What Causes Peak Tailing in HPLC?

Posted by Chrom Tech on 7th Oct 2025

What Causes Peak Tailing in HPLC?

Understanding peak tailing begins with recognizing what defines a “good” chromatographic peak. An ideal peak is symmetrical—often referred to as a Gaussian peak. High-quality peaks with narrow widths and high efficiency are critical for accurate quantification and resolution. Poor peak shapes, including peak fronting and peak tailing, can compromise method performance and data reliability.

How Is Peak Shape Measured?

USP Tailing Factor

USP tailing factor diagram
Calculation of the USP tailing factor (T).
W0.05
Width of the peak measured at 5% of peak height from the baseline.
f
Distance between the peak maximum and the leading edge at W0.05.

Asymmetry

Asymmetry diagram
Measuring chromatographic asymmetry for peak evaluation.

Peak Width at Half Height

Peak width at half height
Peak width measurement at half height for resolution analysis.

Factors Affecting HPLC Peak Tailing

  • Silanol Interactions: Ionized silanols on silica-based columns can interact with basic analytes, increasing tailing, especially at mid pH.
  • pH Effects: Analytes near their pKa may interact unevenly, increasing tailing potential.

Minimize these interactions by using mobile phase additives or selecting an HPLC column with endcapped or polar-embedded bonded phases. Endcapped phases reduce unreacted silanols, while polar embedded phases provide extra shielding for basic compounds.

  • Mobile Phase and Buffer: Avoid pH near analyte pKa. Buffered mobile phases stabilize pH and improve peak symmetry. Adjust organic modifiers (e.g., acetonitrile vs. methanol) for optimization.
  • Extra Column Effects: Minimize tubing length and diameter. Narrow PEEK tubing (e.g., 0.005" ID) reduces dead volume and improves resolution compared to wider tubing.

Why Peak Tailing Matters

Peak tailing indicates potential chromatographic problems affecting reproducibility and result accuracy.

Impact on Data Accuracy

  1. Obscures nearby compounds, reducing quantification accuracy.
  2. Interfering compounds can worsen tailing, complicating identification.

How to Address Peak Tailing

  • Adjust Detection Wavelength: Helps isolate tailing caused by interferents.
  • Enhance Column Efficiency: Longer columns or smaller particles improve symmetry.
  • High-Efficiency Columns: Advanced columns (e.g., JoblingAid HT) reduce tailing for critical separations.

Peak Tailing in Reversed-Phase HPLC

In reversed-phase chromatography, peak tailing arises from hydrophobic retention and secondary polar interactions, particularly with ionized silanol groups. Basic compounds interacting with deprotonated silanols (pH > 3.0) often exhibit pronounced tailing.

High pH for Analyzing Basic Compounds

Operating at higher pH suppresses acid ionization, improving separation of basic analytes. Modern columns with bi- and tridentate ligands protect silica from hydrolysis, allowing stable performance at elevated pH.

Importance of Sample Clean-Up

Effective sample clean-up is critical for minimizing tailing, improving resolution, and protecting columns. Techniques like Solid Phase Extraction (SPE) remove contaminants that affect peak shape.

Benefits of Sample Clean-Up

  • Eliminates interferences from complex matrices.
  • Improves peak symmetry and quantification precision.
  • Enhances sensitivity and lowers detection limits.
  • Prolongs column and instrument lifespan by preventing contamination.

Conclusion

Peak tailing in HPLC affects resolution, accuracy, and reproducibility. Understanding causes—such as silanol interactions, mobile phase conditions, and system factors—enables targeted solutions. Optimizing pH, using high-efficiency columns, and implementing proper sample clean-up ensures sharper, more reliable peaks.

Frequently Asked Questions (FAQ)

What is peak tailing in HPLC?

It occurs when a chromatographic peak has an asymmetric shape with a longer trailing edge, often due to analyte interactions with the stationary phase or system components.

What causes peak tailing?

Common causes include silanol interactions, pH near analyte pKa, extra column dead volume, and sample impurities.

How can I reduce peak tailing?

Use endcapped or polar-embedded HPLC columns, optimize mobile phase pH and buffers, minimize tubing volume, and ensure proper sample clean-up.

Why is peak tailing problematic?

Tailing peaks reduce resolution, obscure nearby compounds, and lead to inaccurate quantification.

Does pH affect peak tailing?

Yes. pH near the analyte’s pKa increases tailing due to uneven interaction with silanol groups.

What is a good USP tailing factor?

A USP tailing factor between 0.9–1.2 indicates a symmetrical peak. Values above 1.5 suggest noticeable tailing.

How does column choice influence tailing?

Columns with advanced bonding or endcapping reduce silanol activity, improving peak symmetry for basic analytes.

Can impurities cause tailing?

Yes. Sample impurities or particulates can interact with the column, causing tailing and decreased reproducibility.

What role does tubing diameter play?

Large-diameter tubing increases dead volume and peak broadening. Narrow PEEK tubing improves efficiency and reduces tailing.

Is peak tailing more common with basic compounds?

Yes. Basic analytes interact strongly with deprotonated silanols above pH 3.0, producing pronounced tailing.