Method and apparatus for sample injection in liquid chromatography
The present invention provides a method and apparatus for substantially eliminating destructive transients of pressure or flow rate which can degrade the efficiency and useful lifetime of chromatography columns. The present invention enables a substantially constant flow of mobile phase liquid to be maintained through the chromatography system by eliminating the flow blockage interval associated with the actuation of sample injection valves. The present invention further provides a method to reduce the pressure and flow rate transients associated with pressurization of the sample loop contents when the sample loop is introduced to chromatography system delivery pressure.
1. A method for eliminating a pressure transient during actuation of a rotary shear-seal injection valve the steps comprising:
maintaining a first flow path from a pump to a column through the valve during a valve transition from a load state to an inject state while establishing a second flow path through the valve between a syringe port and a sample needle port.
2. The method of claim 1 , wherein the valve provides the first flow path from the pump to the column in the load state and wherein the valve provides a third flow path from the pump through a sample loop to the column in the inject state.
3. The method of claim 2 , wherein the third flow path from the pump through the sample loop to the column is the only flow path from the pump to the column in the inject state.