Average Measurement Uncertainty Research Articles

Uncertainty quantification for velocity measurement with 2D2C particle image velocimetry

Abstract In this paper, a theoretical model of dimensionless instantaneous and average velocity measurement uncertainty quantification with 2D2C particle image velocimetry (PIV) is established under the framework of generally adopted international uncertainty quantification standards. The effectiveness of the model is verified using uniform flow field testing data. Combined with semi-quantitative analysis of the theoretical model, uncertainty control suggestions for PIV measurements are given. The major sources affecting the uncertainty of instantaneous velocity measurements are the reference velocity, particle instantaneous pixel displacement, and their correlation term. For average velocity measurement uncertainty quantification, the uncertainty of particle average pixel displacement is effectively controlled by taking a large number of particle images. Thus, three single-component terms — the calibration factor, particle average pixel displacement and reference velocity — and two correlation terms — the particle average pixel displacement–calibration factor and the particle average pixel displacement–reference velocity — all make an important contribution to the average velocity measurement uncertainty. To reduce the uncertainty of PIV velocity measurement, one can reduce the reference velocity measurement uncertainty, optimize the PIV algorithm and improve the calibration factor by applying a high spatial resolution imaging system in experiments. In addition, reducing the reference velocity measurement uncertainty and improving the spatial resolution are key feasible methods.

Electrochemical System for Field Control of Hg2+ Concentration in Wastewater Samples.

The paper presents the validation of an electrochemical procedure for on-site Hg2+ ions determination in wastewater samples using a modified carbon screen-printed electrode (SPE) with a complexing polymeric film based on poly(2,2'-(ethane-1,2-diylbis((2-(azulen-2-ylamino)-2-oxoethyl)azanediyl))diacetic acid) (polyL). Using metal ions accumulation in an open circuit followed by anodic stripping voltammetry, the SPE-polyL electrode presents a linear range in the range of 20 µg/L to 150 µg/L, with a limit of detection (LOD) = 6 µg/L, limit of quantification (LOQ) = 20 µg/L, and an average measurement uncertainty of 26% of mercury ions. The results obtained in situ and in the laboratory using the SPE-polyL modified electrode were compared with those obtained by the atomic absorption spectrometry coupled with the cold vapor generation standardized method, with the average values indicating excellent recovery yields.

Coverage Path Planning for Robotic Quality Inspection With Control on Measurement Uncertainty

The optical scanning gauges mounted on the robots are commonly used in quality inspection, such as verifying the dimensional specification of sheet structures. Coverage path planning (CPP) significantly influences the accuracy and efficiency of robotic quality inspection. Traditional CPP strategies focus on minimizing the number of viewpoints or traveling distance of robots under the condition of full coverage inspection. The measurement uncertainty when collecting the scanning data is less considered in the free-form surface inspection. To address this problem, a novel CPP method with the optimal viewpoint sampling strategy is proposed to incorporate the measurement uncertainty of key measurement points (MPs) into free-form surface inspection. At first, the feasible ranges of measurement uncertainty are calculated based on the tolerance specifications of the MPs. The initial feasible viewpoint set is generated considering the measurement uncertainty and the visibility of MPs. Then, the inspection cost function is built to evaluate the number of selected viewpoints and the average measurement uncertainty in the field of views of all the selected viewpoints. Afterward, an enhanced rapidly exploring random tree algorithm is proposed for viewpoint sampling using the inspection cost function and CPP optimization. Case studies, including simulation tests and inspection experiments, have been conducted to evaluate the effectiveness of the proposed method. Results show that the scanning precision of key MPs is significantly improved compared with the benchmark method.

Precision wavelength calibration for radial velocity measurements using uranium lines between 3800 and 6900 Å

We present here the precise wavelength calibration of a high-resolution spectrum using Uranium (U) lines in the wavelength range of 3809 - 6833 \AA\ for precision radial velocity measurements for exoplanet detection or related astrophysical sciences. We identify 1540 well-resolved U lines from a high-resolution (R=67,000) spectrum of the uranium-argon hollow cathode lamp (UAr HCL) using PARAS spectrograph in the aforesaid wavelength range. We calculate the neutral and first allowed transitions (Ritz wavelength) of U from its known energy levels and compare them with our observed central wavelengths. We measure an offset of -0.15 m\AA\space in our final U line list. The line list has an average measurement uncertainty of 15 m s$^{-1}$ (0.013 pixels or 0.28 m\AA). We included these lines to the PARAS data analysis framework to perform the wavelength calibration and then calculate the multi-order Radial Velocity (RV) of PARAS spectra. The typical dispersion of residuals around the wavelength solution of a UAr spectrum, using U lines, is found to be 0.8 m\AA\space($\sim$45 m s$^{-1}$). With the use of this line list, we present our results for the precision RV of an on-sky source (A RV standard star), and an off-sky source (A HCL) observed with PARAS along with UAr HCL. We measure the dispersion in absolute drift difference between two fibers (inter-fiber drift) for a span of 6.5 hours to be 88 cm s$^{-1}$, and the RV dispersion (${\sigma_{RV}}$) for a RV standard star, HD55575 over the course of $\sim$450 days to be 3.2 m s$^{-1}$. These results are in good agreement with the previous ones measured using the ThAr HCL. It proves that the ThAr HCL with $\sim$ 99\% pure-Th are replaceable with the UAr HCL for the wavelength calibration of the high-resolution spectrographs such as PARAS (R $\leq$ 67,000) to achieve a RV precision of 1-3 m s$^{-1}$ in the visible region.

Extensive Urban Green Roof Shows Consistent Annual Net Uptake of Carbon as Documented by 5 Years of Eddy‐Covariance Flux Measurements

AbstractVegetated roofs or green roofs may supply a number of different urban ecosystem services such as thermal regulation of local air temperature by evaporative cooling or climate change mitigation by sequestration of CO2. However, knowledge about the annual and seasonal variations of green roof carbon uptake due to changes in meteorological conditions and water availability remains scarce. We studied the annual variation of net ecosystem exchange (NEE) by eddy‐covariance flux measurements during a 5‐year period from 2014 to 2019 on a large and unirrigated green roof at the Berlin‐Brandenburg airport (BER) in Berlin, Germany. The roof vegetation was dominated by Sedum species and herbs. The BER green roof showed net uptake of carbon in each of the 5 study years with an average uptake of −141.1 g C m−2 y−1 and an average measurement uncertainty of ±15.5 g C m−2 y−1. The NEE, however, was characterized by significant interannual variation in which the maximum annual uptake of −189 g C m−2 y−1 in a year with above average precipitation roughly doubles the minimum uptake of −95 g C m−2 y−1 in a dry year. The variation of NEE was a function of the annual amount of precipitation and the frequency of rainfall, that is, the number of dry days per year (DDY). The roof might lose its carbon uptake function in a warmer future climate with an increasing number of DDY. Sustainable irrigation of the roof (e.g., rainwater harvesting) could help to maintain the carbon uptake function of the green roof vegetation.

Compound-specific carbon and hydrogen isotope analysis of volatile organic compounds using headspace solid-phase microextraction

Natural flavouring materials are in high demand, and a premium price is paid for all-natural flavourings, making them vulnerable to fraud. At present, compound-specific isotope analysis (CSIA) is perhaps the most sophisticated tool for determining flavour authenticity. Despite promising results, the method is not widely used, and the results are limited to the most common volatile organic compounds (VOCs). This paper describes a robust protocol for on-line measurements of δ13C and δ2H using HS-SPME coupled with GC-C-IRMS and GC-HTC-IRMS for common fruit VOCs. To achieve reproducible and accurate results, a combination of a peak size/linearity correction with drift correction were used. Finally, the results were normalised by multiple point linear regression using the known and measured values of reference materials. Special care was taken to avoid irreproducible isotopic fractionation and the effects of equilibration, adsorption, desorption times and temperatures on δ13C or δ2H values were examined. Method validation was performed, and the average combined measurement uncertainty (MU) was 0.42‰. All the δ13CVPDB values were below ±3*MU, regardless of analytical conditions. In contrast, for δ2HVSMOW-SLAP values, only low temperature (30 °C) with equilibration time (15 min) and shorter adsorption time (between 10 and 20 min) can produce an isotopic difference of <10‰. Therefore, method optimisation can minimise MU, and data normalisation and method validation are essential for obtaining meaningful data for use in flavour authenticity studies.

State of the art in the analysis of brominated flame retardants in biota and sediment: insights from the characterisation of two new certified reference materials

The Joint Research Centre (JRC) of the European Commission has recently released two new Certified Reference Materials (CRMs) for the analysis of brominated flame retardants (BFRs): the freshwater sediment ERM-CC537a and the fish tissue ERM-CE102. The production of these CRMs responds to the need of expanding the offer of quality assurance/quality control tools for the analysis of BFRs in the fields of environmental analysis and food control, especially for compliance purposes. The sediment ERM-CC537a carries certified values for polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD) diastereoisomers in the μg/kg range (dry mass), while the fish tissue ERM-CE102 is certified for PBDEs in the ng/kg range (wet weight). ERM-CC537a is the first reference material ever available with certified values for α-, β- and γ-HBCDD. The assignment of the certified values was performed via an intercomparison of expert laboratories. The evaluation of the data confirms the improving trend, observed in recent years, regarding the comparability of PBDE measurement results. The relative standard deviation (RSD) among laboratories is slightly better for the fish material (8–11%) compared to the sediment (9–15%), despite lower mass fractions in the biota matrix. The RSD of HBCDD data (17%) reveals that they are more challenging analytes. The average measurement uncertainty declared by the participants is about 30%, but an in-depth analysis of their performance reveals that it should be feasible to reduce the uncertainty budget.

Reproducibility of Combined Acquisition and Measurement of Left Ventricular Longitudinal Peak Segmental Strain in Relation to the Severity of Left Ventricular Dysfunction

Whether left ventricular (LV) longitudinal peak systolic segmental strain (LPSS) has sufficient reproducibility to be used in clinical practice (e.g., in patient follow-up) remains unclear. The aim of this study was to assess the reproducibility of combined acquisition and measurements of LPSS across the spectrum of LV ejection fraction (LVEF). In this prospective study, 72 subjects (mean age, 63±14years; 65% men) were included in four equal groups: group 1, LVEF≥50%, healthy; group 2, LVEF≥50%, presence of cardiovascular disease and/or risk factors; group 3, LVEF 30%-49%; and group 4, LVEF≤29%. Two observers performed four sets of image acquisitions and measurements (three during the same session, one after a median of 1day) to account for intraobserver, interobserver, and test-retest reproducibility of combined acquisition and measurements. LPSS was measured in each of the 17 LV segments. On average, the intraobserver and test-retest intraclass correlation coefficients and mean absolute differences of repeated acquisition and measurement of LPSS were similar across groups. However, interobserver intraclass correlation coefficients and mean absolute differences decreased in group 4 compared with groups 1 to 3. The intraobserver, test-retest, and interobserver coefficients of variation of all LV segments became worse as LVEF decreased, especially in group 4, in which LPSS was not reproducible in most segments. Reproducibility of LPSS in basal LV segments was worse compared with apical segments. The average measurement uncertainty (defined as the 95% limits of agreement of repeated acquisition and measurements) of LPSS in a test-retest scenario was ±8.9%, ±11.8%, ±10.7%, and ±9.0% in groups 1, 2, 3, and 4, respectively. The clinical applicability of LPSS is hindered by suboptimal reproducibility, even if a single observer repeats both acquisition and measurements. Changes in LPSS during patient follow-up should be interpreted with caution.

Liquid Viscosity and Surface Tension of n-Hexane, n-Octane, n-Decane, and n-Hexadecane up to 573 K by Surface Light Scattering (SLS).

