Research Based On ICP-MS For Depleted Uranium Dissolution Performance And Determination Of Platinum In Blood

Uranium is a heavy metal having both radiation toxicity and chemical toxicity.Natural uranium is widely present in the water, food and air. Depleted uranium （DU）is a byproduct of the process of extraction²³⁵U of natural uranium. It’s different withnatural uranium from isotopic composition, the²³⁵U content of natural uranium isabout0.7%, the²³⁵U content of DU is about one third of natural uranium（0.2%to0.3%）. As natural uranium, DU is a radioactive heavy metal, whose radioactiveintensity is about sixty percent of natural uranium.Depleted uranium is a long-lived nuclide, its half-life is up to4.5×10⁹years(²³⁸U).As natural uranium, DU has both radiation toxicity and chemical toxicity, andwould be harmful to kidney, lung, immune system and nervous system once enteringinto the body. Because of its high density, easily spontaneous combustion, low prices,etc., depleted uranium has been widely used in the field of commercial and military.DU weapons has been widely used in modern warfare since originally used in theGulf War. After the war, the soldiers who had participated in combat missions suffered"Gulf War syndrome". This aroused the concern of the impacts of depleted uraniumuse on human health and environmental. Public intake uranium mainly from food andwater, uranium in contaminated soil and water would enter the body throughconsumption of contaminated plants, animals or direct inhalation, which pose a healthhazard. Therefore, once the depleted uranium into the environment, its solubility inwater and migration rules in the soil would become an important issue, this wouldhave important guidance on health hazard assessement and uranium pollutionremediation.This study has explored the solubility of depleted uranium in aqueous by staticdissolution experiments，and the migration of depleted uranium in soil by columnmigration simulation. ICP-MS technology was used in the study to determine theconcentration and²³⁵U/²³⁸U ratio of uranium in the sample simultaneously, and todetermine the presence of depleted uranium based on these data.ICP-MS has irreplaceable advantages in trace metal element analysis fieldbecause of its low detection limit, high sensitivity,needing less samples, etc.. Platinum drugs is one of the most widely used anticancer drugs by far. In the study on thesedrugs, to establish pharmacokinetic models and determine the distribution andmetabolism rules of the drugs in vivo is necessary. The sample amount collected inthe platinum drug metabolism experiments is usually small, in the current methods forthe determination of platinum the in biological samples, inductively coupled plasmamass spectrometry （ICP-MS） method can fully meet the demand. In the study,ICP-MS had been applied for establishing a method for determination of platinum inblood, the method could meet the needs of the platinum drugs pharmacokinetic studyon rats and beagle dogs.This thesis mainly consists of three parts:Ⅰ.Apreliminary study on depleted uranium solubility propertiesIn the study, the depleted uranium static dissolution experiments was carried outto determine the depleted uranium dissolution properties in neutral water andsimulated acid rain, as well as the effects of soil and humic acid on depleted uraniumdissolution. ICP-MS technology was used in the study to determine the concentrationand²³⁵U/²³⁸U ratio of uranium in the sample simultaneously, and to determine thedissolution of the depleted uranium based on these data.There were two experiment conditions:neutral water and simulated acid rain（pH=4）. Under each condition, there were three experimental groups, which weredepleted uranium group, depleted uranium+soil group and depleted uranium+humicacid group. In addition, soil and humic acid blank groups were set under bothconditions. Two different depleted uranium powders were used in the experiment,namely DU powders collected in the field and analytical grade U3O8. The resultsshowed: the final pH value of the supernatant were measured, and the value of allgroups is alkaline except humic acid groups, whose pH value is weakly acidic.Thesupernatant of each experimental group was sampled at different time points tomeasure its uranium concentration and²³⁵U/²³⁸U. In each experimental group, the²³⁵U/²³⁸U ratio mainly ranged within0.003to0.004, which is consistent with the²³⁵U/²³⁸U ratio of depleted uranium added in. Uranium concentration results showedthat depleted uranium solubility in the supernatant raised with the initial acidityincrease of the solution; At initial period of time, the rate of depleted uraniumdissolution in simulated acid rain was less than that in water in the presence of soil.After sufficient time, the cumulative dissolution amount depleted uranium insimulated acid rain would exceed