Blank Values Research Articles

MISSMARPLE: MIlan Small-SaMple Automated Radiocarbon Preparation LinE for atmospheric aerosol

Abstract Radiocarbon measurements on the carbonaceous aerosol fractions are an effective tool for aerosol source apportionment. For these measurements, a new sample preparation line (MISSMARPLE: MIlan Small-SaMple Automated Radiocarbon Preparation LinE for atmospheric aerosol) was built in Milan (Italy). MISSMARPLE can separate different carbon fractions (i.e. total carbon (TC), elemental carbon (EC)), automates the sample combustion processes and the CO2 isolation in the “combustion line”, and was designed to handle small samples, of about 50 μg carbon. The CO2 obtained in the combustion line is then reduced to graphite in the graphitization line for subsequent accelerator mass spectrometry (AMS) analysis at the INFN-LABEC in Sesto Fiorentino (Italy). MISSMARPLE was tested for reproducibility of 14C/12C ratio in primary standard samples, for background contamination by the analysis of blank samples (graphite with zero percent Modern Carbon (pMC)), and for accuracy by the analysis of IAEA-C7 for pMC(TC) and NIST RM8785 for pMC(EC) used as secondary standards. Measurements were carried out in different AMS runs. Reproducibility of 14C/12C was within 1.2%; blank values were down to 2.2 ± 0.2 pMC in the latest AMS run, and both IAEA-C7 and NIST RM8785 measurements were within 1σ with the reference value (but for one IAEA-C7 sample within 2.3σ). These results point to MISSMARPLE as a new, valuable tool for aerosol sample preparation for radiocarbon measurements to be exploited not only on traditional 24-h samples but also when small carbon quantities are available (e.g. collected at remote sites or with high temporal resolution).

Isotopic spike 190Os as internal standard and empirical coefficient LA-ICP-MS combined with Sb fire assay for the determination of ultra-trace platinum group elements in geochemical samples

In this work, a novel method of antimony fire assay (Sb-FA) enrichment combined with laser ablation ICP-MS (LA-ICP-MS) for the determination of ultra-trace platinum group elements (PGEs) in geological samples was established. The purification and recycling technology of ultra-clean and high-purity fire assay collector Sb2O3 was proposed, in addition, high-purity quartz crucible was developed to replace the usual clay crucible, then the blank values of PGEs were as low as 0.0007–0.0028 ng g−1 (for 20 g sample). 190Os isotopic diluent was used as internal standard (IS) and quantitatively added into the fire assay ingredients, and fully mixed and balanced with the PGEs in the real samples by means of high temperature melting, cupellation and horizontal rotation of crucible and dish. Both 190Os and PGEs in the real sample were pre-concentrated in microgram level Sb granules (100 mg) through Sb-remaining cupellation. After grinding and polishing, 195Pt, 105Pd, 101Ru, 103Rh, 193Ir, total 189Os and 190Os enriched in Sb slices were determined by LA-ICP-MS, 190Os in the internal standard was calculated by isotope dilution equations. The Certified Reference Materials (CRMs) for PGEs were treated by the same procedure to obtain completely matrix matched Sb slices to solve the problem of no internationally recognized uniform PGEs standard materials for LA-ICP-MS determination. Due to the similar distribution trends of different PGEs in Sb slices by LA-ICP-MS imaging, then matrix-matched internal standard calibration strategy was used to reduce the element fractionation effect and improve the determination precision and accuracy of LA-ICP-MS. The laser frequency, energy density, denudation diameter and dwell times were optimized. Under the optimal conditions, empirical coefficient method was used to fit the standard curve and excellent curve fitting of PGEs were obtained with the correlation coefficient between 0.9990 and 0.9999. The method detection limits (LODs) for PGEs ranged from 0.00042 to 0.010 ng g−1. The established method was successfully applied to analyze real geochemical samples and various matrix Certified Reference Materials (CRMs) domestic and international, the determined values were in good agreement with the results of Sb-FA ICP-MS and the certified values.

