manufacturer:       Hewlett Packard

model:                   1090

annotation:           Dokumente engl.

System Overview

General

The HP 1090 Liquid Chromatograph is an Integration of single modules. The Solvent Delivery System (SDS) delivers flow rates from 1 microliter/min up to 5m|/min per channel by true volumetric displacement. This permits 1%-99% gradients with better than 1% precision even at 100 microliter/min. The SDS has fast response for high-speed gradients and low delay volume for micro bore gradients. Each solvent channel has a Metering Pump that takes the solvent in from a reservoir and meters it into the Low Pressure Compliance which acts as the mixing chamber. With the High Pressure Pump, a high frequency membrane pump, pressures up to 400 bar are generated and flow is delivered to the system via a High Pressure Dumper. Flow ripple is removed and system pressure is measured in this item.

The Automatic Injector can be programmed to inject volumes from 0.5 microliters up to 250 microliters (250 microliter syringe required). During the injection cycle flow from the SDS is bypassed to the injection system by the use of a Rotary Valve Unit. A sample loop is loaded with the amount of sample programmed. Switching the Valve Unit again brings the sample onto the column.

The Automatic Sampler, combined with the Automatic Injector, allows fully automated injection from up to 100 bottles. Access is random and analyses can be run in any sequence and with any method.

The Heated Column Compartment insures temperature homogeneity in the column by pre-heating the solvent in a 2 microliter capillary and by heating the surrounding air in the compartment at the same time. The heat exchanger maintains a temperature precision of +/-0.5°C around setpoint in a range from 15°C above ambient to 100°C.

The Filter-Photometric Detector allows programmable wavelength switching. A filter wheel gives a choice of 7 wavelengths per analysis from 200 to 540 nm. Switching time is under 2 seconds with no offset. Detector response time can be set to three different values. Lamp current of the Deuterium Lamp can be selected high or low. Two analog outputs, each with a range of 0V to 1V (0.5V/AU) and 0V to 100mV (switch on ADA board), are available. The Integrator output has high resolution. For recorder output a low resolution is used. In addition this output is programmable in % offset and attenuation (only FPD).

The Diode Array Detector measures absorbance in a wavelength range of 190 to 600 nm. Details of operation and can be obtained from the Operating Manual section DAD.

The HP85 User Interface is suitable for any system configuration. lt gives the user a single communications point for all modules. HP-IB is the communications link to LC hardware and computer peripherals.

System Operation

Operation of all LC modules integrated into the HP 1090 mainframe is observed and monitored by a two processor system located on the Controller Board (CTL). Almost all modules are connected to the controller via an Interface or driver board which is connected to the 1090I/O Bus. Only some few items get a single control signal from an I/O port or provide a status signal directly to an I/O port or an analog signal to a circuit on the CTL.

The operator interacts with the HP 1090 via the HP85 which is displaying status and actual values on the one hand. lt sends setpoints and commands to the HP 1090 on the other hand. Connection to the 1090I/O Bus is made with an HPIB Interface Board (IBU) that matches the HP1B protocol to the HP 10901/0 Bus. Status and Error signals are also displayed on the System Keyboard at the front of the HP 1090. In addition, POWER, PUMP and DETECTOR can be switched ON and OFF manually. The analysis can be started and stopped with pushbuttons from the keyboard as well.

The Solvent Delivery System (SDS) consists of two different pumps (isocratic configuration) which are coupled together in line. The Metering Pump System takes solvent in from a reservoir and meters it into the Low Pressure Compliance (LPC). The LPC acts as a mixing chamber and serves as a temporary storage device for solvents of each functioning channel during the time where the High Pressure Pump delivers flow to the system and no solvent can go into its cavity. Two stepper motors are required to drive the Metering Pump; the one to move the two piston pumps (servo motor) and the other to turn a Rotary Valve (valve motor). Actual movement of the servo motor is sensed by a shaft encoder and compared with setpoints provided by the controller on the Servo Control Board (SCT).

The resulting error signal is combined with additional information from the controller on the Motor Driver Board (MDR) where an according signal for the servo motor is generated. The valve switching motor is also controlled by the MDR, whereby feedback on proper execution is provided by limit switches and sent to the controller via a circuit on the MDR. Control for flow channel B and C (binary and ternary configuration respectively) is in the same way as described above for channel A. The pressure in the Low Pressure Compliance is sensed and an electrical signal is provided by the Low Pressure Transducer (LPT) and sent to the controller.

The High Pressure Pump delivers the solvent to the column. Operation is started and synchronized with a pulse from the controller to the Primary Board (PRI) where the pump motor is connected to line power. An interrupt signal for further use on the CTL is derived by a Pump Stroke Signal Board (PSS) that senses the movement of the pump motor. This signal is also sed to synchronize switching of the Metering Pumps with the pressure stroke of the High Pressure Pump. Flow on the high pressure side is damped in the High Pressure Damper and the pressure is measured at the same time with the High Pressure Transducer. This signal is also sent to the controller.

A Manual Valve Injector can be used to place the sample onto the column. Moving the valve to the inject position provides a start pulse to the controller. No other signals are required for operation.

The Automatic Injector uses the Injector Sampler Driver Board (ISD) to interface with the controller. Signals to drive valves and stepper motors are connected through the Injector Control Board (ICO). All sensed positions and states are fed to the ISD also through the ICO.

The Automatic Sampler is controlled in exactly the same way as described for the Automatic Injector. Even the driver board (ISD) is the same. Functions of the Sampler Control Board (SCO) are the same as for the ICO, however the hardware design is different.

Oven fan, oven heater and associated sensors, responsible for temperature control of the Heated Column Compartment are connected to the controller via the Oven Interface Board (OVI).

Four external contacts, one of which is a contact closure and three are switching 24V, located on the External Contacts Interface Board (ECI), are controlled directly from the respective I/O ports on the CTL.

Even though any available detector for the HP 1090 is a built-in module there is only a minimum number of connections to the controller. For the Filter Detector only some Status and Error signals are transferred. Data manipulations on the detector signal are made in the detector processor itself. Chromatographic signals are available at the detector outputs. The Diode Array Detector transfers status messages via a single cable to the System keyboard. lt also uses this connection to be turned ON or OFF. Data transfer to mass storage devices uses the HPIB connection to HP85. Two analog signals are generated in the detector module and are available at the detector rear panel.