Getting Started in HPLC

Section 0. The Language of HPLC: C

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

   
C8: a kind of bonded phase commonly used for reversed-phase chromatography; also called OCTYL.


 
C18: a kind of bonded phase commonly used for reversed-phase chromatography; also called ODS or OCTADECYL.


 
CALIBRATION: the assignment of a value (the calibration factor or sensitivity factor) to a calibrator that allows determination of results by LC analysis.


 
CALIBRATION FACTOR: as defined here, the calibration factor CF is equal to the ratio of peak size of compound A in the calibrator to the peak size of the internal standard in the calibrator divided by the ratio of the concentration of compound A in the calibrator to the concentration of the Internal Standard in the calibrator.

The concentration of A in a sample is then given as the ratio of the peak sizes in the sample divided by CF and multiplied by the concentration of Internal Standard added to the sample. See also INTERNAL STANDARD.


   
CALIBRATION PLOT: for the external standard method, a plot of peak size (height or area) on the y-axis (vertical) versus sample concentration the x-axis (horizontal), using a series of samples of known concentration (and equal injection volumes). If the calibration plot is linear, it is sometimes called the calibration line.


The calibration plot is a graphical representation of the relationship between peak size and amount of analyte injected.


   
CALIBRATOR: a solution containing a known concentration of some compound X that is to be determined in different samples by LC analysis. See also STANDARD.


 
CAM: a rotating part attached to the pump motor and to the connecting rod attached to the piston. See Pump.


Cross-sectional diagram of a "generic" single-piston HPLC pump.


   
CAPACITY FACTOR (k'): is one way to measure sample retention; bands which come out in the chromatogram at the column dead time have a k'-value of zero. Later bands have k'-values that increase with band retention time. Values of k' for each band or compound are constant if experimental conditions do not change. k' does not change when flow rate or column dimensions are changed. k' can change when mobile phase composition, stationary phase chemistry, or temperature change.

Also called the RETENTION FACTOR and symbolized by k (ASTM/IUPAC standard).


k' is a measure of retention that is independent of flow and column dimensions.


   
CHECK VALVE: a device inserted into a moving liquid stream that allows flow of the stream in only one direction. Check valves are commonly built into the LC pump.


 
"CHEMICAL GARBAGE": contaminants in a sample that can foul the LC column by irreversibly sticking to the bonded phase.


 
CHROMATOGRAM: a plot or record of the chemical separation produced in HPLC.


This chromatogram has 6 peaks. Ideally, each peak represents a single, unique analyte.


   
CHROMATOGRAPHY: a technique used to separate mixtures of chemical compounds based on different rates of travel through a stationary phase.


 

Flowing solvent (light blue) carries different analytes (green, blue red) through the column at different speeds.


 
   
COLUMN: that part of a chromatographic system where the separation of the sample takes place.


Waters Xterra Columns


   
COLUMN DEAD-TIME (t0): the time it takes for solvent molecules or unretained sample bands (for which k'= 0) to pass through the column. Uracil is often used to measure t0 for reversed-phase columns.


 
COLUMN PACKING: the particulate material packed inside the column; also called STATIONARY PHASE.


 
COLUMN PLATE NUMBER: See PLATE NUMBER.


 
COLUMN VOID: See VOID.


 
CONTACT HEATER: metal plates which wrap around an LC column and are heated electrically. The heating is controlled to hold the column at a constant temperature.


 
CYANO: a type of bonded phase use which can be used for either REVERSED-PHASE LC or NORMAL-PHASE LC.


 
   
 

 


2000, LC Resources Inc. All rights reserved.
Last revised: April 02, 2001.