Characteristics:
Some characteristics of commonly used detectors in HPLC systems are listed in Table.
Table: Performance of some HPLC Detectors
|
Detector property
|
Typical LOD*
(mass)
|
Linear range
|
Commercial availability
|
|
Absorbance
|
10 pg
|
3-4
|
Yes
|
|
Fluorescence
|
10 fg
|
5
|
Yes
|
|
Electrochemical
|
100 pg
|
4-5
|
Yes
|
|
Conductivity
|
100 pg-1 ng
|
5
|
Yes
|
|
Refractive Index
|
1 ng
|
3
|
Yes
|
|
Mass spectrometry
|
<1pg
|
5
|
Yes
|
|
FTIR
|
1µ g
|
3
|
Yes
|
|
Light scattering
|
1µ g
|
5
|
Yes
|
|
Optical activity
|
1 ng
|
4
|
No
|
|
Photo ionization
|
<1pg
|
4
|
No
|
|
Element selective
|
1 ng
|
4-5
|
No
|
*Real LOD will depend on the compound.
It is essential to know the band spreading for estimating detection limit of a particular detection system. Linking tubing must be minimum (not longer than 20 cm). Tubing diameter (< 0.25 mm) is most critical as this would create a 10µ L volume and so also dilution factor is important for detection limit. A detector must have a linear dynamic range so that major and trace components can be determined in a single analysis.