Abstract: Described are embodiments of a pump that can be used, for example, in liquid chromatography applications. The pump includes a seal wash housing, pump head and seal assembly. A wear-resistant coating applied to a sealing surface or gland of the pump head or seal wash housing improves the hardness and chemical compatibility of the sealing surface. Oxidation of the sealing surface is reduced so that the sealing surface is less abrasive to the seal assembly and the lifetime of the seal assembly is increased.

Abstract: Described is a method of reducing liquid composition errors in a low-pressure mixing pump system. Packets representing the switching intervals of each component of the desired fluid mixture are provided to an intake of the mixing pump system. For each packet, a switching time associated with at least one of the components in the packet is modulated. Modulated switching times are based on time offsets that are specifically selected according to the undesirable frequency characteristic of an intake response of the mixing pump system. The average of the volumes contributed by the packets thus modulated is equal to a component volume that achieves a desired proportion of the component in the output flow of the mixing pump system. Modulated switching times enable the reduction or elimination of composition error in the output flow of the mixing pump system.

Abstract: Pumps used in liquid chromatography applications employ actuators for pressurizing and moving liquid. An actuator includes a pump head having a chamber, a gland, a movable rod extending through the gland into the chamber of the pump head, and a plunger seal disposed in the gland around the rod for sealing against fluidic leakage from the chamber. The plunger seal has an annular flange that provides an OD (outer diameter) seal against the gland. The flange defines a seal cavity. The pump head further includes an outlet port and an outlet channel. One end of the outlet channel is in communication with the outlet port and the other end of the outlet channel opens into the seal cavity of the plunger seal. The outlet channel provides a flow path for liquid in the chamber to travel towards the outlet port in response to movement of the rod.

Abstract: Low-pressure and high-pressure reciprocating and rotary applications use seal assemblies to prevent leakage. One embodiment of a seal assembly includes a major annular body having opposing spaced-apart annular lips extending from a heel portion with a bore extending through the heel portion. A first spring is disposed between the lips, biasing the lips apart. A minor annular body extends from one of the lips of the major annular body. The minor annular body has opposing spaced-apart walls that extend from a base region and form a pocket. A second spring is disposed in the pocket between the spaced-apart walls, biasing the walls apart. During actuator operation, pressurized fluid urges one wall of the minor annular body against a pump head surface to produce a face seal and one of the lips of the major annular body against a rod surface to produce a radial seal.

Abstract: Described is a method of reducing liquid composition errors in a low-pressure mixing pump system. Packets representing the switching intervals of each component of the desired fluid mixture are provided to an intake of the mixing pump system. For each packet, a switching time associated with at least one of the components in the packet is modulated. Modulated switching times are based on time offsets that are specifically selected according to the undesirable frequency characteristic of an intake response of the mixing pump system. The average of the volumes contributed by the packets thus modulated is equal to a component volume that achieves a desired proportion of the component in the output flow of the mixing pump system. Modulated switching times enable the reduction or elimination of composition error in the output flow of the mixing pump system.

Abstract: Described are a method and an apparatus for delivering a fluid having a desired mass composition. According to the method, temperatures of the fluids to be mixed are sensed and the densities of the fluids at the sensed temperatures are determined. The volume of each fluid is determined so that a mixture of the fluids at the sensed temperatures has the desired mass composition. The determined volumes of the fluids are combined to create the mixture. In one option, combining the determined volumes includes metering flows of the fluids sequentially into a common fluid channel. Alternatively, combining the determined volumes includes controlling a flow rate of each of the fluids and directing the fluids into a common fluid channel.

Abstract: Described is a method of reducing liquid composition errors in a low-pressure mixing pump system. Packets representing the switching intervals of each component of the desired fluid mixture are provided to an intake of the mixing pump system. For each packet, a switching time associated with at least one of the components in the packet is modulated. Modulated switching times are based on time offsets that are specifically selected according to the undesirable frequency characteristic of an intake response of the mixing pump system. The average of the volumes contributed by the packets thus modulated is equal to a component volume that achieves a desired proportion of the component in the output flow of the mixing pump system. Modulated switching times enable the reduction or elimination of composition error in the output flow of the mixing pump system.

Abstract: Described is an apparatus for reducing a temperature variation of a liquid chromatography sample. A tray drive using at least one of linear or rotational motion moves a sample tray along a path inside a sample compartment of the liquid chromatography system. A control module coordinates the movement of the sample tray by the tray drive and the movement of a sample needle by a needle drive so that any sample in the sample tray can be injected into the mobile phase of the system during a sample load operation. The tray drive is also used to move the sample tray along the path during a temperature averaging period when no loading occurs. Differences in sample temperatures due to variations in the air temperature at different locations inside the sample compartment are reduced, leading to more accurate and repeatable chromatographic measurement results.

Abstract: Described is a self-sealing thermal enclosure. In various embodiments, the self-sealing thermal enclosure includes an enclosure having a wall with an opening. The enclosure is configured to surround a temperature-controlled environment. The self-sealing thermal enclosure also includes a porous seal disposed adjacent to the wall at the opening. The porous seal is compressible and is fabricated from an open cell foam material. When the porous seal has absorbed a fluid such as a condensate, the temperature-controlled environment is sealed from an ambient environment such that the flow of air into or out of the enclosure is substantially reduced or eliminated.

Abstract: A sample manager of a liquid chromatography system implements a thermal system that uses a dual-loop feedback control system to control temperature within a thermal chamber. The sample manager includes an external heatsink disposed externally to the thermal chamber, an internal heatsink disposed within the thermal chamber, and one or more thermoelectric devices thermally coupled to the external and internal heatsinks to transfer heat therebetween in response to a pulse-width modulated power signal. A first temperature sensor disposed within the thermal chamber continuously measures a chamber temperature. A second temperature sensor coupled to the internal heatsink within the thermal chamber continuously measures temperature at the internal heatsink. A feedback control system controls a duty cycle of the pulse-width modulated power signal in response to a target chamber temperature and real-time temperature measurements produced by the first and second temperature sensors.

Abstract: Described are embodiments of a pump having a diagnostic port that enables users and support personnel to diagnose the source of a pump leak. The diagnostic port is monitored visually or with a pressure or liquid detection sensor. In some embodiments, fluid detected at the diagnostic port corresponds to a leak around a circumference defined at an outer sealing surface of a high pressure seal. In other embodiments, fluid detected at the diagnostic port corresponds to a leak around a plunger at the inside diameter of the high pressure seal. Multiple diagnostic ports can be provided to allow separate determinations of leaks about the different portions of the high pressure seal. The embodiments may eliminate the need to disassemble the pump to determine the source of leaks. Thus the effort required to diagnose and repair the pump can be substantially reduced, and fewer misdiagnosed components are ordered or replaced.

Abstract: Systems and methods for operating a stepper motor of a pump at a desired low velocity include memory for storing information corresponding to an intake velocity profile. The intake velocity profile represents an optimized acceleration curve for operating the stepper motor over a range of motor velocities during an intake cycle. A processor of a system controller dynamically accesses the memory during the intake cycle to acquire the information representing the intake velocity profile and issues a series of pulses to the stepper motor based on this information. In response to the pulses, the stepper motor accelerates in accordance with the optimized acceleration curve represented by the intake velocity profile. The optimized acceleration curve is based on the available torque of the stepper motor across a range of motor velocities and enables the motor to operate with greater torque utilization and less margin than traditional linear acceleration profiles.

Abstract: Described is a method of reducing liquid composition errors in a low-pressure mixing pump system. Packets representing the switching intervals of each component of the desired fluid mixture are provided to an intake of the mixing pump system. For each packet, a switching time associated with at least one of the components in the packet is modulated. Modulated switching times are based on time offsets that are specifically selected according to the undesirable frequency characteristic of an intake response of the mixing pump system. The average of the volumes contributed by the packets thus modulated is equal to a component volume that achieves a desired proportion of the component in the output flow of the mixing pump system. Modulated switching times enable the reduction or elimination of composition error in the output flow of the mixing pump system.

Abstract: A method of liquid chromatography includes providing one or more solvent reservoirs, providing a solvent pump, drawing one or more solvents into the pump in response to a pressure drop that promotes outgassing of the solvents, and dispersing outgassed bubbles into smaller bubbles to promote re-dissolution of the gas. A liquid-chromatography apparatus includes at least two solvent reservoirs, a pump, at least one bubble-dispersing unit that receives a pressurized flow of proportioned solvents from the pump, and a control unit. The control unit includes a processor and a memory that stores instructions; the control unit controls proportioning of solvents to obtain a preselected solvent composition, and pumping at flow rates to support preparative-scale or process-scale liquid chromatography.