Just in case anyone is still interested...
We are able to get a D.L. of less than 30 ppt (n=10) for Hg using an
>We never fully investigated the detection limit for Hg on our Optima 3300.
>We did however complete several trials examing wash-out characteristics.
>Standards of 10, 20, and 50 ppb were prepared in both 1% HCl (v/v) + 1%
>(w/v) thiourea and 1% HNO3 (v/v)+ 1% thiourea (w/v). The reductant solution
>was a 1% sodium tetrahydroborate (w/v NaBH4) in 0.1 M NaOH. Both acid
>matrices worked, however we concentrated mainly on the HCl stds. Typical
>calib coeff's were 0.9999+ and RSD's were always <3% for the 10 ppb std
>(net signal intensity of ~1200 counts for 3 pt int.). From this info. I
>would predict a DL of less than 1 ppb which might meet your requirements.
>The washout time required for the 50 ppb std. was on the order of two
>minutes (99% criteria). The addition of the thiourea is key to the low
>wash-out time (HSAB), and it also provides signal enhancement for the VG
>process. If you need to determine sulfur in the samples then you will
>probobly have to switch the thiourea with gold, which is not as effective
>in mitigating memory effects.
>Here are the instrumental conditions used on the Optima
>Sample Introduction: MSIS operated in vapour generation mode
>Sample Uptake - 1.0 mL/min
>Reductant Uptake 1.0 mL/min
>Nebulizer Uptake - Not used**
>Plasma Ar - std 15 L/min
>Aux Ar - std 0.5 L/min
>Neb Ar - 0.25 (for VG mode only)
>**Note washout times were improved by nebulizing a 1% HNO3 + 1% Thiourea
>blank during the VG process.
>>I have been asked to dive into the mercury analyis world. I currently have
>>at my disposal a DV ICP-OES and hot plate digestion capabilities. What I am
>>looking for is to analyze with confidence 5 ppm Hg ( to which the
>>instrument would be looking for 200 ppb in sol'n). I have poked around the
>>archives and am familar with volitization issues, cleanout etc. I would
>>like to analyze other volitale elements as well such as Se and As. Am I
>>spinning my wheels with what I got? Any advice is greatly appreciated.
> >Erich Jacobsen
> >Quality Assurance Chemist
> >Prince Agri-Products