Better peak quality in HPLC

High temperature liquid chromatography (HTLC) specialist Selerity Technologies has demonstrated, under experimental conditions, that analyte focusing is possible if the preheater is programmed differently than the column compartment during thermal gradient runs.

The findings supplement earlier work carried out by Selerity on the benefits of mobile phase preheating.

Temperature programming produces sharper peaks and greatly improves resolution.

In these latest experiments, the low-mass, low-volume preheater was programmed independently from the column compartment and Polaratherm total temperature controller launched by Selerity during summer 2003.

Selerity has developed its new highly responsive low-volume, low-mass solvent preheater to help laboratory technicians take advantage of the full benefits of HTLC, including speed, increased efficiencies, decreased organic solvent usage and rapid column re-equilibration, when runs are performed at high temperatures.

With the new design, the amount of tubing required for preheating the mobile phase remains low without invading the fluid path.

Selerity chose a selection of over-the-counter analgesics and separated them using a thermal gradient.

The analyses were performed using the same column, mobile phase and temperature programme at three different flow rates.

At each flow rate, the preheater was programmed at the same temperature as the column, or programmed to lead or lag the oven temperature setting by 10C.

The width and asymmetry of the acetaminophen peak were carefully monitored and analysed.

Analyte peak focusing is at its most efficient when the peak is narrow and the asymmetry value is close to one.

The analysis revealed that the best asymmetry values were found when the preheater lagged the thermal gradient of the column compartment by 10C.

A free technical note (number 805) summarising these findings is available by e-mail from Selerity.