Poor peak area reproducibility with e2695 - WKB95709

SYMPTOMS

• The area reproducibility of 6 injections exceeds 2% RSD
• Problem caused by individual outliers

ENVIRONMENT

• Alliance HPLC System
• 2695 Separations Module
• Isocratic method using a mixture of water, buffer salt, and acetonitrile

CAUSE

Because the buffer salt stays in the V3 valve for a long time, it may precipitate crystals and cause the V3 not to close tightly, which causes occasional inaccurate sampling of the syringe and affects area reproducibility.

FIX or WORKAROUND

Use a mixture of acetonitrile and water (as in method's mobile phase, without buffer salt) to purge the injector. After the wet prime and equilibrium are completed, use this mobile phase to purge the injector three times, equilibrate for 30 minutes, and then inject. Ensure that after the total injection volume reaches about 200 µL (the volume of the V2-V3 pipeline), purge the injector another three times.

ADDITIONAL INFORMATION