RESUMO
An analytical method was developed for determination of low-level uranium isotopes in vegetation samples. Dry ashing method was employed to decompose organic matters of vegetation. The sample ash was further digested using multiple acids. Uranium in the prepared sample solution was separated and purified by an extraction chromatography using UTEVA resin. The chemical recovery of uranium in the separation procedure was more than 94% , and more than 99% of Na, K, Ca and other matrix elements and interfering elements were removed. Three natural uranium isotopes were finally measured with high sensitivity ICP-MS/MS. The detection limits of the method for 238U, 235U, 234U were 3. 05, 0. 34 and 0. 04 pg/g, respectively. The detection limits for 238U and 235U were 10 times better than the reported values. Analysis result of U in GBW-10046 standard reference material was in good agreement with reference value, indicating that this method was reliable. The method was successfully applied to determination of uranium isotopes in the vegetation samples collected in Xi′an region, and it was found that the uranium concentrations and isotopic ratios in these vegetation samples fall well into natural level, and there was no significant artificial uranium contamination. This was the first survey of the three natural uranium isotopes in vegetation samples in this region.
RESUMO
The psbA-trnH regions of Dendrobium species of Fengdous were sequenced by our research group. The psbA-trnH sequences of fifteen Dendrobium species were analyzed with software MEGA 4.0. The results showed that the lengths of sequences varied from 721 to 767 bp. The variable sites were 42 while the informative sites were 11. Genetic distances were calculated using the Kimura 2-parameter model. Genetic distances varied from 0.0013-0.0183 among fifteen species while the average genetic distance was 0.0148. The interspecies differences of psbA-trnH regions were demonstrated. Six indels happened in this fragment, which led to the great difference of sequence lengths among fifteen species. We found that there were no population differences in the psbA-trnH region of various species of Fengdous so far. By using the database of various Dendrobium species of Fengdous and two genetics software, the botanical origin of the inspected species of Fengdous was authenticated successfully by sequencing the psbA-trnH regions. The psbA-trnH region of cpDNA can be used as a candidate marker for authentication of Dendrobium species of Fengdous.