A method and system for determining the dissociation constant (K.sub.d) of a reversible binding pair of a first compound and a second compound. The method comprises: injecting a sample into a capillary tube via one or more valves, wherein the sample comprises the first compound, the second compound, and a first compound-second compound complex; injecting a mobile phase into the capillary tube via said one or more valves, the sample flowing through the capillary tube under laminar flow conditions, wherein the second compound and the first compound-second compound complex is separated from the first compound by transverse diffusion; measuring time dependence of a signal that is proportional to the concentration of the first compound, both unbound and bound to the second compound using a measurement component; and determining the equilibrium dissociation constant based on the measured signal versus time dependence.

A first solution is supplied from a first pump. A second solution is supplied from a second pump. A flow path from the first pump and the second pump to a column is switched between a first flow path and a second flow path. In the first flow path, a first mixer is located upstream of an injection part for a sample, and the second mixer is located downstream of the injection part. In the second flow path, the first mixer and the second mixer are located upstream of the injection part. The first flow path is formed in a first mode in which the sample is diluted before introduction into the column. The second flow path is formed in a second mode in which the sample is not diluted before introduction into the column.

A first solution is supplied from a first pump. A second solution is supplied from a second pump. A flow path from the first pump and the second pump to a column is switched between a first flow path and a second flow path. In the first flow path, a first mixer is located upstream of an injection part for a sample, and the second mixer is located downstream of the injection part. In the second flow path, the first mixer and the second mixer are located upstream of the injection part. The first flow path is formed in a first mode in which the sample is diluted before introduction into the column. The second flow path is formed in a second mode in which the sample is not diluted before introduction into the column.

A method for collecting a sample for sample analysis includes drawing a first portion of the sample into a sample storage portion of a chromatography system while the chromatography system is in a first configuration. The method further comprising switching the chromatography system to a second configuration; sealing an end of a sample pick-up needle and draining a portion of a liquid from the second tubing; switching the chromatography system to a third configuration; drawing a second portion of the sample into the sample storage portion of the chromatography system; switching the chromatography system to an injection configuration; and fluidly connecting the sample storage portion to the chromatography column and supplying the first portion of the sample and the second portion of the sample from the sample storage portion to the chromatography column.

A method for collecting a sample for sample analysis includes drawing a first portion of the sample into a sample storage portion of a chromatography system while the chromatography system is in a first configuration. The method further comprising switching the chromatography system to a second configuration; sealing an end of a sample pick-up needle and draining a portion of a liquid from the second tubing; switching the chromatography system to a third configuration; drawing a second portion of the sample into the sample storage portion of the chromatography system; switching the chromatography system to an injection configuration; and fluidly connecting the sample storage portion to the chromatography column and supplying the first portion of the sample and the second portion of the sample from the sample storage portion to the chromatography column.

Valve with two-piece stator assembly for use with liquid chromatography or other analytical systems. A separate and removable stator plate is provided with a mounting device to provide a two-piece stator assembly. The mounting device is adapted on one side to engage and contact the stator plate, and on the other side includes a plurality of ports for fluidic connections which are in fluid communication with fluid passageways in the stator plate.

A liquid chromatograph includes at least one mobile phase supply flow path (6; 42), at least one cleaning solution supply flow path (8; 44) joining the mobile phase supply flow path (6; 42), an analysis flow path (4) provided with a separation column (14), a sampling flow path (2) provided, at a tip end thereof, with a sampling needle (12), a switcher (10; 26) including a high-pressure valve (10) having an injection port (16) and configured to switch a flow path configuration of the liquid chromatograph between a loading state in which the analysis mobile phase supply flow path (6) and the analysis flow path (4) are connected in a fluid manner without the sampling flow path (2) and an injecting state in which the sampling flow path (2) is interposed between the analysis mobile phase supply flow path (6) and the analysis flow path (4) when a tip end of the needle (12) is inserted into the injection port (16), and a controller (50) configured to execute, when a predetermined condition is satisfied, the cleaning operation of supplying the mobile phase and the cleaning solution to the analysis flow path (4) and/or the sampling flow path (2) to temporally change the composition of liquid flowing in the analysis flow path (4) and/or the sampling flow path (2).

A liquid chromatograph includes at least one mobile phase supply flow path (6; 42), at least one cleaning solution supply flow path (8; 44) joining the mobile phase supply flow path (6; 42), an analysis flow path (4) provided with a separation column (14), a sampling flow path (2) provided, at a tip end thereof, with a sampling needle (12), a switcher (10; 26) including a high-pressure valve (10) having an injection port (16) and configured to switch a flow path configuration of the liquid chromatograph between a loading state in which the analysis mobile phase supply flow path (6) and the analysis flow path (4) are connected in a fluid manner without the sampling flow path (2) and an injecting state in which the sampling flow path (2) is interposed between the analysis mobile phase supply flow path (6) and the analysis flow path (4) when a tip end of the needle (12) is inserted into the injection port (16), and a controller (50) configured to execute, when a predetermined condition is satisfied, the cleaning operation of supplying the mobile phase and the cleaning solution to the analysis flow path (4) and/or the sampling flow path (2) to temporally change the composition of liquid flowing in the analysis flow path (4) and/or the sampling flow path (2).

An injector is configured for injecting a fluidic sample from an injector path into a mobile phase in a separation path between a fluid drive and a sample separation unit of a sample separation device. The injector includes a control unit configured for generating a first overpressure in a blocked first partial path of the injector path by a first pressure source, for generating a second overpressure in a blocked second partial path of the injector path by a second pressure source, for subsequently fluidically coupling the first partial path with the second partial path for generating an expansion stroke for releasing a gas bubble in the injector path, and for rinsing the released gas bubble from the injector path.

A sample pre-compression valve for liquid chromatography applications is described. The valve enables a sample pre-compression while the solvent pump continues to conduct solvent to the chromatography column. Furthermore, the sample pre-compression valve includes an INJECT position, a LOAD position and a PUMP PURGE position, in which all connecting grooves of the valve are flushed with liquid. A use of the sample pre-compression valve is described as part of a sampler for liquid chromatography applications.