Procedural Blanks Research Articles

An interlaboratory comparison study for the determination of dialkyl phthalate esters in environmental and biological samples

A series of interlaboratory comparison exercises were conducted to assess the accuracy of dialkyl phthalate ester (DPE) concentration measurements in environmental and biological samples. Five laboratories participated in analyses to determine DPE concentrations in standard test solutions; marine sediments; three certified reference materials, including CARP-2 (fish muscle) and BCR-07 (fortified milk powder); and several livestock samples (sheep's milk, liver, and muscle). In addition, one laboratory determined DPE residue concentrations in 20 municipal sewage sludge samples, previously analyzed as part of the 2006/2007 U.S. Environmental Protection Agency's Targeted National Sewage Sludge Survey (TNSSS). The results showed relatively good interlaboratory agreement for analyses of di-ethylhexyl phthalate (DEHP). Three independent laboratories (Labs A, B, and C) reported concentrations of DEHP (ng/g wet wt) in fish muscle (CARP-2) of 1,550 ± 148, 1,410 ± 193, and 1,380 ± 187, respectively. Similarly, DEHP concentration measurements in sewage sludge samples showed good agreement with those reported in the 2006/2007 TNSSS report. Measured concentrations of individual DPEs and C6-C10 isomeric mixtures in these samples of municipal sewage sludge, which have not been previously reported, ranged between 1 and 200,000 ng/g dry weight. The results demonstrate that environmental monitoring of DPEs is often hampered by high method detection limits (MDLs), due to contamination of procedural blanks. It is important to note, however, that when background contamination is minimized (<10 ng/sample), relatively low MDLs (<0.1 ng/g) can be achieved, allowing for low-level quantification of DPEs in environmental and biological samples. Future efforts to develop better protocols to lower MDLs, as well to develop reference materials, would greatly benefit future DPE monitoring initiatives.

Determination of bismuth in open ocean waters by inductively coupled plasma sector-field mass spectrometry after chelating resin column preconcentration

A novel low-blank method is described for the analysis of bismuth in seawater based on preconcentration using an ethylenediaminetriacetic acid chelating resin column followed by determination with inductively coupled plasma sector-field mass spectrometry (ICPSFMS). A sample is siphoned into and drains through the column with the flow rate being kept constant by using a flotation device. Bi in 250mL of acidified seawater is extracted onto the column in this process and eluted with 2mL of 3M HNO3 followed by 3mL of ultra-high purity water. The concentration of Bi in the eluate is measured by ICPMS. The benefits of the method compared to others are its simplicity, a smaller amount of seawater, and lower procedural blanks and detection limits at pgkg−1 levels. Data on dissolved Bi in open ocean reference samples of SAFe and GEOTRACES programs are presented for the first time.

Protein Quantitation Using Ru-NHS Ester Tagging and Isotope Dilution High-Pressure Liquid Chromatography–Inductively Coupled Plasma Mass Spectrometry Determination

An accurate, simple, and sensitive method for the direct determination of proteins by nonspecies specific isotope dilution and external calibration high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS) is described. The labeling of myoglobin (17 kDa), transferrin (77 kDa), and thyroglobulin (670 kDa) proteins was accomplished in a single-step reaction with a commercially available bis(2,2'-bipyridine)-4'-methyl-4-carboxybipyridine-ruthenium N-succinimidyl ester-bis(hexafluorophosphate) (Ru-NHS ester). Using excess amounts of Ru-NHS ester compared to the protein concentration at optimized labeling conditions, constant ratios for Ru to proteins were obtained. Bioconjugate solutions containing both labeled and unlabeled proteins as well as excess Ru-NHS ester reagent were injected onto a size exclusion HPLC column for separation and ICPMS detection without any further treatment. A (99)Ru enriched spike was used for nonspecies specific ID calibration. The accuracy of the method was confirmed at various concentration levels. An average recovery of 100% ± 3% (1 standard deviation (SD), n = 9) was obtained with a typical precision of better than 5% RSD at 100 μg mL(-1) for nonspecies specific ID. Detection limits (3SD) of 1.6, 3.2, and 7.0 fmol estimated from three procedure blanks were obtained for myoglobin, transferrin, and thyroglobulin, respectively. These detection limits are suitable for the direct determination of intact proteins at trace levels. For simplicity, external calibration was also tested. Good linear correlation coefficients, 0.9901, 0.9921, and 0.9980 for myoglobin, transferrin, and thyroglobulin, respectively, were obtained. The measured concentrations of proteins in a solution were in good agreement with their volumetrically prepared values. To the best of our knowledge, this is the first application of nonspecies specific ID for the accurate and direct determination of proteins using a Ru-NHS ester labeling reagent.

Application of an improved ion exchange technique for the measurement of δ34S values from microgram quantities of sulfur by MC-ICPMS

Motivated by limitations of the existing solution-based Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) studies to low sulfur concentrations, analytical procedures are reported for δ34S measurements (2σ precision of 0.24–0.34‰) at sulfur concentration [S] of 2 μg mL−1, following its purification by anion exchange resin (AER). δ34S values of International Atomic Energy Agency (IAEA) standards S-1, S-2 and S-3, and IAPSO seawater measured in this study agree (within uncertainties) with the consensus values measured by conventional techniques. These values also are in close agreement with the reported numbers by an MC-ICPMS study in which δ34S was measured at [S] of 20 μg mL−1 following its purification by cation exchange resin (CER). Anion exchange purification offers significant advantages of less sample requirement (2 μg S vs. 500 μg S), lower procedural blanks (∼12 ng vs. ∼250 ng of S), and less chemical requirements and sample processing times, over the cation exchange; therefore, δ34S measurements attempted in this study would suffer significantly from procedural blank if CER is used. It is believed that the procedures reported in this study would establish the application of MC-ICPMS to δ34S measurements in low sulfur containing samples, and should find widespread application especially in studies related to glacier, snow, rainwater and aerosol samples.

High precision nitrogen isotope measurements in oceanic basalts using a static triple collection noble gas mass spectrometer

We describe a new system for the simultaneous static triple‐collection of nitrogen isotopes at the &lt;10μcm3 STP [N2] (&lt;1 × 10−5 cm3STP; &lt;0.5 nmol) level using a modified VG‐5440 noble gas mass spectrometer. The system consists of an internal N2‐STD with aδ15N value of −0.11 ± 0.22 ‰ (1σ) calibrated against an air‐standard (Air‐STD). The N2‐STD was measured repeatedly with an average uncertainty on an individualδ15N measurement being 0.03 ‰ (1σ) versus an average single day reproducibility of 0.38 ‰ (1σ). Additional refinements include (1) monitoring of interfering CO contributions at mass 30, allowing a comprehensive CO correction to be applied to all samples, (2) quantification of procedural N2 blanks (n = 22) in both size (4.2 ± 0.5 μcm3 STP) and isotopic composition (δ15N = 12.64 ± 2.04 ‰), allowing consistent blank corrections to all samples, and (3) independent measurement of N2/Ar ratios using a quadrupole mass spectrometer (QMS). The new system was tested by measuring nitrogen isotopes (δ15N), concentrations and N2/Ar ratios on 11 submarine basalt glasses. Results show that the uncertainty on the δ15N data is improved as a consequence of multiple standards being run per day. Reduced analytical times, afforded by triple collection, also minimize sample depletion and memory effects, thus improving measurement statistics. Additionally, we show that CO corrections can be accomplished using mass 30 to monitor CO interferences, leading to substantial improvements in reproducibility and the overall accuracy of results when the contribution of CO is significant.

