The present disclosure describes a differential refractometer for gradient chromatography. In an exemplary embodiment, the differential refractometer includes a solvent delay volume, an eluent flow meter coupled to an eluent inlet of a sample cell, a solvent flow regulator coupled to an outlet of the solvent delay volume and coupled to a solvent inlet of a reference cell, an instrument controller configured to receive the eluent flow rate from the eluent flow meter, configured to receive the solvent flow rate from the solvent flow regulator, configured to receive a flow rate ratio from a flow rate ratio data source, wherein the flow rate ratio indicates a ratio of the eluent flow rate to the solvent flow rate, and an optical bench configured to measure a difference between a refractive index of the eluent present in the sample cell and a refractive index of the solvent present in the reference cell.

Described is a mixer for a chromatography system. The mixer includes an inlet manifold channel, an outlet manifold channel and a plurality of transfer channels. The inlet manifold channel has an inlet at a proximal end of the inlet manifold channel for receiving an inlet flow. The transfer channels are fluidly connected between the inlet and outlet manifold channels. The respective fluid connections are distributed along each of the inlet and outlet manifolds channels. The transfer channels have different volumes. The mixer may be formed of a plurality of layer and the layers may be diffusion bonded to each other.

Described is a mixer for a chromatography system. The mixer includes an inlet manifold channel, an outlet manifold channel and a plurality of transfer channels. The inlet manifold channel has an inlet at a proximal end of the inlet manifold channel for receiving an inlet flow. The transfer channels are fluidly connected between the inlet and outlet manifold channels. The respective fluid connections are distributed along each of the inlet and outlet manifolds channels. The transfer channels have different volumes. The mixer may be formed of a plurality of layer and the layers may be diffusion bonded to each other.

A pump unit includes a pump and a metal ion trap. The pump includes a metal member that comes into contact with a mobile phase. The pump pumps a mobile phase through a flow path. The metal ion trap includes a filter element. The filter element includes a metal ion retention structure for retaining metal ions by interacting with the metal ions included in a mobile phase. The filter element is provided in the flow path for a mobile phase pumped by the pump. The pump unit may be provided in a chromatograph.

A system for blending solutions and a buffer solution is disclosed. In this system a switch valve is present capable of flowing one or more solutions, a low pressure pump for pumping the one or more solutions through the switch valve and a T-joint capable of receiving the one or more solutions through the low pressure pump and blending the one or more solutions with a buffer solution. A high pressure pump is present for collecting a blended solution.

A system for blending solutions and a buffer solution is disclosed. In this system a switch valve is present capable of flowing one or more solutions, a low pressure pump for pumping the one or more solutions through the switch valve and a T-joint capable of receiving the one or more solutions through the low pressure pump and blending the one or more solutions with a buffer solution. A high pressure pump is present for collecting a blended solution.

Described is a method for determining a dwell volume of a liquid chromatography system and a liquid chromatography system that can determined the system dwell volume. The method includes mixing a flow of a first solvent with a flow of a second solvent to form a solvent mixture. The flows of the first and second solvents are decreased and increased, respectively, to generate a gradient composition. A system pressure of the liquid chromatography system is measured to determine a pressure trace defined as the measured system pressure as a function of time. The dwell volume of the system is determined from a time delay determined between the gradient composition at the mixing location and the pressure trace. The method can be performed with a liquid chromatography system having a chromatographic column or a flow restrictor used in place of the chromatographic column.

A liquid chromatograph includes: an analysis column; a sample loop that temporarily contains a mixed liquid of a sample and a mixture solvent; and a passage switch valve capable of switching a passage between a load position where the mixed liquid is temporarily held in the sample loop and an injection position where the mixed liquid held in the sample loop is sent to the analysis column. In the liquid chromatograph, a specific passage is formed in each of the load position and the injection position.

A chromatography system comprising at least two pumps, a first pump which is connectable or connected with a liquid reservoir for a first fluid, and a second pump which is connectable or connected with a liquid reservoir for a second fluid, wherein the pump outlet lines from the first pump and the second pump are connected with a connection piece and, viewed in the direction of flow, a chromatography column is provided downstream of this connection piece, wherein, viewed in the direction of flow, an addition unit is provided upstream of the connection piece and a mixer switching valve and a mixer switchable by way of the mixer switching valve are provided between the connection piece and chromatography column, wherein the mixer switching valve has at least two switching positions, wherein the mixer is connectable in a first position and the mixer is bypassable in a second position.

A chromatography method in which the system is used and a conversion kit for converting a high-performance liquid chromatography system into a chromatography system for supercritical fluid chromatography are also disclosed.

A chromatography system comprising at least two pumps, a first pump which is connectable or connected with a liquid reservoir for a first fluid, and a second pump which is connectable or connected with a liquid reservoir for a second fluid, wherein the pump outlet lines from the first pump and the second pump are connected with a connection piece and, viewed in the direction of flow, a chromatography column is provided downstream of this connection piece, wherein, viewed in the direction of flow, an addition unit is provided upstream of the connection piece and a mixer switching valve and a mixer switchable by way of the mixer switching valve are provided between the connection piece and chromatography column, wherein the mixer switching valve has at least two switching positions, wherein the mixer is connectable in a first position and the mixer is bypassable in a second position.

A chromatography method in which the system is used and a conversion kit for converting a high-performance liquid chromatography system into a chromatography system for supercritical fluid chromatography are also disclosed.