The effect of alkyl chain on the corrosion inhibition of benzyldimethylammonium chloride in acidic environments

Incorporating quaternary ammonium salts (QAS) during pickling is an efficient and eco-friendly approach to mitigating metal corrosion. This study investigated the effectiveness of Benzyldimethylhexadecylammonium chloride (HDBAC) and Benzyldimethyltetradecylammonium chloride (TDBAC) in inhibiting the corrosion of Q235 steel in H2SO4, utilizing electrochemical methods, atomic force microscopy (AFM), scanning electron microscopy (SEM), and theoretical calculations. The electrochemical results demonstrated that compared with the blank impedance value of 40.68Ω cm2, HDBAC and TDBAC at 5 mM concentration showed impedance values of 997.69Ω cm2 and 676.17 Ω cm2 at 298 K, indicating that they can effectively prevent the corrosion of Q235. SEM and AFM further showed the formation of a protective barrier film by HDBAC and TDBAC on the steel surface, effectively isolating it from the corrosive medium. Theoretical calculations further elucidated the mechanism by which these inhibitors create this protective barrier. The experiment also verified the hypothesis that the length of the hydrophobic chain of surfactants affects the adsorption behavior and the inhibition efficiency. When comparing their inhibitory effects at 5 mM concentrations, HDBAC exhibited superior performance (95.92 %) against Q235 in 0.5 M H2SO4, compared to TDBAC (94.09 %). These findings provide valuable insights for developing more effective and sustainable corrosion inhibitors for industrial applications.

In-situ analysis of sub-nanomolar level of Fe(II) in open-ocean waters

Iron (Fe) in seawater is an essential micronutrient for marine phytoplankton, and Fe deficiency limits their growth in high-nutrient, low-chlorophyll areas. The bioavailability of Fe for phytoplankton largely depends on its chemical speciation in seawater. In surface water, the reduction of Fe(III) to Fe(II) is an important step in the uptake of Fe by phytoplankton. However, the marine biogeochemical cycle of Fe(II) in the open ocean has not been fully investigated. In oxic open-ocean waters, Fe(II) is rapidly oxidized and exists at sub-nanomolar levels, making it difficult to determine the Fe(II) concentration of seawater. In this study, we applied the flow analytical method of determining the Fe(II) concentration of seawater using luminol chemiluminescence in an in-situ analyzer (geochemical anomaly monitoring system, GAMOS). In the onboard laboratory, we successfully detected sub-nanomolar levels of Fe(II) in seawater using the GAMOS. In the central Indian Ocean, this analyzer was deployed at a depth of 1000 m to determine the Fe(II) concentration in the water column. During deployment, the detection limit (0.48 nM) was insufficient to determine the concentration. Therefore, we need to lower the blank values and enhance the stability of signal of the in-situ analytical method for application to open-ocean seawater samples.Graphical abstract

Low Cycle Fatigue and Damage Evaluation on 16MnCr5 Alloy Steel

The 16MnCr5 alloy steel samples are evaluated in a normalized condition and put through low cycle fatigue (LCF) under constant amplitude strains of εa = 0.2%, 0.25%, 0.4%, and 0.6%. Mechanical properties are reported based on the LCF results. Fatigue damage is checked in specimens that have reached 80% of their nominal fatigue life by two methods that are different from traditional electronic microscopy: measuring the roughness of the surface and looking at it through full‐field optical microscopy. In addition, the electric resistivity is determined for the test specimens. It presents an increment from the blank value of 6.5 × 10−8 Ωm (free of fatigue damage) to 1.25 × 10−7 Ωm for the fatigue test specimen (εa = 0.6%). Finally, X‐ray diffraction patterns are determined for analyzing the residual equivalent strain at the microscale for the fatigued samples. The residual equivalent strain exhibits a trend toward increasing. For instance, it increases from 18.5 (blank value) to 34.0 με for the fatigue test specimen with εa = 0.6%.

Insights into adsorbable organic halogen analysis: Two overlooked factors impacting water quality assessment

