GB2174016A - Improvements in or relating to high performance liquid chromatography systems - Google Patents

Abstract

Ancillary apparatus for a high-performance liquid chromatography (HPLC) system, has valve means for shutting down the mobile phase liquid solvent supply of the system and replacing it by a wash liquid supply. The pump of the system is activated by a timer to flush the autosampler, separation column and detector units of the system, with the wash liquid, into a waste outlet. After the timed period, a switch isolates the electric supply to the HPLC. The ancillary apparatus is pulse-triggered into operation by the HPLC at the completion of the system measurement, and operates to render the HPLC in readiness for its next operation before switching-off the HPLC system.

Description

SPECIFICATION Improvements in or relating to high performance liquid chromotography systems In the field of liquid chromotography, modern systems for automatic analysis comprise a separation column, an autosampler or injector for introducing a sample into the column, a pump for passing a mobile phase solvent through the column, a detector for identifying separation components of the sample passing from the column, on a time scale, and some form of data recorder. Such apparatus is known as a high-performance liquid chromotography system, or HPLC system.

The present invention relates to HPLC systems and provides ancillary apparatus for automatically replacing the mobile phase solvent flow by a wash flow at the end of normal operation of the HPLC system and, after a predetermined time interval, shutting down both the HPLC system and the ancillary apparatus itself by removing the electric power supply to all units of the combined system.

Accordingly, the present invention provides apparatus including an input from a mobile phase liquid solvent source, an input from a wash liquid source, valve means for selecting an input from either one of said sources, an output for the liquid thus selected, for connection to an HPLC system pump, timing means for timing the duration of wash liquid supply, trigger means actuated by a trigger pulse generated by the HPLC system at the conclusion of an analysis operation, said trigger means initiating the operation of said timing means and electric switch means, actuated at the conclusion of said wash liquid supply, for disconnecting the electric supply to the HPLC system.

The invention further provides an HPLC system comprising the known units defined in the first paragraph of this specification in combination with the units of the ancillary apparatus defined in the last foregoing paragraph.

Short Description of the Drawings One embodiment of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which the same elements are indicated by the same reference numerals in the several figures and in which: Fig. 1 is a part block-schematic, part diagrammatic representation of an HPLC system and ancillary apparatus according to the invention; Fig. 2 is a block-schematic diagram showing more particularly the electrical components of the apparatus according to the invention; Fig. 3 is a schematic circuit diagram of the electronic components of the apparatus; Fig. 4 shows the electrical supply control circuit for the HPLC system units; Fig. 5 shows the electrical supply circuit for the apparatus of the invention; and Fig. 6 shows the circuit diagram of an optional computer signal trigger interface. Description of the Embodiment Fig. 1 shows, in block schematic form, an HPLC system comprising a separation column 1,an autosampler and injector unit 2, a pump 3, a detector 4 and a recorder 5, in known manner.

The apparatus of the invention is shown generally at 10 and includes an input tube 11 from a mobile phase liquid solvent source 12, an input tube 13 from a wash liquid source 14, an input tube 15from a pressure gas source, not shown, and an output tube 16foreithersolventorwash liquid.

A power input line 17 connects to an alternating current mains supply 18 and a power output line 19 supplies a multiple socket power receptacle 20.

Power receptacle sockets 21,22, 23 and 24 respectively supply power to the HPLC pump, autosampler/injector, detector and recorder units by way of their individual power supply cables.

The two inputs 11 and 13, the gas input 15 and liquid output 16 are grouped together at a multiple port 25. The liquid output 16 is connected to the input of pump 3, from whence liquid is pumped through the autosampler/injector 2, column 1 and detector 4 before being output to waste at 6.

A signal line 26 carries a trigger pulse generated by the HPLC unit 2 to the input of the apparatus 10.

Referring now to Fig. 2, there is shown a resettable monostable unit 30, having an input on signal line 26 from the autosampler (2), and connected by line 31 two a latching bistable unit 32.

The latching bistable unit 32 is connected by line 33 to a pulse generator and timing counter 34 and by line 35 to a valve solenoid 36. By means of a mechanical link 37, the solenoid 36 controls the setting of a valve 38, which selects the input of mobile phase liquid solvent from input tube 11 or the input of wash liquid from input tube 13 and supplies that liquid to outputtube 16. The pulse generator and timing counter 34 has a further input on line 39 from a resettable monostable unit 40. The unit 34 is connected by line 41 to control a solidstate mains-supply relay 42. The relay 42 has a mains supply input on input line 17 and controls the supply to output line 19. Line 19 supplies the power receptacle 20, the sockets 21,22, 23 and 24 and hence the pump (3), autosampler (2), detector (4) and recorder (5), as shown in Fig. 1.The valve combination 36/38 and the resettable monostable unit 40 are both reset by a manually-operated button 43.

Referring next to Fig. 3, there is shown a schematic circuit diagram of the electronic components of the apparatus of the invention, in which the various circuit parts are boxed by broken lines to identify the units of the block schematic diagram of Fig. 2 and referenced by the same numerals in both figures.

Certain of the components used are commercially-available proprietary components.

Thus, the liquid control valve used is a rotary spool valve available from Clippard Minimatic of Cincinnati, Ohio, U.S.A. This valve is operated by solenoid with pressure gas, or air, assistance. The pressure gas input is shown at 15, Fig. 1, and the control solenoid is shown at 36, within the block 32, of Fig. 3. The pulse generator of unit 34 is a One Second/One Minute Precision Clock and Reference Generator, type ICM 7213, available from Intersil Inc.

of Cupertino, California, U.S.A. and is indicated by reference 51 in block 34 of Fig. 3. The timing counter of unit 34 is an Electronic Predetermining Counter, type KP 100, available from Landis & Gyr of North Acton, London W3, England and is indicated by reference 52 in block 34 of Fig. 3. The internal construction, circuitry and manner of operation of these components need not be further described herein.

Understanding of the manner of operation of the apparatus of the invention will be facilitated by a general description, before considering the circuitry of Fig.3 in detail.

During the normal run sequence of the HPLC system the solid-state relay 42 is ON, so that power is supplied to the receptacle 20 and thence to the various units of the HPLC system. The rotary spool valve 38. Fig. 2, is set by its relay 36, Fig. 2 and Fig. 3, and the pressure gas supply at 15, Fig. 1,so that it passes the mobile phase solvent. At this time, the latching bistable unit 32 is in its latched condition and the counter generator 34 is inhibited. When the last sample has been injected into the column 1 and its analysis recorded, a trigger pulse is generated, either by an electrical contact within the HPLC system or by a computer-generated signal, if such is used, and fed to the input 26 of the monostable unit 30. This unit changes state and resets itself again.In so doing, the monostable unit 30 unlatches the bistable unit 32, which itself changes state and latches in its new state. This action has two consequences. Firstly a signal is sent to the valve trigger 36, whereby the spool valve 38 is reset to cut off the supply of mobile phase solvent and to permit the flow of wash liquid to the pump 3, Fig. 1.

Secondly, the inhibit to the pulse generator 51, Fig.

3, is removed and the timing operation by the timing counter 52 begins. The timing counter is preset to a required time interval. When the pulse count reaches parity with the preset count, its internal control relay operates to provide an output signal.

This signal controls the relay 42 to its OFF state.

Power supply to the receptable 20 is cut off and the HPLC units connected are isolated from the supply.

The inhibit two the pulse generator 51 is reestablished. The entire HPLC system is thus washed out, shut down and in readiness for its further use, when required.

Referring again to Fig. 3, a switch 53 selects one of the alternative inputs at 26, that is the contact generated pulse input from the HPLC auto-sampler 2, Fig. 1, or the computer generated pulse, derived by way of the interface of Fig. 6, for feeding to a first gate 54. The switch 53 also energises one of two indicator LEDs 55 and 56 to indicate the pulse source selected. An input pulse to gate 54 causes the monostable unit 30 to pulse, the pulse being stretched by the resistance-capacitance network 58 following gate 57. The resultant square pulse, successively inverted by gates 59,60 and 61, is fed to a MOSFET transistor 62, type BST70A, the output of which operates a relay 63.

