Coupled Plasma Mass Spectrometric Analysis Research Articles

Chlorine-free Microwave Digestion of Stainless Steel for Inductively Coupled Plasma Mass Spectrometric Analysis

Chlorine-free Microwave Digestion of Stainless Steel for Inductively Coupled Plasma Mass Spectrometric Analysis

Precision geochemical (ICP-MS) analysis of Precambrian rocks: the method and accuracy estimation

The article discusses the results of measuring the composition of Early Precambrian mafic rocks and granitoids of the eastern part of the Fennoscandian Shield by inductively coupled plasma mass spectrometric analysis (ICP-MS). It is demonstrated that the bul kprobe sample composition can be determined both by acid digestion of samples in an open system and by autoclave digestion. The accuracy and reproducibility of the analysis were monitored by analyzing the international and Russian standards and the in-house reference sample: BHVO-2, SHD-2A, GSP-2, C-1412

Mineralogical and sulfur isotopic characteristics of Archean greenstone belt‐hosted gold mineralization at the Tau deposit of the Mupane gold mine, Botswana

AbstractThe Mupane gold deposit, which is one of the numerous gold occurrences in the Tati Greenstone Belt in the northeastern part of Botswana, consists of four orebodies, namely Tau, Tawana, Kwena, and Tholo deposits. The present research, which focuses on the genesis of the Tau deposit, was based on ore petrography, mineral chemistry of sulfides, and sulfur isotope data. Mineralogical characteristics of the host rocks indicate that banded iron formation at the Tau deposit includes iron oxides (magnetite), carbonates (siderite and ankerite), silicates (chlorite and amphibole), and sulfides (arsenopyrite and pyrrhotite). The deposit features arsenopyrite‐rich zones associated with biotite‐chlorite veins, which are indicative of the precipitation of arsenopyrite concomitant with potassic alteration. The replacement of magnetite by pyrrhotite in some samples suggests that sulfidation was likely the dominant gold precipitation mechanism because it is considered to have destabilized gold‐thiocomplexes in the ore‐forming fluids. Based on textural relationships and chemical composition, arsenopyrite is interpreted to reflect two generations. Arsenopyrite 1 is possibly early in origin, sieve textured with abundant inclusions of pyrrhotite. Arsenopyrite 1 was then overgrown by late arsenopyrite 2 with no porous textures and rare inclusions of pyrrhotite. Gold mineralization was initiated by focused fluid flow and sulfidation of the oxide facies banded iron formation, leading to an epigenetic gold mineralization. The mineralogical assemblages, textures, and mineral chemistry data at the Tau gold deposit revealed two‐stage gold mineralizations commencing with the deposition of invisible gold in arsenopyrite 1 followed by the later formation of native gold during hydrothermal alteration and post‐depositional recrystallization of arsenopyrite 1. Laser ablation inductively coupled plasma mass spectrometric analysis of arsenopyrite from the Tau deposit revealed that the hydrothermal event responsible for the formation of late native gold also affected the distribution of other trace elements within the grains as evidenced by varying trace elements contents in arsenopyrite 1 and arsenopyrite 2. The range of δ34S of gold‐bearing assemblages from the Tau deposit is restricted from +1.6 to +3.9‰, which is typical of Archean orogenic gold deposits and indicates that overall reduced hydrothermal conditions prevailed during the gold mineralization process at the Tau deposit. The results from this study suggest that gold mineralization involved multi‐processes such as sulfidation, metamorphism, deformation, hydrothermal alteration, and gold remobilization.

Evaluation of elements in human dental tissue in terms of determination of postmortem interval: Experimental study

Despite many methods, there has not been a method yet that exactly determines PMI. This study aims to examine the relationship between the element levels in the dental tissue and the postmortem process in a corpse whose exact time of death is unknown and in the open field and to evaluate its use in determining the time of death by evaluating the increase-decrease-changes. For the study, the healthy and extracted third molars of the patients who applied to the Oral and Maxillofacial Surgery Polyclinic for the extraction of their third molars for various reasons and whose third molars were extracted by the dentists were taken. The samples were divided into 6 groups, with 10 samples in each group. The teeth were left to decay in the open air in a jaw-like plastic model. Na, Mg, P, Ca, Fe, Mn, Co, Zn, Cd, Pb, and Si elements were measured using Inductively Coupled Plasma-Mass Spectrometer analysis method. In our study, it was determined that there were statistically significant changes in the Na, Mg, Fe, Co, Pb, Si elements in the tooth structure. For the Co and Na elements, 2 regression equations were created that can be used to predict the time of death. This work showed that postmortem tooth element concentration changes can be used to predict the time of death. As a result of experiments that will cover longer periods with more elements and be carried out in different environments, a great contribution will be made to the subject of estimation of time of death which is not clear yet.

