Preconcentration Device Research Articles

Add-On Device Powered by Parallelized Adsorption Traps for Preconcentrator-GC-MS Measurement of sub-pmol/mol Levels of NF3.

In this study, an add-on preconcentration device powered by parallelized pretraps (PPTs) was utilized to measure the sub-pmol/mol levels of NF3 in N2. The add-on preconcentrator was coupled to the detachable trap preconcentrator (DTP) with a gas chromatograph-mass spectrometer [Anal. Chem. 2019, 91, 3342-3349]. The breakthrough volume of the parallel configuration was found to be substantially higher than that of the serial configuration with the same amount of adsorbent (HayeSep D). Liquid oxygen (LO2) cooling (-183 °C) exhibited better preconcentration performance for NF3 in N2 compared to NF3 in air (N2 + O2) with liquid nitrogen cooling (-195 °C) and NF3 in air with LO2 cooling. The DTP unit was essential to discriminate residual species, such as N2, O2, CO2, and CF4, of which the preconcentrated portion in the PPT can be excessive, enabling the overwhelm filtering capability of the quadrupole mass spectrometer. The limit of detection of NF3 in N2 of the PPT/DTP/gas chromatograph-mass spectrometer was 0.01 ppt, which is significantly better than that determined without using the add-on preconcentration device (0.21 ppt).

(Invited) Electric-Driven Preconcentrating Microfluidic Device for Enhancing Biomolecular Sensing

Preconcentration of biomolecules for detection on microfluidic platforms based on electrical kinetic trapping (EKT) through ion concentration polarization (ICP) has been well developed in the past decade. Biomolecules can be entrapped due to the equilibrium of forces between electro-osmosis and ICP when applying a voltage to the system. In tis study, I will introduce different type of ICPs including theory, mechanism and their limitation. I will also clarify the experimental ICP results based on different microfluidic channel design. A triboelectric nanogenerator (TENG)-driven nanofluidic preconcentrating device that is able to trigger ICP and subsequently cause the EKT of the biomolecules without using a conventional electrical power source was also introduced. The EKT and electrical characteristics of the TENG-based nanofluidic preconcentrator were studied. The preconcentration factors of the device can be found to be ~1000 folds. Several examples of preconcentration device integrating to biosensing techniques are presented in this talk. Some biomarkers are also demonstrated. Further, I will also demonstrate that these biosensors, combining with preconcentrators, can be integrated to a smartphone reader.

Determination of Critical Dimensions of Microchannels to Ensure the Electrokinetic Biomolecule Preconcentration: Analytical and Numerical Studies.

Preconcentration of biomolecules based on ion concentration polarization (ICP) has been splendidly applied to various biomedical and chemical processes. However, in many circumstances, biomolecule preconcentration could not occur due to the lack of full studies on the preconcentration mechanism, especially on the effect of microchannel dimensions. In this work, we provide analytical studies on the critical dimensions (minimum and maximum) of microchannels for the preconcentration of biomolecules. These formulas are verified with the numerical results by fully solving the coupled governing equations: Poisson-Nernst-Planck and Navier-Stokes experiments with appropriate boundary conditions and assumptions. In addition, we examine the impact of operational parameters, such as electric potentials and critical external pressures, on the formation of the preconcentration. Moreover, two important results are provided for the first time, including the position of the preconcentrated biomolecule region and the concentration enhancement factor of the biomolecules. These analytical and numerical results are consistent with experimental observations and, therefore, could provide sharp insight into the mechanism of biomolecule preconcentration and give useful guidelines to better design and optimize ICP-based microfluidic preconcentration devices.

Employing electrochemically derived pH gradients for Lab-on-PCB protein preconcentration devices

