The AMD 2 System with winCATS by CAMAG

Gradient elution in Thin-Layer Chromatography

AMD = Automated Multiple Development

Only the AMD procedure can be successfully employed for reproducible gradient elution with silica gel as the stationary phase. In column liquid chromatography, gradient elution is common on reversed phases only because a silica gel column would call for a time consuming reconditioning or be irreversibly degraded, which is not acceptable in a technique depending on multiple use of the stationary phase. In thin-layer chromatography this is not relevant.

The principle of the CAMAG AMD procedure

• The HPTLC plate is developed repeatedly in the same direction
• Each successive run extends over a longer solvent migration distance than the one before.
• Between runs, the solvent is completely removed from the developing chamber and the layer is dried under vacuum.
• Each successive run uses a solvent of lower elution strength than that of the one used before. In this way, a stepwise elution gradient is formed.
• The combination of focusing effect and gradient elution results in extremely narrow bands. Their typical peak width is about 1 mm. This means that, with the available separation distance of 80 mm, up to 40 components can be completely resolved, i.e. with base line separation.

Key features of the AMD 2 at a glance:

• Multiple development, gradient elution
• Separation power improved over regular HPTLC by a factor 3
• Data input and monitoring through winCATS
• Utilizing time also after working hours
• Compliant with requirements of GMP/GLP
• Installation Qualification (IQ) and Operation Qualification (OQ) provided
• Usage in a 21 CFR Part 11 environment under winCATS.