The operation of relay 63 serves to unlatch the bistable unit 32, when a switch 64 is in its AUTO setting. Switch 64 has an alternative HOLD setting in which the bistable unit 32 is held in its latched condition. The setting of switch 64 is indicated by a pair of LEDs 65 and 66. Switched to its AUTO setting, as stated above, closure of relay 63 contact unlatches the bistable combination of gate 67 and gate 68 the output from which is fed to a MOSFET transistor 69, type BST70A, the output of which operates a relay 70. A switch 71 may be set either to an AUTO or a MANUAL setting, the setting chosen being indicated by a pair of LEDs 72 and 73.

When the pulse generator 51 starts to operate, a gate 74 receives negative-going pulses at onesecond intervals and outputs positive-going square pulses correspondingly. A gate 75 receives negative-going pulses at one-minute intervals and outputs positive-going square pulses correspondingly. The one-second interval pulses, fed through a stretcher gate 76 and inverter gate 77 to a MOSFET transistor 78, type BST70A, operate an indicator LED 79. The one-minute interval pulses are fed to a MOSFETtransistor80,type BST70A, and operate a relay 81. The closure of relay 81 contact lowers the input of counter 52 to zero potential corresponding to an input count.

The counter 52, having been preset to count a required interval, counts the input one-minute pulses and, when parity with the preset count is reached, triggers solid-state relay 42 to its OFF condition. Referring to Fig. 4, it will be seen that solid state relay 42 thus isolates the power receptacle 20 and thereby isolates all of the HPLC units supplied therefrom at sockets 21 to 24.

Automatic reset of the apparatus of Fig. 2 is not practicable since it would result in the HPLC system being put into operation again without purpose.

Reset is effected manually, when required, by a manual reset button switch 82, closure of which raises the input voltage of a gate 83 which supplies an output pulse to gate 84, resistance-capacitance network 85, gates 86,87 and 88 and MOSFET transistor 89, to control a relay 90. These components operate in exactly similar manner to the similar components of unit 30 described in detail above. Closure of relay 90 contact lowers the potential at the second input of counter 52, which is thereby reset and inhibited.

The power supply to the components of the apparatus of Fig. 3 is standard and is shown in Fig.

Claims (10)

1. Four a high-performance liquid chromatography system, apparatus including an input from a mobile phase liquid solvent source, an inputfrom a wash liquid source, valve means for selecting an input from either one of said sources, an outputforthe liquid thus selected, for connection to an HPLC system pump, timing means for timing the duration of wash liquid supply, trigger means actuated by a trigger pulse generated by the HPLC system at the conclusion of an analysis operation, said trigger means initiating the operation of said timing means and electric switch means, actuated at the conclusion of said wash liquid supply, for disconnecting the electric supply to the HPLC system.

2. Apparatus as claimed in Claim 1, in which said selectable inputs and said output are combined in valve means which is solenoid actuated.

3. Apparatus as claimed in Claim 2, in which said valve means is solenoid actuated by a trigger pulse generated by said HPLC unit, by way of a resettable monostable unit and a latching bistable unit.

4. Apparatus as claimed in Claim 3, in which said bistable unit also initiates said timing means.

5. Apparatus as claimed in Claim 4, in which said timing means is a pulse generator and counter adapted, at a predetermined count, to supply a control pulse to said electric switch means.

6. Apparatus as claimed in Claim 5, in which said electric switch means is a solid state device connected to control the power supply to a power distribution unit.

7. Apparatus as claimed in Claim 6, in which said power distribution unit is connected for supplying power to units ofthe HPLC system.

8. Apparatus as claimed in Claim 1, substantially as described herein with reference to the accompanying drawings.

9. In combination, an HPLC system including pump, autosampler, separation column and detector units, controlled by ancillary apparatus as claimed in any one of Claims 1 to 8.

10. Apparatus as claimed in Claim 9, substantially as described herein with reference to the accompanying drawings.