Gold trap

Gold trap is a tube filled by gold. The gold trap selectively forms a mercury amalgam. Mercury is adsorbed and desorbed from the gold. Thus interference from other compounds like SO2 is eliminated.



The cycle of analysis using the gold trap in mercury analysis nedes following steps:
adsorption of mercury vaporsfast heating and mercury desorptioncooling the gold trap

The collection time (absorption phase) for the gold trap can be chosen depending upon the concentration leves to be measured. For typical measurements of 1 to 10 ug/m3 the collection time is about 2 to 3 minutes. For lower levels, the collection time can be increased.

The gold trap drastically enhances detection sensitivity, to values lower than 1 ng/l. Using ultra pure reagents and adequate procedures for analysis at ultra trace levels, the AULA 254 (Mercury Instruments) can achieve measuring range from 1 ppt to 5000 ppt (AAS detector) and the range from 0.05 ppt to 5000 ppt (AFS detector).

Gold trap module (AULA 254, Mercury Instruments)
Gold trap (AULA 254, Mercury Instruments)

Example of the gold trap cycle (2 min) during analysis stack gases (EcoChem Stack Analyser)

Phase
 Time
Measuring of dark signal of the photometer
 8 sec
Loading phase - flue gas passes over gold trap to form mercury amalgamation
 32 sec
Transition phase - flue gas is removed from photometer and gold trap
 8 sec
Heating of the gold trap to desorb the mercury
 12 sec
Cooling of the gold trap for next loading cycle
 60 sec