Metrohm 791 VA Detector - Manual (Page 22)

3 Operation
791 VA Detector
16
Structural formula Classes/substances Polarization voltage
R SH Mercaptans + 800 mV
Miscellaneous
Ascorbic acid
Carotenes
Purine derivatives
Vitamin A + 800 mV
+ 800 mV
+ 1000 mV
+ 1000 mV
R
O
O Quinones
Vitamin K
1
– 700 mV
R NO
2
Nitro compounds
Nitrophenol
Nitroglycerin
Isosorbidedinitrate – 700 mV
– 800 mV
– 800 mV
R
Inorganic anions
Nitrite
Sulfide
Thiosulfate
Chlorite
Bromide
Iodide
Cyanide
Thiosulfate
Thiocyanate + 1100 mV
+ 0 mV
+ 1100 mV
+ 1100 mV
+ 150 mV
+ 150 mV
+ 0 mV
+ 1100 mV
+ 1200 mV
3.1.2 Influence on detector signal
The sensitivity of detection, i.e. the height of the detector signal and the
background current in the electrochemical detection depend on the fol-
lowing parameters:
• polarization voltage
• temperature (approx. 1.5 %/°C)
• flow rate of eluent
• surface of electrodes and interior of cell
• Eluent composition
(pH value, type and concentration of conductive salt,
type and concentration of organic components, etc.)
Each change of one of these parameters will change the background
current and the detector signal. Therefore, every parameter change
needs a stabilization time to elapse; this is normally a few minutes for