▁to ▁zero , ▁and ▁solving ▁for ▁the ▁optim um ▁velocity ▁yields ▁the ▁following : ▁ ▁Pl ate ▁count ▁The ▁plate ▁height ▁given ▁as : ▁ ▁with ▁ ▁the ▁column ▁length ▁and ▁ ▁the ▁number ▁of ▁theoretical ▁pl ates ▁can ▁be ▁estimated ▁from ▁a ▁chrom at ogram ▁by ▁analysis ▁of ▁the ▁ret ention ▁time ▁ ▁for ▁each ▁component ▁and ▁its ▁standard ▁deviation ▁ ▁as ▁a ▁measure ▁for ▁peak ▁width , ▁provided ▁that ▁the ▁el ution ▁curve ▁represents ▁a ▁Gaussian ▁curve . ▁ ▁In ▁this ▁case ▁the ▁plate ▁count ▁is ▁given ▁by : ▁ ▁By ▁using ▁the ▁more ▁practical ▁peak ▁width ▁at ▁half ▁height ▁ ▁the ▁equation ▁is : ▁ ▁or ▁with ▁the ▁width ▁at ▁the ▁base ▁of ▁the ▁peak : ▁ ▁Exp and ed ▁van ▁De em ter ▁The ▁Van ▁De em ter ▁equation ▁can ▁be ▁further ▁expanded ▁to : ▁ ▁Where : ▁▁ ▁H ▁is ▁plate ▁height ▁▁ λ ▁is ▁particle ▁shape ▁( with ▁regard ▁to ▁the ▁pack ing ) ▁ ▁d p ▁is ▁particle ▁diameter ▁▁ γ , ▁ ω , ▁and ▁R ▁are ▁constants ▁ ▁D m ▁is ▁the ▁diffusion ▁coefficient ▁of ▁the ▁mobile ▁phase ▁ ▁d c ▁is ▁the ▁cap ill ary ▁diameter ▁ ▁df ▁is ▁the ▁film ▁thick ness ▁ ▁D s ▁is ▁the ▁diffusion ▁coefficient ▁of ▁the ▁station ary ▁phase . ▁ ▁u ▁is ▁the ▁linear ▁velocity ▁ ▁Rod rig ues ▁equation ▁The ▁Rod rig ues ▁equation , ▁named ▁for ▁Al í rio ▁Rod rig ues , ▁is ▁an ▁ ▁extension ▁of ▁the ▁Van ▁De em ter ▁equation