Acrylamide determination in atmospheric particulate matter by high-performance liquid chromatography/electrospray ionisation tandem mass spectrometry

A method has been developed for the determination of acrylamide at the picogram per cubic metre level in particulate-phase outdoor aerosol using high-performance liquid chromatography with triple quadrupole tandem mass spectrometric detection. Acrylamide was identified by positive ion electrospray mass spectrometry using m/z 72.00/54.90 as monitoring ion transition. The limit of detection, defined as three times the standard deviation of the procedural blanks, was 0.4 pg m−3 (173 pg absolute amount injected); the repeatability was 8% (evaluated as the relative standard deviation of five consecutive measurements on cleaned quartz fibre filters of acrylamide standard spikes) and the recovery was 52 ± 4%. The accuracy of the method (evaluated as relative error) has been estimated to be −2%. This methodology was used to determine acrylamide concentrations in particulate-phase outdoor aerosol in the Venice Lagoon with concentrations ranging between 0.4 and 12.9 pg m−3 with an average value of 3.1 pg m−3.

Controlling Contamination for Determination of Ultra-Trace Levels of Cr and Ni in Biological Materials in a Conventional Laboratory

The determination of ultra-trace levels of chromium and nickel in biological samples had previously been very difficult due to serious contamination problems in conventional laboratories. Contamination control in a conventional laboratory was studied and contamination due to various sources was minimized systematically. In addition to chromium and nickel, zinc was also determined as an indicator element prone to contamination. Measurements were carried out using electrothermal atomic absorption spectrometry (ETAAS). Contamination from the sample handling steps, digestion vessels, atmospheric fallout, and the effect of the liquid contact area were studied. In the sample handling steps, even simple procedures, such as transferring the sample solution from the volumetric flask by pouring, led to significant contamination due to the large area of liquid contact. This contamination source was eliminated by transferring the sample solution using an automatic pipette. The most suitable method for decontamination of the digestion vessels was steaming with boiling nitric acid as opposed to leaching with nitric acid at room temperature. Quartz was found to be a more suitable digestion vessel material than Teflon-PFA when Cr and Ni were determined. For Zn determination, Teflon-PFA was more suitable. Contamination from atmospheric fallout was highest in the fume hood and was reduced by simply closing the labware into Minigrip® bags before use. The surface area of the labware in contact with the handled liquid volume should be kept at a minimum because even a simple procedure, such as preparing standard solutions in volumetric flasks, can lead to significant contamination if the vessel surface area is too large. Finally, low enough contamination was achieved so that the total procedure blanks were below the instrumental detection limits for Cr and Ni.

An evaluation of a single-step extraction chromatography separation method for Sm–Nd isotope analysis of micro-samples of silicate rocks by high-sensitivity thermal ionization mass spectrometry

A single-step separation scheme is presented for Sm–Nd radiogenic isotope system on very small samples (1–3 mg) of silicate rock. This method is based on Eichrom ® LN Spec chromatographic material and affords a straightforward separation of Sm–Nd from complex matrix with good purity and satisfactory blank levels, suitable for thermal ionization mass spectrometry (TIMS). This technique, characterized by high efficiency (single-step Sm–Nd separation) and high sensitivity (TIMS on NdO + ion beam), is able to process rapidly (3–4 h), with low procedure blanks (<10 pg) and very small sample (1–3 mg). Replicate measurements by TIMS on 143Nd/ 144Nd ratios and Sm–Nd concentrations are presented for eleven international silicate rock reference materials, spanning a wide range of Sm–Nd contents and bulk compositions. The analytical results show a good agreement with recommended values within ±0.004% for the 143Nd/ 144Nd isotopic ratio and ±2% for Sm–Nd quantification at the 95% confidence level. It is noted that the uncertainty of this method is about 3 times larger than typical precision achievable with two-stage full separation followed by state-of-the-art conventional TIMS using Nd + ion beams which require much larger amounts of Nd. Hence, our single-step separation followed by NdO + ion beam technique is preferred to the analysis for microsamples.

A novel extraction chromatography and MC-ICP-MS technique for rapid analysis of REE, Sc and Y: Revising CI-chondrite and Post-Archean Australian Shale (PAAS) abundances

A new analytical protocol is introduced for rapid measurement of rare-earth elements (REE), Sc and Y in meteoritic and geological materials by multi-collection inductively coupled plasma mass spectrometry (MC-ICP-MS). A simple purification step was devised to reduce REE, Sc and Y abundances in commercial lithium metaborate (LiBO 2) for low-blank flux fusion. Separation of the analytes from the rock matrix was achieved by using a single TODGA extraction chromatography step. A dynamic multi-collector cup configuration was developed to measure REE, Sc and Y using a desolvating nebulizer and standard-sample bracketing technique. To test the accuracy of this analytical protocol, we analyzed aliquots of USGS geological reference materials BHVO-1, BIR-1, BCR-2, PCC-1, W-2, G-2 and G-3, specifically selected to encompass a wide range of REE, Sc and Y concentrations and mineral compositions. Elemental abundances in reference materials are indistinguishable within analytical uncertainties from compilations of literature values analyzed by various ICP-MS techniques. The average external reproducibility on REE, Sc and Y concentrations (reported as RSD = 100 × standard deviation/average) was ~ 2% based on replicates of G-3. With the exception of PCC-1, which has low REE concentrations, adjustments for poly-atomic interferences and procedural blanks in the reference materials were negligible. In order to re-visit the terrestrial and cosmic abundances of REE, Sc and Y, aliquots of nine Post Archean Australian Shales (PAAS), Allende (CV-3), Tagish Lake (C2-ungrouped), Alais (CI1), Orgueil (CI1) and Ivuna (CI1) meteorites were measured using our new analytical procedure. The REE patterns of PAAS, normalized to the mean of CI-chondrites from this study, are smoother and show less dispersion compared with literature measurements. Eu/Eu*, ΣLREE/ΣHREE, and La/Sc ratios remain constant in these samples. The recommended PAAS composition based on these new measurements is (in μg g − 1 ): Sc = 15.89, Y = 27.31, La = 44.56, Ce = 88.25, Pr = 10.15, Nd = 37.32, Sm = 6.884, Eu = 1.215, Gd = 6.043, Tb = 0.8914, Dy = 5.325, Ho = 1.052, Er = 3.075, Tm = 0.4510, Yb = 3.012 and Lu = 0.4386. The REE pattern in Allende is similar to group II-type Ca–Al-rich inclusions (CAIs) that typically show enrichment in light REE (LREE), depletion in heavy REE (HREE), and negative and positive anomalies for Eu and Tm, respectively. The REE in Tagish Lake and Alais do not show significant fractionations and closely resemble the relatively flat pattern observed in Orgueil. Based on eight high-precision multi-collection ICP-MS measurements of Orgueil (n = 5), Ivuna (n = 2) and Alais (n = 1), we recommend a new CI-composition for REE, Sc and Y normalization and refine the cosmic abundances of these elements (in μg g − 1 ): Sc = 5.493, Y = 1.395, La = 0.2469, Ce = 0.6321, Pr = 0.0959, Nd = 0.4854, Sm = 0.1556, Eu = 0.0599, Gd = 0.2093, Tb = 0.0378, Dy = 0.2577, Ho = 0.0554, Er = 0.1667, Tm = 0.0261, Yb = 0.1694 and Lu = 0.0256.

Cadmium determination in natural waters at the limit imposed by European legislation by isotope dilution and TiO2 solid-phase extraction

The cadmium content in surface water is regulated by the last European Water Framework Directive to a maximum between 0.08 and 0.25 μg L(-1) depending on the water type and hardness. Direct measurement of cadmium at this low level is not straightforward in real samples, and we hereby propose a validated method capable of addressing cadmium content below μg L(-1) level in natural water. It is based on solid-phase extraction using TiO(2) nanoparticles as solid sorbent (0.05 g packed in mini-columns) to allow the separation and preconcentration of cadmium from the sample, combined to direct isotope dilution and detection by inductively coupled plasma mass spectrometry (ID-ICP-MS). The extraction setup is miniaturised and semi-automated to reduce risks of sample contamination and improve reproducibility. Procedural blanks for the whole measurement process were 5.3 ± 2.8 ng kg(-1) (1 s) for 50 g of ultrapure water preconcentrated ten times. Experimental conditions influencing the separation (including loading pH, sample flow rates, and acid concentration in the eluent) were evaluated. With isotope dilution the Cd recovery rate does not have to be evaluated carefully. Moreover, the mathematical model associated to IDMS is known, and provides transparency for the uncertainty propagation. Our validation protocol was in agreement with guidelines of the ISO/IEC 17025 standard (chapter 5.4.5). Firstly, we assessed the experimental factors influencing the final result. Secondly, we compared the isotope ratios measured after our separation procedure to the reference values obtained with a different protocol for the digested test material IMEP-111 (mineral feed). Thirdly, we analysed the certified reference material BCR-609 (groundwater). Finally, combined uncertainties associated to our results were estimated according to ISO-GUM guidelines (typically, 3-4% k = 2 for a cadmium content of around 100 ng kg(-1)). We applied the developed method to the groundwater and wastewater samples ERM-CA615 and BCR-713, respectively, and results agreed with certificate values within uncertainty statements.

Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases

All terrestrial organisms depend on nucleic acids (RNA and DNA), which use pyrimidine and purine nucleobases to encode genetic information. Carbon-rich meteorites may have been important sources of organic compounds required for the emergence of life on the early Earth; however, the origin and formation of nucleobases in meteorites has been debated for over 50y. So far, the few nucleobases reported in meteorites are biologically common and lacked the structural diversity typical of other indigenous meteoritic organics. Here, we investigated the abundance and distribution of nucleobases and nucleobase analogs in formic acid extracts of 12 different meteorites by liquid chromatography-mass spectrometry. The Murchison and Lonewolf Nunataks 94102 meteorites contained a diverse suite of nucleobases, which included three unusual and terrestrially rare nucleobase analogs: purine, 2,6-diaminopurine, and 6,8-diaminopurine. In a parallel experiment, we found an identical suite of nucleobases and nucleobase analogs generated in reactions of ammonium cyanide. Additionally, these nucleobase analogs were not detected above our parts-per-billion detection limits in any of the procedural blanks, control samples, a terrestrial soil sample, and an Antarctic ice sample. Our results demonstrate that the purines detected in meteorites are consistent with products of ammonium cyanide chemistry, which provides a plausible mechanism for their synthesis in the asteroid parent bodies, and strongly supports an extraterrestrial origin. The discovery of new nucleobase analogs in meteorites also expands the prebiotic molecular inventory available for constructing the first genetic molecules.

Quantification of PCDD/Fs and dioxin-like PCBs in small amounts of human serum using the sensitive H1L7.5c1 mouse hepatoma cell line: Optimization and analysis of human serum samples from adolescents of the Flemish Environment and Health Study (FLEHS II)

Since the CALUX (Chemically Activated LUciferase gene eXpression) bioassay is a fast and inexpensive tool for the throughput analysis of dioxin-like compounds in a large number of samples and requires only small sample volumes, the use of this technique in human biomonitoring programs provides a good alternative to GC–HRMS. In this study, a method for the separate analysis of PCDD/Fs and dioxin-like PCBs (dl-PCBs) in human serum with the new sensitive H1L7.5c1 mouse hepatoma cell line was optimized.Sample dilution factors of 5 and 2.4 were selected for routine analysis of respectively the PCDD/Fs and dl-PCBs. The validation studies showed that repeatability and within-lab reproducibility for the quality control (QC) standard were within the in-house criteria. A long-term within-lab reproducibility of 25% for the PCDD/F fraction and 41% for the dl-PCB fraction for the analysis of pooled serum samples, expressed as pgBEQ/gfat, was determined. CALUX recoveries of the spiked procedural blanks were within the acceptable in-house limits of 80–120% for both fractions and the LOQ was 30.3pgBEQ/gfat for the PCDD/Fs and 14.5pgBEQ/gfat for the dl-PCBs. The GC–HRMS recovery of a C13-spiked pooled serum sample was between 60 and 90% for all PCDD/F congeners and between 67 and 82% for the non-ortho PCBs. An adequate separation between both fractions was found. The CALUX/GC–HRMS ratio for a pooled serum sample was respectively 2.0 and 1.4 for the PCDD/Fs and the dl-PCBs, indicating the presence of additional AhR active compounds. As expected, a correlation was found between human serum samples analyzed with both the new H1L7.5c1 cell line and the more established H1L6.1c3 cell line. The geometric mean CALUX-BEQ values, reported for the adolescents of the second Flemish Environment and Health Study (FLEHS II) recruited in 2009–2010, were 108 (95% CI: 101–114)pgCALUX-BEQ/gfat for the PCDD/Fs and 32.1 (30.1–34.2)pgCALUX-BEQ/gfat for the dioxin-like PCBs.

The timing of epigenetic gold mineralization on the Baie Verte Peninsula, Newfoundland, Canada: new evidence from Re–Os pyrite geochronology

The absolute timing of epigenetic mineralization, including most types of gold deposits, is difficult to resolve due to the absence of suitable minerals in veins and replacement zones. However, gold is commonly closely associated with pyrite and arsenopyrite, which may be amenable to Re–Os geochronology, providing sufficient Re and Os are present within them. This short paper outlines the use of this method to date two gold deposits in Newfoundland using pyrite. Although the Os contents of the pyrites are extremely low (≪0.1 ppb), the Os is almost exclusively radiogenic 187Os, and data are amenable to model age calculations, as used in Re–Os molybdenite dating. The pyrites from these deposits correspond to low-level highly radiogenic sulphides, as defined by other studies. The Stog’er Tight and Pine Cove gold deposits yield mean Re–Os model ages of 411 ± 7 Ma (n = 4) and 420 ± 7 Ma (n = 5), respectively, which agree with isochron regression of 187Os against 187Re. The Re–Os age for Stog’er Tight is within uncertainty of a previous U–Pb age from ‘hydrothermal’ zircon (420 ± 5 Ma) in spatially related alteration. A latest Silurian–earliest Devonian age for the mineralization is consistent with indirect age constraints from some other gold deposits in central Newfoundland and suggests a broad temporal link to the mid-Silurian Salinic Orogeny. However, the gold mineralization appears to be younger than most plutonic activity associated with this event. The results illustrate the potential value of Re–Os pyrite geochronology in understanding the temporal framework of epigenetic mineralization, especially if future improvements in analytical precision and reductions in procedural blanks allow wider application to material with similarly low Re and Os concentrations.

Determination of rare earth elements and other trace elements (Y, Mn, Co, Cr) in seawater using Tm addition and Mg(OH)2 co-precipitation

This paper reports on a novel procedure for determining trace element abundances (REE and Y, Cr, Mn, Co) in seawater by inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The procedure uses a combination of pre-concentration using co-precipitation onto magnesium hydroxides and addition of thulium spike. The validity of the method was assessed onto 25ml volumes of certified reference materials (NASS- and CASS-4) and in house seawater standard. Procedural blanks were determined by applying the same procedure to aliquots of seawater previously depleted in trace elements by successive Mg(OH)2 co-precipitations, yielding estimated contributions to the studied samples better than 1.1% for all elements, with the exception of Cr (<3.3%) and Co (up to 8%). The reproducibility of the method over the six month duration of the study was smaller than 11% RSD for all the studied elements. Results obtained for NASS-5 and CASS-4 agree well with published working values for trace elements.

Single Column Sequential Extraction of Ra, Nd, Th, Pa and U from a Natural Sample

A new procedure allowing the sequential extraction of Ra, Nd, Th, Pa and U from the same initial natural sample (sea or river waters, particles, sediments, rocks) is proposed. Extraction recoveries were better than 90%. Procedural blanks ranged from 80 pg (for Nd) to below 1 fg, the detection limit of the MC‐ICP‐MS used (for Pa); all were negligible compared with the amounts of elements currently determined. Based on classical anionic resins attached to a peristaltic pump allowing precise flow rate control, this procedure allowed a consequent reduction of the sample size, which improved the sampling resolution and reduced the sampling cost. It also ensured a better consistency of the samples for the five tracers.

Analysis of PCDD/Fs and dioxin-like PCBs in atmospheric deposition samples from the Flemish measurement network: Optimization and validation of a new CALUX bioassay method

Since the CALUX (Chemically Activated LUciferase gene eXpression) bioassay is a fast, sensitive and inexpensive tool for the analysis of a high number of samples, validation of new methods is urgently needed. In this study, a new method for the analysis of PCDD/Fs and dioxin-like PCBs in atmospheric deposition samples with the CALUX bioassay was developed, optimized and validated. The method consists of 4 steps: filtration, extraction, clean up and bioassay analysis. To avoid the use of large amounts of toxic solvents, new techniques were used for filtration and extraction: a C18 filter was used instead of a liquid/liquid extraction and an Accelerated Solvent Extractor (ASE) was used instead of the traditional soxhlet extraction. After pre-oxidation of the sample extract, clean up was done using a multi-layer silica gel column coupled to a carbon column. The PCDD/F and PCB fractions were finally analyzed with the H1L7.5c1 and/or the H1L6.1c3 mouse hepatoma cell lines. The limit of quantification was 1.4 pg CALUX-BEQ m −2 d −1 for the PCBs and 5.6 pg CALUX-BEQ m −2 d −1 for the PCDD/Fs, when using the new sensitive H1L7.5c1 cell line. The GC–HRMS recovery for all PCDD/F congeners was between 55% and 112%, with a mean recovery of 90%. CALUX recoveries of spiked procedural blanks were between the accepted ranges of 80–120%. Repeatability and reproducibility were satisfactory and no interferences from metals were detected. The first results from the Flemish measurement program showed good correlation between CALUX and GC–HRMS.

A straightforward protocol for Hf purification by single step anion-exchange chromatography and isotopic analysis by MC-ICP-MS applied to geological reference materials and zircon standards

A straightforward one-step Hf purification protocol for geological samples using common anion-exchange chromatography and isotopic measurements by multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) is described in this paper. The sample is dissolved in concentrated HF–HNO 3 mixtures with round-bottom Savillex™ Teflon screw-top capsules or high-pressure stainless steel jacketed Teflon bombs. After complete dissolution, the chemical separation between Hf and isobarically interfering elements such as Lu, Yb, and matrix elements like Ti, is performed and achieved simultaneously using a common one-step anion exchange resin (AG1-X8). The Hf yields are >90% and total procedural blanks are lower than 20 pg. This protocol not only avoids using multiple-stage ion exchange resins, but also eliminates perchloric acid to break down fluorides after HF treatment of the sample. In addition to whole rock, this protocol is also practical for zircon and baddeleyite Hf purification prior to isotopic measurement. New Hf isotopic data for zircon 91500, Temora, CN92-1 and FM0411, together with Phalaborwa baddeleyite are presented for this method. Multiple analyses of the international geological reference materials and standard zircon and baddeleyite used in U–Pb geochronology demonstrate that this method is simple, economic, efficient and reproducible.

A new method integrating high-precision U–Pb geochronology with zircon trace element analysis (U–Pb TIMS-TEA)

