FOR USP COLUMN COMPARISON
Column comparison function (F)
Formula for F calculation:
Hydrophobicity (Hy)
It is measured by the retention factor or capacity factor of hydrophobic analytes. In the case of NIST SRM 870, the hydrophobic analyte is ethylbenzene.
Chelating Tailing Factor (CTF)
The retention behavior of quinizarin is an indication of the presence or absence of metals. Columns demonstrate one of two types of behavior: - low activity toward chelating reagents is indicated by symmetric peak shape; - high activity toward chelating reagents is indicated by tailing, asymetric peak shape. The lower the peak asymmetry for quinizarin, the lower the presence of interfering metals on the stationary phase.
Tailing factor (T)
A measure of peak symmetry, is unity for perfectly symmetrical peaks and its value increases as tailing becomes more pronounced (See Figure). In some cases, values less than unity may be observed. As peak assymetry increases, integration, and hence precision, becomes less reliable.
Capacity Factor Amitriptyline (CFA)
Tailing Factor of Amitriptyline (TFA)
Amitriptyline is a basic compound (pKa = 9.4). Elution of organic bases with severe peak tailing is often associated with high silanol activity. However, the elution of such compounds with symmetrical peak shape is considered indicative of column deactivation. The lower the peak asymmetry for amitriptyline, the lower the silanol activity.
Bonding density (BD) in μmol/m2
In which:
X = surface coverage (mol/m2)
%C = percent carbon loading of the bonded silica
nC = number of carbon atoms in the bonded ligand
MW = molecular weight of the bonded ligand
SA surface area of silica substrate (m2/g)
FOR PQRI COLUMN COMPARISON
Column comparison function (F)
The Fs value of this column relative to the one you have selected. Fs is essentially thedistance separating two columns in a six-dimensional parameter space. The Fs value is the basis for ranking the similarity/difference between two columns. In general, Fs values below 3 are considered excellent matches, Fs values below 5 are considered reasonable matches, and Fs values above 5 are considered poor matches.
Column Hydrophobicity (Hy)
H increases for a more hydrophobic column, resulting in increased retention of hydrophobic (less polar) solutes.
Steric selectivity (S)
S decreases for columns which provide greater steric hindrance to the penetration of bulky solute molecules into the stationary phase.
Column hydrogen-bond acidity (A)
Columns with larger values of A provide increased retention of solutes that are hydrogen-bond acceptors (e.g., aliphatic amides).
Column hydrogen-bond basicity (B)
Columns with larger values of B provide increased retention of solutes that are hydrogen-bond donors (e.g., phenols, carboxylic acids).
Column cation exchange (C)
Columns with a greater negative charge (ionized silanols) and resulting larger values of C
provide increased retention of protonated bases and decreased retention of ionized acids.
Values of C are given for pH 2.8 and pH 7.0.