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Resolution of Capillary Chromatography

Shows how a difference between the distribution coefficient of two components can lead to separation in capillary gas chromatography. Students select column length, column internal diameter, thickness of stationary phase, diffusion coefficient in mobile phase, viscosity of carrier gas, flow rate, ambient temperature, and column temperature. The simulation calculates the phase ratio, capacity factor, selectivity, linear velocity of carrier, retention time of unretained peak, retention time of the two components, plate height, efficiency (plate count), peak base width, and resolution. Displays plot of simulated chromatogram showing two component peaks and an unretained peak.

Download links: Capillary.wkz;

Wingz player application and basic set of simulation modules, for windows PCs or Macintosh

OpenOffice Calc format: Capillary.ods
Excel format: Capillary.xls

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Cell definitions and equations:
Inputs:
column length, cm	L	
column internal diameter, cm	id	
thickness of stationary phase, cm	df	
diffusion coefficient in mobile phase, cm2/min	Dm	
viscosity of carrier gas,  poise	eta	
volumetric flow rate, mL/min	Fo	
distribution coefficient of component a	Kda	
distribution coefficient of component b	Kdb	
ambient temperature, K	Ta	
column temperature, K	Tc	
ambient pressure, psi	Pa	
vapor pressure of water, psi	Pwater	

Outputs:
phase ratio	 =i d/(4*df)
capacity factor of component a	ka = Kda/beta
capacity factor of component b	kb = Kdb/beta
selectivity	a = kb/ka
adjusted flow rate, mL/min	Fc = Fo*(Tc/Ta)*(Pa-Pwater)/Pa
linear velocity of carrier, cm/min	v = Fc/(3.14159*(id/2-df)^2)
retention time of unretained peak, min	to = L/v
retention time of component a, min	tra = (ka*to)+to
retention time of component b, min	trb =( kb*to)+to
plate height, cm	h = (2*Dm)/v+((id/2)^2*((1+6*kb+11*kb*kb)/(24*(1+kb)*(1+kb)))/Dm)*v
efficiency (plate count)	N = L/h
peak base width a, min	twa = tra/sqrt(N/16)
peak base width b, min	twb = trb/sqrt(N/16)
resolution	R = sqrt(N)*((alpha-1)/alpha)*(kb/(1+kb))/4

(c) 1991, 2000, Prof. Tom O'Haver , Professor Emeritus, The University of Maryland at College Park. Comments, suggestions and questions should be directed to Prof. O'Haver at toh@umd.edu. Number of unique visits since May 17, 2008: