Liquid chromatography system

In a method for periodically injecting small predetermined amounts of sample liquid into a high pressure stream of carrier liquid for introduction into a liquid chromatography apparatus for analysis, the improvement comprising the steps of:

• 1. supplying carrier liquid under a predetermined high pressure in a primary flow path to said column;
• 2. periodically closing said primary flow path;
• 3. sensing a predetermined small upstream pressure increase in said pressurized carrier liquid when said primary flow path is closed;
• 4. immediately diverting all of said high pressure carrier liquid into a second flow path to said column in response to said small upstream pressure increase in said carrier liquid pressure in said primary flow path;
• 5. accumulating a predetermined amount of sample liquid in said primary flow path;
• 6. thereafter opening said primary flow path to introduce the accumulated sample liquid into said carrier liquid;
• 7. sensing a predetermined small upstream pressure decrease in said pressurized carrier liquid when said primary flow path is opened;
• and
• 8. immediately closing said second flow path in response to said small upstream pressure decrease to redirect all of said carrier liquid into the primary flow path and thereby maintain at all times a substantially constant high pressure flow of carrier liquid to said column.

In a liquid chromatography apparatus including a liquid-separation column, pump means and conduit means for continuously delivering a flow of carrier liquid to said column under a predetermined high pressure, and means positioned in said conduit means between said pump means and said column for introducing a predetermined amount of liquid sample into said pressurized carrier liquid for passage into said column;

• the improvement wherein said sample introducing means comprises:
• means for selectively blocking a primary flow path of said pressurized carrier liquid from said pump means to said column;
• normally closed pressure-actuated valve means for diverting the entire flow of said pressurized carrier liquid into a secondary flow path from said pump means to said column in response to a predetermined small pressure increase in said pressurized carrier liquid upstream of said blocking means when said primary flow path is blocked;
• means for storing a selected volume of liquid sample in said primary flow path when said primary flow path is blocked;
• and
• means for selectively re-opening said primary flow path whereby said volume of liquid sample is carried to said column by the entire flow of said pressurized carrier liquid;
• said pressure-actuated valve means closing to block said secondary flow path in response to a predetermined small pressure decrease in said pressurized carrier liquid upstream of said pressure-actuated valve when said primary flow path is re-opened, thereby maintaining a substantially constant high pressure flow of carrier liquid to said column.