Adsorbable organic halogen (AOX) represents the total amount of halogenated organics that can be adsorbed on activated carbon (AC) from samples. Measuring AOX is crucial for assessing water quality, and any erroneous estimation of AOX risks misleading decision-makers. This study demonstrated two overlooked factors that may introduce biases to AOX measurement. The first one relates to impurities in the gas transfer tubes of AOX combustion system and in the pressurized gas of AOX separation system, which resulted in significant fluctuations and high blank values (8.5–118.0 μg-Cl/L). The solutions of above issues are to warming up the combustor for several runs and replacing the pressurized air with argon gas in the separator, which could drop the blank AOX values to 9.1–10.0 μg-Cl/L. The second one involves coexisting chloride ion (Cl−) during AOX analysis, which interfered with AOX measurements (T. test, p < 0.05) even at low concentration levels (e.g., 10 mg/L Cl− in samples with 100 μg-Cl/L p-chlorophenol). Results show that AC captured 0.02–0.11 % of Cl−, resulting in 17.7–24.5 μg-Cl/L AOX responses in control samples containing 15–130 mg/L Cl− only. Furthermore, a significant mass imbalance of Cl− (3.58–8.39 %) during analysis process suggests a potential impact of residual Cl− on subsequent samples. By comparing synthetic and actual waters, samples with low dissolved organic carbon (DOC) were more susceptible to interference from Cl− on AOX measurement than those with high DOC. These findings underscore the pressing need to optimize existing AOX methods or develop alternative analytical methods to ensure accurate water quality assessment.

Accurate Determination of Trace Sulfur in Superalloys and Its Application

The accurate determination technology of trace sulfur in superalloys adopts the latest infrared carbon/sulfur analyzer CS844ES, and carries out technological innovation in five aspects: the three calibrations technology at both ends, the ultrapure composite flux, the reference material traceability technology, the blank influence value determination technology, and the criteria for the accurate determination of trace sulfur. The lower limit of sulfur measurement is extended to 0.5ppm. After appraisal, it has reached the international advanced level. Two reference materials of wrought superalloy GH4169 with trace Sulfur concentration were developed by this technology. Finally, the accurate determination technology of trace Sulfur in superalloys, independent intellectual property rights and trace sulfur reference materials constitute a “Trinity” technical system. This technical system was used to measure GH4169 superalloy in the United States and China at the same time, and the results showed that there are differences in sulfur content among them. This technology is mainly applied independently and has been applied in relevant units and won many technical awards.

A Soft Sensor for Multirate Quality Variables Based on MC-CNN.

In recent years, data-driven soft sensor modeling methods have been widely used in industrial production, chemistry, and biochemical. In industrial processes, the sampling rates of quality variables are always lower than those of process variables. Meanwhile, the sampling rates among quality variables are also different. However, few multi-input multi-output (MIMO) sensors take this temporal factor into consideration. To solve this problem, a deep-learning (DL) model based on a multitemporal channels convolutional neural network (MC-CNN) is proposed. In the MC-CNN, the network consists of two parts: the shared network used to extract the temporal feature and the parallel prediction network used to predict each quality variable. The modified BP algorithm makes the blank values generated at unsampled moments not participate in the backpropagation (BP) process during training. By predicting multiple quality variables of two industrial cases, the effectiveness of the proposed method is verified.

Nanogram-scale boron isotope analysis through micro-distillation and Nu Plasma 3 MC-ICP-MS

The determination of boron isotopes (δ11B) represents a powerful tool for a variety of applications such as the reconstruction of past ocean pH and atmospheric pCO2 from the analysis of marine biogenic carbonates. In recent years, MC-ICP-MS has gained popularity over other techniques thanks to its superior sample throughput and high ionization efficiency. This study evaluates, for the first time, the performance of the Nu Instruments Plasma 3 MC-ICP-MS for measuring δ11B using different sample introduction systems and detector configurations. The main goal is to provide a detailed methodology for nanogram-scale boron isotope analysis through a straightforward approach that can be easily adopted. Boron (B) purification from the carbonate matrix was performed through micro-distillation, using a temperature of 95 °C and a minimum heating duration of 15 h, allowing the full recovery of B from up to 3 mg of carbonate mass. We attained blank values (on average 14 ± 6 pg, 1 SD, n = 27) comparable to the lowest micro-distillation blanks reported in the literature. Three sample introduction systems were tested, and the 30 μL min−1 nebuliser system outperformed the 50 and 170 μL min−1 systems in terms of signal intensity per mass of B. Two detector configurations were used based on the total boron signal intensity achieved: (1) FC11/FC12, with two Faraday cups fitted to 1011 Ω and 1012 Ω amplifier resistors to detect 11B and 10B ion beams, respectively, and (2) FC12/IC, with which we investigated, for the first time, the feasibility of combining an ion counter for detecting 10B, and a Faraday cup fitted to a 1012 Ω amplifier for 11B. The FC12/IC configuration provided accurate results compared to the use of two Faraday cups for total boron signals lower than 0.35 V (∼12 ng of B in the analysed solution). The proposed analytical procedure was validated through the analysis of several reference materials with varying boron amounts, including clam JCt-1, coral JCp-1, NIST RM 8301 Foram and Coral solutions, and boric acid ERM-AE121. Furthermore, the long-term reproducibility was assessed with two in-house standards (coral CLD-1 and foraminifera GINF-1), providing values of 25.68 ± 0.23 ‰ (2SD, n = 53; with 14–36 ng of B) and 14.90 ± 0.16 ‰ (2SD, n = 12; with 11–16 ng of B), respectively.