Maritime pollution in the Indian Ocean after the MV X-Press Pearl accident

The MV X-Press Pearl marine debacle severely affected the marine environment in the Indian Ocean. The objective of this study is to monitor environmental pollution along the west coast of Sri Lanka. Beach sand samples were collected from 40 locations. Visual and microscopic observations, plastic pellets pollution index (PPI), and degradation effects of plastic nurdles were examined. Chemical and thermal characteristics were investigated using Inductively Coupled Plasma Mass Spectrometric analysis (ICP-MS) and Fourier Transform Infra-Red Spectroscopic analysis (FTIR) analyses, respectively. Cylindrical-shaped plastic nurdles (>0.2 cm in size) were observed in off-white (mainly), yellow, and black colours. The white colour plastic nurdles change to yellow at 240 °C and black at 300 °C. Epamulla (PPI = 1940–3364) and Sarakkuwa (PPI = 2158–3466) beaches were recognized as the most contaminated beaches during the initial sampling (i.e., after six to eight days of the explosion of the vessel). Well-rounded small plastic nurdles (i.e., after one year of the disaster) can indicate degradation effects. FTIR results confirm (i) plastic nurdles as low-density polyethylene (LDPE) and (ii) alteration of the chemical composition of nurdles at a low temperature of 60 °C. In this case, a significant amount of microplastics have been added to the environment under the influence of UV irradiation and abrasion against beach sand. In addition, the presence of heavy metals (e.g., arsenic, cadmium, lead, and copper) in swash zone sediments is a great threat to marine animals and plants. Consequently, the ingestion of microplastics and heavy metals would be increased in a wide range of marine organisms and can be bio-accumulated in humans through seafood and salt.

Highly sensitive detection of arsenic in groundwater by paper-based electrochemical sensor modified with earth-abundant material

The toxicity of arsenic and its hazards to the human body are well known and its timely, accurate, and cost-effective detection in water and foodstuffs and other environmental matrices is highly essential. Herein, we present a simple and easy method for the synthesis of reduced graphene oxide-ceria (rGO-CeO2) nanocomposite and its use for low-level detection of As(III) in water up to 0.93 μg/L. The presence of CeO2 on rGO surface is attributed to the enhanced electron transfer rate. The material characterization was performed with different analytical techniques including scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD), Infrared spectroscopy (FTIR) and Electrochemical Impedance Spectroscopy (EIS). The electrochemical behaviour of the rGO-CeO2 modified screen-printed electrodes (SPE) has been investigated by using Cyclic Voltammetry (CV) and Differential Pulse Stripping Voltammetry (DPSV). A highly linear response with a correlation coefficient of 0.9986 is achieved with a detection limit of 0.39 μg/L. Finally, the sensor was also tested with real-world groundwater samples collected from the arsenic-contaminated areas and acceptable recoveries were observed in the range of 85–95% as compared to Inductively Coupled Plasma Mass Spectrometer (ICP-MS) analysis. The electroanalytical performances of rGO-CeO2 modified SPE confirm that the as prepared sensor can be used for practical applications owing to its high sensitivity, good selectivity, robustness, low cost, high reproducibility, reusability, and ease of high scale production.

Evaluation of internal standards for inductively coupled plasma-mass spectrometric analysis of arsenic in soils.

Arsenic (As) is a common contaminant in soils, and analysis of soils by inductively coupled plasma-mass spectrometry (ICP-MS) is often used to detect As in soil extracts. Internal standards (ISs) are part of ICP-MS analyses to enhance precision and accuracy by compensating for instrument variability; however, an improper choice of IS can result in negative analytical bias. The goal of this study was to develop a protocol for evaluating ISs commonly used in ICP-MS. Three soils of varying clay content and total As were extracted with a dilute electrolyte [0.005mol L-1 Mg(NO3 )2 ] and an acid digest. Arsenic concentrations were quantified by ICP-MS using typical ISs: 6 Li, 45 Sc, 69 Ga, 89 Y, 103 Rh, 115 In, 159 Tb, and 209 Bi. Standard addition was used as a benchmark for As quantification. The most consistent IS was 115 In. Elevated, naturally occurring concentrations were detected for several of the ISs, particularly in the total digests, emphasizing the necessity for screening soils prior to analysis.

Mineral foraging and etching by the fungus Talaromyces flavus to obtain structurally bound iron

Fungi possess remarkable abilities to acquire mineral nutrients through foraging for and weathering minerals, and these fungal behaviors are influenced by the physiochemical properties of the minerals. Here, we investigated the dynamic processes underlying these behaviors in the interactions between the common fungus Talaromyces flavus and two serpentine minerals (antigorite and lizardite) and quartz as a control. In the culture of T. flavus on solid Czapek medium with these minerals, we found that the elongation rates of T. flavus hyphae toward antigorite and lizardite particles were similar, and both were much higher than those toward quartz particles. After reaching the minerals, the growth of T. flavus was promoted significantly by antigorite and lizardite. Atomic force microscopy measurements uncovered the production of distinct dissolution channels with a depth of 29.34 ± 6.18 nm on the lizardite surface, but no local dissolution was found on the antigorite surface. Laser ablation multicollector inductively coupled plasma mass spectrometric analysis indicated that the total Fe in T. flavus hyphae grown on the surfaces of lizardite and antigorite flakes was ~8.3 and 2.3 times, respectively of those grown on the surface of medium. Whewellite was ubiquitously found at the hyphal tips and their vicinity during T. flavus interactions with lizardite. These results demonstrate that fungal hyphae have a remarkable capacity to sense and respond to minerals and to extract structurally bound inorganic nutrients, and highlight that the instant weathering of minerals by fungi represents an important but unassessed contributor to the short-term release of mineral nutrients and should be incorporated into biogeochemical models.

Trace Elements in Apatite as Genetic Indicators of the Evate Apatite-Magnetite Deposit, NE Mozambique

The Evate deposit is a Neoproterozoic (~590 Ma) magnetite-apatite-carbonate body emplaced parallel to foliation of the Monapo granulite complex in NE Mozambique. A complicated history of the deposit is recorded in apatite textures visualized in cathodoluminescence (CL) images. In spite of different solid and fluid inclusions, mineral assemblages, and the CL textures, electron probe microanalyses indicate relatively consistent apatite compositions corresponding to fluorapatite (XF = 0.51–0.73, XOH = 0.21–0.47, XCl = 0.02–0.06) with limited belovite- and cesanite-type substitutions. Laser ablation inductively coupled plasma mass spectrometric analyses show that apatites from unaltered magnetite-forsterite-spinel ores are depleted in Y, REE, Ba, and Sr compared to apatites from carbonate-anhydrite ores. Hydrothermally overprinted apatites with complex patchy domain CL textures are enriched in Y-REE in greenish-grey zones, Fe-U-Th in blue zones, and Mn-Sr-Ba in brown domains. Observed CL-emissions in the Evate apatites result from very subtle variations in REE, Mn, and U contents controlled by the variability of redox conditions. The decreased Th:U ratio in the hydrothermally overprinted apatites reflects the oxidation and partial removal of U4+ from the apatite structure during the interaction with oxidizing aqueous fluids capable of transporting U6+. Flat, LREE (La-Sm)-enriched chondrite-normalized patterns with Eu/Eu* = 0.7–1.4 and Ce/Ce* = 0.9–1.5, together with concentrations of diagnostic trace elements (Sr, Mn, Y, REE) are consistent with apatites from magmatic carbonatites and phoscorites. This study corroborates that the Evate deposit is a post-collisional orogenic carbonatite genetically linked with mafic plutonic rocks intruding the Monapo granulite complex after granulite-facies metamorphism, and later overprinted by intensive hydrothermalism. The Evate apatite is peculiar in retaining its pristine magmatic signature despite the extensive hydrothermal-metasomatic alteration accompanied by dissolution-reprecipitation.

Zircon U–Pb dating, Lu–Hf isotopic composition and geological significance of granites in the Haobugao Pb–Zn deposit, southern Great Xing’an Range, China

The Haobugao Pb–Zn deposit located in the southern Great Xing’an Range (SGXR) is one of the most important deposits within the Huanggangliang–Ganzhuermiao polymetallic metallogenic belt. Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite are present in the ore area and are assumed to be closely related to the mineralization. In this study, a new isotopic dating technique, zircon U–Pb laser ablation inductively coupled plasma mass spectrometer analysis, was applied to the granites; the analyses indicate that the Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite were emplaced at 143.9 ± 1.1 Ma and 151.3 ± 1.4 Ma, respectively. Geochemically, these A-type granites are characterized by relatively high SiO2 and K2O contents, low Al2O3 content, and negative Eu anomalies. Additionally, both granites display strong Rb, Th, U, and Ce enrichment and Ba, K, Sr, and Ti depletion. Their relatively high eHf (t) values (with averages of 7.13 and 7.87, respectively) and young two-stage Nd and Hf model ages indicate that the two granites may have predominantly derived from the partial melting of a juvenile lower crust, followed by fractional crystallization during magma ascent. The geological, elemental, and isotopic evidence shows that the Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite formed due to the upwelling of mantle-derived alkaline magma and partial melting of the crust, with a certain degree of mixed dyeing, under a tectonic background of asthenosphere upwelling and lithosphere extension via the subduction of the ancient Pacific plate.

Nano-Magnesium Oxide: A Novel Bactericide Against Copper-Tolerant Xanthomonas perforans Causing Tomato Bacterial Spot

Bacterial spot caused by Xanthomonas perforans causes significant damage on tomato in Florida. Due to the presence of copper (Cu)-tolerant X. perforans strains, Cu bactericides are not effective in disease management. Hence, there is a critical need to find alternatives for Cu. Antibacterial activity of magnesium oxide (Nano-MgO), and other metal oxide nanoparticles, were evaluated against a Cu-tolerant and -sensitive X. perforans strain. In vitro experiments demonstrated high antibacterial activity of Nano-MgO against both strains compared with the commercial Cu. The minimum inhibitory concentration of Nano-MgO is 25 µg/ml and the minimum bactericidal concentration is 100 µg/ml against a Cu-tolerant X. perforans strain after 4 h of exposure. Structural changes in the bacterial membrane following exposure to Nano-MgO treatments compared with the controls were observed using transmission electron microscopy. In two greenhouse experiments with a Cu-tolerant strain, bacterial spot severity was significantly reduced by Nano-MgO at 200 µg/ml compared with Cu-ethylene bis-dithiocarbamate (grower standard), and the untreated control (P = 0.05). In three field experiments, Nano-MgO at 200 µg/ml significantly reduced disease severity with no negative impact on yield compared with the untreated control. Inductively coupled plasma mass spectrometric analysis of the fruit confirmed that Nano-MgO application did not lead to the accumulation of Mg, Cu, Ca, K, Mn, P, and S. This study is the first to demonstrate the potential of Nano-MgO against bacterial spot of tomato.

Marshallsussmanite, NaCaMnSi3O8(OH), a new pectolite-group mineral providing insight into hydrogen bonding in pyroxenoids

