General Flashcards
How does temperature affect the C term (mass transfer resistance aka partitioning) in van Deemter equation?
↑T ↑Rate of partitioning ↑# of partitioning events ↓C ↓H ↑N
What is multiple paths aka eddie diffusion - A term in van Deemter equation?
When A>0 and applies and applies only for packed columns
A peak broadening contributing factor for analytes that can take different paths through a packed column thus influencing flow velocities/elution times of the same analyte.
What is mass transfer resistance - C term in van Deemter equation?
aka finite equilibrium and is a number for the decrease (resistance) of partitions (interactions with stationary phase) allowed to happen for an analyte. Want mass transfer to be high.
Want as fast mass transfer as possible. To decrease time spend going in and out of sp… ↓Film thickness ↓Bead diameter
What is longitudinal diffusion - B term in van Deemter equation?
A thermodynamic law with regards to concentration. Even though their will be a net flow towards the eluent flow the analyte will diffuse in every direction to some degree. With time this gets more pronounced. Thus most important with low flow rate. ↑ux ↓Residence time… ↓diffusion ↓H ↑N
Notice B/ux longitudinal diffusion is inversely related to flow rate
