JP2002014084A - Liquid chromatograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid chromatograph fro gradient elution analysis, that solves such a problem that difference in analysis results among devices are generated, even under identical analysis conditions, and can apply the same analysis conditions to another device universally. SOLUTION: In this liquid chromatograph having a gradient liquid-feeding mechanism for feeding liquid while changing the composition of mobile phase liquid according to a specific program, a sample-injecting mechanism for injecting a sample into the mobile phase liquid, and a controller 10 for controlling them, the value (or a value related to this) of the inner volume of a mobile phase liquid channel from a mixing point M, where a plurality of mobile phase liquids merge to a sample injection point S is stored in the controller 10, the time when the composition of the mobile phase liquid starts to change at the sample injection point S is calculated from the value, and the timing for injecting the liquid at the sample-injecting mechanism is determined, based on the result. Accordingly always simultaneously to starting of the change in the mobile phase composition in a column 6 as soon as the sample enters the column 6 and eliminating the difference in analysis results due to the difference in the inner volume among the devices.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid chromatograph for performing gradient elution.

[0002]

2. Description of the Related Art Gradient elution is a technique in which two or more mobile phase liquids in a liquid chromatograph are used, and analysis is performed while changing the mixing ratio with time. FIG.
FIG. 3 is an example of a diagram (gradient profile) in which the mixing ratio of two liquids is represented by using the horizontal axis as a time axis. In this example,
Two liquids, A and B, were used as mobile phase liquids.
The mixture ratio is 90% for solution B and 10% for solution B.
After o has elapsed, the ratio of the solution B gradually increases, and reaches 100% at the end of the analysis. In order to control the mixing ratio of the two liquids as described above, the flow paths of the mobile phase liquids are joined via the respective valves on the suction side of the liquid sending pump, and the opening and closing of these valves in small increments. A predetermined mixture ratio is obtained by controlling the time ratio (opening degree). The above is a method called a low pressure gradient. In addition, there is a high pressure gradient in which each mobile phase liquid is mixed on the discharge side of the liquid sending pump, but there is no essential difference.

[0003]

In the gradient elution analysis in the conventional liquid chromatograph, a sample is usually injected at the same time as the start of the gradient program. Generally, a liquid chromatograph device has an internal volume in a mobile phase liquid flow path from a confluence point (mixing point) of two liquids to a point (injection point) at which a sample is injected, and furthermore, the arrangement and internal structure of each part are different for each device. Therefore, the value of the internal volume differs individually. For this reason, there is a time difference between the time when the sample enters the column and the time when the composition of the mobile phase liquid starts to change, and the time difference differs depending on the device. As a result, when the analysis conditions set in a certain apparatus are applied to other apparatuses as they are, the same analysis results are not always obtained.

[0004] The present invention has been made in view of such circumstances, and solves the above-described problem of causing a difference in analysis results between apparatuses, and universally applies the same analysis conditions to other apparatuses. It is an object to provide a liquid chromatograph for a possible gradient elution analysis.

[0005]

In order to solve the above problems, in the liquid chromatograph of the present invention, the internal volume of the mobile phase liquid flow path from the mixing point where a plurality of mobile phase liquids join to the sample injection point is determined. A value (or a value related thereto) is stored, a time until the composition of the mobile phase liquid starts to change at the sample injection point is calculated from this value, and the timing of sample injection is determined based on the result. I made it. As a result, it becomes possible to apply the analysis conditions set for a certain apparatus as they are to another apparatus.

[0006]

FIG. 1 shows an embodiment of the present invention. The figure shows an example of a two-liquid low-pressure gradient elution analysis system, where 1a and 1b are containers (reservoirs) of mobile phase liquids A and B, respectively, and 2 is a deaerator for removing gas dissolved in the mobile phase liquid. Here, a two-channel type is used, and each channel is used for deaeration of the liquids A and B, respectively. 3
Reference numerals a and 3b denote valves for controlling the mixture ratio of the two liquids by controlling the degree of opening. The flow paths of the two liquids merge at a point M (mixing point) on the outlet side of the valves. , B flow as mobile phase liquids mixed at a predetermined ratio. Numeral 4 is a liquid sending pump which can be called a heart of the liquid chromatograph apparatus, which makes the above-mentioned mobile phase liquid a predetermined flow at a predetermined flow rate in a direction indicated by an arrow in the figure. Reference numeral 5 denotes a sample injection section, which automatically injects a sample into the flow of the mobile phase liquid by an injector valve or the like. The injected sample is separated while passing through the column 6 while riding on the flow of the mobile phase liquid, and is taken out by the detector 7 as a signal representing the analysis result. The liquid that has passed through the detector 7 is discharged to a waste liquid reservoir 8. Reference numeral 9 denotes a thermostat for keeping the column 6 at a predetermined temperature for analysis, and a controller 10 having a built-in computer controls these components. The dotted line in the figure is
A signal for controlling each unit from the controller 10 is shown.