AbstractMarshallsussmanite (IMA2013-067) is a new pyroxenoid mineral from the Wessels mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Marshallsussmanite has ideal formula NaCaMnSi3O8(OH) and triclinic P$\bar{1}$symmetry. Marshallsussmanite forms vitreous pink bladed crystals to 2.1 cm. The mineral shows perfect cleavage on both {100} and {001}. The chemical composition from electron microprobe (average of 20 analyses) and inductively coupled plasma mass spectrometer analysis (average of three analyses) is Li2O 0.43, Na2O 8.06, MgO 0.08, CaO 15.33, MnO 21.79, SiO251.71; totalling 97.40 wt.%. The empirical formula, normalized to 3 Si and assuming 1 H apfu is Li0.100Na0.906Ca0.953Mg0.007Mn1.071Si3O8(OH). Unit-cell parameters from single crystal X-ray diffraction area= 7.7854(4),b= 6.9374(4),c= 6.8516(3) Å, α = 90.683(3)°, β = 94.330(3)°, γ = 102.856(3)°,V= 359.59(3) Å3;Z= 2. The crystal structure refinement converged withRobs= 0.0248 and site occupancy refinement gives crystal chemistry [Na0.948Li0.052][Ca0.793Mn0.207] [Mn0.937Ca0.063]Si3O8(OH). Marshallsussmanite is a single chain silicate with a repeat interval of three tetrahedra (i.e.dreierchain). Marshallsussmanite is a member of the pectolite group of pyroxenoids, which also includes barrydawsonite-(Y), cascandite, pectolite, serandite and tanohataite. Parallel silicate chains form layers, intercalated with well-ordered cation layers. Calcium and Mn both exhibit octahedral coordination, while Na has four bonded interactions in a coordination sphere (radius 3 Å) of seven separate O atoms. Procrystal electron density and bond valence modelling results are compared. The mineral has an unusually strong hydrogen bond with O4⋅⋅⋅O3 separation of 2.458(2) Å. Unlike pectolite and serandite, O4 in marshallsussmanite acts as an H-bond donor and O3 is an H-bond acceptor. Cation ordering in pyroxenoids has a substantial impact on the H position and corresponding H-bonding schemata.

Stanniferous magnetite composition from the Haobugao skarn Fe–Zn deposit, southern Great Xing'an Range: Implication for mineral depositional mechanism

The Great Xing'an Range in north‐eastern China hosts numerous super‐large Ag–Pb–Zn deposits and some Fe–Sn deposits. The Mesozoic Haobugao Fe–Zn polymetallic skarn deposit in the southern Great Xing'an Range is contemporaneous with the regional Ag–Pb–Zn mineralization. Numerous ore bodies are hosted in the Lower Permian carbonate strata or along the contact with the Early Cretaceous granite. According to the field and systematic petrography and mineralography research, the Haobugao mineralization phases are divided into 3 paragenetic stages: prograde stage, retrograde stage, and sulphide stage. Magnetite mainly occurred in the retrograde stage and replaced the anhydrous skarn minerals (e.g., garnet and diopside). Two types of magnetite (Mag1 and Mag2), including 6 subtypes, can be distinguished based on the scanning electron microscopy and back scattered electron images. Electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometer analysis were used to determine major and trace elements in different types of magnetite. Mag1 has higher Ti and V concentrations than Mag2, indicating a relatively higher depositional temperature. Mag1 also contains relatively higher Mg and Mn concentrations, coupled with much lower Si and Al concentrations, which reflects a low fluid/rock ratio at the site of Mag1 deposition. Element variation features of Mag1 and Mag2 reveal that the Haobugao mineralization fluids gradually evolved from high‐temperature and low fluid/rock ratio fluids to relatively low‐temperature and high fluid/rock ratio fluids. However, electron probe microanalysis data of Mag2 display significantly higher Sn concentrations (up to 2.82 wt.%) than that in Mag1, which indicates that Sn can be incorporated into magnetite crystal lattice. We propose a possible substitution mechanism of Sn4+ + Mn2+ = 2Fe3+, supported by the strongly positive correlation between Sn4+ and Mn2+, whereby a substitution of Sn4+ for Fe3+ in octahedral sites of magnetite requires a compensatory substitution of Mn2+ for Fe3+ to maintain the charge balance.

Direct electrokinetic injection of inorganic cations from whole fruits and vegetables for capillary electrophoresis analysis

A novel approach for the direct injection from plant tissues without any sample pre-treatment has been developed by simply placing a small piece of the tissue into a capillary electrophoresis vial followed by application of a voltage for electrokinetic injection. Separations of sodium, potassium, calcium and magnesium were achieved using a BGE comprising 10mM imidazole and 2.5mM 18-crown-6-ether at pH 4.5. The addition of 2% (m/v) hydroxypropylmethyl cellulose to the separation buffer allowed for precise and accurate electrokinetic injection of ions from the plant material by halting the movement of tissue fluid into the capillary. This method provides both qualitative and quantitative data of inorganic cations, with quantitation in zucchini, mushroom and apple samples in agreement with Sector Field Inductively Coupled Plasma Mass Spectrometric analysis (r2=0.98, n=9). This method provides a new way for rapid, quantitative analysis by eliminating sample preparation procedures, and has great potential for a range of applications in plant science and food chemistry.

