Material surface preparation techniques solvent cleaning

While surface preparation is not always required - some adhesives cope extremely well with poor surfaces - simple steps such as cleaning and degreasing are often needed. Components made from materials with weak or loose surface layers, or prone to stress cracking, solvent attack or water migration require special treatment. Techniques to ensure adhesion with even the most difficult of materials are available and widely published Table 4.3 reviews some general methods suitable for common materials. 

The columns are generally packed with silica gel. For the separation to be successful, the size of the silica gel particles should be 40-63 pm. A concentrated solution of the sample is prepared. The sample solution is applied at the top of the column, and the walls of the column are washed with a few milliliters of eluent. Solvent is added to the column, and air pressure is applied at a flow rate of 2 in./min to rapidly elute the desired impurity and/or degradant. Separation is based upon the differential interactions between the solute molecules and the adsorbent surface of the silica gel. Fractions are continuously collected and monitored by chromatographic techniques (HPLC with UV detection, GC, or TLC). The fractions containing the compound of interest are combined and evaporated to dryness. The isolated material is cleaned (post isolation cleanup, such as small-scale column or analytical HPLC reinjection, is essential) and submitted for LC-MS and NMR analysis. 

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