In a liquid chromatograph having such a structure,
For example, when the liquid is sent in accordance with the gradient profile shown in FIG.
The opening degree is controlled so that the solution B concentration starts to increase after a lapse of time To from the start of the program (start of change in the composition of the mobile phase), and thereafter, the solution B concentration is increased at a constant speed. Assuming that the mobile phase liquid composition is observed at the mixing point M, the pattern becomes almost the same as the pattern shown by the solid line in the figure, that is, the gradient profile. The mobile phase composition change point c in the figure moves in the mobile phase liquid flow path at the same speed as the flow rate of the mobile phase liquid. Therefore, if the mobile phase liquid composition is similarly observed at the downstream injection point S, a pattern as indicated by a dotted line should be drawn a little later. At the injection point S, after starting the program, The change in the mobile phase composition starts after the elapse of the time Ts. If the sample is injected at this timing Ts, the sample is injected just at the mobile phase composition change point, and the separation of the sample starts at the same time as the mobile phase composition starts changing at the tip of the column 6. Controlling such that the sample is injected at such a timing is one of the conditions for implementing the present invention.

Here, assuming that the internal volume of the mobile phase liquid flow path from the mixing point M to the injection point S is V, and the flow rate (flow velocity) of the mobile phase liquid is F, V = F × (Ts−To) ... (1) holds. By further transforming this equation, the following is obtained: Ts = V / F + To (2) When calculating the internal volume from equation (1), the mobile phase liquid flow rate F and the timing To at which the mobile phase composition starts to change on a program can be easily obtained from the set value of the analysis conditions. It is necessary to actually measure the change start timing Ts (this is also the sample injection timing as described above). Various methods are conceivable for actually measuring Ts, but the simplest method is to connect the detector 7 temporarily to the position of the sample injection unit 5 and observe the mobile phase composition at the injection point S in FIG. The goal is to measure the time at which the mobile phase composition change point appears. In this case, a slight error may occur due to the inner volume of the detector 7, but this may be corrected as appropriate. This measurement should initially be 1 unless the equipment is modified or reconfigured.
Just do it once. Using the value of Ts thus measured, the internal volume V is obtained from the equation (1), and this is stored in the memory of the controller 10 as a value unique to the apparatus.

When changing the analysis conditions, a new F, To
Is applied to the equation (2), and a proper value of the sample injection timing Ts is calculated by a computer (not shown) built in the controller 10, and the controller 10 calculates the sample at the newly calculated Ts timing. The sample injection unit 5 is controlled to inject the sample. Thus, even if the analysis conditions change, the sample always enters the column together with the mobile phase composition change point, and the condition that the mobile phase composition change and the separation of the sample start simultaneously in the column 6 is maintained. You.

In another liquid chromatograph, similarly to the above, the value of the internal volume V of the mobile phase liquid flow path from the mixing point to the injection point of each device is set in each controller as a value unique to each device. If this value is used to determine the sample injection timing Ts, the sample will always enter the column at the same time as the mobile phase composition change point. Even when the method is applied to an applied device, there is no difference in the analysis result between the devices.

As can be seen from equation (1) or (2),
When the analysis conditions are changed, the variables are the mobile phase liquid flow rate F and the timing To where the mobile phase composition starts to change on the program.
Therefore, no matter what shape the profile after To has, for example, when it has a complicated pattern that changes stepwise, there is no effect when applying the present invention.

In the above description, it is assumed that the sample is injected at the mobile phase composition change point. However, in principle, it is not always necessary to inject the sample exactly at the mobile phase composition change point, and the sample is slightly shifted before and after the injection. There is no practical problem. In short, it is only necessary to inject the sample while maintaining a certain time relationship with the mobile phase composition change point.However, in order to match the conditions among many devices, just inject the sample at the mobile phase composition change point. It is easiest and reasonable to set it to

In the above description, the value of the internal volume is stored in each device as it is. However, a coefficient obtained by dividing the value of the internal volume of each device by the value of the internal volume of a standard device may be stored. Alternatively, other numerical values related to the internal volume may be stored. The case of the two-liquid low-pressure gradient has been described above as an example.
The present invention is also applicable to a gradient liquid sending or more.

[0014]

As described in detail above, according to the present invention,
The same separation pattern can be obtained under the same analysis conditions irrespective of the type of liquid chromatograph, etc., and the analysis conditions can be made universal.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a gradient profile.

[Explanation of symbols]

 1a, 1b: Mobile phase liquid container 2: Degassing device 3a, 3b: Valve 4: Liquid feed pump 5: Sample injection unit 6: Column 7: Detector 8: Waste liquid reservoir 9: Constant temperature bath 10: Controller

Claims (1)

[Claims] 1. A gradient liquid sending mechanism for sending a liquid while changing the composition of two or more mobile phase liquids according to a predetermined program; a sample injection mechanism for injecting a sample into the mobile phase liquid flow; In a liquid chromatograph provided with a controller that performs
A numerical value related to the internal volume of the mobile phase liquid flow path from the junction of the mobile phase liquid or more to the sample injection mechanism is stored, and the controller controls the timing of sample injection in the sample injection mechanism based on this numerical value. A liquid chromatograph characterized in that: