Effects of y-Irradiation on MeHg Content

The effects of various y-doses on the stabilization of MeHg were studied by determining the content in five bottles submitted to doses of 4, 8, 12.5, 25 and 

50 kGy. No significant differences were observed in the results, which varied from (54.3 3.3) to (56.4 1.8) g kg as MeHg. It was hence concluded that methylmercury is not affected by y-irradiation and that this procedure could be used safely for the stabilization of the material used in this study and for the candidate reference material [92], 

As an introductory remark to the discussion, at first glance the very high results submitted by one method (obtained with a technique involving extrac-tion/CVAFS with no separation step) clearly showed its inadequacy for sediment analysis due to the extraction of inorganic mercury at the same time as MeHg. The overall set of data showed three outliers (596 48) pg kg , (317 43) pg kg and (184 21) pg kg , which were first discussed. 

One set obtained by HPLC demonstrated that this technique was not optimized for sediment analysis. Doubts were thrown on the extraction as well as on the separation in addition, complexation with mercaptoethanol was not considered to be well adapted. This technique was not considered to be suitable for certification at this stage. Considerable improvements were desirable. 

The coupled GC-QFAAS technique (involving cold trapping and derivatiza-tion with tetraethylborate) was faced with difficulties in the analysis of this organic-rich sediment. It was suspected that alkaline digestion was not suitable in this case and that the technique should be tested using other alternative digestion procedures. 

---