In the present study, the simultaneous and accurate determination of liquid viscosity and surface tension of the n-alkanes n-hexane (n-C6H14), n-octane (n-C8H18), n-decane (n-C10H22), and n-hexadecane (n-C16H34) by surface light scattering (SLS) in thermodynamic equilibrium is demonstrated. Measurements have been performed over a wide temperature range from 283.15 K up to 473.15 K for n-C6H14, 523.15 K for n-C8H18, and 573.15 K for n-C10H22 as well as n-C16H34. The liquid dynamic viscosity and surface tension data with average total measurement uncertainties (k = 2) of (2.0 and 1.7) % agree with the available literature and contribute to a new database at high temperatures. Over the entire temperature range, a Vogel-type equation for the dynamic viscosity and a modified van der Waals equation for the surface tension represent the measured data for the four n-alkanes within experimental uncertainties. By also considering our former SLS data for n-dodecane (n-C12H26) and n-octacosane (n-C28H58), empirical models for the liquid viscosity and surface tension of n-alkanes were developed as a function of temperature and carbon number covering values between 6 and 28. Agreement between these models and reference correlations for further selected n-alkanes which were not included in the development procedure was found.

Test Rig for Applied Experimental Investigations of the Thermal Contact Resistance at the Blade-Rotor-Connection in a Steam Turbine

Recent studies have shown that in a prewarming, respectively, warm-keeping operation of a steam turbine, the blades and vanes transport most of the heat to the thick-walled casing and rotor. Thereby, a thermal bottle-neck arises at the connection between the blade root and the rotor. The thermal contact resistance (TCR) at these interfaces affects the temperature distribution and thus the thermal stresses in the rotor. The present paper introduces an experimental setup, which is designed to quantify the TCR at the blade-rotor-connection of a steam turbine. An uncertainty analysis is presented, which proves that the average measurement uncertainties are less than one percent. The experiments especially focus on the investigation of the contact pressure, which is a function of the rotational speed. Therefore, the results of several steady-state measurements under atmospheric and evacuated atmosphere using a high temperature-resistant chromium-molybdenum steel are presented. For the evaluation of the TCR, a numerical model of the specimen is developed in addition to a simplified 1D approach. The results show a significantly increasing TCR with decreasing contact pressure, respectively, rotational speed.

A Practical Approach for Collecting Large‐n Detrital Zircon U‐Pb Data sets by Quadrupole LA‐ICP‐MS

A measurement procedure for the rapid acquisition of U‐Pb dates for detrital zircons by quadrupole LA‐ICP‐MS was developed. The procedure achieves a threefold increase in measurement efficiency compared with the most commonly used methods. Utilising reduced background counting times and a shortened ablation period, a throughput of ~ 130 measurements/h can be achieved. The measurement procedure was characterised and validated using data from thirty‐nine sessions acquired over a twelve‐month period. Systematic measurement error in 206Pb/238U dates for reference materials used for quality control with ages between 28.2 and 2672 Ma was &lt; 1.5%. Average measurement uncertainty, including both random and systematic components, was 1–4% (2s). Interrogation of time‐resolved calculated dates and signal intensities for each measurement allows for the detection and elimination of portions of measurements exhibiting age heterogeneities, zoning, lead loss and contamination by common lead. The measurement procedure diminishes the need to acquire cathodoluminescence imagery for routine detrital zircon applications further increasing throughput and reducing cost. The utility of the measurement procedure is demonstrated by the measurement of samples previously characterised by LA‐MC‐ICP‐MS.

Towards tributyltin quantification in natural water at the Environmental Quality Standard level required by the Water Framework Directive

The European Union (EU) has included tributyltin (TBT) and its compounds in the list of priority water pollutants. Quality standards demanded by the EU Water Framework Directive (WFD) require determination of TBT at so low concentration level that chemical analysis is still difficult and further research is needed to improve the sensitivity, the accuracy and the precision of existing methodologies. Within the frame of a joint research project “Traceable measurements for monitoring critical pollutants under the European Water Framework Directive” in the European Metrology Research Programme (EMRP), four metrological and designated institutes have developed a primary method to quantify TBT in natural water using liquid–liquid extraction (LLE) and species-specific isotope dilution mass spectrometry (SSIDMS). The procedure has been validated at the Environmental Quality Standard (EQS) level (0.2ngL−1 as cation) and at the WFD-required limit of quantification (LOQ) (0.06ngL−1 as cation). The LOQ of the methodology was 0.06ngL−1 and the average measurement uncertainty at the LOQ was 36%, which agreed with WFD requirements. The analytical difficulties of the method, namely the presence of TBT in blanks and the sources of measurement uncertainties, as well as the interlaboratory comparison results are discussed in detail.

Three-dimensional temperature field compensation technology for large-scale ultrasonic positioning system

Large-scale ultrasonic positioning systems have recently shown substantial improvement, according to the current great interest concerning large-scale metrology applications in many different fields of manufacturing industry. However, the sound velocity is greatly influenced by the ambient temperature especially in large-scale applications. The traditional sound velocity compensation method mainly uses the average temperature in measurement space based on an assumption that the temperature field is uniform and stable. As the assumption is invalid in most cases, especially in industrial measurement environments, the traditional compensation method will bring obvious errors. To reduce these errors caused by sound velocity, this article proposes a novel compensation method by constructing a three-dimensional temperature field of measurement space through heat transfer theory as well as the finite element method, and then estimating the distance accurately using a couple iterating algorithm. Verification experiments demonstrate that the ranging deviation estimated through the proposed method may keep within 0.5 mm in 5.4×2 m measurement space, whereas the average distance measurement uncertainty is about 0.25 mm.

Analysis from the new solar radiation Atlas for Saudi Arabia

This paper presents one of the first discussions on the new Solar Atlas of Saudi Arabia, which was launched in February 2014. It assesses selected solar resource and surface meteorological measurements available from the new Renewable Resource Atlas for Saudi Arabia developed by the King Abdullah City for Atomic and Renewable Energy (KACARE) as part of the Renewable Resource Monitoring and Mapping (RRMM) Program. The Solar Atlas provides live data recorded from 41 stations across the country. Accurate solar resource data is critical in reducing technical and financial risks of deploying utility-scale solar energy conversion systems. This paper presents solar maps of the country over time, showing that the direct normal irradiance (DNI) in various regions of the country ranges from approximately 9000Wh/m2/day in the summer months to 5000Wh/m2/day in the winter months. Global horizontal irradiance (GHI) in various regions can be as high as 8.3kWh/m2/day. One year of ground based solar radiation measurements from new stations at KACARE Headquarters Riyadh and Qassim University are compared with satellite-based model estimates of long-term DNI and GHI solar resources on a monthly mean daily total basis. Comparing the locally measured DNI data at KACARE Headquarters Riyadh with GeoModel, the average difference is about 6.9% of the reported values, the average measurement uncertainty being 8.4%. For GHI measured at KACARE Headquarters Riyadh, a fairly good agreement can be seen between the RRMM values and GeoModel with the average difference being about 5.6%, while the average measurement uncertainty being 6.7%. It might be noted that the GeoModel has data uncertainties for monthly mean daily total radiation in the range of ±8% to ±15% for DNI, and ±4% to ±8% for GHI. Finally, the paper reviews data from the recording station at Qassim University (QU), which is equipped with a variety of instruments for measuring solar radiation and surface metrological conditions. The measured values of DNI at QU varied from a maximum of 8367Wh/m2/day in July to a minimum of 4702Wh/m2/day in January. In terms of percentages, the average difference between the measured monthly mean daily total radiation and the GeoModel estimates is about 5.4% of the reported values, the average measurement uncertainty being 5.1%. In most cases, the observed differences between measured and modeled data were within the combined estimated uncertainty. The results from Solar Atlas are critical in guiding policies, reducing the risks for deploying solar facilities and providing judicious information for construction of solar facilities.

High precision differential abundance measurements in globular clusters: chemical inhomogeneities in NGC 6752★

We report on a strictly differential line-by-line analysis of high quality UVES spectra of bright giants in the metal-poor globular cluster NGC 6752. We achieved high precision differential chemical abundance measurements for Fe, Na, Si, Ca, Ti, Cr, Ni, Zn, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu and Dy with uncertainties as low as ~0.01 dex (~2%). We obtained the following main results. (1) The observed abundance dispersions are a factor of ~2 larger than the average measurement uncertainty. (2) There are positive correlations, of high statistical significance, between all elements and Na. (3) For any pair of elements, there are positive correlations of high statistical significance, although the amplitudes of the abundance variations are small. Removing abundance trends with effective temperature and/or using a different pair of reference stars does not alter these results. These abundance variations and correlations may reflect a combination of (a) He abundance variations and (b) inhomogeneous chemical evolution in the pre- or proto-cluster environment. Regarding the former, the current constraints on Delta Y from photometry likely preclude He as being the sole explanation. Regarding the latter, the nucleosynthetic source(s) must have synthesised Na, alpha, Fe-peak and neutron-capture elements and in constant amounts for species heavier than Si; no individual object can achieve such nucleosynthesis. We speculate that other, if not all, globular clusters may exhibit comparable abundance variations and correlations to NGC 6752 if subjected to a similarly precise analysis.

Statistical and Mathematical Concepts and Principles Applicable to Uncertainty Calculations for the Measurement of In Vivo Bone Lead by 109Cd K X Ray Fluorescence

This work discusses the statistical and mathematical concepts and principles applicable to in vivo 109Cd K X Ray Fluorescence measurements ( 109 Cd KXRF) of lead in human bone. The primary aim of this paper is to examine divergent views about the quantitative methods applied to estimate in vivo bone lead concentrations and their uncertainty when using the 109 Cd KXRF technique. The emphasis is on the potential effect of covariance between quantities of interest on the result of an in vivo measurement of bone lead by 109 Cd KXRF, a question which has received little attention in view of the long standing problem of why the average measurement uncertainty is less than the standard deviation of repeated measurements.

Multi-probe scanning system comprising three laser interferometers and one autocollimator for measuring flat bar mirror profile with nanometer accuracy

a b s t r a c t This paper describes a multi-probe scanning system comprising three laser interferometers and one autocollimator to measure a flat bar mirror profile with nanometer accuracy. The laser interferometers probe the surface of the flat bar mirror that is fixed on top of a scanning stage, while the autocollimator simultaneously measures the yaw error of the scanning stage. The flat bar mirror profile and horizon- tal straightness motion error are reconstructed by an application of simultaneous linear equations and least-squares method. Measurement uncertainties of the flat bar mirror profile were numerically eval- uated for different installation distances between the laser interferometers. The average measurement uncertainty was found to be only 10 nm with installation distances of 10 and 21 mm between the first and second, and first and third interferometers, respectively. To validate the simulation results, a prototype system was built using an X-Y linear stage driven by a stepper motor with steps of 1 mm along the X direction. Experiments were conducted with fixed interferometers distances of 10 and 21 mm, as in the simulation, on a flat bar mirror with a profile known to an accuracy of � = 632.8 nm. The average value of two standard deviations (95%) of the profile calculated over ten experiments was approximately 10 nm. Other results from the experiment showed that the system can also measure the yaw and horizontal straightness motion errors successfully at a high horizontal resolution. Comparing with the results mea- sured by ZYGO's interferometer, our measured data excluding some edge points showed agreement to within approximately 10 nm. Therefore, we concluded that our measurement profile has an accuracy in the nanometer range.

Evaluation of the LTQ‐Orbitrap mass spectrometer for the analysis of polymerase chain reaction products

We have investigated the potential and robustness of the off-line coupling of polymerase chain reaction (PCR) with electrospray ionization mass spectrometry (ESI-MS), for further applications in the screening of single-nucleotide polymorphisms (SNPs). This was based on recently reported data demonstrating that anion-exchange solid-phase extraction was the most efficient technique for efficiently desalting PCR products, with a recovery of ∼70%. Results showed that this purification approach efficiently removes almost all the chemicals commonly added to PCR buffers. ESI-MS analysis of a model 114-bp PCR product performed on the LTQ-Orbitrap instrument demonstrated that detection limits in the nM range along with an average mass measurement uncertainty of 9.15 ± 7.11 ppm can be routinely obtained using an external calibration. The PCR/ESI-MS platform was able to detect just a few copies of a targeted oligonucleotide. However, it was shown that if two PCR products are present in a mixture in a ratio higher than 10 to 1, the lower abundance one might not be reproducibly detected. Applications to SNPs demonstrated that an LTQ-Orbitrap with a resolution of 30 000 (at m/z 400) easily identified a single (A ↔ G) switch, i.e. a 16 Da difference, in binary mixtures of ∼ 35 kDa PCR products. Complementary experiments also showed that the combination of endonucleases and ESI-MS could be used to confirm base composition and sequence, and thus to screen for unknown polymorphisms in specific sequences. For example, a single (T ↔ A) switch (9 Da mass difference) was successfully identified in a 114-bp PCR product.

Base Composition Profiling of Human Mitochondrial DNA Using Polymerase Chain Reaction and Direct Automated Electrospray Ionization Mass Spectrometry

We describe an automated system for high-resolution profiling of human mitochondrial DNA (mtDNA) based upon multiplexed polymerase chain reaction (PCR) followed by desolvation and direct analysis using electrospray ionization mass spectrometry (PCR/ESI-MS). The assay utilizes 24 primer pairs that amplify targets in the mtDNA control region, including the hypervariable regions typically sequenced in a forensic analysis. Profiles consisting of product base compositions can be stored in a database, compared to each other, and compared to sequencing results. Approximately 94% of discriminating information obtained by sequencing is retained with this technique. The assay is more discriminating than sequencing minimum HV1 and HV2 regions because it interrogates more of the mitochondrial genome. A profile compared to a population database can be subjected to the same statistics used for assessing the significance of concordant mtDNA sequences. The assay is not hindered by length heteroplasmy, can directly analyze template mixtures, and has a sensitivity of <25 pg of total DNA per reaction. Analysis of 3331 independent trials of the same sample over 28 months produced an average mass measurement uncertainty of 10.1 +/- 8.0 ppm, with >99% of trials producing a full profile with automated analysis. The technique has direct application to analysis of forensic biological evidence.

Precise and accurate in situ U–Pb dating of zircon with high sample throughput by automated LA-SF-ICP-MS

We present an automated method for U–Pb age dating of zircon by single collector laser ablation-magnetic sectorfield-inductively coupled plasma-mass spectrometry (LA-SF-ICP-MS). The high sensitivity of SF-ICP-MS allows routine analysis with spot diameter of 20 to 30 μm and ablation time of 30 s, resulting in an ablation crater depth of ∼ 15–20 μm (∼ 35 to ∼ 65 ng of zircon). Zircon consumption is therefore limited to < 3% of a typical crystal and only by a factor of 6–10 times larger compared to secondary ion mass spectrometry (SIMS) based techniques. Precision and accuracy has been assessed using a number of well-characterised zircons as secondary quality control standards and are comparable to those of laser ablation- and ion-microprobe based techniques that use more complex and time-consuming approaches. Average measurement uncertainties (2σ, mean analytical uncertainty) based on 402 analyses of the Plešovice zircon standard were 2.2%, 3.1% and 2.1% for the 206Pb/ 238U, 207Pb/ 235U and 207Pb/ 206Pb ratios, respectively, comparable with those attainable by SIMS. The weighted mean of all 402 analyses yielded a 206Pb/ 238U age of 338 ± 1 Ma, which is in excellent agreement with the ID-TIMS 206Pb/ 238U age of 337.1 ± 0.4 Ma reported for the Plešovice zircon. Data acquisition is done in automated mode for up to 16 h/day with analytical points pre-set with only minimal operator presence during the data acquisition. Individual U–Pb zircon analysis last ≤ 75 s, and sample throughput is more than an order of magnitude higher (∼ 1000 U–Pb ages/day) compared to SIMS techniques and 3–5 fold higher compared to conventional LA-ICP-MS techniques. The methods presented here are therefore expected to have significant impact on many aspects of zircon U–Pb geochronology, with particular benefits for studies on the Archean crustal evolution and the provenance of detrital zircon crystals from clastic sediments where a large number of high-quality stand-alone in situ zircon U–Pb age determinations are needed.