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To economically perform preparatory chromatography, a plurality of pumps each having a corresponding one of a plurality of pistons and a corresponding one of a plurality of cylinders are driven by one motor to draw and pump solvent simultaneously into corresponding columns. To form a gradient, the p

To economically perform preparatory chromatography, a plurality of pumps each having a corresponding one of a plurality of pistons and a corresponding one of a plurality of cylinders are driven by one motor to draw and pump solvent simultaneously into corresponding columns. To form a gradient, the pumps are connected to two-way valves that are connected alternately to a first solvent and a second solvent, whereby the time said valve is in a first position controls the amount of solvent drawn from the first reservoir into said pumps and the amount of time in said second position controls the amount of said second solvent drawn from the second reservoir into said pumps and the solvent is mixed in the pumping systems. The detectors are photodiodes mounted to light guides in the flow cells that generate signals related to light absorbance and communicate with a controller, whereby the controller receives signals indicating solute between the light guides and causes collection of solute. An over-pressure system compensates for pressure over a predetermined level.

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1. A liquid chromatographic system including:at least one pumping system; a plurality of flow cells; a plurality of photodetectors; said pumping system supplying solvent to at least one flow cell of said plurality of flow cells; at least one light source; said at least one light source applying ligh

1. A liquid chromatographic system including:at least one pumping system; a plurality of flow cells; a plurality of photodetectors; said pumping system supplying solvent to at least one flow cell of said plurality of flow cells; at least one light source; said at least one light source applying light to at least one of said plurality of photodetectors after the light has passed through a corresponding one of said flow cells; a time division multiplex circuit having a plurality of input means and a multiplex cycle time during which it multiplexes at least some of said plurality of input means for a time division whereby the time division multiplex circuit conducts signals from each individual input means of said some of said plurality of input means for a time division; at least one circuit means arranged to receive energy from at least one of said photodetectors for a substantial portion of said multiplex cycle time and apply it to a corresponding one of said plurality of multiplex circuit input means during said time division said at least one circuit means being a non-switching circuit with low bandwidth, whereby sensitivity is improved. 2. A liquid chromatographic system including:at least one pumping system; a plurality of flow cells; a plurality of photodetectors; said pumping system supplying solvent to at least one flow cell of said plurality of flow cells; at least one light source; said at least one light source applying light to at least one of said plurality of photodetectors after the light has passed through a corresponding one of said flow cells; a time division multiplex circuit having a plurality of input means and a multiplex cycle time during which it multiplexes each of at least some of said plurality of input means for a time division whereby the time division multiplex circuit conducts signals from each individual input means of said some of said plurality of input means for a time division; and at least one circuit means arranged to receive energy from at least one of said photodetectors for a substantial portion of said multiplex cycle time and apply it to a corresponding one of said plurality of multiplex circuit input means during said time division; said at least one circuit means being a non-switching circuit with low bandwidth, whereby sensitivity is improved; said at least one circuit means having a fast rise time, flat topped response to an impulse and a pulse duration that lasts at least a substantial portion of the multiplex cycle time. 3. A liquid chromatographic system including:at least one pumping system; a plurality of flow cells; a plurality of photodetectors; said pumping system supplying solvent to at least one flow cell of said plurality of flow cells; at least one light source; said at least one light source applying light to at least one of said plurality of photodetectors after the light has passed through a corresponding one of said flow cells; a time division multiplex circuit having a plurality of input means and a multiplex cycle time during which it multiplexes each of at least some of said plurality of input means for a time division whereby the time division multiplex circuit conducts signals from each individual input means of said some of said plurality of input means for a time division; at least one circuit means arranged to receive energy from at least one of said photodetector for a substantial portion of said multiplex cycle time and apply it to a corresponding one of said plurality of multiplex circuit input means during said time division; said at least one circuit means is a non-switching circuit with low bandwidth, whereby sensitivity is improved; at least one of a plurality of first light guides receiving light from said light source and transmitting the light to said at least one flow cell; and at least one of a plurality of second light guides positioned to receive light from said at least one of a plurality of first light guides and transmit the light to at least one of said plurality of photodetectors; said at least one of a plurality of first and one of a plurality of second light guides having a corresponding one of its ends positioned within a flow cell adjacent to each other so that light passes from an end of said first light guide through solute in said flow cell and into an end of the second light guide, whereby light is diminished within said flow cell by absorbance by solute. 