Liquid Chromatography Blog

PEEK Follow-up

PEEK (poly-ether-ether-ketone) tubing and fittings have become a standard part of most HPLC systems today. The flexibility and ease of cutting the tubing, coupled with the convenience of finger-tightened fittings make a combination that is hard...

Method Adjustment vs Change Part 7: Follow-up

In the previous articles in this series (Part 1Part 2Part 3Part 4Part 5, Part 6), we have explored the concept of the adjustment of HPLC methods. In particular, we have tried to determine the difference between method adjustment and...

Method Adjustment vs Change Part 6: Interactions

This is the last in a six-part series on allowed adjustments to HPLC methods. In the previous instalments (Part 1, Part 2, Part 3, Part 4, Part 5), we’ve looked at each of the specific variables listed in Table 1.


The separation power of HPLC combined with the very high sensitivity and selectivity of MS detection is widely used to develop analytical methods that are required to achieve ultra-low detection and quantification limits. Examples of such...

Sample Solvent in HILIC

The sample solvent, also called dissolution solvent or injection solvent, is the solvent used to prepare the solution in which the compound to be analysed by HPLC is dissolved. The choice of the sample solvent is fundamental for a successful...

Column Equilibration in HILIC

It is matter of fact that the samples most chromatographers have to face are rather complex for sample number and compound variety. In these situations, gradient elution is largely preferred for the separation of analytes with different retention...

Column temperature in HILIC

Mostly in HILIC conditions, by increasing column temperature a decrease in the retention time is observed.

HILIC Mobile Phase: pH

The pH of the mobile phase should be selected in order to enhance the hydrophilicity of the analytes.

HILIC Mobile Phase: Salt Content

The addition of salt to HILIC mobile phases is strongly recommended to improve reproducibility and peak shape. Do you know how to solubilize the salt in mobile phases at high acetonitrile content?

HILIC Mobile Phase: Solvents

In HILIC, small variations of the elution conditions often result in differences in the retention greater than the ones observed in RPLC. Therefore, particular attention has to be paid to the selection and the preparation of the eluents. 

HILIC Stationary Phases

A common and useful classification of the HILIC stationary phases is on the basis of the presence of functional groups on the surface and their charged state: they can be divided in unbounded and bonded phases, and these ones are classified in...

Method Adjustment vs Change Part 5: Volume, Column Temperature and Detector Wavelength

In the last few articles we've focused on the guidelines for method adjustment listed in the European Pharmacopoeia (EP) and United States Pharmacopoeia (USP). We looked at pH (Part 1), mobile-phase composition (Part 2), column dimensions (Part 3...

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