Qemko - 11-6-2006 at 14:41
Here it goes:
Experiments using cold vapor atomic fluorescence.
In glass tubes i place 15ml of desionized water and 1ppm HgCl2
In polyropilene tubes i place 6.3ml of desionized water and 1ppm HgCl2. At T=0, i collect an aliquot of 1ml of each and prepare solutions. The tubes
are placed at 37ºC and with 120 rpm.
At t=24H and t=48H i remove more aliquots.
When i go analyse in have losses of mercury at 48H of 70% in PP vessels and 50% in glass vessels. Using HNO3 at 65% i wash each of the vessels and can
only recover about 10-20%. Can somebody tell me what the hell is happening. Some people said it was dismutation, other said volatilization, other said
you don't make good calibration curves! Does anyone experienced mercury losses from solution from 20ppb to 1 ppm? I know losses are supposed to
happen, but with 1ppm?
Help me!!! yayayayayyyyaaaaaaaaaaaa (ripping hair)
chemoleo - 11-6-2006 at 19:53
I don't really think you have losses, it's measurement error. 1ppm - that is 1 mg/litre, and you are wondering about the recovery of 15 micrograms in
15 ml? Hmmmm....
During transfer of analysis you are bound to lose way more than that. Correct me if I am wrong, maybe you have some incredible analysis
methods/techniques.
Do you rinse your containers properly, after the 'incubation'? Are the tubes stoppered? Is the difference between PP (polyropilene?) and glass tubes
reproducible? What errors do you get, considering that you can only recover between '10-20%'?
unionised - 12-6-2006 at 10:12
Chemoleo,
"Correct me if I am wrong, maybe you have some incredible analysis methods/techniques"
The method is capable of measuring down to low ng/litre levels (yes I mean that; a few parts in a million million by weight).
Tranfering samples at ppm and ppb levels is perfectly routine in analytical chemistry.
There's clearly some sort of loss. If it were absorbtion I would expect it to be quick and the recovery at 24 or 48hrs would be smilar to T=0.
My guess (and it's not much more than that) is that the stuff is being lost by evaporation.
mick - 13-6-2006 at 11:48
If you consider basic chemisry nothing can be lost, it is just you do not know where it has gone.
mick