LIQUID CHROMATOGRAPH

Abstract: This invention relates to a liquid chromatograph com­ posed of a solvent tank, a pump, a sample injection part, a column and a detector which are connected successively through passages. The column is connected between the pump and a sample solution inlet of the detector and. furthermore, a flow controller is connected in parallel to the column between the pump and a reference solution inlet of the detector.

Description: This invention relates to a liquid chromatograph composed of a solvent tank, a pump, a sample injection part, a column and a detector which are connected successively through passages. The column is connected between the pump and a sample solution inlet of the detector and, furthermore, a flow controller is connected in parallel to the column between the pump and a reference solution inlet of the detector. BACKGROUND OF THE INVENTION This invention relates to a liquid chromatograph. This type of the conventional liquid chromatograph is shown in Figure 4, wherein (1) is a solvent tank, (2) is a pump, (3) is a sample injection part, (4) is a column, (5) is a detector, and (6) is a recycle cock for returning the solvent out of the detector (5) to the detector (5) as a reference solution or exhausting the solvent into a waste tank (7). Such conventional liquid chromatograph had a difficulty in flowing the solvent at a minutely fixed flow rate and, therefore, was hard to maintain a high stability of the measured value. This problem becomes revealed particularly when a high sensitive detector is applied or a volatile solvent such as tetrahydrofuran and the like is used as solvent. Namely, not only experiences have proved that a high stability can be obtained when the solvent is flowed at a minutely fixed flow rate, but also a much more flow of the solvent increases waste consumption of the solvent unecomonically, the solvent (reference solution) becomes easy to be affected by thermal influence in the detector, and a stable baseline cannot be obtained as drift is caused by thermal expansion of the reference solution. Moreover, when a minutely fixed flow rate of the solvent is not maintained, fluctuation of retention time (time until reported a measured value) prevents accurate measurement and such inconvenience is caused that the measured value cannot be subjected to computer-processing. One solution to this problem is discussed in U.S. Patent No. 4016074 in which a reference column similar to the sample column is connected in parallel with the sample column so that pressure and temperature fluctuations will be similar in the sample and reference solutions. However, the reference column cannot of course limit or prevent such fluctuations. French Patent FR-A-2018031 discloses a gas pressure controller to be used in gas chromatography and in which the gas pressure is limited because increased gas pressure causes movement of an actuating rod to bring a plate across the aperture through which the gas enters. This would not be a particularly suitable system for liquid flow control. OBJECT OF THE INVENTION It is an object of this invention to provide a liquid chromatograph whereby the flow rate of a reference solution (solvent) can be controlled at a minutely fixed flow rate and, at a result, the reference solution (solvent) becomes hard to be affected by thermal influence in the detector even in the case of using a highly sensitive detector or using a volatile solvent, resulting in prevention of drift caused by thermal expansion and in maintenance of a stable baseline and, moreover, computer-processing becomes possible as retention tame is stabilized to afford accurate measurement. The object is solved by the device according to Claim 1. BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a structural diagram illustrating an embodiment of a liquid chromatograph of this invention, Figure 2 is a sectional view illustrating an embodiment of a flow controller related to this invention, Figure 3 is a sectional view taken substantially on line (3)-(3) of Figure 2, and Figure 4 is a structural diagram illustrating an example of conventional liquid chromatograph. DETAILED DESCRIPTION OF THE INVENTION An embodiment of this invention is illustrated based on the structural diagram shown in Figure 1. In the drawing, (1) is a solvent tank, (2) is a pump, (3) is a sample injection part, (4) is a column, (8) is a flow controller, (5) is a detector, and (7) is a waste tank, and these are connected successively through passages. A pipe (a) on the exhaust side of the pump (2) is branched into two (a1) and (a2) to connect the sample injection part (3) and the column (4) with the one pipe (a1) and the flow controller (8) with the other pipe (a2) and, thus, the column (4) and the flow controller (8) are connected in parallel to each other on the exhaust side of the pump (2). Furthermore, a pipe (b) on the outlet side of the column (4) is connected to the sample inlet of the detector (5) and a pipe (c) on the outlet side of the flow controller (8) is connected to the reference solution inlet of the detector (5). As the detector (5), those which are conventionally public known, e.g., a differential refrectometer, an ultraviolet photometer, a fluorescent detector, an electrochemical detector, an ion-exchange detector, and the like, can be employed independently or in a proper combination thereof. Next, the flow controller (8) which is a main component material of this invention is illustrated based on Figure 2 and Figure 3. This flow controller (8) is composed of an upper chamber (11) and a lower chamber (12) comparted by a diaphragm (10), which are formed in a unit (9), a passage (14) to connect the upper chamber (11) with a solvent inlet (13), an adjustment valve (15) positioned inside said passage (14) one end of which is fixed on the above-said diaphragm (10), an adjustment passage (17) to connect the upper chamber (11) with the lower chamber (12) and to connect with a solvent outlet (16), a needle valve (18) positioned in face of the inside of this adjustment passage (17), a micrometer head (19) to adjust the needle valve (18), and a compression spring (20) to compress the above-said diaphragm (10) from the lower chamber (12) side. Namely, the upper chamber (11) and the lower chamber (12) comparted by the diaphragm (10) are formed in the unit (9) and, furthermore, the said unit is provided with the passage (14) to connect the upper chamber (11) with the solvent inlet (13) and the adjustment passage (17) to connect the upper chamber (11) and the lower chamber (12) each other and to connect with the solvent outlet (16). The said diaphragm (10) is prepared in the form of a wave plate in order to widen the surface area as much as possible, and the adjustment valve (15) is positioned inside the passage (14) leading to the above-said upper chamber (11). This adjustment valve (15) is provided to adjust the flow rate of the solvent entering from the solvent inlet (13), one end of the said valve being connected to the diaphragm (10) to operate together with the diaphragm (10) and the other end being compressed by the spring (20) in order not to operate inadvertently. The needle valve (18) is positioned in face of the inside of the adjustment passage (17) to connect the above-said upper chamber (11) with the lower chamber (12) and the solvent outlet (16). This needle valve (18) is provided to adjust the flow rate out of the solvent outlet (16) of the fluid coming through the adjustment passage (17), and the opening degree of the said valve is adjusted by the micrometer head (19) attached to the unit (9). The micrometer head (19) has a similar mechanism to those of micrometers, moving the needle valve (18) minutely. The inside of the above-said lower chamber (12) is provided with the compression spring (20) to compress the diaphragm (10) always toward the upper chamber (11) side. In the drawing, (22) is a drain for use in exchange of the solvent and the like. To the solvent inlet (13) of the flow controller (8) thus composed is connected the other pipe (a2) of the exhaust side pipe (a) of the pump (2), and to the solvent outlet (16) is connected the pipe (c) connecting to the reference solution inlet of the detector (5). In this way, the solvent exhausted from the pump (2) is branched, through the exhaust side pipe (a), into the pipe (a2) of the flow controller (8) side and the pipe (a1) of the column (4) side, and a sample is added to the solvent of the column (4) side from the sample injection part (3) and separated by the column (4) to be provided to the sample solution inlet of the detector. On the other hand, the solvent branched to the flow controller (8) side enters in the upper chamber (11) from the inlet (13) through the passage (14) and flows from the upper chamber (11) through the passage (7) to be divided into a part entering into the lower chamber (12) through the needle valve (18) and a part leading to the outlet (16). The compressive force of the compression spring (20) and the pressure of the outlet (16) side are added to the lower chamber (12), and the pressure of the solvent entering into the upper chamber (11) is adjusted so as to maintain the balance with these pressures. In this way, since the pressure balance between the upper chamber (11) and the lower chamber (12) is maintained and the difference before and behind the needle valve (18) is always fixed, the flow rate of the solvent is adjusted minutely only by opening degree of the needle valve (18), or adjustment by the micrometer head (19), and provided to the reference solution inlet of the detector (5) without being affected by any pressure fluctuation of the solvent entering from the inlet (13) at all. The flow controller (8) thus composed can afford a high stability in a short time and pulsation of the pump (2) can be also controlled by widening the surface area of the diaphragm (10). As apparent from the descriptions so far, according to the liquid chromatograph of this invention, the flow rate of the reference solution side can be controlled at a minutely fixed flow rate and, therefore, a high stability can be obtained even in the case of using a volatile solvent or using a highly sensitive detector. Namely, since the flow rate of the reference solution can be controlled at a minutely fixed flow rate, the solvent (reference solution) becomes hard to be affected by thermal influence in the detector, resulting in prevention of drift caused by thermal expansion and in maintenance of a stable baseline and, furthermore, computer-processing becomes possible as retention time is stabilized to afford accurate measurement.

