Aciorojnce-w/UkrArV-Flgure 1. Lead interference at the Sb 217.58-nm line using Sb lamp, 20-µ depositions of 1, 10, 25 pg/tvL Pb and a 0.5-nm (top trace) and a 2-nm bandwidth(2) Spectral Interference by Sb on the Determination of Pb at 217.00 nm. The absorbance of 10 Mg/mL Sb is equivalent to that of 0.005 /¿g/mL Pb, a ratio of about 2000:1. Even this small effect can be avoided by using the very good Pb line at 283.33 nm, where there are no known spectral interferences.(3) Spectral Interference by Ni on the Determination of Sb at 231.15 nm. The absorbance of 1000 µg/mL Ni is equivalent to that from 0.02 µg/mL Sb, a ratio of 50000:1. Moreover, the Sb line at 231.15 nm is rarely used, because the 217.58-nm line is generally preferable. LITERATURE CITED(1) Koizumi, H.

0b°Values as high as 4800 have been reported by others (15, 16). 6 Values as high as 700 have been reported by others (15, 16).regarding the validity of the reported results; they can only be considered as qualitatively suggestive of accuracy. SUMMARYThe present results have shown that fluoride compounds are fairly rapidly converted to CaF2 in the arc in the presence of excess calcium, that complete vaporization of the CaF2

investigated elements to the right of silver. For example, a minor increase of either the activation cross section or the highest observed concentration of molybdenum will extend the isolation time drastically, from 700 years up to more than the half-life of 93Mo (3.5 X 103 years). Among those elements molybdenum, niobium, and technetium are the more hazardous ones, as one can see in Figure 4.Using the data presented in Figures 4 and 5 in the way described, it is possible to determine a mimimum isolation time necessary (here 700 years) if one does not want to rely on possible dilution or immobilization of radionuclides in aquifers or if the release of the radioactive inventory to the groundwater might excessively affect a population, i.e., the potential biological hazard is too large.Registry No. 160Sm, 14907-33-6; 152Sm, 14280-32-1; 161Sm,

A microwave digestion sample preparation technique for the determination of environmentally significant elements in marine sediments is discussed. Samples were digested with nitric and hydrochloric acids in unvented PFA vessels for periods of up to 20 min. The digestion time compared favourably with the 3 h required for a conventional hot-plate procedure. Recoveries of metals (using inductively coupled plasma atomic emission spectrometry and graphite furnace atomic absorption spectrometry) from an in-house reference sediment and National Research Council of Canada reference materials MESS-I and BCSS-1 were comparable or superior to those attained by the conventional procedure (89-140%). Significant improvements in precision at the 95 and 99% confidence levels and a reduction in analytical blank levels were noted. Elements with the poorest precision by the conventional method showed the greatest improvement. Diluting the concentrated acids for digestion increased recoveries by 20-30%. The PFA vessels have been found to be resilient to repeated (>loo) digestions of a wide variety of samples if properly annealed before use.

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