4. A liquid chromatographic system including:at least one pumping system; a plurality of flow cells; a plurality of photodetectors; said pumping system supplying solvent to at least one flow cell of said plurality of flow cells; at least one light source; said at least one light source applying light to at least one of said plurality of photodetectors after the light has passed through a corresponding one of said flow cells; a time division multiplex circuit having a plurality of input means and a multiplex cycle time during which it multiplexes each of at least some of said plurality of input means for a time division whereby the time division multiplex circuit conducts signals from each individual input means of said some of said plurality of input means for a time division; at least one circuit means arranged to receive energy from at least one of said photodetectors for a substantial portion of said multiplex cycle time and apply it to a corresponding one of said plurality of multiplex circuit input means during said time division; said at least one circuit means being a non-switching circuit with low bandwidth, whereby sensitivity is improved; at least one of a plurality of first light guides receiving light from said light source and transmitting the light to said at least one flow cell; at least one of a plurality of second light guides positioned to receive light from said at least one of a plurality of first light guides and transmit the light to at least one of said plurality of photodetectors; said at least one of a plurality of first and one of a plurality of second light guides having a corresponding one of its ends positioned within a flow cell adjacent to each other so that light passes from an end of said first light guide through solute in said flow cell and into an end of the second light guide, whereby light is diminished within said flow cell by absorbance by solute; said ends of said first and second light guides being spaced in the region of 0.02 to 5 millimeters apart. 5. A liquid chromatographic system according to claim 4 in which said light source includes:at least one lamp; means for focusing light from said at least one lamp onto a diffraction grating; means for focusing light from the diffraction grating onto an opening; and at least some of a plurality of light guides having an end in said opening whereby said at least some of said plurality of light guides receive light from said diffraction grating. 6. A liquid chromatographic system in accordance with claim 5 including at least one column wherein:said at least one pumping system comprises a plurality of pumps; said at least one column comprises a plurality of columns, each of said plurality of columns communicates with a different one of said plurality of pumps; said at least one photodetector comprises a plurality of photodetectors, each of said plurality of photodetectors communicating with a different one of said plurality of columns, whereby each of said photodetectors detects a signal; and each of said photodetectors includes a corresponding photodiode positioned against one end of said second light guide. 7. A liquid chromatographic system in accordance with claim 6 in which each of said light guides is in intimate contact with a different photodiode.8. A method of performing liquid chromatography comprising the steps of:pumping solvent through a plurality of flow cells; transmitting light through at least one of said plurality of flow cells to a corresponding one of a plurality of photodetectors; multiplexing signals from at least some of said plurality of photodetectors during a multiplex cycle time from at least one of said plurality of photodetectors to an output terminal during one stroke portion of said multiplex cycle time; transmitting energy from said at least one of said photodetectors for a substantial portion of said multiplex cycle time to a corresponding one of a plurality of multiplex circuit input means connected between a corresponding one of said photodetectors and a multiplex circuit that multiplexes the signals from at least some of said plurality of photodetectors during said stroke time, wherein said energy from said multiplex circuit input means is transmitted to said output terminal during said stroke time; transmitting light through said at least one photodetector from a first light guide; receiving light passing through solute from said first light guide by a second light guide; and transmitting light received by said second light guide to a second photodetector, wherein said first and second light guides have their ends positioned within a flow cell adjacent to each other so that light passes from an end of one light guide through solute in said flow cell and into an end of the second light guide, whereby light is diminished within said flow cell by absorbance by solute. 9. A method of performing chromatography comprising the steps of:pumping solvent through a plurality of flow cells; transmitting light through at least one of said plurality of flow cells to a corresponding one of a plurality of photodetectors; multiplexing signals from at least some of said plurality of photodetectors during a multiplex cycle time from at least one of said plurality of photodetectors to an output terminal during one stroke portion of said multiplex cycle time; transmitting energy from said at least one of said photodetectors for a substantial portion of said multiplex cycle time to a corresponding one of a plurality of multiplex circuit input means connected between a corresponding one of said photodetectors and a multiplex circuit that multiplexes the signals from at least some of said plurality of photodetectors during said stroke time, wherein said energy from said multiplex circuit input means is transmitted to said output terminal during said stroke time; transmitting light through said at least one photodetector from a first light guide; receiving light passing through solute from said first light guide by a second light guide; transmitting light received by said second light guide to a second photodetector, wherein said first and second light guides have their ends positioned within a flow cell adjacent to each other so that light passes from en end of one light guide through solute in said flow cell and into an end of the second light guide, whereby light is diminished within said flow cell by absorbance by solute; said step of transmitting light including the substeps of: transmitting light from at least one lamp; focusing light from said at least one lamp onto a diffraction grating; and focusing light from the diffraction grating onto an opening wherein at least some of a plurality of light guides having an end in said opening whereby said at least some of said plurality of light guides receive light from said diffraction grating. 