Liquid chromatography (LC) is fundamental to analytical workflows, spanning from initial research phases to regulated quality control. However, even proven methods can encounter difficulties when transitioning to routine operation. Minor changes in configuration, mobile phase preparation, gradient timing, or injection parameters can introduce variability that only becomes apparent after numerous runs.
In a recent Separation Science webinar, Expert Answers: LC Troubleshooting and Best Practices, Jim Grinias, Professor of Chemistry and Biochemistry at Rowan University, unpacks these challenges through audience-driven questions and real troubleshooting scenarios. Rather than offering a checklist, he focuses on how experienced chromatographers think when methods stop behaving as expected.
Grinias suggests that troubleshooting should begin with the fundamentals, specifically by verifying the separation's stability before considering potential hardware issues. "If the retention time is shifting, the number of possible issues grows dramatically," making stable retention the logical first step in any analysis.
“We’re making a big assumption that the retention time is stable. If not, we’re kind of going into a whole new world,” he adds. That divide—stable chromatography versus shifting separation—anchors the rest of the discussion.
Working in analytical science?
Register for a FREE Separation Science account to subscribe to the Separation Science Newsletter.
Start With the Separation
Across audience questions, Grinias separates LC variables from detection effects. Changes in peak area often stem from injector behavior rather than detector performance. Incorrect injection volumes, autosampler leaks, inadequate needle washes, or carryover within unflushed flow paths can all create apparent signal loss or gain.
In workflows involving liquid chromatography coupled with mass spectrometry (LC-MS), this distinction becomes even more important. Carryover from hydrophobic analytes, dilution from residual wash solvent, or inconsistent sample pickup can introduce trends that resemble true analytical shifts. Analysts often assume signal changes originate in the mass spectrometer. In practice, the root cause often lies upstream—in injection geometry, elution gradient composition, or incomplete equilibration between runs. The session demonstrates how to isolate these variables logically instead of adjusting multiple parameters at once.
Method Design and Validation Must Be Fit for Purpose
Troubleshooting does not begin at the instrument; it begins with intent. “The biggest thing is what is the actual question you’re trying to answer?” Grinias explains. Validation must follow purpose, not habit.
“It’s got to be a fit-for-purpose method that meets the specific needs of the analysis.” Not every workflow demands the same quantitative rigor, but every workflow must be defensible in context—whether supporting exploratory research, lot release, impurity profiling, or regulatory submission.
He cautions against treating validation as a box-checking exercise. Accuracy, precision, linearity, specificity, recovery, and stability remain essential, particularly in regulated environments. But over-optimizing throughput—through overlapped injections or aggressive sequence compression—can subtly alter gradient conditions, dwell volumes, or sample pickup timing.
“Make it as rigorous as the specific application requires,” he advises.
Understanding Noise, Carryover, and Ghost Peaks
Background noise and unexpected peaks persist because their causes are rarely obvious. What appears to be a detector issue often originates earlier—in equilibration, mobile phase behavior, or incomplete clearing of prior injections.
Grinias explores how incomplete elution, insufficient wash strength, or poorly characterized dwell volumes can create patterns that surface only during sequence runs. These patterns can mislead analysts into attributing electronic noise or detector instability when the underlying issue lies in the method structure.
“Ghost peaks” provide a clear example. Rather than new contaminants, they often signal that a method has not fully accounted for everything moving through the system. Subtle choices in method timing, washing strategy, gradient design, and equilibration can allow late-eluting components to appear unexpectedly—sometimes several injections later.
Additional troubleshooting topics covered in the webinar include: injector leaks and robotics affecting reproducibility; how storage conditions and freeze–thaw cycles influence LC–MS response; when autosampler carryover mimics signal gain; how gradient methods complicate overlapped injections; and why small changes in tubing dimensions, system dead volume, or mixer configuration can alter performance.
LC–MS troubleshooting
In LC–MS workflows, Grinias addresses challenges at the interface between separation and detection. He discusses distinguishing LC-driven variability from ionization effects, recognizing when injector behavior drives apparent sensitivity loss, and understanding how source conditions, tune files, and integration settings influence quantitative results.
Key Takeaways for Analytical Laboratories
Grinias closes by prompting analysts to examine their own workflows:
- Are you confirming separation stability before reacting to signal changes?
- Have you ruled out injector mechanics, sample preparation variables, and carryover before adjusting detector settings?
- Do wash solvents, gradients, and equilibration steps reflect analyte chemistry?
- Is validation aligned with actual regulatory or operational risk?
- Where might throughput optimizations introduce variability across long sequences?
- Are noise and unexpected peaks treated as system-level symptoms rather than isolated anomalies?
- How confident are you that today’s method will behave consistently across instruments, operators, and days?
The on-demand webinar expands on these themes through real troubleshooting scenarios and audience discussion. For scientists responsible for method performance, data quality, or regulatory confidence, the session offers insight into how an experienced chromatographer approaches complex LC problems—especially when the answer is not immediately obvious.