Claims: A liquid chromatograph composed of a solvent tank (1), a pump (2), a sample injection part (3), a column (4) and a detector (5) which are successively connected through passages, the column (4) being connected between said pump (2) and a sample solution inlet of said detector (5) and a flow controller (8) being connected in parallel to the above-said column (4) between said pump (2) and a reference solution inlet of said detector (5) characterised in that; said flow controller (8) is composed of an upper chamber (11) and a lower chamber (12) which are compartmented by a diaphragm (10) in a unit (9), a passage (14) to connect the upper chamber (11) with a liquid inlet (13), an adjustment valve (15) positioned on the inside of said passage (14) one end of which is fixed on the above-said diaphragm (10), an adjustment passage (17) to connect the above-said upper chamber (11) with the lower chamber (12) and to connect with the liquid outlet (16), a needle valve (18) positioned in said adjustment passage (17), a micrometer head (19) to adjust said needle valve (18), and a compression spring (20) in the lower chamber (12) to compress the diaphragm (10) toward the upper chamber side (11).

Inventors: AKIHIKO, NAGAI, AKIO, KANEKO, KAZUO, HIRAIZUMI, KOZO, SHIRATO
Applicants: ERMA CR. INCORPORATION
Application year: 1985
Main classification: G01N30
IPC codes: B01D15, G01N30