Facile Synthesis of 3D Hierarchical Flower-like Co3-xFexO4 ferrite on Nickel Foam as High-Performance Electrodes for Supercapacitors

A facile hydrothermal method combined with a post solution reaction is developed to synthesize interconnected three-dimension (3D) hierarchical Co3-xFexO4 ferrite (CF) on nickel foam. By controlling the experimental parameters, the structures of the products are tailored from nanoflowers to microflowers with different sized void interiors. The obtained 3D hierarchical flower-like CF are characterized by field emission scanning electron microscopy, X-ray diffraction, and inductively coupled plasma mass spectrometer analysis. The 3D hierarchical flower-like CF-nickel foam with the rational structural feature could be used as binder and conductive agent-free supercapacitor electrodes directly. Such integrated electrodes exhibit a high specific capacitance and well cycling stability when the charge-discharge current density is high. Remarkably, the 3D hierarchical CF microflowers exhibit specific capacitance values of 768Fg−1 at a constant current density of 6Ag−1. The CF microflowers also show high charge-discharge reversibility with an efficiency of 79.2% after 5000 cycles.

Flammability and thermal behavior of polypropylene composites containing dihydrogen phosphate anion‐intercalated layered double hydroxides

Dihydrogen phosphate anion‐intercalated layered double hydroxides (M‐LDHs) was prepared by modification of Mg‐Al‐CO32− layered double hydroxides (LDHs) with anion exchange procedure. The structure of the M‐LDHs was characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscope (TEM). Polypropylene (PP)/LDHs and PP/M‐LDHs composites were prepared by melt compounding. The morphology of PP composites was investigated by TEM and XRD, which demonstrated that M‐LDHs could be well dispersed in PP matrix to form a nano‐scale exfoliated structure. Thermogravimetric analysis showed that thermal stability of PP composites was improved by the presence of LDHs and M‐LDHs. The flammability of PP composites was characterized by limited oxygen index, vertical burning test (UL‐94), FTIR, and cone calorimeter test, and the result showed the fire performance were significantly improved after the addition of LDHs and/or M‐LDHs which can remarkably decrease the heat release rate, total heat release, and the fire performance index. It was proposed that the lamellar structure of LDHs can block the heat, dilute the flammable gases and decrease the temperature, while the replaced H2PO4− into LDHs molecules can enhance the charred layer formation during burning procedure. Inductively coupled plasma mass spectrometer analysis showed that most phosphorus remained in the char layer, suggesting the replaced H2PO4− in LDHs molecules mainly function in the condensed phase. POLYM. COMPOS., 36:2230–2237, 2015. © 2014 Society of Plastics Engineers

Laser Ablation Inductively Coupled Plasma Mass Spectrometric Analyses of Base Metals in Arctic Char (Salvelinus alpinus) Otoliths Collected from a Flooded Base Metal Mine

Otoliths from arctic char recovered from the water body formed from an abandoned open-pit nickel-copper mine contain a trace element record related to the geology of the immediate watershed, past mining activity in the area, and the fish's diet. Laser ablation inductively coupled plasma mass spectrometric analyses across the annular structure of the otoliths detected trace amounts of nickel, copper, and chromium believed to be related to the metal-bearing, mafic-ultramafic minerals in the pit. Oscillatory strontium, barium, and zinc profiles may reflect changing water temperature, diet, or fish metabolism. Lead was detected in very low concentrations and may be related to anthropogenic influence. This closed lake system provides a unique opportunity to study an introduced exotic species in a setting where neither migration nor recruitment have been possible. The fish have successfully occupied the lake and continue to breed despite the influence of the surrounding rocks and local contamination. The chemical record retained within otoliths provides a method of monitoring trace elements affecting fish on a yearly basis and may be regarded as a useful assessment tool for examining the exposure of wild organisms to trace elements.

