The Knowledge Hub
Practical troubleshooting guides for working analytical chemists — HPLC, UHPLC, LC-MS, GC, and reagent prep. Each guide is diagnostic-first and linked to the tool that resolves it.
How to Optimize HPLC Selectivity: A Systematic pH, Solvent and Temperature Screen
To optimize HPLC selectivity, work through the levers in order and track the critical pair: scout mobile-phase pH against the analytes’ pKa…
Extra-Column Dispersion: Where Efficiency Is Lost Outside the Column
Extra-column dispersion is the peak broadening that the injector, connecting tubing, fittings and detector add outside the column; their variances, not their…
Injection Solvent Effects: How Diluent Strength and Injection Volume Distort Peaks
A sample diluent stronger than the mobile phase carries the analyte band through the column inlet inside the injected plug until that…
Choosing an HPLC Column for a Regulated Method: USP L-Designations, Equivalency and Revalidation
A USP L-designation names a packing type, not a column: many dissimilar C18 columns are all L1. To replace the column in…
HPLC Column Dimensions and Particle Size: How to Scale a Method Correctly
To scale an HPLC method to a new column, keep column chemistry unchanged, hold the length-to-particle-size ratio (L/dp) within −25% to +50%,…
When Should You Switch from Reversed-Phase HPLC to HILIC?
Use HILIC instead of reversed phase when polar or ionized analytes stay weakly retained after pH adjustment and aqueous-stable reversed-phase columns have…
How to Choose an Orthogonal HPLC Column for Impurity Profiling
Choose an orthogonal HPLC column for impurity profiling by its selectivity, not its label. Pick a phase whose interactions differ from the…
Type A vs Type B Silica and Endcapping: Why Basic Analytes Tail Differently
Basic analytes can tail differently on nominally similar HPLC columns because their silica surfaces expose different secondary interaction sites. Older Type A…
C18 vs C8 vs Phenyl vs PFP vs HILIC: How Stationary-Phase Chemistry Changes Selectivity
C18 and C8 primarily retain analytes through hydrophobic interactions, while phenyl and pentafluorophenyl (PFP) phases can alter selectivity through aromatic, dipolar and…
LC-MS/MS Carryover Localization: Autosampler, Column, Tubing or Source?
To localize LC-MS/MS carryover, first establish whether a clean blank acquires analyte-associated response after a high sample. Then compare an injected blank…
Stable Isotope Labeled Internal Standards in LC-MS/MS: What They Correct and What They Don’t
A stable isotope labeled internal standard (SIL-IS) corrects LC-MS/MS results only for disturbances it shares with the analyte. Extraction losses that happen…
Post-Extraction Spike in LC-MS/MS: Matrix Factor, Recovery and Process Efficiency
A post-extraction spike experiment measures how much co-eluting matrix changes LC-MS/MS response, separately from how much analyte the sample preparation loses. Three…