Patent Description:
In a liquid chromatograph, a liquid mixture of an aqueous solution including salt (hereinafter simply referred to as an aqueous solution) and an organic solvent may be used. For example, the aqueous solution and the organic solvent are mixed in a common bottle in advance, so that a liquid mixture is produced. In this case, precipitation of salt in the aqueous solution hardly occurs. Even if precipitation of salt occurs, it is possible to re-dissolve the salt in the liquid mixture by stirring the liquid mixture in the bottle.

In the meantime, an aqueous solution and an organic solvent are stored in separate bottles, and a liquid mixture may be produced by mixing of the aqueous solution and the organic solvent that are supplied from the bottle in a common flow path at the time of analysis of a sample. In this case, the concentration of the organic solvent is high at the interface where the aqueous solution and the organic solvent come into contact with each other, so that precipitation of salt is likely to occur. When the concentration of the organic solvent is high, this problem becomes more apparent.

<CIT> describes a mobile phase supply device that supplies a liquid mixture of a buffer in which salt is dissolved (hereinafter simply referred to as a buffer) and an organic solvent as a mobile phase. In this mobile phase supply device, the buffer stored in a first storage tank is supplied to a liquid sending pump through a first electromagnetic valve, a first check valve and a mixing flow path. Further, the organic solvent stored in the second storage tank is supplied to the liquid sending pump through a second electromagnetic valve, a second check valve and the mixing flow path. The buffer and the organic solvent are mixed in a pump chamber of the liquid sending pump.

<CIT> describes a sensor array for a fluid handling system, particularly for controlling the mobile phase drive to a sample separation system such as a high performance liquid chromatography application.

<CIT> describes a method for heating or cooling the mobile phase fluid of a chromatographic system prior to its entry into the chromatographic column.

<CIT> describes a mobile phase solvent delivery module for liquid chromatography and supercritical fluid chromatography systems.

In the mobile phase supply device described in <CIT>, even in the case where precipitation of salt occurs when the buffer and the organic solvent come into contact with each other in the mixing flow path, salt is prevented from entering the first and second electromagnetic valves by first and second check valves. However, precipitation of salt itself cannot be prevented, and stable supply of a mobile phase may be prevented by the precipitated salt.

An object of the present invention is to provide a liquid chromatograph, a liquid chromatograph analysis method that enable stable supply of a mobile phase.

In the liquid chromatograph as described below, the mobile phase produced by the mobile phase supply device and the sample are supplied to the injector. The mobile phase and the sample that have been supplied to the injector are introduced to the column, and the sample that has passed through the column is detected by the detector.

In the mobile phase supply device, the aqueous solution including salt stored in the first storage is led to the mixer through the first pipe, and the organic solvent stored in the second storage is led to the mixer through the second pipe. The aqueous solution and the organic solvent are mixed by the mixer, so that the mobile phase is produced. Here, at least the portion of the first pipe and at least the portion of the second pipe are heated by the heater such that the temperature of the mobile phase produced by the mixer is equal to or higher than the dissolution temperature of salt included in the aqueous solution.

With this configuration, the aqueous solution and the organic solvent are heated at positions further upstream than the mixer such that the temperature of the mobile phase is equal to or higher than the dissolution temperature of salt included in the aqueous solution. Therefore, even when the aqueous solution and the organic solvent come into contact with each other, precipitation of salt is prevented regardless of the concentration of the organic solvent. Therefore, salt does not prevent stable supply of the mobile phase. Thus, the mobile phase can be stably supplied.

In the liquid chromatograph as described below , it is not necessary to provide the heater for heating at least the portion of the first pipe and at least the portion of the second pipe separately from the column oven. Thus, the mobile phase supply device can be made compact while the cost of the mobile phase supply device is reduced.

In the mobile phase supply device as described below, even when the aqueous solution comes into contact with the organic solvent, precipitation of salt is prevented regardless of the concentration of the organic solvent. Therefore, salt does not prevent stable supply of the mobile phase. Thus, the mobile phase can be stably supplied.

The liquid chromatograph analysis method as described below prevents precipitation of salt regardless of the concentration of the organic solvent even when the aqueous solution and the organic solvent come into contact with each other in the mobile phase supply device. Therefore, salt does not prevent stable supply of the mobile phase. Thus, the mobile phase can be stably supplied.

In the liquid chromatograph analysis method as described below, the mobile phase supply device can be made compact while the cost of the mobile phase supply device is reduced.

Even when the aqueous solution and the organic solvent come into contact with each other, the mobile phase supply method as described below prevents precipitation of salt regardless of the concentration of the organic solvent. Therefore, salt does not prevent stable supply of the mobile phase. Thus, the mobile phase can be stably supplied.

Other features, elements, characteristics, and advantages of the present invention will become more apparent from the following description of preferred embodiments of the present invention with reference to the attached drawings.

Details of a mobile phase supply device, a liquid chromatograph, a mobile phase supply method and a liquid chromatograph analysis method according to an embodiment of the present invention will be described below with reference to drawings. <FIG> is a diagram showing the configuration of the liquid chromatograph according to one embodiment of the present invention. The liquid chromatograph <NUM> of <FIG> is an HPLC (High-Performance Liquid Chromatograph).

As shown in <FIG>, the liquid chromatograph <NUM> includes a mobile phase supply device <NUM>, an injector <NUM>, a column oven <NUM> and a detector <NUM>. The column oven <NUM> includes a heater. A column <NUM> is stored inside of the column oven <NUM>, and the temperature inside of the column oven <NUM> is adjusted to a certain constant temperature.

The mobile phase supply device <NUM> includes pipes <NUM>, <NUM>, <NUM>, storages <NUM>, <NUM>, a mixer <NUM>, a degassing device <NUM> and a liquid sender <NUM>. Further, in the present embodiment, the mobile phase supply device <NUM> includes a portion (the heater) of the column oven <NUM>. The storage <NUM> is a chemical liquid bottle and stores an aqueous solution including salt (hereinafter simply referred to as an aqueous solution). The storage <NUM> is a chemical liquid bottle similar to the storage <NUM> and stores an organic solvent. The storages <NUM>, <NUM> are examples of first and second storages, respectively.

The mixer <NUM> is a low-pressure gradient unit, for example, and includes ports A, B, C. The storage <NUM> and the port A of the mixer <NUM> are connected to each other by the pipe <NUM>. The storage <NUM> and the port B of the mixer <NUM> are connected to each other by the pipe <NUM>. The pipes <NUM>, <NUM>, are examples of first and second pipes, respectively. The pipe <NUM> is connected to the port C of the mixer <NUM>. The mixer <NUM> produces a mobile phase by mixing the aqueous solution that has been supplied from the storage <NUM> to the port A through the pipe <NUM> and the organic solvent that has been supplied from the storage <NUM> to the port B through the pipe <NUM>, and outputs the produced mobile phase from the port C.

In the following description, the upstream and downstream are defined in the liquid chromatograph <NUM> based on the flow of the aqueous solution or the organic solvent. At least respective portions of the respective pipes <NUM>, <NUM> located at positions further upstream than the mixer <NUM> are heated such that the temperature of the mixed mobile phase is equal to or higher than the dissolution temperature of salt included in the aqueous solution. In the present embodiment, the respective portions of the respective pipes <NUM>, <NUM> are arranged in the column oven <NUM>. Thus, in the column oven <NUM>, heat exchange can be carried out on the aqueous solution and the organic solvent to make the temperature of the mixed mobile phase be equal to or higher than the dissolution temperature of salt.

The respective portions of the respective pipes <NUM>, <NUM> arranged in the column oven <NUM> may be formed to be loop-like. In this case, the respective portions of the respective pipes <NUM>, <NUM> arranged in the column oven <NUM> can be maintained compact while being sufficiently long. As a result, the above-mentioned heat exchange can be more easily carried out.

The degassing device <NUM> is provided at the pipes <NUM>, <NUM> and removes the gas included in the aqueous solution flowing through the pipe <NUM> and the gas included in the organic solvent flowing through the pipe <NUM>. The liquid sender <NUM> is a pump unit, for example, and is provided at the pipe <NUM>. The liquid sender <NUM> sends the mobile phase that is output from the port C of the mixer <NUM> downstream under pressure.

The injector <NUM>, the column <NUM> and the detector <NUM> are provided in this order at positions further downstream than the liquid sender <NUM> in the pipe <NUM>. A sample to be measured is supplied to the injector <NUM> and introduced into the column <NUM> together with the mobile phase that is sent by the liquid sender <NUM> under pressure. The sample that has been introduced into the column <NUM> is separated into its components, and the components are respectively eluted in different lengths of time. The detector <NUM> detects the eluted sample from the column <NUM>.

<FIG> is a diagram showing the configuration of a liquid chromatograph <NUM> according to a first modified example. As shown in <FIG>, the liquid chromatograph <NUM> according to the first modified example includes heaters <NUM>, <NUM>. Although not including the degassing device <NUM>, the liquid chromatograph <NUM> according to the first modified example may include the degassing device <NUM>. The same also applies to a liquid chromatograph <NUM> according to the second modified example, described below.

The heaters <NUM>, <NUM> may be a hot water bath , an electric heater, a peltier element or the like, and at least respective portions of respective pipes <NUM>, <NUM> are heated such that the temperature of a mixed mobile phase is equal to or higher than the dissolution temperature of salt included in an aqueous solution. In this case, respective portions of the respective pipes <NUM>, <NUM> do not have to be arranged in the column oven <NUM>. Instead of the heaters <NUM>, <NUM>, the liquid chromatograph <NUM> according to the first modified example may include a common heater that heats a mixer <NUM>.

<FIG> is a diagram showing the configuration of a liquid chromatograph <NUM> according to a second modified example. As shown in <FIG>, the liquid chromatograph <NUM> according to the second modified example includes liquid senders 15a, 15b similar to the liquid sender <NUM> instead of the liquid sender <NUM>. Further, a mixer <NUM> is not a low-pressure gradient unit but a mixer unit, for example.

The liquid sender 15a is provided at a pipe <NUM> and sends an aqueous solution stored in a storage <NUM> towards the mixer <NUM>. The liquid sender 15b is provided at a pipe <NUM> and sends an organic solvent stored in a storage <NUM> towards the mixer <NUM>. In this case, the aqueous solution and the organic solvent are sent by separate liquid senders 15a, 15b. Thus, a sample can be analyzed using a high-pressure gradient method.

The liquid chromatograph <NUM> according to the second modified example may include the heaters <NUM>, <NUM> similar to the heaters of the first modified example or a common heater that heats the mixer <NUM>. In this case, respective portions of the respective pipes <NUM>, <NUM> do not have to be arranged inside of a column oven <NUM>.

In the liquid chromatograph <NUM> according to the present embodiment, the mobile phase produced by the mobile phase supply device <NUM> and the sample are supplied to the injector <NUM>. The mobile phase and the sample that have been supplied to the injector <NUM> are introduced into the column <NUM> stored in the column oven <NUM>, and the sample that has passed through the column <NUM> is detected by the detector <NUM>.

In the mobile phase supply device <NUM>, the aqueous solution including salt stored in the storage <NUM> is led to the mixer <NUM> through the pipe <NUM>, and the organic solvent stored in the storage <NUM> is led to the mixer <NUM> through the pipe <NUM>. The mobile phase is produced by the mixture of the aqueous solution and the organic solvent by the mixer <NUM>. Here, at least the portion of the pipe <NUM> and at least the portion of the pipe <NUM> are stored in the column oven <NUM>. At least the portion of the pipe <NUM> and at least the portion of the pipe <NUM> are heated by the column oven <NUM> such that the temperature of the mobile phase produced by the mixer <NUM> is equal to or higher than the dissolution temperature of salt included in the aqueous solution.

With this configuration, the aqueous solution and the organic solvent are heated at positions further upstream than the mixer <NUM> such that the temperature of the mobile phase is equal to or higher than the dissolution temperature of salt included in the aqueous solution. Therefore, even when the aqueous solution comes into contact with the organic solvent, precipitation of salt is prevented regardless of the concentration of the organic solvent. Therefore, salt does not prevent stable supply of the mobile phase. Thus, the mobile phase can be stably supplied.

Further, because at least the portion of the pipe <NUM> and at least the portion of the pipe <NUM> are heated by the column oven <NUM> in the present embodiment, it is not necessary to provide a heater separately from the column oven <NUM>. Thus, the mobile phase supply device <NUM> can be made compact while the cost of the mobile phase supply device <NUM> is reduced.

In an inventive example <NUM>, a pre-cooled phosphate potassium buffer and pre-cooled acetonitrile were used as an aqueous solution and an organic solvent respectively, and a mobile phase was supplied with use of the mobile phase supply device <NUM> of <FIG>. Hereinafter, a phosphate potassium buffer is referred to as a liquid A, and acetonitrile is referred to as a liquid B. The same applies to a comparative example <NUM> and inventive examples <NUM> and <NUM>, described below.

Specifically, in the inventive example <NUM>, <NUM> mmol/L of the liquid A was stored in the storage <NUM>, and <NUM> mmol/L of the liquid B was stored in the storage <NUM>. The mixer <NUM> was controlled such that the liquid A and the liquid B were sent at the flow rate ratio of <NUM>:<NUM> from these storages <NUM>, <NUM>. Here, the mixer <NUM> is a low-pressure gradient unit.

Further, the portion having the length corresponding to <NUM> in each of the pipes <NUM>, <NUM> was arranged in the column oven <NUM> such that the liquids A, B that respectively flow through the pipes <NUM>, <NUM> stayed in the column oven <NUM> for about <NUM> minutes and were heated. The liquids A and B were heated by the column oven <NUM>, mixed by the mixer <NUM> and sent downstream by the liquid sender <NUM>.

<FIG> is a diagram showing the temporal change of a pressure indication value of the liquid sender <NUM> in the inventive example <NUM>. As shown in <FIG>, in the inventive example <NUM>, the pressure applied by the liquid sender <NUM> was substantially constant and did not change. Thus, in the inventive example <NUM>, even when the liquids A and B were mixed, precipitation of salt did not occur. Thus, it was confirmed that a mobile phase could be stably supplied.

In the meantime, in the comparative example <NUM>, a mobile phase was supplied similarly to the inventive example <NUM> by a liquid chromatograph having the configuration similar to that of the mobile phase supply device <NUM> of <FIG> except that the configuration for heating the pipes <NUM>, <NUM> is not provided. Therefore, the liquids A and B were mixed by the mixer <NUM> without being heated and then sent downstream by the liquid sender <NUM>.

<FIG> is a diagram showing the temporal change of a pressure indication value of the liquid sender <NUM> in the comparative example <NUM>. As shown in <FIG>, in the comparative example <NUM>, the pressure applied by the liquid sender <NUM> was substantially constant for about <NUM> minutes after the liquid sending was started and did not change. It was considered that the reason for this was that, because the temperature of the liquid sender <NUM> at the time of start of liquid sending was high, precipitation of salt did not occur. However, after <NUM> minutes has elapsed since the start of the liquid sending, the pressure applied by the liquid sender <NUM> changed little by little and drifted largely. Thus, the mobile phase could not be supplied stably. It was considered that the reason for this was that, because the temperature of the liquid sender <NUM> has decreased, precipitation of salt occurred.

In the inventive example <NUM>, a sample was analyzed with use of the liquid chromatograph <NUM> of <FIG>. The sample is a thiuram standard liquid, which is an agricultural chemical. Specifically, thiuram standard liquids, concentrations of which were <NUM>/L, <NUM>/L, <NUM>/L and <NUM>/L, were sequentially supplied to the injector <NUM> and introduced into the column <NUM> by the mobile phase that had been produced under the same conditions as those of the inventive example <NUM>. Here, the column <NUM> is an ODS (octadecylsilyl) column, and the temperature of the column <NUM> is <NUM>. The flow rate and the supply rate of the mobile phase are <NUM>/min and <NUM>µL, respectively.

<FIG> is a diagram showing the results of analysis of the samples in the inventive example <NUM>. In <FIG>, the abscissa indicates the time, and the ordinate indicates the detection intensity of the sample. Further, the results of analysis of the samples, the concentrations of which are <NUM>/L, <NUM>/L, <NUM>/L and <NUM>/L, are indicated by a solid line, a dotted line, a one-dot and dash line and a two-dots and dash line, respectively. As shown in <FIG>, in the inventive example <NUM>, the baseline of the detection intensity did not change regardless of the concentration of the sample. Thus, it was confirmed that the mobile phase was supplied stably, and the sample was detected and analyzed stably.

In the inventive example <NUM>, the gradient analysis of a sample was carried out. Specifically, a thiuram standard liquid, the concentration of which was <NUM>/L, was used, and the ratio of the liquid A to the liquid B were changed consecutively in the range from <NUM>:<NUM> to <NUM>:<NUM>. The other analysis conditions were the same as the analysis conditions in the inventive example <NUM>.

<FIG> are diagrams showing the results of gradient analysis of the samples in the inventive example <NUM>. The abscissas in <FIG> indicate the common time, the ordinate in <FIG> indicates the ratio (concentration) of the liquid B, the ordinate in <FIG> indicates an indication value of the pressure applied by the liquid sender <NUM>, and the ordinate in <FIG> indicates the detection intensity of the sample.

As shown in <FIG>, even when the concentration of the liquid B was increased from <NUM> % to <NUM> %, the pressure applied by the liquid sender <NUM> did not change little by little. Thus, even when the liquid A was mixed with the liquid B having a high concentration, precipitation of salt did not occur. Therefore, it was confirmed that the mobile phase could be supplied stably. Further, as shown in <FIG>, the baseline of the detection intensity did not change. Thus, it was confirmed that the sample was detected stably and the gradient analysis was performed stably.

Claim 1:
A liquid chromatograph comprising:
a mobile phase supply device (<NUM>) that supplies a mobile phase to be used in liquid chromatograph analysis of a sample;
an injector (<NUM>) to which a mobile phase produced by the mobile phase supply device (<NUM>) and a sample are supplied;
a column (<NUM>) into which the mobile phase and the sample that have been supplied to the injector (<NUM>) are introduced;
a detector (<NUM>) that detects the sample that has passed through the column (<NUM>); and
a column oven (<NUM>) that stores the column (<NUM>) and adjusts a temperature of the column (<NUM>),
wherein the mobile phase supply device (<NUM>) includes:
a first storage (<NUM>) that stores an aqueous solution including salt;
a second storage (<NUM>) that stores an organic solvent;
a mixer (<NUM>) that produces the mobile phase by mixing the aqueous solution stored in the first storage (<NUM>) with the organic solvent stored in the second storage (<NUM>);
a first pipe (<NUM>) that connects the mixer (<NUM>) to the first storage (<NUM>);
a second pipe (<NUM>) that connects the mixer (<NUM>) to the second storage (<NUM>); and
a heater that heats at least a portion of the first pipe (<NUM>) and at least a portion of the second pipe (<NUM>),
wherein the heater is configured to adjust a temperature of the mobile phase produced by the mixer (<NUM>) to a temperature that is equal to or higher than a dissolution temperature of salt included in the aqueous solution, and
wherein the column oven (<NUM>) includes the heater and heats at least the portion of the first pipe (<NUM>) and at least the portion of the second pipe (<NUM>) while further storing at least the portion of the first pipe (<NUM>) and at least the portion of the second pipe (<NUM>).