Analysis of Sediment Samples

Ben and his group are planning to analyze some sediment samples for Cs. Ben contacted Paul seeking advice and recommendations. Specifically, he wondered if an HF digestion will be required or if aqua-regia would be sufficient.

	RE: Analysis of Sediment Samples Dear Ben,      I am assuming that you are using ICP-MS as the measurement tool. The bad news is that Cs is monoisotopic. It is large enough in mass that the M++ interference is not an issue. The main concern is the MO+ interference from Sn, which, if present may be a problem. A lesser concern is Ba at 3-4 orders of magnitude greater in conc. than the Cs (look for intensity at 134). Typical detection limits using conventional quadrupole mass filtered systems is between 2 and < 1 ppt (we typically get into the ppq range). If the dissolved solids content is high, dilute the sample such that it is < or = 100 ppm total dissolved solids to minimize the quenching effect on the Cs signal. I would suggest Rh as the internal standard since one of the Rare Earths could realistically be present in a sediment sample (they are not as rare as we would like to think).      In short, I don't believe you'll run into any serious problems, just the usual stuff. In regards to your question about digestion, I would prefer just nitric and then compare the results to a Nitric/HF digestion. The EPA Methods 3050B and 3052 (acid digestion methods designed for sediments, sludge, and soils) could be your guide.      The 3050B uses nitric acid and hydrogen peroxide and 3052 uses nitric and HF in combination. The 3052 is considered a total method as compared to 3050B which gets 'extractables'. Please contact me with any other concerns. Best of luck.     Paul R. Gaines, Ph.D. Serving you in chemistry