Increased precision in isotope-dilution thermal ionization mass spectrometry (ID-TIMS) U–Pb geochronology has revealed age complexities in zircon populations that require new tools for understanding how the growth of zircon is related to geologic processes. U and Pb are routinely separated from other elements in dated minerals by ion exchange separation prior to TIMS isotope measurement. We develop a method in which trace elements in the exact same volume of zircon are redissolved and analyzed using solution nebulization inductively coupled plasma sector-field mass spectrometry with matrix-matched external liquid calibration. Using <0.5 ml solution, resulting concentrations are between <1 ppt for elements such as Ti, Nb and Ta and tens of ppb for Zr. By analyzing a series of standard solutions, zircons and procedural blanks, we show that accurate measurements are performed on Zr, Hf, Y, Sc, and the HREE while low-concentration elements can be measured accurately to <5 ppt. We performed combined U–Pb ID-TIMS geochronology with trace element analysis (here called U–Pb TIMS-TEA) on zircons from eight volcanic rocks comprising several volcanic systems and one metamorphic sample. Similar to previous in situ trace element analyses, zircon geochemistry is distinct between different samples and records petrogenetic processes such as fractional crystallization, assimilation and/or magma mixing. Unique from in situ analysis, U–Pb TIMS-TEA can trace geochemical evolution in accessory minerals with adequate age precision to resolve magmatic processes in rocks at least 200 million years old. This provides a means to identify auto-, ante- and xenocrystic zircon and lead to more robust age interpretations in ID-TIMS U–Pb geochronology. One suite of Cretaceous andesitic zircons shows correlations in geochemistry and absolute time that record evolution of a magmatic system over ∼250 ka prior to eruption. Future work will combine U–Pb TIMS-TEA with solution isotopic analysis of Nd, Sr and Hf and will be applied to a host of datable minerals such as monazite, sphene, apatite, rutile, xenotime, and baddeleyite. These combined tools will provide access to an improved understanding of a wide range of igneous and metamorphic processes as a function of time.

Chromatographic pre-concentration of Hg from dilute aqueous solutions for isotopic measurement by MC-ICP-MS

Previous studies have demonstrated both mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes in the environment and the potential for their application in biochemistry and geochemistry. However, little has been reported for Hg isotope geochemistry in natural aqueous environment due to the very low concentration (1–20 ng/L). We report here, for the first time, a new protocol for directly pre-concentrating Hg using AG 1 × 4 ion-exchange resin, which allows the measurement of Hg isotope composition in freshwater samples. The protocol is validated by testing both synthetic and natural solutions of varying concentrations, and by assessing the effect of Hg recovery and organic complexants on the reproducibility and the accuracy of measured isotopic ratios. The method results in acceptable procedural blanks and quantitative yields (101% ± 6%) in the final Hg eluates. The instrumental mass bias was corrected using modified empirical external normalization (MEEN) with Tl as internal dopant. The sensitivity of the method to the solution matrix (Hg/Tl ratio, organic matter concentration) was also evaluated. The pre-concentration and isotopic measurement protocol was applied to 16 natural water samples with Hg concentrations ranging from 0.9 ng/L to 15600 ng/L. The result showed a total variation of 2.4‰ for δ202Hg and evident MDF and MIF of Hg isotopes. Our study demonstrates that more research is required to fully understand the behavior of Hg isotopes in the aqueous environment.

A highly sensitive method for the reassessment and quantification of 239Pu in urine samples based on a 1 MV accelerator mass spectrometry system

A new and highly sensitive method for the determination of 239Pu in human urine has been developed permitting the reassessment of planchets initially prepared for alpha spectrometry (AS) analysis in the context of internal dosimetry. A set of urine samples (volume: 500 mL) was spiked with known quantities of 239Pu, ranging from 2 to 120 fg (4.6 μBq–0.3 mBq), employing 14 pg (2.05 mBq) of 242Pu as internal standard. The Pu was purified by ion-chromatography using BioRad AG1X2 anion-exchange resins (Bio-Rad Laboratories Inc.). The chemical yield was determined by alpha-spectrometry, being about 80%. Afterwards, the planchets so obtained were leached with diluted HNO3 and the dissolved plutonium was determined by Accelerator Mass Spectrometry (AMS) at the Centro Nacional de Aceleradores (CNA) in Seville, Spain. The minimum detectable activity (MDA) for the AMS measurements was determined through the study of a set of procedural blanks, giving figures of about 0.44 fg (∼1 μBq) per sample. This contrasts with the MDA obtained by AS for the same set of samples, of about 50 fg (∼0.1 mBq). The results now presented helps to demonstrate that the routine measurement of 239Pu at ultra trace levels in human urine samples is possible with the new-generation of compact AMS systems, offering a highly sensitive method for the reassessing of planchets prepared for bioassay purposes.