234U determination

Figure 4 Measurements of (A) uranium activity ratios, UARs (234U 238U) and U concentrations (B) across a salinity gradient off the Amazon River mouth (1996). UARs were determined by thermal ionization mass spectrometry (TIMS) at Caltech (D. Porcelli) U concentrations by ICPMS...

The counting of 222Rn is relatively simple no attempt was made to achieve backgrounds less than 0.1 counts/min. If the activity was higher than 0.2 counts/min, the sample was counted for approximately two weeks to ensure that the activity had the 3.8-day half-life. The problem with 222Rn is that it is difficult to obtain reproducible results, particularly after the sample is removed from and reinserted into the extraction line. This type of reproducibility is necessary if 230Th and 234U are to be reliably determined on aliquots of melt water. 

In Greece, the cave of Petralona has yielded a skull of a variety of Homo erectus. A number of workers including the present writer have attempted to determine the age of this site [25-27]. Although the samples of travertine cannot be very accurately located with respect to the former location of the skull, the various analysts concur that these travertine layers must be greater than 350 ky in age. Liritzis has attempted to estimate the age on the basis of 234U/238U ratios 500 50 ky the assumptions in such a date are however very shaky. 

Karpas et al. reported on the determination of the 234U/238U isotope ratio (54.9 x 10-6) by MC-ICP-MS and ICP-QMS compared to a-spectrometry in hair, nail and water samples.46 A correlation of 0.99 was found between the two ICP-MS methods and of 0.98 with a-spectrometry for the water sample. The measurement time of the water sample after dilution for ICP-MS was 1 min and 1000 min (including uranium separation and counting time) for a-spectrometry.46... 

U and 230Th determination in marine sediments with on-line column separation using FI ICP-MS 142... 

The ability to detect DU contamination depends on the uncertainty in the determination of the 234U/238U and activity or mass concentration ratios as well as... 

Karpas, Z., Lorher, A., Sela, H. et al. (2006). Determination of 234U/238U ratio Comparison of multi-collector ICPMS and ICP-QMS for water, hair and nails samples and comparison with alpha spectrometry for water samples, Radiat. Prot. Dosimetry 118, 106-110. 

The alpha activity of uranium in soil samples from Slovakia was determined after a relatively simple sample preparation procedure (Donoval and Matel 2001). The soil samples were dried, ground, and ashed at 550°C, leached with HNO3 + HCl and HNO3 + HF. This was followed by solvent extraction, chromatographic separation of uranium from thorium, deposition with NdFj and alpha spectroscopy for the determination of the 238U/234U ratio. 

A method for the precise determination of the 234 /233 jj, (jjg pgu ocean was described (Andersen et al. 2010). Uranium was extracted and separated from the seawater matrix by iron co-precipitation, followed by two chromatographic resins (TRU-spec and U-TEVA-spec). Analysis was carried out by a multicollector ICPMS for precise isotope composition determination. The results showed a deviation of 146.8 0.1%o (almost 15%) of the marine 234u/23su ratio from that expected on the basis of secular equilibrium. 

Highlights The determination of the uranium content and isotopic composition in surface water samples is normally easier than in ocean water due to the generally lower salt content in the former. Matrix effects could cause a bias in the nranium content measurements that can be corrected with an internal standard or separation of uranium and care must be taken to avoid precipitation or absorption of uraninm in the sample container. The 234u/23su ratio may yield interesting geological information. 

Andersen, M.B., Stirling, C.H., Zimmermann, B. et al. (2010). Precise determination of the open ocean 234u/23su composition, Geochem. Geophys. Geosyst. 11, 1-8. 

Halicz, L., Segal, L, Gavrieli, I. et al. (2000). Determination of the 234U/238U ratio in water samples by inductively coupled plasma mass spectrometry, Anal. Chim. Acta 422, 203-208. 

Hollenbach, M., Grohs, J., Kroft, M., and Mamich, S. (1995). Determination of 230Th, 234U, 239Pu, and 240Pu in soils by ICP-MS using flow-injection preconcentration. ASTM Spec. Tech. Publ., p. 99. 

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