A highly sensitive sandwich-type electrochemical aptasensor using a pair of novel truncated aptamers for the detection of vaspin

Visceral adipose tissue-derived serpin (vaspin) is a biomarker associated with obesity and type 2 diabetes, both of which are prevalent and increasing in numbers worldwide. However, the sensitivity of existing aptasensors for vaspin detection does not yet match the reported serum levels. Aptamer sequences could contain nonessential nucleotides, which can be truncated out to potentially enhance their functionality and applicability. In this study, we developed a novel truncation method, a nonessentials-guided in situ truncation strategy to generate high-affinity aptamers by directly removing the nonessential portions of the aptamer sequences using exonucleases from the aptamer-protein complex kept stably. We applied this novel strategy to the original vaspin-binding aptamers, V1 and V49, resulting in two truncated aptamers, V1(3′-5′)–26 and V49(3′-5′)–30. These truncated aptamers showed enhanced binding affinity and specificity compared to their original aptamers. Confirmed to have different binding sites, this pair of truncated aptamers was successfully incorporated into a sandwich-type electrochemical aptasensor. This aptasensor achieved 16-fold higher sensitivity than the one using untruncated aptamers and enabled specific detection of vaspin in a buffer and even sensitive detection in serum within the physiological range. The reduced size of the aptamers could potentially cover the surface of the sensing platform, blocking nonspecific binding, thereby lowering the blank value, and improving the signal-to-noise ratio and limit of detection. This approach highlights the potential of the nonessentials-guided in situ truncation strategy for developing improved truncated aptamers, examining aptamer binding sites, and enhancing the analytical performance of biosensing platforms.

Ultra-sensitive photoelectrochemical sensor for copper ion detection based on ITO/BiVO4 photoelectrode

In this work, a photoelectrochemical sensor for Cu2+ trace detection was prepared based on the excellent semiconductor material BiVO4 modified ITO electrode. It was found that Cu2+ formed a doping effect by adsorption on the surface of ITO/BiVO4 electrode, which inhibited the photogenerated electron complex and thus caused an increase in photocurrent. In addition, due to the complexation effect of EDTA on Cu2+, the Cu2+ adsorbed on the electrode surface is desorbed and the photocurrent returns to the blank value, making it possible to reuse electrodes. Under optimal conditions, the linearity range was measured between 0.1 pM and 0.1 μM and the detection limit was 0.063 pM. The PEC sensor exhibits the advantages of high sensitivity and reusability for Cu2+ detection. This provides a novel PEC detection platform for Cu2+ monitoring in environmental water samples.

A method to produce low lead blank silicon dioxide gel as an emitter for isotopic analysis of sub-nanogram lead sample

Lead (Pb) isotopes have been widely used in isotopic dating and geochemical tracing. The rapid development in Earth sciences requires high precision and accuracy of isotopic measurements of low Pb contents or small amounts of samples. However, low ionization efficiency can significantly affect the sensitivity and precision of the measurement. Emitters, such as silicon dioxide (SiO2) gel used in the thermal ionization mass spectrometer (TIMS) measurement of Pb isotopes, can reduce Pb loss at the low-temperature stage and improve Pb ionization efficiency at the high-temperature stage, but they inevitably introduce Pb blank and affect the quality of the results. Therefore, the emitters should possess the features of both high ionization efficiency and low Pb blank. In the present study, a SiO2 gel solution was produced via a double-bottle method and then purified by the Sr-spec® resin. We further measured Pb blank value of this emitter using the isotopic dilution method and examined its ionization efficiency via measuring isotopic composition of standard reference materials of Pb solution and rock powders using different amounts of Pb. Analytical data show that Pb blank values of the twice-purified SiO2 gel solution are lower than 1 pg/μL (lowest value of ∼0.3 pg/μL). Moreover, it can effectively improve Pb ionization, and maintain high and stable ion signal intensity during the measurement runs. Analytical results of Pb isotopic compositions, obtained from nano- to subnano-gram Pb amounts of reference materials, all fall in the ranges of their reference values, meeting the requirements in precision and accuracy for the measurements on micro-samples. This emitter is useful for Pb isotopic measurement of micro-samples and predictable to promote the application of Pb isotopic geochemistry.

Closed-Vessel Conductively Heated Digestion of Dry Dog Food for Spectrometric Determination of Essential Nutrients

The closed-vessel conductively heated digestion system (CHDS) was evaluated to digest dry dog foods for further determination of K, Na, Cu, Fe, Mn, and Zn by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). The CHDS method was optimized using a fractional factorial design with five variables (HNO3 concentration, H2O2 volume, temperature, holding time, and pre-digestion time) at two levels. The accuracy of the CHDS procedure was checked by the analysis of reference materials from the National Institute of Standards and Technology (NIST SRM 1577b Bovine Liver and 2976 Mussel Tissue) and Brazilian Agricultural Research Corporation (Embrapa MR-E1002A Fish Food). Also, the digestion efficiencies were calculated from residual carbon contents (RCCs). The RCC and blank values in the CHDS digested samples were consistently low, which is suitable for determinations using ICP OES and ICP-MS techniques. For comparison, all samples were also digested by microwave-assisted digestion in closed vessels (MW-AD). Results for Na, K, Cu, Fe, Mn, and Zn determined in sample digests obtained by CHDS were not statistically different at a 95% confidence level from those observed for MW-AD. Limits of quantification (LOQ) calculated from digests in CHDS and MW-AD were comparable, and the values provided adequate limits for elemental determinations in dog foods. Data from mineral composition and moisture were employed in a clustering analysis (HCA) and the discrimination of the samples among different manufacturers and food for dogs at different life stages was possible.

Effect of Full Baking on Carbon Measurement by High Frequency Induction Combustion Infrared Absorption Method

In this study, the sample and multicomponent flux are put into the crucible and fully baked. The color change of multicomponent flux during baking indicates the degree of baking, which is appropriate when multicomponent flux turns light red. Through specific tests, different grades of superalloys are used to carry out the comparison test between full baking and non-baking. The measurement precision after full baking is generally higher than that without baking. The difference in value cannot be predicted. Also, the difference cannot be eliminated by adding a correction factor, it can only be eliminated by full baking. After full baking, it can be seen quantitatively from the blank influence value that the blank has little interference with the measurement of low carbon, and the influence on the measurement of high carbon is negligible.

Thallium isotopes as indicators of ore mineralization at the Zn-rich sediment-hosted massive sulfide TL Deposit, British Columbia, Canada

Few studies have focused on the application of the Tl isotopic system for geochemical exploration. We report ε 205 Tl values of rock samples from the TL Deposit, British Columbia, Canada – a sediment-hosted massive sulfide (SHMS) deposit with characteristics of a Broken Hill-type deposit – and investigate relationships with major and trace element geochemistry. Maps generated using Tl isotope and trace element data indicate that ε 205 Tl values can potentially be used to fingerprint ore mineralization at the TL Deposit. The sources of Tl and other metals (Ag, Pb, Zn) are assessed using Tl isotope data. Measured ε 205 Tl values exhibit positive correlations with Pb, sedimentary exhalative metal index (Zn + 100*Pb + 100*Tl), and the redox proxy, U/Th, and negative correlations with Be, Cd, Ce, La, Ni and Th. Individual lithologies have distinct Tl isotopic compositions. Metal-rich heavily altered samples have relatively high ε 205 Tl values (−5.0 to −2.5 ε -units) reflecting the euxinic conditions of the global Paleoproterozoic ocean and hydrothermal influence. Samples with lower ε 205 Tl values (−15 to −7.6 ε -units) reflect a combination of their mineralogy (phyllosilicate minerals such as biotite and clinochlore), Tl from sediments reflecting the Tl isotopic composition of modern seawater, and possible low-temperature alteration processes. Samples with high Pb and Ag contents have high ε 205 Tl values, indicating a hydrothermal origin of these metals, whereas Zn is highest in samples with low ε 205 Tl values, indicating a low-temperature or sedimentary origin. Thallium isotopes, paired with conventional geochemical data, show promise as a useful tool for exploration of SHMS deposits with Broken Hill-type characteristics. Supplementary material: Major, minor and trace element contents of samples and reference materials, blank values, correlation coefficient values, and XRD patterns are available at https://doi.org/10.6084/m9.figshare.c.6370671 Thematic collection: This article is part of the Geochemical processes related to mined, milled, or natural metal deposits collection available at: https://www.lyellcollection.org/topic/collections/geochemical-processes-related-to-mined-milled-or-natural-metal-deposits

THE IMPACT OF LEACHING ON RADIOCARBON AGES OF SMALL-SIZED FORAMINIFERA SAMPLES

ABSTRACTReliable radiocarbon (14C) ages of foraminifera are a prerequisite to generate robust high-resolution age-depth models or to obtain precise understanding of past carbon cycle dynamics. With the advance of small-scale 14C measurements, instrumental precision and levels of contamination (extraneous carbon introduced during sample pretreatment or analysis) became increasingly important to consider. To reduce the effect of carbon contamination, an attempt can be made to remove it by leaching the surface with weak acids. Alternatively, mathematical corrections (e.g., subtraction) based on processing blanks can be applied. We report on 14C analyses of monospecific foraminifera samples compared between different blank corrections (correction against 14C-free CO2, IAEA-C1 and foraminifera) and sample treatments (i) to examine whether chemical pretreatment and mathematical blank subtraction are comparable, and (ii) to determine limitations hindering reliable 14C dating with ever smaller sample sizes. The data show that chemical pretreatment of foraminifera corrected against IAEA-C1 does remove surface contamination and that the same effect can be achieved for untreated samples that were mathematically corrected for blank values determined from sample size-matched 14C-free foraminifera. Leaching only has a beneficial effect on 14C data for older samples, where the isotopic difference between untreated and chemically pretreated samples exceeds the analytical precision.

Preliminary progress report on 10Be and 26Al sample preparation at the IHEG, CAGS AMS laboratory

Based on previous experimental methods, this study explored the separation of quartz from other minerals and an extraction protocol for 10Be and 26Al. The results showed that paramagnetic minerals are removed with current multistage physical and chemical purification process. A dowex 50 W × 8 (H+) ion-exchange resin column was used for 10Be and 26Al chromatography. The optimal elution fractions for separating Be using 1.1 M HCl were 40–140 ml with a recovery rate of 83 % and those for separating Al using 6 M HCl were 170–230 ml with a recovery rate of only 33 %. The blank values of 10Be/9Be and 26Al/27Al ratios were 4.59E−15 and 2.49E−14, respectively. Two granite pebbles samples were analyzed using the experimental procedure established in this study, and the 10Be/9Be and 26Al/27Al ratios were (4.72 ± 0.23)E−13, (2.99 ± 0.22)E−13, and (7.28 ± 0.40)E−13, (2.83 ± 0.29)E−13, respectively.

Artifact characterization and mitigation techniques during concurrent sensing and stimulation using bidirectional deep brain stimulation platforms.

