The Application Of Inductively Coupled Plasma Mass Spectrometry In Elemental Analysis

In this thesis, quadrupole-based inductively coupled plasma mass spectrometry was used for determination of elemental contents, high-performance liquid chromatography hyphenated with inductively coupled plasma mass spectrometry was used for speciation analysis, and multicollector inductively coupled plasma mass spectrometry was used for precise measurement of isotopic ratios. The thesis was divided into four parts:(1) Sample PreparationBased on the decomposition of biological standard reference materials including bush twigs and leaves ( GBW07602 , GBW07603), poplar leaves ( GBW07604) and tea ( GBW07605) with either dry ashing method or wet digestion method, all kinds of fine particles left in the solution were collected and examined carefully by a scanning electron microscope (SEM) , and their chemical composition were investigated by a SEM-afflliated energy-dispersive X-ray spectrometer at the same time. Moreover, the concentrations of some metal elements distributed among four different tea SRM-originated particle fractions extracted following the BCR sequential extraction procedure were determined by AAS and ICP-AES. It was found that the decomposition methods have a great influence on the structure of fine particles. When dry ashing method was used, the grey-colored, fluffy and porous partices could be produced, whereas the white-colored, compact particles could be produced when wet digestion method was used. As for chemical composition, all kinds of fine particles remained almost the same, with silicon and aluminium as their main constituents, and calcium, iron, potassium, titanium and so on as their minor ones. The elemental distribution in four different particle fractions between two kinds of plant-originated particles differed from element to element, which could result in severe negative errors when plant samples were decomposed and determined for elemental concentrations. A preliminary conclusion could be drawn that the wet digestion method seems to be much better than the dry ashing method for getting precise analytical results of elemental contents analysis.(2) Determination of Elemental ContentsBased on a closed wet decomposition, the comparison of elemental contents including Al, Ba, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, La, Mg, Mn, Na, Ni, Pb, Rb, Sb, Sr, Th, U, Y and Zn between thirteen Chinese tea samples and six Japanese tea samples were conducted by ICP-MS combined with ICP-AES, a standard reference material tea (GBW07605) was used to verify the accuracy and the precision of analytical method. It was demonstrated that a closed wet decomposition was useful for getting accurate and precise analytical results of elemental content analysis in the tea samples. Compared with the Japanese tea samples, the contents of Cd, Co, Cr, Cs, Fe, Pb, Rb, Sb, Th, U and Zn in Chinese tea samples are significantly high, which may suggest that the atmosphere contamination in China is more severe than in Japan. Moreover, it was found that the contents of La, Ce, Th, U in all of tea samples well correlate with each other, and a method was proposed to evaluate whether or not tea was polluted by lead originated from human activities.(3) Speciation AnalysisBased on a microwave decomposition, the contents of Ag, Al, As, Au, B, Ba, Bi, Ca, Cd, Cr, Co, Cu, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sb, Se, Sn, Sr, Ti, V and Zn in the fruiting bodies of Agaricus blazei Murrill produced in three different cultivation regions of southern China were determined by ICP-OES, AAS and AFS, and the mercury species were separated and determined by HPLC-ICP-MS, biological standard reference materials (SRMs) were used to verify the accuracy and the precision of analytical method. Moreover, the distribution patterns of ds-block elements and some related elements were investigated in Agaricus blazei Murrill. Compared with other mushrooms, Agaricus blazei Murrill has a peculiar characteristic of accumulating ds-block elements including Cu, Zn, Ag, Cd and Hg. Only two mercury species are present in Agaricus blazei Murrill, with a great majority of accumulated mercury in a form of Hg²⁺, and the ratio of CH₃Hg⁺/Hg_total in all samples is under 15.0%. The contents of Cu, Zn, Ag, Cd and Hg in Agaricus blazei Murrill become gradually higher from low stipe to high stipe, from centric pileus to outer pileus. Additionally, P seems to facilitate the accumulation of ds-block elements, while Ca seems to have an opposite role.(4) Precise Measurement of Isotopic RatiosThe samples of camphor(cinnamomum camphora) tree bark collected from Hiroshima and Kyoto were studied by EDXS and SEM for their matrix element composition and morphology of the outer surface, respectively. Based on a dry ashing method, DWEX^? 1-X8 anion exchange resin was used to separate uranium from the matrix elements in these samples, the ²³⁵U/²³⁸U isotope ratio in purified uranium solutions was determined by MC-ICP-MS. It has been demonstrated that the outer surface of these camphor tree bark samples is porous and rough, with Al, Ca, Fe, K, Mg, Si and C, O, S as its matrix element composition. It was also found that the contents of La, Ce, Th, U in all of these samples well correlate with each other. Uranium could be efficiently separated and quantitatively recovered from the matrix element composition. Compared with those collected from Kyoto, the camphor tree bark samples collected from Hiroshima contained significantly high uranium, which might be due to the increased aerosol mass concentration during the city reconstruction. Moreover, the ²³⁵U/²³⁸U isotope ratio in a few of camphor tree bark samples collected from Hiroshima are higher than 0.00725.