 9 flows dividedly into the dilution tube 3 and the bypass tube 19, 
the sample is injected from the injector 16 into the dilution liquid 9 
moving in the dilution tube 3, and the sample and the dilution liquid 9 
divided into the bypass tube 19 are converged by the three port valve 17. 
Accordingly, since the sample is diluted by a large quantity of the 
dilution liquid 9, it can easily be absorbed to the condensation column 23 
by diluting the sample after the solvent is replaced by the dilution 
liquid 9 even in the case where the solvent dissolving the sample is large 
in strength. 
Thereafter the dilution liquid 9, which has diluted the sample, is 
introduced into the mixer 18 where the sample and the dilution liquid 9 
are fully mixed. Thereafter, the sample is condensed and accumulated in 
the condensation column 23. 
In this case, because the sample and the dilution liquid 9 are fully mixed 
and the sample is uniform in condensation, the column filler of the 
condensation column 23 and the sample act in a stable manner so that the 
condensation efficiency of the sample is increased to ensure the 
condensation. 
Thereafter, the six port valve 2 is switched so that the condensed sample 
in the condensation column 23 is eluted in the elutes 31, 32 and sent into 
the analytical tube 5 where the sample is separated in the analytical 
column 24. 
After completion of analysis, the switch valve 11 is operated to have the 
cleaning tube 12 communicated with the cleaning liquid 14 and then the 
liquid feed pump 10 is activated. 
By doing so, the cleaning liquid 14 is moved through the dilution tube 2 
and the bypass tube 19 to clean the inside of the tubes, and further moved 
through the mixer 18, the condensation tube 4 and the condensation column 
23 to clean an impurity temporarily adhered thereto, so that generation of 
a peak by the impurity is prevented and a reproduction of the next 
analysis is maintained. 
The afore-mentioned cleaning is particularly important for the analysis of 
ingredients contained in exhaust gas from automobiles, which gas contains 
a large quantity of impurities. 
FIGS. 10 through 12 show another embodiment of the present invention, in 
which those parts corresponding to the construction of the 
previously-mentioned embodiment are denoted by identical reference 
numerals. 
In this embodiment, a plurality of electromagnetic stones 66 (three or more 
in this embodiment) are arranged around a magnetic agitator 67 instead of 
the agitator 51 and the rotor 52, so that the supply of current to an 
electromagnetic coil of each electromagnetic stone 66 is controlled to 
rotate the magnetic agitator 67. 
By doing so, there is no need of a provision of the agitation motor 51. 
Accordingly, the mixer can be designed smaller in size and lighter in 
weight to that extent. 
In case a plurality of electromagnetic stones 66 are provided, if an iron 
core 69 of each electromagnetic stone 66 is bent in a generally C-shape 
such that opposite end portions 69a face each other with magnetic agitator 
67 placed therebetween, the number of electromagnetic stones 66 can be 
reduced by half. 
The features of the present invention are listed as follows. 
According to a first aspect of the invention, a mixer for a liquid 
chromatograph for mixing plural kinds of liquids comprises a first mixer 
for forcibly agitating liquid, a second mixer for agitating liquid in 
accordance with a flow rate, a liquid passage for the first mixer and a 
liquid passage for the second mixer being in communication with each 
other, and the first and second mixers being integrally mounted. Owing to 
this feature, a sufficient mixing effect, as well as enhancement of mixing 
efficiency, can be obtained. In addition, the number of parts can be 
reduced and an installation space can be easily obtained. As a 
consequence, the mixer can be designed small in size and light in weight. 
According to a second aspect of the invention, the first and second mixers 
are arranged in proximal relation. Owing to this feature, the liquid 
passage between the first and second mixers can be reduced in volume, and 
degradation of the mixing state can be prevented. In addition, the mixer 
can be designed to be small in size and light in weight. 
According to a third aspect of the invention, the first mixer can perform 
selective agitation of liquid between forcible agitation and agitation in 
accordance with a flow rate. Owing to this feature, a single mixer can 
conveniently be used as both a so-called dynamic mixer and static mixer. 
According to a fourth aspect of the invention, the first mixer is arranged 
in a liquid passage on an upstream side of the second mixer. Owing to this 
feature, liquids to be mixed can be forcibly mixed in the first place, 
thereby increasing the mixing efficiency. 
According to a fifth aspect of the invention, the first mixer includes a 
mixing chamber in conmnunication with the liquid passages and an agitator 
rotatably received in the mixing chamber. Owing to this feature, the 
liquid can be forcibly mixed by rotation of the agitator. 
According to a sixth aspect of the invention, the first mixer includes a 
single mixing chamber having a small volume and in communication with the 
liquid passages, and a single agitator. Owing to this feature, the mixer 
can be reduced in dead volume, and therefore the mixing effect in the 
mixer can be enhanced. 
According to a seventh aspect of the invention, the agitator is variable in 
speed of rotation within a range from zero to a predetermined speed. Owing 
to this feature, various ways of use can be selected in accordance with 
the mixing conditions and the mixer can be used as a static mixer when the 
speed of rotation is zero. 
According to an eight aspect of the invention, the second mixer includes an 
outer sleeve with a plurality of lead grooves spirally formed in an inner 
surface thereof, and an inner sleeve with a plurality of lead grooves 
formed in a peripheral surface thereof, the inner sleeve being dimensioned 
such that it can be inserted into the outer sleeve. Owing to this feature, 
there can be provided a versatile mixer which is small in size, light in 
weight and large in length. 
According to a ninth aspect of the invention, a plurality of spiral 
passages having various sectional configurations and sectional areas are 
formed between the lead grooves in the outer sleeve and a peripheral 
surface and lead grooves in the inner sleeve. Owing to this feature, the 
mixing effect and mixing efficiency can be enhanced by moving the liquid 
to the various passages. 
Specifically, the liquid can be moved to the spiral passage to enhance 
mixing of the liquid by secondary flow, so that a condensation gradient in 
the flowing direction can be maintained. As a consequence, mixing 
correctly following a mixing program can be obtained. 
According to a tenth aspect of the invention, an outside diameter of the 
inner sleeve is smaller than an inside diameter of the outer sleeve, and a 
small gap is formed between the inner sleeve and the outer sleeve. Owing 
to this feature, there can be provided a liquid passage which is formed of 
a gap other than the lead groove. 
According to an eleventh aspect of the invention, the small gap can 
communicate with the passage. Owing to this feature, pulsation of the 
liquid can be reduced and prevented. 
According to a twelfth aspect of the invention, each pitch of the lead 
grooves of at least one of the outer and inner sleeves is axially 
gradually increased or decreased. Owing to this feature, a passage having 
various sectional configurations and various sectional areas can be 
formed. 
According to a thirteenth aspect of the invention, the mixer for liquid 
chromatograph is a gradient mixer. Owing to this feature, the mixture as a 
gradient mixer, can correctly follow a mixing program while maintaining 
the concentration gradient which is varied with the passage of time. 
According to a fourteenth aspect of the invention, the agitator is rotated 
by electromagnetic force of a rotor capable of rotating at a variable 
speed. Owing to this feature, the agitator can be rotated reliably and in 
a stable manner. 
According to a fifteenth aspect of the invention, a plurality of 
electromagnetic stones are arranged around the agitator and the agitator 
can be rotated at a variable speed by controlling the supply of current to 
an electromagnetic coil of each of the electromagnetic stones. Owing to 
this feature, since the rotor is not rotated by a motor or the like, the 
generation of noise and vibration can be prevented, and in addition, the 
mixer can be designed to be small in size and light in weight.