Protein preconcentration is an essential sample preparation step for analysis in which the targeted proteins exist in low concentrations, such as bodily fluids, water, or wastewater. Nonetheless, very few practical implementations of miniaturized protein preconcentration devices have been demonstrated in practice, and even fewer have been integrated with other microanalytical steps. Existing approaches rely heavily on additional chemicals and reagents and introduce complexity to the overall assay. In this paper, we propose a novel miniaturized isoelectric focusing-based protein preconcentration screening device based on electrochemically derived pH gradients rather than existing chemical reagent approaches. In this way, we reduce the need for additional chemical reagents to zero while enabling device incorporation in a seamlessly integrated full protein analysis microsystem via Lab-on-PCB technology. We apply our previously presented Lab-on-PCB approach to quantitatively control the pH of a solution in the vicinity of planar electrodes using electrochemical acid generation through redox-active self-assembled monolayers. The presented device comprises a printed circuit board with an array of gold electrodes that were functionalized with 4-aminothiophenol; this formed a self-assembled monolayer that was electropolymerized to improve its electrochemical reversibility. Protein preconcentration was performed in two configurations. The first was open and needed the use of a holder to suspend a well of fluid above the electrodes; the second used microfluidic channels to enclose small volumes of fluid. Reported here are the resulting data for protein preconcentration in both these forms, with a quantitative concentration factor shown for the open form and qualitative proof shown for the microfluidic.

CleanEx: A Versatile Automated Methane Preconcentration Device for High-Precision Analysis of 13CH4, 12CH3D, and 13CH3D.

The relative abundance of methane isotopologues offers key insights into the global methane (CH4) cycle. Advances in laser spectroscopy enable routine high-precision measurements even for rare deuterated methane isotopologues, 12CH3D and 13CH3D, provided there are sufficiently high methane amount fractions and reproducible measurement conditions, which can be achieved by CH4 adsorption-desorption techniques. We present a new cryogen-free automated preconcentration device─CleanEx─designed for quantitative extraction of CH4 from large volumes of sample gas and for cleaning by stepwise temperature-controlled desorption to separate interferant gases. We show that CleanEx has the capability to preconcentrate methane by almost 2000-fold from ∼18 L of air. The performance is demonstrated in a range of methane amount fractions between 2 ppm (μmol mol-1), which corresponds to the present-day ambient air, up to 1000 ppm, representative for close to source or process conditions. Advantages over existing devices are a significantly larger primary adsorption trap and a secondary cryo-focusing step, which ensures separation of methane from major atmospheric compounds, i.e., O2, Ar, and CO2. We have demonstrated quantitative extraction of methane, with no significant isotopic fractionation and high repeatability of 0.2‰, 0.6‰, and 0.8‰ (n = 42) for the studied isotopologue ratios, 13CH4/12CH4, 12CH3D/12CH4, and 13CH3D/12CH4, during cryogenic adsorption-desorption on HayeSep D material. The developed device in combination with a suitable laser spectrometer offers a robust and autonomous method for precise continuous monitoring of δ13C-CH4 and δD-CH4 in ambient air and optionally Δ13CH3D in process-derived methane.

Polymeric micro gas preconcentrators based on graphene oxide and carbon nanopowder adsorbents for gas detection application

In this study, an application of novel polymer-based microfluidic channels for preconcentration and detection of methane gas is investigated. Poly (methyl methacrylate) (PMMA) microfluidic channel is filled by graphene oxide (GO) as a new adsorbent for thermal preconcentration and carbon nanopowder is loaded into a polydimethylsiloxane (PDMS) microfluidic channel. The effective microfluidic channels area is 14 mm × 10 mm. The laser cutting and etching followed by thermally-solvent bonding process are used for PMMA microfluidic channel fabrication. Also, PDMS microfluidic channel is fabricated by SU-8 molding technique, lithography process, and oxygen plasma bonding on glass. SEM, Raman spectroscopy, and FTIR characterizations are carried out for investigation of the synthesized GO. The amount of electrical power consumption of devices is also investigated by simulation and experiment. The performance of both micro preconcentrators (μPCs) are compared through the similar experimental tests which exhibit the suitable performance of fabricated μPCs with proper repeatability for preconcentration purposes. The effect of gas flow rate, heating rate, gas exposure time, and gas concentration are investigated for both microfluidic channels and their optimized values were obtained. According to the lower desorption temperature of GO, despite its slightly lower response (10.41) compared to carbon nanopowder μPCs (12.34), due to its almost half power consumption (0.375 W in comparison with 0.8 W), it can be an appropriate candidate for preconcentration applications. PMMA and PDMS-based microfluidic channels show promising choices in the preconcentration application for the adsorbents with low desorption temperatures. As a result, PMMA as a low-cost material with a simple fabrication process in microchannels and GO as the novel adsorbent material can be suitable candidates in low working temperature and rapid preconcentration devices. • Microfluidic channels are fabricated based on poly (methyl methacrylate) (PMMA), and polydimethylsiloxane (PDMS) • Graphene oxide (GO) and carbon nanopowder are used as the adsorbent materials for PMMA and PDMS microfluidic channels, respectively. • The effect of gas flow rate, heating rate, gas exposure time, and gas concentration are investigated to achieve the optimized values. • The power consumption and temperature distribution of heater are studied through the simulation.

Novel High-Pressure Gas Sampling and –Preconcentration Device: Application to Biomethane's Trace Compounds Characterization

Novel High-Pressure Gas Sampling and –Preconcentration Device: Application to Biomethane's Trace Compounds Characterization

A Pre-Concentration System Design for Electronic Nose via Finite Element Method

Volatile organic compounds (VOCs), which is measured by electronic nose (e-nose), have utilities as biomarkers for classification and detection. However, the concentration of biomarker in VOCs is usually lower than the detection limit of gas sensors of e-nose, which results in systematic failure. The VOCs enrichment technology can be used to break through the limitations via enriching the low concentration of VOCs with adsorption tubes. In this brief, a pre-concentration system is designed based on the finite element method. Through the finite element analysis, the pre-concentration system can efficiently determine parameters to control the temperature field. In addition, with the expanded adsorption range of VOCs C3-C30, the lower bound of adsorption is analytically proved by C3H8O (including n-propanol and isopropanol). Moreover, the conformal technique is exploited to improve the enrichment efficiency. Also, the upper bound of adsorbable VOCs can be further improved via the double adsorption tubes structure design. Finally, gas chromatography-mass spectrometry (GC-MS) and e-nose are used to detect the concentration of the different sample gas before and after the pre-concentration device, and the results show the effectiveness of the design.

Continuous vapor sampling of volatile organic compounds associated with explosives using capillary microextraction of volatiles (CMV) coupled to a portable GC–MS

The dynamic sampling and preconcentration device, capillary microextraction of volatiles (CMV), is coupled to a portable GC–MS for the rapid field detection of volatile organic compounds (VOCs) associated with explosives. The results of the portable GC–MS were compared to a benchtop GC–MS throughout this study. Sub-nanogram (ng) instrumental detection limits were achieved for each of the following analytes of interest (3-NT, 2,4-DNT, DPA, EC, DBP and 2-NDPA). Three different dynamic sampling methods were used with the CMV to sample and preconcentrate the volatiles prior to analysis. The headspace of a closed system was sampled over 10 min resulting in recoveries between 0.3 and 12%. Simulated open-air vapor sampling using a previously described vapor source resulted in an improvement of analyte recovery (ranging from 1.6 to 25%), for the same 10-minute sampling. A novel, continuous vapor delivery and sampling system was used, for the first time, to facilitate the delivery of sub-nanogram quantities of explosive analytes. The new continuous delivery system achieved significantly higher recoveries (3.0–89%) for all the analytes while requiring less sampling time (∼5 min) and sampling volumes than the other sampling techniques. The rapid sampling and preconcentration of sub-ng levels of VOCs in field scenarios was coupled to a ∼10-minute portable GC–MS method that compares favorably to the analytical figures of merit achieved by laboratory benchtop instruments and approximates the detection limits reported for canines.

Techniques for measuring carbon and oxygen isotope compositions of atmospheric CO2 via isotope ratio mass spectrometry.

Measuring the stable isotope compositions of atmospheric CO2 is common in earth and atmospheric sciences, and various analytical methods have been developed utilizing continuous-flow (CF) or dual-inlet (DI) isotope ratio mass spectrometry (IRMS). Air is typically collected via passive, manual, or automated collection methods and the volume of the air sample ranges from 10 to 300 mL for CF-IRMS to >1 L for DI-IRMS to yield a measurable amount of atmospheric CO2 gas. It has been determined that the integrity of vials and flasks for air sample storage can be compromised after 3 days of air collection for δ13 C values and within 10 hours for δ18 O values. Air samples must be purified after collection to remove constituents of air, such as Ar, O2 , N2 , N2 O, and water vapor, to avoid isobaric interferences during mass spectrometric measurement. Purification is generally undertaken by utilizing commercial or custom-made preconcentration devices, the blanking method for CF-IRMS, or an offline/online cryogenic separation using a vacuum line for DI-IRMS. Ambient N2 O is a component of air that may affect analytical results and thus must either be corrected for or be removed using a gas chromatographic column. In some cases, water is removed during air collection by using a common chemical desiccant, magnesium perchlorate (Mg(ClO4 )2 ), or by a dry ice/alcohol mixture (-78°C). Lastly, a linearity issue for IRMS due to the low amount of purified CO2 from a typical ambient air sample must be considered. In general, analytical precisions of 0.02-0.21‰ and 0.04-0.34‰ for CF-IRMS and 0.01-0.02‰ and 0.01-0.02‰ for DI-IRMS are expected for δ13 C and δ18 O measurements, respectively.

