Why not solvent extraction? that way you avoid doing the oxidation of
the naptha, reducing the potential loss of Hg, and you would end up with
a matrix way more amicable for reduction than an HNO3 matrix?...
according to my analytical chemsitry book, EDTA-Hg is quite stable at
pH=6, probably enough for you to strip all Hg from the the naphta,
additionally, tiourea might work even better...
Dr. Juan Pablo Bernal Uruchurtu
Departamento de Geoquímica
Instituto de Geología, UNAM
Ciudad de México
ph: +52-55-56224285 ext 136
(Geoff Tyler) wrote:
> Hello everyone
> I have a puzzle that hopefully someone can help me.
> We have a need to determine sub ppb (ug/L in solution) of Hg in naphtha by ICP-OES.
> While the peltier cooled Spray chamber on the ICP-OES will get us to about 5 ppb Hg, we need to think of digestion & pre-concentrate for aqueous hydride generation Hg determination to achieve the goal of sub ppb LOQ. (so the LOD needs to be < 0.2ppb).
> I have thoughts of conc HNO3 attack on neat naphtha & then careful pre-concentration. I can see of sorts of problems like:
> 1 Would Conc HNO3 digest all the naphtha?
> 2 How to pre-concentrate the digested aqueous solution, without loss of Hg
> maybe a closed vessel microwave oven will solve that ?
> 3 How to ensure oxiding state is not too strong to prevent NaBH4 (or SnCl2) reduction to enable reduction to Hg vapour.
> There is insufficient need to justify a specific low level Hg analyser in petroleum ( like that supplied by PSA )
> Any ideas?
> Geoff TYLER
> Longjumeau, France