Upscaling the Hyperpolarization Sample Volume of an Automated Hydrogenative Parahydrogen-Induced Polarizer

Improved underwater Helmholtz resonator with an open cavity for sample volume estimation

Effects of pore-scale dispersion, degree of heterogeneity, sampling size, and source volume on the concentration moments of conservative solutes in heterogeneous formations

Improved biodiversity detection using a large-volume environmental DNA sampler with in situ filtration and implications for marine eDNA sampling strategies

A method of measuring the tritium in seawater based on electrolytic enrichment and ultra-low background liquid scintillation counting techniques was established. The different factors influencing the detection limit were studied, including the counting time, the electrolytic volume of the seawater samples, the selection of background water, scintillation solution and their ratio. After optimizing the parameters and electrolyzing 350 mL volume of samples, the detection limit of the method was as low as 0.10 Bq/L. In order to test the optimization of system for this method, of the 84 seawater samples collected from the Arctic Ocean we measured, 92% were above the detection limit (the activity of this samples ranged from 0.10 Bq/L to 1.44 Bq/L with an average of (0.30±0.24) Bq/L). In future research, if we need to accurately measure the tritium activity in samples, the volume of the electrolytic samples will be increased to further reduce the minimum detectable activity.

In Doppler ultrasound as applied to blood flow estimation, pulsatile movement of the vessel wall and surrounding tissue result in a Doppler clutter signal whose spectrum changes over the cardiac cycle and which, when the sample volume (SV) is close to the arterial wall, can cause serious difficulties. Because the clutter signal can be 40 dB greater than that from the red blood cells (RBC) and its time varying spectrum can overlap with the spectrum of the desired signal, the clutter becomes very difficult to identify and remove. This paper proposes a new method for clutter suppression based on the use of information from two sample volumes and Weiner filtering. A Doppler simulation model was developed and used to identify the spectra in two SVs, the primary SV within the vessel lumen and a secondary SV centered within the arterial wall. Data from both SVs were obtained from every backscattered pulse using two range gates. In the primary SV, the clutter signal strength is significantly greater than that from the blood when it is located near the arterial wall However, a secondary SV placed within the arterial wall will contain very little blood signal as the lumen will be within the attenuated portion of the SV energy distribution and the RBC backscattered intensity is already weak. The secondary SV can therefore be assumed to contain just the clutter signal. Wiener filtering was then applied to recover the blood signal from the primary SV. The Wiener filter uses the auto-correlation of the secondary SV and the cross-correlation between the SVs to estimate the clutter signal in the primary SV. This estimated clutter signal was then subtracted from the primary SV to recover the RBC spectrum. Preliminary simulation results using the Wiener filter have shown good agreement to the traditional high-pass FIR filtering method for clutter-to-RBC signal ratios up to 40 dB. Use of the Wiener filtering technique can have significant advantages over traditional filtering methods due to its adaptability to spectral variation over the cardiac cycle.

Total alkalinity measurements in small samples: methods based on CO2 equilibration and spectrophotometric pH.

Atmospheric CO2 has increased by > 40% since pre-industrial times leading to significant global warming. The ocean absorption of CO2 is saturating, possibly leading to much more serious consequences than predicted. The latest IPCC special report SR15 warns that a 1.5 oC average temperature increase by 2030 is likely and associated CO2 ocean acidification is projected to amplify the adverse effects of warming. The ocean CO2 system is characterized by measuring at least 2 out of 4 canonical “master variables”: total dissolved inorganic carbon (DIC), total alkalinity (AT), partial CO2 (pCO2), and acidity (pH). Understanding this system is of fundamental importance yet CO2 continues to be chronically under-sampled in both space (including depth profiles) and time. Unfortunately, pCO2 and pH are very sensitive to temperature/pressure, hence autonomous measurements of DIC or AT are much preferred but have yet to be realized. Observations are almost exclusively limited to the surface and use large sensors, e.g. spectrophotometry, NDIR and mass spectrometry, attached to expensive research vessels. These large systems are unlikely candidates for miniaturisation. Very large uncertainties therefore still remain in the CO2 budget.The Argo float network, a global array of >3,000 untethered battery-operated floats with satellite data transfer, enables continuous monitoring of ocean salinity and temperature depth profiles. This float infrastructure awaits new autonomous chemical sensor technology but will impose severe constraints on device footprint, volume, power consumption and long-term environmental stability under high pressure cycling (up to 200 atm). Instantaneous measurement of DIC during float ascent or descent is not possible as the CO2 has to be extracted from the seawater first. Hence at each depth, an autonomous device would have to collect and store a seawater sample for subsequent analysis while the float is at park depth (~1500m). This analysis involves several chemical reactions and partial or complete equilibration across a membrane with high precision conductivity measurements. Microfluidic ocean-relevant chemical sensors have received limited attention. Research efforts have concentrated on colorimetric or luminescence techniques at shallow depths.We investigate a potential miniaturised version of a standard bench technique for DIC measurement based on flow injection conductimetric measurements.[1] To achieve a fully functioning DIC profiling system requires microfluidic lab on chip structures with sample volumes ≤ 1uL (to minimise 3 years of reagent payload), precision channel patterning, multi-layer thermoplastic bonding, and liquid-liquid membrane separation of CO2, with incompatible gas-permeable ion blocking materials, suitable for >3-year ocean deployment at high pressures. Recently we demonstrated long-term PDMS membrane bonding within a thermoplastic manifold [2] as well high pressure resilient thermoplastic bonding for multi-layer and multi-channel devices. [3] We have established the principle of precision micro-metering to inject HCl acid into the seawater sample. [4] The detection principle is based on CO2, transferred across the membrane, dissolves in high strength NaOH leading to a reduction in conductivity. [5] Conductivity electrodes are limited in size by sample volume and must operate continuously in a highly corrosive environment (NaOH, pH12). Previously we attempted a capacitively-coupled approach using thin-film protective insulating layer on copper tracks. However, this resulted in severe signal attenuation. Here we report direct metal contact conductivity cells with active volumes between 0.5 mL and 2.0 mL for DIC detection in the seawater range 1900 – 2400 mmol Kg-1. For these volumes, the use of macroscopic wires or plates as electrodes is not feasible and instead, we developed a thin film metallisation process onto PMMA using a sputtered thin film of gold (< 200 nm) on top of a 10 nm adhesion promoting inter-layer of sputtered Ti.After transfer across the membrane, the eluted CO2 in a NaOH carrier, was drawn through a < 2 mL conductivity cell where the change in impedance versus time was measured. Minimum precision values obtained from relative standard deviation were ~ 0.2 % from peak height and 0.5% from area under curve. This compares favourably with precision values of ~ 0.25 % obtained using a large C4D electrophoresis headstage of similar active measurement volume. The required sample and reagent volumes amounted to ~ 500 mL in total due to the incorporation of a planar membrane into a small volume exchange cell. This compares very favourably with reported attempts at conductivity based DIC analysis where total volumes between 5,000 mL and 10,000 mL were required as, in order to achieve the required precision, bulk wire electrodes and 20cm long membrane tubes were used. We show therefore the first microfluidic-based DIC sensor with accuracy, precision and reagent payload that offers a route to global autonomous ocean CO2 depth profiling. P. Hall and R. Aller, Limnol. Oceanogr., 1992, 37, 1113 https://doi.org/10.4319/lo.1992.37.5.1113 M. Tweedie et al, Lab Chip, 2019, 1287 https://doi.org/10.1039/C9LC00123A D. Sun et al., Microfluid. Nanofluid., 2015, 913 https://doi.org/10.1007/s10404-015-1620-2 M. Tweedie et al. https://arxiv.org/abs/1909.01845 M. Tweedie et al., https://doi.org/10.26434/chemrxiv.8852087.v1 Figure 1

Metamaterials have drawn interest in the sensor community due to their extreme dielectric-sensitive resonant behavior. Although these structures are studied in a wide range of frequencies, the ultrahigh frequencies are of special interest due to their compatibility with RF electronics. Unlike spectroscopic methods, where each material has its specific fingerprint, the response of these resonant structures depends on the electromagnetic properties, the volume of the material under test, and the resonator's design itself. Thus, implementing a metamaterial-based sensor for biological and chemical applications requires some mechanism to fix the sample's location and volume. Since most biological and chemical samples are liquids, microfluidics is the most promising candidate for this task. Here, we propose a dielectric sensing platform with a cost-effective fabrication method that allows fluid detection inside the microfluidic channel. The device proposed here is designed numerically, fabricated and measured, and finally validated via an analytical lumped model. It consists of a microstrip line coupled with a split ring resonator as the transducer and a microfluidic structure to control the sample and generate microdroplets. The fluid under test inside the microfluidic channel can be characterized based on the change in its dielectric constant or loss factor. The device shows a 600 kHz resonance shift in response to the dielectric change in sample volumes as low as 10 nl. We also demonstrate the platform's capability to generate and detect octanol–water microdroplets. The method reported here offers a fast prototyping method suitable for various microfluidic sensing applications.

Evaluation of Pb-Spec ® for flow-injection solid-phase extraction preconcentration for the determination of trace lead in water and wine by flame atomic absorption spectrometry

Evaluation of the Effects of Sample Dilution and Volume in Hydrophilic Interaction Liquid Chromatography

Atmospheric CO2 has increased by > 40% since pre-industrial times leading to significant global warming. The ocean absorption of CO2 is saturating, possibly leading to much more serious consequences than predicted. The latest IPCC special report SR15 warns that a 1.5 oC average temperature increase by 2030 is likely and associated CO2 ocean acidification is projected to amplify the adverse effects of warming. The ocean CO2 system is characterized by measuring at least 2 out of 4 canonical “master variables”: total dissolved inorganic carbon (DIC), total alkalinity (AT), partial CO2 (pCO2), and acidity (pH). Understanding this system is of fundamental importance yet CO2 continues to be chronically under-sampled in both space (including depth profiles) and time. Unfortunately, pCO2 and pH are very sensitive to temperature/pressure, hence autonomous measurements of DIC or AT are much preferred but have yet to be realized. Observations are almost exclusively limited to the surface and use large sensors, e.g. spectrophotometry, NDIR and mass spectrometry, attached to expensive research vessels. These large systems are unlikely candidates for miniaturisation. Very large uncertainties therefore still remain in the CO2 budget.The Argo float network, a global array of >3,000 untethered battery-operated floats with satellite data transfer, enables continuous monitoring of ocean salinity and temperature depth profiles. This float infrastructure awaits new autonomous chemical sensor technology but will impose severe constraints on device footprint, volume, power consumption and long-term environmental stability under high pressure cycling (up to 200 atm). Instantaneous measurement of DIC during float ascent or descent is not possible as the CO2 has to be extracted from the seawater first. Hence at each depth, an autonomous device would have to collect and store a seawater sample for subsequent analysis while the float is at park depth (~1500m). This analysis involves several chemical reactions and partial or complete equilibration across a membrane with high precision conductivity measurements. Microfluidic ocean-relevant chemical sensors have received limited attention. Research efforts have concentrated on colorimetric or luminescence techniques at shallow depths.We investigate a potential miniaturised version of a standard bench technique for DIC measurement based on flow injection conductimetric measurements.[1] To achieve a fully functioning DIC profiling system requires microfluidic lab on chip structures with sample volumes ≤ 1uL (to minimise 3 years of reagent payload), precision channel patterning, multi-layer thermoplastic bonding, and liquid-liquid membrane separation of CO2, with incompatible gas-permeable ion blocking materials, suitable for >3-year ocean deployment at high pressures. Recently we demonstrated long-term PDMS membrane bonding within a thermoplastic manifold [2] as well high pressure resilient thermoplastic bonding for multi-layer and multi-channel devices. [3] We have established the principle of precision micro-metering to inject HCl acid into the seawater sample. [4] The detection principle is based on CO2, transferred across the membrane, dissolves in high strength NaOH leading to a reduction in conductivity. [5] Conductivity electrodes are limited in size by sample volume and must operate continuously in a highly corrosive environment (NaOH, pH12). Previously we attempted a capacitively-coupled approach using thin-film protective insulating layer on copper tracks. However, this resulted in severe signal attenuation. Here we report direct metal contact conductivity cells with active volumes between 0.5 mL and 2.0 mL for DIC detection in the seawater range 1900 – 2400 mmol Kg-1. For these volumes, the use of macroscopic wires or plates as electrodes is not feasible and instead, we developed a thin film metallisation process onto PMMA using a sputtered thin film of gold (< 200 nm) on top of a 10 nm adhesion promoting inter-layer of sputtered Ti.After transfer across the membrane, the eluted CO2 in a NaOH carrier, was drawn through a < 2 mL conductivity cell where the change in impedance versus time was measured. Minimum precision values obtained from relative standard deviation were ~ 0.2 % from peak height and 0.5% from area under curve. This compares favourably with precision values of ~ 0.25 % obtained using a large C4D electrophoresis headstage of similar active measurement volume. The required sample and reagent volumes amounted to ~ 500 mL in total due to the incorporation of a planar membrane into a small volume exchange cell. This compares very favourably with reported attempts at conductivity based DIC analysis where total volumes between 5,000 mL and 10,000 mL were required as, in order to achieve the required precision, bulk wire electrodes and 20cm long membrane tubes were used. We show therefore the first microfluidic-based DIC sensor with accuracy, precision and reagent payload that offers a route to global autonomous ocean CO2 depth profiling. 1. P. Hall and R. Aller, Limnol. Oceanogr., 1992, 37, 1113 https://doi.org/10.4319/lo.1992.37.5.11132. M. Tweedie et al, Lab Chip, 2019, 1287 https://doi.org/10.1039/C9LC00123A3. D. Sun et al., Microfluid. Nanofluid., 2015, 913 https://doi.org/10.1007/s10404-015-1620-24. M. Tweedie et al. https://arxiv.org/abs/1909.018455. M. Tweedie et al., https://doi.org/10.26434/chemrxiv.8852087.v1 Figure 1

The analytical performance of methods for the determination of hydride forming elements has been improved recently by the development of procedures in which the hydride is trapped on the interior surface of a graphite furnace atomizer. The signal for a given concentration increases with increase in sample volume and it is often implied that a decrease in the limit of detection may also be achieved by increasing the sample volume. To evaluate this claim, a simple equation was derived which predicts the relationship between detection limit and sample volume when all the contributions to the blank are proportional to sample volume. A time-based approach to the variation of sample volume was developed to ensure that the analyte introduced from reagent contamination was, in fact, proportional to sample volume. Detection limits were measured for a series of sample volumes between 156 and 1560 µl. As the sample volume was increased, the detection limit improved significantly from 0.3 to around 0.05 µg l–1 up to a volume of about 500 µl. Between 500 and 1000 µl, a further improvement, to around 0.02 µg l–1, was obtained, but for volumes larger than 1000 µl no further significant improvement was obtained. Good agreement between the predicted and experimentally determined variations in detection limit with sample volume was obtained and thus the underlying inverse proportionality of the relationship between detection limit and sample volume was confirmed. This rectangular hyperbolic relationship has practical consequences for the extent to which detection limits can be improved by increasing the sample volume, even when the blank is very low or zero.

To investigate the influence of sample volume and contact lens material on osmolality measurements made with a Wescor vapor pressure osmometer. Accuracy: Sample volumes of 0.8, 2.0, and 10.0 microL were tested with 290, 320, and 1000 mmol/kg after the osmometer was calibrated with the intended sample volume. Influence of sample volume: Sample volumes ranging from 0.5 to 1.1 microL (0.1 steps) were applied with solutions of 290, 320, 500, and 1000 mmol/kg after the osmometer was calibrated with 0.8 microl, independent of the intended sample volume. Influence of contact lens material: Lens discs of 3.4 millimeters were trephined from the center of Lotrafilcon B, Nelfilcon A, Balafilcon A and Etafilcon A lenses, and equilibrated in phosphate buffered saline with 290 mmol/kg after dehydration for 16 h. The osmometer was calibrated with 0.8 microl and lens discs were inserted into the small sample holder of the osmometer. There were no significant differences between the nominal and measured osmolalities for each sample volume and solution combination (all p > 0.05). Influence of sample volume: Differences of more than 0.1 microl between the calibration and sample volume significantly affected osmolality readings, with sample volumes larger than calibration volume resulting in lower readings, and smaller volumes resulting in higher readings. Influence of contact lens material: Measured osmolalities of Lotrafilcon B (358.8 +/- 45.4 mmol/kg) and Balafilcon A (356.7 +/- 38.7 mmol/kg) were not significantly different to each other (p = 0.999) but were significantly higher than Etafilcon A (298.2 +/- 15.9 mmol/kg) and Nelfilcon A (281.2 +/- 12.2 mmol/kg, p < 0.05). There was no significant difference between Etafilcon A and Nelfilcon A lenses (p = 0.056). The main factors associated with measured osmolality were water content, sample volume and their interaction (r(2) = 0.716). Osmolality readings varied with calibration and sample volume, and with different contact lens materials.

Swimming behaviors of bonnethead sharks (Sphyrna tiburo) were observed in response to chemical stimulation. Large volume (10 ml) samples were introduced into the path of swimming sharks. In still water, tight turning and circling were observed while samples introduced in the presence of a water current elicited a swimming pattern of connected loops moving downcurrent. A headmount attached to the shark allowed small volume (0.5 ml) samples to be directed into the olfactory capsules. Stimulation in still water produced the turning and circling behaviors as observed for the large volume samples and stimulation in moving waters produced the same connected loops pattern. Other experiments confirmed that the small volume samples quickly dilute below threshold and therefore the behaviors observed in response to the 0.5 ml samples are swimming patterns released by the chemical signal but are presumed to be modulated by factors other than chemical cues. Additionally, it was demonstrated that bonnethead sharks can ...

A prompt gamma-ray neutron activation (PGNA) system was simulated by the Monte Carlo N-Particle transport code (MCNP-4A) to estimate the level at which the scattered photon fluence rate, the absolute efficiency of the HPGe-detector, the volume of the concrete sample and the <TEX>$^{35}$</TEX> /Cl(n, <TEX>${\gamma}$</TEX>) reaction rate in this sample contribute to the count rate in the NaCl concentration measurement. The n- <TEX>${\gamma}$</TEX> fluence rates at the ST-2 beam tube exit of the HANARO reactor were used as input data, and the GAMMA-X type HPGe detector was modeled to tally 1.1649 MeV <TEX>${\gamma}$</TEX> -rays emitted from the <TEX>$^{35}$</TEX> Cl(n, <TEX>${\gamma}$</TEX>) reaction in the concrete sample. For three cylindrical concrete samples of 13.8, 46.8 and 157.1 ㎤ volumes, respectively, the relations between the NaCl weight fractions of 0.1, 1, 2 and 5 % in each of the concrete samples and the 1.1 649 MeV pulses created in the HPGe detector model were studied. As a result, it was found that the count rate at the same NaCl concentration nearly depends on the volume of the samples in a simulated condition of the same NaCl concentration samples, and that the linearities of the NaCl concentration calibration curves were reasonable in the narrow range of the NaCl weight fraction.