Bidirectional deep brain stimulation (DBS) platforms have enabled a surge in hours of recordings in naturalistic environments, allowing further insight into neurological and psychiatric disease states. However, high amplitude, high frequency stimulation generates artifacts that contaminate neural signals and hinder our ability to interpret the data. This is especially true in psychiatric disorders, for which high amplitude stimulation is commonly applied to deep brain structures where the native neural activity is miniscule in comparison. Here, we characterized artifact sources in recordings from a bidirectional DBS platform, the Medtronic Summit RC + S, with the goal of optimizing recording configurations to improve signal to noise ratio (SNR). Data were collected from three subjects in a clinical trial of DBS for obsessive-compulsive disorder. Stimulation was provided bilaterally to the ventral capsule/ventral striatum (VC/VS) using two independent implantable neurostimulators. We first manipulated DBS amplitude within safe limits (2-5.3 mA) to characterize the impact of stimulation artifacts on neural recordings. We found that high amplitude stimulation produces slew overflow, defined as exceeding the rate of change that the analog to digital converter can accurately measure. Overflow led to expanded spectral distortion of the stimulation artifact, with a six fold increase in the bandwidth of the 150.6 Hz stimulation artifact from 147-153 to 140-180 Hz. By increasing sense blank values during high amplitude stimulation, we reduced overflow by as much as 30% and improved artifact distortion, reducing the bandwidth from 140-180 Hz artifact to 147-153 Hz. We also identified artifacts that shifted in frequency through modulation of telemetry parameters. We found that telemetry ratio changes led to predictable shifts in the center-frequencies of the associated artifacts, allowing us to proactively shift the artifacts outside of our frequency range of interest. Overall, the artifact characterization methods and results described here enable increased data interpretability and unconstrained biomarker exploration using data collected from bidirectional DBS devices.

Automated workflow utilizing saponification and improved epoxidation for the sensitive determination of mineral oil saturated and aromatic hydrocarbons in edible oils and fats

Refined edible oils and fats are known to contain olefins resisting the typical epoxidation used for the sample preparation of mineral oil saturated and aromatic hydrocarbons (MOSH and MOAH). These olefins can be misinterpreted as MOAH and are therefore an important reason for inconsistent results between laboratories. Collaborative trials confirm this assumption for low MOAH contents near the quantitation limits regularly. In the scope of this work, a new epoxidation approach was developed. Persistent olefins in refined oils could be successfully epoxidized with performic acid. The reaction kinetics was investigated using model substances for biogenic olefins and MOAH. It was rationalized why certain olefins resist epoxidation and which MOAH can potentially get lost. A prominent peak cluster in the MOAH fraction of refined palm oils could be identified by means of GC-MS and explained why it cannot be epoxidized. Based upon this, an automated and streamlined workflow for sample preparation and analysis was composed tackling major problems identified in previously published methods. Optimized and miniaturized saponification, extraction, epoxidation, and enrichment paired with online LC-GC-FID led to a robust method that was tested and validated for edible oils and fats (RSDR < 7% for MOSH and MOAH at values of 14.9 and 2.1 mg/kg, respectively). Due to increased sample amount and minimized blank values, quantitation limits below 1 mg/kg for MOSH and MOAH were achieved. The trueness of the method was verified by analyzing collaborative trial samples.

Ultra-trace determination of mercury by platinum-coated tungsten coil trapping cold vapour atomic absorption spectrometry

ABSTRACT Within the scope of this study, a simple, highly sensitive and rapid trapping method for the determination of mercury (Hg) was developed. In this method, the surface of the tungsten coil (W-coil) was coated with platinum using the electrolytic deposition technique. Scanning electron microscopy–energy-dispersive X-ray analyses were performed to examine the surface morphology of Pt-coated W-coil. During the experiment, firstly, Hg vapour generated by tetrahydroborate, used as a reducing agent, was efficiently trapped on the Pt-coated W-coil at collection temperature in hydrochloric acid medium. Subsequently, Hg trapped on the surface of the Pt-coated W-coil was revolatilised by the effect of releasing-stage gases at the optimised releasing temperatures and transported to quartz T-tube atomiser. The experimental conditions have been optimised. Under the optimised conditions, a limit of detection (LOD) of 8.8 ng L−1 was obtained using three times the standard deviation of blank values using Pt-coated W-coil trap cold vapour atomic absorption spectrometry (CVAAS) system. The precision of the measurements was evaluated by relative standard deviation of 4.4%, which is obtained by 11 consecutive measurements of reagent blanks for a collection volume of 6.83 mL corresponding to 90 s collection. The enhancement factors for both LOD (3 s) and characteristic concentration (Co) were found to be 5.09 and 5.02 when compared with the regular CVAAS system without trap. The accuracy of the proposed method was evaluated by analysing BCR 146 R (Sewage sludge), RTC (Sandy Loam 7), ERM-BD151 (skimmed milk powder) and NIST 1641e (mercury in water) certified reference materials (CRMs). There was a good agreement between certified and found values for all CRMs. The results of the application of the developed method in seawater showed the spike recovery ranges from 94.2% to 102.4%.