Varian Associates, Inc.

Stephen J Luchetti

John C Helmer

Detlef R Boehme

Ahmad Abu-Shumays

Kenneth C Judah

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.

Single-pump multiple stroke proportioning for gradient elution liquid

A damper for use with a high pressure pumping system, such as a liquid chromatography system, which incorporates a reciprocating pump. The device is a generally enclosed canister including an internally formed flow volume. Inlet and outlet passages through the canister communicate with the flow volume, the inlet passage being connectable to receive the high pressure flow. A compressible body, e.g. of Teflon is positioned in the flow volume. The dimensions of the body are slightly smaller than those of the surrounding volume, whereby the high pressure flow passing between the inlet and outlet flows through the space between the body and the internal canister walls. The compression and decompression of the body in response to the pulsations in the flow dissipate the energy carried by the pulses, thereby damping same.

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Berkeley, CA, United States of America

Stephen J Luchetti