Determination of platinum and rhodium in environmental matrixes by solid sampling-electrothermal vaporization-inductively coupled plasma mass spectrometry

Electrothermal vaporization from a graphite furnace was used in combination with inductively coupled plasma mass spectrometry (ICPMS) for the determination of Pt and Rh in environmental matrixes. Solid samples of tunnel dust, grass, and atmospheric aerosol collected on a cellulose filter could be analyzed directly, such that sample dissolution-which is not self-evident for the determination of platinum group metals-could be avoided. By heating the graphite furnace according to a multistep temperature program, spectral interferences were avoided, since a "dry" plasma was obtained, while "parent" ions such as Cu, Zn, and Pb, giving origin to interfering molecular ions, were vaporized during the thermal pretreatment step. For tunnel dust, the most demanding sample matrix, a mixture of HCl and HF was used as a modifier to stimulate the vaporization of matrix components during the thermal pretreatment step and, hence, to alleviate matrix-induced analyte signal suppression during the actual vaporization step. Calibration was accomplished by means of single standard addition with an aqueous standard solution. The results obtained agreed within the experimental uncertainty with the corresponding reference values (certified values or results obtained using pneumatic nebulization ICPMS), while relative standard deviations of < or = 15% were typical for both Pt and Rh. In all samples, a Pt/Rh ratio of approximately 6-8 was established. For a typical sample mass of 2 mg, limits of detection were 0.35 ng/g for Pt and 0.05 ng/g for Rh.     

顶空-固相微萃取-气相色谱-电感耦合等离子体质谱法联用测定大气颗粒物中的无机汞和甲基汞

大气中的汞有不同的存在形态,对环境的影响程度不同,目前对大气颗粒中汞的测定研究及其形态分析尚非常薄弱。该文尝试将顶空-固相微萃取与气相色谱-电感耦合等离子体质谱法联用测定大气颗粒物中的无机汞和甲基汞。该方法对甲基汞和无机汞的检出限分别为2 ng/L(0.02 ng)和0.5 ng/L(0.005 ng),测定下限分别为8 ng/L(0.08 ng)和2 ng/L(0.02 ng)。可实现大气颗粒物中无机汞的准确测定,也可以用于甲基汞污染情况下污染源废气或污染区大气颗粒物中甲基汞的监测。     

新型冷蒸气发生-原子吸收光谱测定汞及甲基汞

建立了紫外光化学蒸气发生或超声波化学蒸气发生-原子吸收光谱测定汞及甲基汞的新方法,考察了相关的实验条件和仪器条件.在超声波的条件下测定无机汞(检出限为0.1μg·L-1),在紫外光的条件下测定总汞,然后通过差减法来实现不经色谱分离测定汞和甲基汞(汞和甲基汞检出限为0.08μg·L-1).实际样品的加标回收率在94%～110%之间,该方法具有简单、绿色、灵敏的特点.     

On-line preconcentration and determination of mercury in biological and environmental samples by cold vapor-atomic absorption spectrometry

An on-line procedure for the determination of traces of total mercury in environmental and biological samples is described. The present methodology combines cold vapor generation associated to atomic absorption spectrometry (CV-AAS) with preconcentration of the analyte on a minicolumn packed with activated carbon. The retained analyte was quantitatively eluted from the minicolumn with nitric acid. After that, volatile specie of mercury was generated by merging the acidified sample and sodium tetrahydroborate(III) in a continuous flow system. The gaseous analyte was subsequently introduced via a stream of Ar carrier into the atomizer device. Optimizations of both, preconcentration and mercury volatile specie generation variables were carried out using two level full factorial design (2(3)) with 3 replicates of the central point. Considering a sample consumption of 25mL, an enrichment factor of 13-fold was obtained. The detection limit (3sigma) was 10ngL(-1) and the precision (relative standard deviation) was 3.1% (n=10) at the 5microgL(-1) level. The calibration curve using the preconcentration system for mercury was linear with a correlation coefficient of 0.9995 at levels near the detection limit up to at least 1000microgL(-1). Satisfactory results were obtained for the analysis of mercury in tap water and hair samples.     

测汞仪直接测定空气颗粒物中的总汞

采用配备热解装置的测汞仪直接测定空气颗粒物中的总汞,通过对实验条件的筛选及优化,得到最佳条件。采用石英纤维滤膜采集一定空气颗粒物样品,将石英纤维滤膜放在石英舟中,然后将样品舟插入到原子化器中对样品进行解析,可直接测量样品中汞的含量。该方法的线性相关系数r=0.999 7、精密度RSD=4.1%、回收率准确度在93%~118%之间,方法检出限可达到8×10~(-3)ng/m~3。该方法测量空气颗粒物的汞无需任何试剂和消解,测定速度快、操作简便,适合空气颗粒物中汞的测定。     

Determination of methylmercury, ethylmercury, and inorganic mercury in mouse tissues, following administration of thimerosal, by species-specific isotope dilution GC-inductively coupled plasma-MS

Isotopically enriched HgO standards were used to synthesize CH3(200)Hg+ and C2H5(199)Hg+ using Grignard reagents. These species were employed for isotope dilution GC-ICPMS to study uptake and biotransformation of ethylmercury in mice treated with thimerosal, (sodium ethylmercurithiosalicylate) 10 mg L(-1) in drinking water ad libitum for 1, 2.5, 6, or 14 days. Prior to analysis, samples were spiked with aqueous solutions of CH3(200)Hg+, C2H5(199)Hg+, and 201Hg2+ and then digested in 20% tetramethylammonium hydroxide and extracted at pH 9 with DDTC/toluene. Extracted mercury species were reacted with butylmagnesium chloride to form butylated derivatives. Absolute detection limits for CH3Hg+, C2H5Hg+, and Hg2+ were 0.4, 0.2, and 0.6 pg on the basis of 3sigma of five separate blanks. Up to 9% of the C2H5Hg+ was decomposed to Hg2+ during sample preparation, and it is therefore crucial to use a species-specific internal standard when determining ethylmercury. No demethylation, methylation, or ethylation during sample preparation was detected. The ethylmercury component of thimerosal was rapidly taken up in the organs of the mice (kidney, liver, and mesenterial lymph nodes), and concentrations of C2H5Hg+ as well as Hg2+ increased over the 14 days of thimerosal treatment. This shows that C2H5Hg+ in mice to a large degree is degraded to Hg2+. Increased concentrations of CH3Hg+ were also observed, which was found to be due to impurities in the thimerosal.     

Direct determination of tellurium in geological samples by inductively coupled plasma mass spectrometry using ethanol as a matrix modifier

Direct determination of tellurium in geological samples by inductively coupled plasma mass spectrometry (ICP-MS) is often complicated by its low abundance, poor analytical sensitivity, and the presence of xenon interferences. Therefore, a simplified and rapid method for direct determination of nanogram levels of tellurium in geological samples using ICP-MS by reduction of interferences and improvement of sensitivity was developed. It is impossible to resolve 126Te and 128Te from isotope interferences of Xe even by currently available high-resolution magnetic mass spectrometry due to the extremely small mass difference (0.001-0.002 amu). However, the addition of 4% ethanol was found to suppress the interferences of Xe by a factor of 6 and increases the sensitivity of Te determination in ICP-MS by a factor of 3 relative to the values obtained in conventional 3% (v/v) HNO3 solution at the corresponding optimum operating conditions, respectively. The detection limits of 126Te and 128Te were reduced by a factor of 7.2 and 8.8, respectively, and the limit of quantitation (LOQ) for 126Te in the presence of 4% ethanol was 1.5 ng g(-1) (the LOQ is expressed as the concentration in the solid samples, thereby taking into account the dilution factor of 1000). The agreement between the determined Te concentration values (r = 0.998) in various geological samples (n = 140) by using isotopes of 126Te and 128Te indicates negligible contributions of polyatomic interferences produced by the addition of ethanol at these m/z. The proposed method was successfully applied to the direct determination of nanogram levels of Te in a series of international geological reference materials.     

