System volume issue leads to split peaks, shoulder peaks, and inconsistent peak shape between injections on 1525/2489/7725i Breeze system - WKB84698

SYMPTOMS

• Split peaks, shoulder peaks, and inconsistent peak shape between injections on 1525/2489/7725i Breeze system

ENVIRONMENT

• 1525 chromatographic pump
• 2489 UV Detector
• 7725i manual injector,10-μL loop

CAUSE

Based on analysis of the experimental results, the possible causes: under the specific experimental conditions of the customer, insufficient mixing occurred due to a system volume issue that significantly impacted the chromatographic behavior of the sample.

FIX or WORKAROUND

1. Test injection was performed using caffeine, and the peak shape was normal. Therefore, we inferred that the symptoms were application-specific. See experimental conditions (which were somewhat unusual) in ADDITIONAL INFORMATION.
2. According to feedback from the client, the peak shape was normal on both the PL system and the full-loop system when using the 2707 autosampler. We inferred that the difference in physical structure of the 7725i and 2707 caused the different results in that specific application.
3. Replacing the original 10-μL loop with a 100-μL loop on the 2707 did not solve the problem.
4. Reconnecting the connecting tube from 2707 to 7725i and performing a test injection, the peak shape was normal.
5. Ultimately, the 7725i inlet tube was replaced with a 0.04-inch ID, 30-cm tube, and the test results met expectations.

ADDITIONAL INFORMATION

Experimental Conditions

      a. Column: TSKgel

      b. Mobile phase A: Trics (2.42 g Trics dissolved in 1 L water, pH adjusted to 9 using formic acid); B: Trics+NaCl (2.42 g Trics and 58.44 g NaCl were weighed and dissolved in 1 L water, pH adjusted to 9 using formic acid)

      c. LC conditions: