Why metal-free chromatography?

Many pharmaceutical active substances are rich in oxygen and can therefore interact with metal (Fe).  Tests have shown the N-hydroxypyridine-2-on – the chelating part of the anti-fungal cyclopirox molecule – is a powerful probe for metal activity.  In one experiment, a PEEK™ lined ProteCol™-P C18 HQ105 coated column was compared to a stainless steel ProteCol™ C18 HQ105 column where the connection tubing also varied between stainless steel and PEEKsil™ (PEEK™ coated fused silica tubing). 

As shown, peak tailing was minimized with the reduction of metal in the flow path resulting in increased peak height and hence, sensitivity.

A second experiment was conducted with tetracycline antibiotics.  Tetracycline and related drugs have a number of potential chelating groups aligned on one side of the molecule and are known to form metal complexes (dietary calcium and iron render the antibiotic ineffective). 

The chromatogram of tetracycline and its major degradation product demonstrates the improved peak sensitivity using the PEEK™ lined ProteCol™-P C18 HQ105 column format.  Note the peak broadening on the base of the peak run through the stainless steel column.

The inset shows the tetracycline molecule depicting the three potential chelating groups.