What is the Role of Tailing Factor in HPLC

Table of content

• Introduction
• Tailing factor
• Definition
• Tailing factor acceptance criteria
• Applications
• Conclusion

Introduction and Background; Role of Tailing Factor in HPLC and GC

The tailing factor is widely used in system suitability tests in HPLC analysis and GC. In this post, I will share my skill-based knowledge on “Role of Tailing Factor in HPLC and GC“; Which will include calculation of tailing factor, its application in chromatographic method development and various factors affecting the tailing factor. Having read this article you will be able to answer question like:

What is the tailing factor and how it is calculated?

What are the applications of tailing factor in chromatographic analysis?

What are the applications of the tailing factor in the chromatographic analysis?

What are the acceptance criteria for the tailing peak?

Tailing factor

Tailing factor is one of the widely used parameters in chromatographic analysis. It tells about the symmetry /shape of the the peak.

In the above chromatogram peak-2 is symmetrical whereas in peak-1 is deforming from the front side and peak-3 is deforming from tail side. Peak-1 is called the ideal peak, peak-2 is called the fronting peak and peak-3 is called the tailing peak.

Definition of the tailing factor

The Tailing factor is defined as the distance from the front edge of the peak to the back edge, divided by the distance from the front edge to the centre line with all distances measured at 5% ( or 1/20) of the maximum peak height (see figure-2). It is also called USP tailing and it is denoted by T

Where: X is the front half width and Y is the back half width at 5% of the peak height

Calculation of the tailing factor

T = (X+Y)⁄2

Tailing factor acceptance criteria

Practically it is impossible to get a symmetrical peak in chromatographic analysis. Following are the acceptance criteria for the tailing factor:

• Peak with T ≤1.5 is preferable and it is accepted by all regulatory agencies
• But for typical molecules like T ≥ 2 is also acceptable by regulatory agencies

Factors affecting tailing factor

• Structure of the molecule: Generally basic molecules show more tailing
• Shape of the peak: Broad peaks have more tailing compared to sharp peaks.
• pH of the mobile phase: Some of the molecules are highly pH sensitive and beyond beyond that pH shows tailing in the peak
• Buffer concentration: Tailing is directly proportional to the buffer concentration of the mobile phase.
• Solvents used in the mobile phase; Some of the molecules are highly solvent selective and show taling if other solvents are used. Generally, the mobile phase with Acetonitrile solvent peaks with no tailing or less tailing compared to mobile phase with methanol.
• Column temperature: Tailing factors is directly proportional to the column temperature
• Column stationary phase (chemistry and purity): Tailing factor also depends upon the chemistry and purity of the stationary phase
• Elution time: T is inversely proportional to the peak elution time
• Column efficiency: T is directly proportional to the column efficiency
• Injection volume:T is inversely proportional to the peak injection volume
• Nature of the diluent:T also depends upon the nature of the diluent

Application of the tailing factor

It is used as a system suitability parameter in the chromatographic analysis. Lower the tailing factor better is than the method.

Conclusion

Try to keep the tailing factor with limit, T ≤1.5 as one of the system suitability parameter during method development. For higher tailing factor scientific justification must be given to avoid any regulatory query. This is all about this article. For any question related to this post write in the comment section and i will answer on the priority basis.

Abbreviation

• T: Tailing factor

References

• Thai Pharmacopeia
• Pharmaceutical analysis by James. W. Munson., page-109