ILLUSTRATED POCKET DICTIONARY OF CHROMATOGRAPHY pps

[...]... collapse backpressure The measure of the resistance to flow through a chromatographic system Barring any constriction at the point of entry of the mobile phase into the system, the backpressure is a measure of the pressure of the system at the top of the column In general, decreased particle size and increased mobile-phase viscosity increase the system backpressure Common units of pressure are atmospheres,... eluted sample that has passed through the detector (2) Defines the range of Illustrated Pocket Dictionary of Chromatography, by Paul C Sadek ISBN 0-471-20021-2 Copyright © 2004 John Wiley & Sons, Inc 15 16 BAR wavelengths that pass through a monochrometer in a UV-visible detector Linearity is better as bandwidth decreases, but the trade-off is that the radiation that reaches the sample decreases with decreasing... extremes should extend beyond the lower and upper concentration limits of the working range Sample concentrations are targeted to fall within the working range to give the most precise and accurate results capacity The concentration of sample that is analyzed without overloading the column or the detector Illustrated Pocket Dictionary of Chromatography, by Paul C Sadek ISBN 0-471-20021-2 Copyright © 2004... polarization (levorotatory) CH3 H H OH OH CH3 CH3 O CH3 O CH3 S-Ibuprofen R-Ibuprofen COOH COOH H L-phenylalanine CH3 H NH2 NH2 D-phenylalanine CHIRAL chiral recognition The basis for the separation of enantiomeric molecules It describes the differential interaction of a chiral bonded phase with one of the pair of enantiomers and is the basis of the chromatographic separation The stronger interaction leads... index), b A quantitative means of calculating the change of a solution pH on the addition of acid or base to the solution Mathematically the buffer index is written as: b = dCb dpH (for base addition), or b = - dCa dpH (for acid addition) where Cb and Ca are the concentrations of base and acid, respectively Buffer capacity: The plot is a representation of the ability of a solution to resist a change... adsorption-desorption steps will occur down the length of the column The relative amount of time A spends on the surface versus in the mobile phase determines its elution time 6 ADSORPTION ISOTHERM adsorption isotherm A plot constructed from the equilibrium concentration of an analyte in the mobile phase per mass of sorbent The shape of the isotherm and the relative concentration of the analyte with respect to the sorbent... COLUMN capacity factor, k¢ The capacity factor is a way of expressing the retention of a compound (as a multiple of the void volume of the system): k¢ = (tr - to ) to where tr is the retention time of the retained analyte and to is the time required for an unretained nonexcluded peak (i.e., a void volume marker) to elute See retention factor Calculation of the capacity factor for a peak depends on determining... adsorption or denaturation bleed (1) The process of release of volatile/soluble components of a GC or HPLC stationary phase (2) Associated with the decomposition or release of volatile materials from a septum in GC The most critical aspects of bleed occur in GC and LC/MS applications, where the bonded-phase or septum breakdown leads to the appearance of these moieties in the detector This is not the... thermodynamic equilibrium, kinet- ADSORPTION CHROMATOGRAPHY 5 ically slow, or irreversible It is controlled by one or more interactions: hydrogen bonding and van der Waals interactions The condition of rapid, reversible thermodynamic equilibrium is the desired one in most separations adsorption chromatography Adsorption chromatography, also called liquid-solid chromatography (LSC), uses unmodified solid... For a defined system and set of operating conditions, the volume of eluent needed to elute a defined percentage of solute (e.g., 1%) This parameter is particularly important for flow injection analysis (determines the time between injections) and solid-phase extraction (determines the fraction to discard or collect) It is a function of system volume, flow rate, and the retention of the analyte Brockmann activity .