Matrix effects on the multi-collector inductively coupled plasma mass spectrometric analysis of high-precision cadmium and zinc isotope ratios

Resin-derived contaminants added to samples during column chemistry are shown to cause matrix effects that lead to inaccuracy in multi-collector inductively coupled plasma mass spectrometry measurement of small natural variations in Cd and Zn isotopic compositions. These matrix effects were evaluated by comparing pure Cd and Zn standards and standards doped with bulk column blank from the anion exchange chromatography procedure. Doped standards exhibit signal enhancements (Cd, Ag, Zn and Cu), instrumental mass bias changes and inaccurate isotopic compositions relative to undoped standards, all of which are attributed to the combined presence of resin-derived organics and inorganics. The matrix effect associated with the inorganic component of the column blanks was evaluated separately by doping standards with metals at the trace levels detected in the column blanks. Mass bias effects introduced by the inorganic column blank matrix are smaller than for the bulk column blank matrix but can still lead to significant changes in ion signal intensity, instrumental mass bias and isotopic ratios. Chemical treatment with refluxed HNO 3 or HClO 4/HNO 3 removes resin-derived organic components resulting in matrix effects similar in magnitude to those associated with the inorganic component of the column blank. Mass bias correction using combined external normalization-SSB does not correct for these matrix effects because the instrumental mass biases experienced by Cd and Zn are decoupled from those of Ag and Cu, respectively. Our results demonstrate that ion exchange chromatography and associated resin-derived contaminants can be a source of error in MC-ICP-MS measurement of heavy stable element isotopic compositions.

Inductively coupled plasma mass spectrometric analysis of the total amount of platinum in DNA extracts from peripheral blood mononuclear cells and tissue from patients treated with cisplatin

We present a highly sensitive method for the determination of platinum (Pt) in DNA extracts of peripheral blood mononuclear cells (PBMCs) and tissue samples from patients treated with cisplatin. The method is based on the measurement of Pt by inductively coupled plasma mass spectrometry (ICP-MS) and allows quantification of Pt-DNA adducts in PBMCs isolated from 10mL blood and 1mg tissue. The lower limit of quantification is 0.75pg Pt or 7.5fg Pt μg(-1) DNA when using 100μg DNA. The method proved to be accurate and precise. The results obtained using the ICP-MS method were in good agreement with results from the alternative (32)P-postlabelling assay. The ICP-MS method was, however, more sensitive and proved to be less laborious. The advantages of the presented ICP-MS technique were demonstrated by the analysis of PBMCs, normal gastric tissue, and gastric tumour tissue of patients treated with cisplatin.

Oxidation of alkyl nitronates catalyzed by 2-nitropropane dioxygenase from Hansenula mrakii

2-Nitropropane dioxygenase from Hansenula mrakii was expressed in Escherichia coli cells and purified in active and stable form using 60% saturation of ammonium sulfate and a single chromatographic step onto a DEAE column. MALDI-TOF mass spectrometric and spectrophotometric analyses of the flavin extracted by heat or acid denaturation of the enzyme indicated that FMN, and not FAD as erroneously reported previously, is present in a 1:1 stoichiometry with the protein. Inductively coupled plasma mass spectrometric analysis of the enzyme established that H. mrakii 2-nitropropane dioxygenase contains negligible amounts of iron, manganese, zinc, and copper ions, which are not catalytically relevant. Anaerobic substrate reduction and kinetic data using a Clark oxygen electrode to measure rates of oxygen consumption indicated that the enzyme is active on a broad range of alkyl nitronates, with a marked preference for unbranched substrates over propyl-2-nitronate. Interestingly, the enzyme reacts poorly, if at all, with nitroalkanes, as suggested by lack of both anaerobic reduction of the enzyme-bound flavin and consumption of oxygen with nitroethane, nitrobutane, and 2-nitropropane. Finally, both the tight binding of sulfite (Kd=90μM, at pH 8 and 15°C) to the enzyme and the formation of the anionic flavosemiquinone upon anaerobic incubation with alkyl nitronates are consistent with the presence of a positively charged group in proximity of the N(1)C(2)O atoms of the FMN cofactor.