Temporal shifting: a hidden key to the skewed peak puzzle.
The recorder-provided peak position for flow-type chemical instruments has been verified mathematically as being comprised of a "spatially-non-existent" shift, which is generated due to the relativity in accounting for the detection at a fixed point. This shift, denoted as Phi, can be approximated by Phi approximately 0.5micro(t)2, where micro(t) is the temporal expanding coefficient of the system given. For flow injection analysis, the shift is correlated to a longitudinal dispersion coefficient D and the flow speed u, i.e., Phi approximately D/u2. For linear chromatography, it is correlated to a dynamic partition ratio k'' and a scaling factor f of the column used, i.e., Phi approximately 0.5k''f. In combination, the temporal shift can be expressed as Phi approximately 0.5k''f+D(k''+1)2/u2. Although the shift may be small in scale, it provides a clue to decipher the basic parameters from a recorded peak. Under a linear isotherm, this parameter can be estimated readily from an experimental peak following a very simple procedure.
Pai
Su-Cheng
SC
Division of Marine Chemistry, Institute of Oceanography, National Taiwan University, Taipei, Taiwan. scpai@ntu.edu.tw
Chiao
Ling-Yun
LY
D000465:Algorithms; D002845:Chromatography / Q000295:instrumentation / Q000379:methods*; D017022:Flow Injection Analysis / Q000295:instrumentation / Q000379:methods; D008962:Models, Theoretical; D013816:Thermodynamics