Getting Started in HPLC

Section 0. The Language of HPLC: D

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DATA SYSTEM: a versatile data processor that, can simultaneously serve several different LC systems; it may also control some of the system modules (pumps, detectors, etc.) and carry out other functions.


 
DATA PROCESSOR: a module that converts the detector readings for an LC run into final results: concentrations of each compound in the sample, retention times for each band to permit identification of each band in the chromatogram, etc. In this course, data processors include integrators, data systems, and computers.


 
DEAD-TIME See COLUMN DEAD-TIME.


 
DEAD-VOLUME: small spaces within the LC system where remixing of separated sample bands occurs, or where the initial sample is diluted with mobile phase. Extra-column dead-volume should be minimized in an LC system, especially when small-volume columns of high plate number are used.


 
DEGASSING: the practice of removing air from the mobile phase; degassing can be achieved by helium sparging, applying vacuum to the mobile phase (either directly or across a semipermeable membrane), ultrasonification, or heating.


Helium sparging is one of the most effective ways of removing dissolved gas from the mobile phase.


   
DELIVERY STROKE: movement of the pump piston so as to push mobile phase into the lines leading to the injector and column.


   
DETECTOR: the LC module that measures the concentration of sample bands as they leave the column, thus furnishing a chromatogram.


Waters 996 Photodiode Array Detector


   
DILUTION FACTOR (DF): for dilution of a sample by pipetting V1 mL of sample into a volumetric flask of volume V2, the dilution factor is equal to V2/V1; it is the ratio by which sample concentrations in the original sample are decreased in the diluted sample. The final (diluted) concentration C2 is related to the initial sample concentration C1 as C2 = C1 / DF.


 
DIOL: a type of bonded phase use for NORMAL-PHASE LC.


 
"DIRTY" SAMPLES: samples obtained from biological, environmental, or other sources that contain compounds that might foul the LC column, by irreversibly sticking to the bonded phase.


 
   
 

 


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Last revised: April 06, 2001.