10. A method in accordance with claim 9 further including the step of detecting light with photodiodes positioned against one end of said second light guide.11. A liquid chromatographic system including:at least one pumping system; a plurality of flow cells; a plurality of photodetectors; said pumping system supplying solvent to at least one flow cell of said plurality of flow cells; at least one light source; said at least one light source applying light to at least one of said plurality of photodetector after the light has passed through a corresponding one of said flow cells; a time division multiplex circuit having a plurality of input means and a multiplex cycle time during which it multiplexes each of at least some of said plurality of input means for a time division whereby the time division multiplex circuit conducts signals from each individual input means of said some of said plurality of input means for a time division; at least one circuit means arranged to receive energy from at least one of said photodetectors for a substantial portion of said multiplex cycle time and apply it to a corresponding one of said plurality of multiplex circuit input means during said time division; said at least one circuit means is a non-switching circuit with low bandwidth, whereby sensitivity is improved; at least one of a plurality of first light guides receiving light from said light source and transmitting the light to said at least one flow cell; and at least one of a plurality of second light guides positioned to receive light from said at least one of a plurality of first light guides and transmit the light to at least one of said plurality of photodetectors; said at least one of a plurality of first and one of a plurality of second light guides having a corresponding one of its ends positioned within a flow cell adjacent to each other so that light passes from an end of said first light guide through solute in said flow cell and into an end of the second light guide, whereby light is diminished within said flow cell by absorbance by solute; and said flow cell is sufficiently large to permit fluid to flow around said first and second light guides. 12. A liquid chromatographic system including:at least one pumping system; a plurality of flow cells; a plurality of photodetectors; said pumping system supplying solvent to at least one flow cell of said plurality of flow cells; at least one light source; said at least one light source applying light to at least one of said plurality of photodetectors after the light has passed through a corresponding one of said flow cells; a time division multiplex circuit having a plurality of input means and a multiplex cycle time during which it multiplexes each of at least some of said plurality of input means for a time division whereby the time division multiplex circuit conducts signals from each individual input means of said some of said plurality of input means for a time division; at least one circuit means arranged to receive energy from at least one of said photodetectors for a substantial portion of said multiplex cycle time and apply it to a corresponding one of said plurality of multiplex circuit input means during said time division; said at least one circuit means is a non-switching circuit with low bandwidth, whereby sensitivity is improved; at least one of a plurality of first light guides receiving light from said light source and transmitting the light to said at least one flow cell; and at least one of a plurality of second light guides positioned to receive light from said at least one of a plurality of first light guides and transmit the light to at least one of said plurality of photodetectors; said at least one of a plurality of first and one of a plurality of second light guides having a corresponding one of its ends positioned within a flow cell adjacent to each other so that light passes from an end of said first light guide through solute in said flow cell and into an end of the second light guide, whereby light is diminished within said flow cell by absorbance by solute; said flow cell is sufficiently large to permit fluid to flow around said first and second light guides; and said flow cell is sufficiently large for preparatory chromatography. 13. A liquid chromatographic system including:at least one pumping system; a plurality of flow cells; a plurality of photodetectors; said pumping system supplying solvent to at least one flow call of said plurality of flow cells; at least one light source; said at least one light source applying light to at least one of said plurality of photodetectors after the light has passed through a corresponding one of said flow cells; a time division multiplex circuit having a plurality of input means and a multiplex cycle time during which it multiplexes each of at least some of said plurality of input means for a time division whereby the time division multiplex circuit conducts signals from each individual input means of said some of said plurality of input means for a time division; at least one circuit means arranged to receive energy from at least one of said photodetectors for a substantial portion of said multiplex cycle time and apply it to a corresponding one of said plurality of multiplex circuit input means during said time division; said at least one circuit means being a non-switching circuit with low bandwidth, whereby sensitivity is improved; at least one of a plurality of first light guides receiving light from said light source and transmitting the light to said at least one flow cell; at least one of a plurality of second light guides positioned to receive light from said at least one of a plurality of first light guides and transmit the light to at least one of said plurality of photodetectors; said at least one of a plurality of first and one of a plurality of second light guides having a corresponding one of its ends positioned within a flow cell adjacent to each other so that light passes from an end of said first light guide through solute in said flow cell and into an end of the second light guide, whereby light is diminished within said flow cell by absorbance by solute; said ends of said first and second light guides being spaced sufficiently close to block bubbles from passing between them.