Direct analysis of biological tissue by paper spray mass spectrometry

Paper spray mass spectrometry (PS-MS) is explored as a fast and convenient way for direct analysis of molecules in tissues with minimum sample pretreatment. This technique allows direct detection of different types of compounds such as hormones, lipids, and therapeutic drugs in short total analysis times (less than 1 min) using a small volume of tissue sample (typically 1 mm(3) or less). The tissue sample could be obtained by needle aspiration biopsy, by punch biopsy, or by rubbing a thin tissue section across the paper. There exists potential for the application of paper spray mass spectrometry together with tissue biopsy for clinical diagnostics.     

Isotope dilution gas chromatography/mass spectrometry for the determination of nickel in biological materials

Precise and accurate methods are required to measure nickel in urine and serum samples to identify clinical states of either deficiency or toxicity. This paper presents an isotope dilution gas chromatography/mass spectrometry method for the measurement of nickel in biological samples. The method involves the preparation of a thermally stable and volatile nickel chelate using lithium bis(trifluoroethyl)dithiocarbamate as the chelating agent. Conditions were optimized for the digestion of the sample and quantitative preparation of chelate as well as the precise and accurate measurements of the isotope ratios using a capillary column gas chromatograph with a general purpose mass spectrometer. The memory effect between samples of different isotope ratios was evaluated and was found to be negligible. The quantitative accuracy of isotope dilution was validated by measuring nickel in the NIST freeze-dried urine reference material, SRM 2670, with comparison to the recommended value.     

Aqueous and vapor phase mercury sorption by inorganic oxide materials functionalized with thiols and poly-thiols

The objective of the study is the development of sorbents where the sorption sites are highly accessible for the capture of mercury from aqueous and vapor streams. Only a small fraction of the equilibrium capacity is utilized for a sorbent in applications involving short residence times (e.g., vapor phase capture of mercury from coal-fired power plant flue gases). So, dynamic capacity rather than equilibrium capacity is more relevant for these kinds of situations. Rapid sorption rates and higher dynamic capacity can be achieved by increasing the accessibility of active sites and decreasing the diffusional resistance to mass transport for the adsorbing species. This requires the use of open structured sorbent materials and attachment of functional groups on the external surface area of supports. The strong interaction of sulfur containing ligands (e.g., thiol) with mercury makes them suitable candidates for immobilization on these types of materials. In this study, inorganic oxide supports like alumina and silica are functionalized with thiol moieties like mercapto silane, cysteine and poly-cysteine for capturing mercury from aqueous and vapor phase. Aqueous phase Hg (II) sorption studies with cysteine/poly-cysteine functionalized silica showed that high dynamic capacity can be achieved by attaching active sites (thiol) on the external area of supports. Vapor phase Hg capture studies with thiol-functionalized mesoporous silica (Hg⁰ concentration = 3.37 mg/m³ with N₂ as the carrier, gas temperature = 70 ^°C) yielded a capacity of 143 g Hg/g for the sorbent. Although the sulfur content for the sorbent was low (0.80 wt. %) the molar ratio of Hg captured to sulfur was comparatively high (2.86×10^–3) pointing to the high accessibility of sulfur sites.     

Direct profiling of proteins in biological tissue sections by MALDI mass spectrometry

The direct profiling of proteins present in tissue sections for several organs of the mouse has been accomplished using matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS). Fresh tissue was sectioned and blotted on a conductive polyethylene membrane. The dried membrane blot was coated with matrix, typically sinapinic acid, and directly analyzed in the mass spectrometer. Generally, well over 100 peptide/protein signals in the 2000-30,000 Da range were observed, with 30-50 having relatively high signal intensities. Analysis of different areas of the same tissue gave remarkably similar mass spectra with greater than 90% homology. However, different parts of a segmented tissue, such as the proximal, intermediate, and distal colon, gave some unique protein signals. After treatment of the tissue blot with protease and subsequent MALDI MS analysis using postsource decay methods for peptide sequencing, some of the proteins were identified. The unique protein profiles measured from these tissue blots also showed differences from strain to strain of the mouse, with genetically similar strains having very similar patterns.