Column goodness

The quaternized copolymer of vinylpyrrolidone and dimethylaminoethylmetha-crylate (poly-VP/DMAEMA) has been analyzed successfully with Ultrahydrogel columns and a mobile phase of a 0.1 M Tris pH 7 buffer with 0.3 or 0.5 M lithium nitrate (14). In this study, poor recovery of a poly-VP/DMAEMA sample was noticed when 0.2 M lithium nitrate was used for KB-80M, SB806-MHQ, and TSK GM-PWxl columns. Good recovery was achieved with 0.4 M lithium nitrate, and M of the poly-VP/DMAEMA were found to be 290,000, 300,000, and 320,000 for the respective columns. This demonstrates the equivalence of these columns for SEC of cationic polymers. 

Trace enrichment or preconcentration by LC-LC methods are based on the possibility that the analytes will be retained as a narrow zone on the top of the first column when a large volume of sample is pumped trough the column. Good reproducibility can be achieved when the column capacity is not exceeded and the column is not overloaded. Trace enrichment is usually performed when relatively non-polar... 

SE4 Electrons created in the optical column owing to scattering from the walls and transported down the column. Good design of the column, using well-placed spray apertures, generally suppresses this contribution. 

Even with packed columns, good sample injection technique can improve the recoveries of fatty acids and the resolutions attainable. The syringe needle should be inserted rapidly but steadily into the column until it reaches a predetermined depth. Just below the surface of the packing material, when the plunger is pressed in firmly the needle is left in place for about one second and is then removed rapidly. 

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