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AssigneeVarian Associates, Inc.
InventorsAhmad Abu-Shumays, John C. Helmer, Stephen J. Luchetti
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In a high-performance, high-pressure liquid chromatography system, gradient elution of solvent components from a plurality of component reservoirs can be accomplished according to a programmed temporally variable ratio by a single reciprocating pump. The pumping cycle comprises a plurality of fill strokes with intervening pumping strokes. During one of the fill strokes of the cycle, a proportioned mixture of solvent components is admitted to the pump chamber from the respective reservoirs by means of proportioning valves. During each of the other fill strokes of the cycle, only a single solvent component is admitted to the pump chamber. Consequently, a relatively low concentration of a particular component can be delivered by the pump with precision over a complete pumping cycle, although a comparatively higher and therefore more accurately measurable concentration of that component is admitted to the pump chamber during any given fill stroke. The opening and closing of the proportioning valves during the component proportioning fill stroke is sequenced to minimize deviations of the relative concentrations from the programmed concentration ratio. Proper sequencing of the proportioning valves reduces inaccuracies that would otherwise tend to occur, especially at the upper and lower concentration limits, due to effects related to the compressibility of residual solvent remaining in the pump chamber at the end of each pumping stroke.
In a high pressure, high performance liquid chromatography system a method for providing gradient proportioning of a plurality of solvent components, said system comprising:
A method for providing in a high pressure, high performance liquid chromatography system an accurately proportioned mixture of components in the liquid outflow from a single reciprocating pumping means near zero and one hundred percent concentrations, said components being admissible by proportioning valves from separate reservoirs into said pumping means according to a programmed concentration distribution that may vary for different fill strokes of said pumping means, said components being delivered by said pumping means to a single chamber wherein mixing of said components can occur, said outflow mixture having a specified concentration distribution for the components thereof over a pumping cycle for said reciprocating pumping means, said pumping cycle comprising a plurality of fill strokes for said pumping means, the method for providing said mixture of components comprising the admission of components into said pumping means during the fill strokes of said cycle in accordance with a program that provides for a characteristic concentration distribution for said components particular to each of said fill strokes, the characteristic concentration distribution particular to at least one of said fill strokes being different from the selected concentration distribution for said outflow mixture over said pumping cycle, during the fill stroke of said at least one fill stroke having a different characteristic concentration;
Dependencies are inferred from the claim text.