the amount in water; In the presence of humic acid, the amount of depleted uranium dissolution was very low, it could be a few tenth ofthe amount of depleted uranium group at least. It was found that U3O8has a bettersolubility than DU powder samples in neutral water as well as in simulated acid rain.Experimental results showed that depleted uranium did have dissolved into thesupernatant; The acidity increases would raise depleted uranium solubility of depleteduranium; the existence of soil could improved depleted uranium solubility insufficient time; Humic acid strongly inhibited depleted uranium dissolution. DUpowder samples contained a large number of impurities which wrapped around orembedded in the uranium oxide, and uranium oxide particle size is different; U3O8had single component, uniform particle size, it also had better dissolutionperformance due to these morphology and composition differences.Ⅱ. Impact of humic acid on depleted uranium migration in the soil under acidrain conditionThe migration of uranium in the soil would be influenced by acid rain and humicacid. On the basis of the results of the preliminary study, laboratory simulated columnexperiments under simulated acid rain condition were carried out to explore thedepleted uranium migration rules in the soil under the conditions of acid rain andhumic acid.Two different depleted uranium powders were still used in the experiment,namely DU powders and analytical grade U3O8, each of which six experimentalgroups were set. In the experiments, soil added in no HA,2%HA or5%HA wasleached by pH=4or pH=3simulated acid rain, uranium concentrations and²³⁵U/²³⁸Uisotope ratios in the soil could determine the depth of the depleted uranium migration.Results showed that: Under pH=4simulated acid rain conditions, migration depth ofthe groups added HA was greater than groups added no HA, the groups added2%HA had maximum migration depth, this law is consistent with previously reportedthat under normal rainfall conditions; Under pH=3simulated acid rain conditions, thesituation is opposite, the groups added5%HA had minimum migration depth. UnderpH=4simulated acid rain conditions, the presence of HA resulted in depleted uraniummigration depth in the soil increasing, the role of HA was to promote depleteduranium migration, the effect of2%HA was more obvious than5%HA; Under pH=3simulated acid rain conditions, the presence of HA resulted in depleted uraniummigration depth in the soil decreasing, the role of HA was to inhibit depleted uraniummigration, the effect of5%HA was more obvious than2%HA. Under simulated acid rain conditions, depleted uranium migration not only related with soil HA content alsowith acidity. In the same conditions, the migration rules of DU powder sample andU3O8in the soil was consistent. But migration depth of DU powder sample in thesoil was less than U3O8. The reason was that DU powder samples contained a largenumber of impurities wrapped around or embedded in the uranium oxide, resultingin reducing of the DU powder sample solubility in the eluent. In all the groups,regardless of depleted uranium migration depth, more than90%of the depleteduranium was remained in the2cm layer of soil surface. The results showed that afew of the depleted uranium aerosol falling on the soil surface would achieve greatervertical depth through migration, most of them was still remained in the surface layerof the soil.Ⅲ. To establish of the method for the determination of platinum content in bloodby ICP-MSIn the study, ICP-MS had been applied for establishing a method fordetermination of platinum in blood, the method could meet the needs of the platinumdrugs pharmacokinetic study on rats and beagle dogs.Plasma samples were processed by Direct dilution method, consuming lesssample, easy to operate. Ir was chosen as internal standard element, Pt standard curvehad good linearity in2²50μg·L^-1concentration range, r≥0.9996. In determinationprocess, rapid analysis was achieved due to the autosampler injection, the count of theinternal standard element Ir was stable（RSD<5%）, the lowest detection limit was low.The accuracy of the method was high, the relative error was in the range of±5%; the intra-day precision and inter-day precision of the method was high,RSD<4.0%. Plasma samples after dilution had good stability and high accuracy whenplaced in4℃for24h, freezed and thawed after placed in-20℃for24h orplaced at room temperature for24h, the relative error within a range of±10%.This method was applied for plasma samples determination of Wistar rats/beagledogs, the trends of plasma platinum concentration-time curve was clear, and theresults were satisfactory. This method could also be applicable to the determinationplatinum concentration of plasma ultrafiltration samples, and could meet the needs ofplatinum drugs pre-clinical pharmacokinetic studies.