Device improves sensitivity and effectiveness of point-of-care tests

A quick and effective high-pressure preconcentration device improves point-of-care testing sensitivity and effectiveness.

Analysis of pressure-driven membrane preconcentration for point-of-care assays.

Point-of-care diagnostic devices for both physicians and patients themselves are now ubiquitous, but often not sensitive enough for highly dilute analytes (e.g., pre-symptomatic viral detection). Two primary methods to address this challenge include (1) increasing the sensitivity of molecular recognition elements with greater binding affinity to the analyte or (2) increasing the concentration of the analyte being detected in the sample itself (preconcentration). The latter approach, preconcentration, is arguably more attractive if it can be made universally applicable to a wide range of analytes. In this study, pressure-driven membrane preconcentration devices were developed, and their performance was analyzed for detecting target analytes in biofluids in the form of point-of-care lateral-flow assays (LFAs). The demonstrated prototypes utilize negative or positive pressure gradients to move both water and small interferents (salt, pH) through a membrane filter, thereby concentrating the analyte of interest in the remaining sample fluid. Preconcentration up to 33× is demonstrated for influenza A nucleoprotein with a 5 kDa pore polyethersulfone membrane filter. LFA results are obtained within as short as several minutes and device operation is simple (very few user steps), suggesting that membrane preconcentration can be preferable to more complex and slow conventional preconcentration techniques used in laboratory practice.

High Sensitivity Determination of Antimony with Application for the Characterization of Its Migration in Bottled Water by a Dielectric Barrier Discharge (DBD) Coupled with Hydride Generation – Atomic Fluorescence Spectrometry (HG-AFS)

An in situ dielectric barrier discharge (DBD) employed as a preconcentration device was coupled with hydride generation atomic fluorescence spectrometry (HG-AFS) for the determination of antimony (Sb) that migrated from plastic to bottle water. In the presence of oxygen under a 7.5 kV discharge, Sb was completely trapped on the surface of dielectric barrier discharge quartz tube. After 50 s of Ar carrier sweeping, water vapor interference was effectively eliminated and Sb was rapidly released by a discharge containing hydrogen using 6.8 kV. In addition, the investigation of Sb migration from bottle materials to water was carried out considering temperature and bottle materials. Under the optimized conditions, the detection of limit (LOD) was 9 pg or 5 pg/mL. The linearity of the calibration relationship R2 exceeded 0.996 for concentrations from of 0.05 to 50 μg/L. In addition, the determined Sb levels of water certified reference materials (CRMs) were in good agreement with the certified values. The spiked recoveries for bottled water samples were from 95% to 104% with 3% to 8% relative standard deviation values. In comparison, the HG-in situ DBD-AFS method is capable to increase the analytical sensitivity using the peak height by 7-fold compared to standard HG-AFS. DBD offers gas phase enrichment at room temperature with instrumental miniaturization for elemental analysis with low energy consumption, small size and low cost.

An Automated SeaFAST ICP-DRC-MS Method for the Determination of 90Sr in Spent Nuclear Fuel Leachates.

To reduce uncertainties in determining the source term and evolving condition of spent nuclear fuel is fundamental to the safety assessment. ß-emitting nuclides pose a challenging task for reliable, quantitative determination because both radiometric and mass spectrometric methodologies require prior chemical purification for the removal of interfering activity and isobars, respectively. A method for the determination of 90Sr at trace levels in nuclear spent fuel leachate samples without sophisticated and time-consuming procedures has been established. The analytical approach uses a commercially available automated pre-concentration device (SeaFAST) coupled to an ICP-DRC-MS. The method shows good performances with regard to reproducibility, precision, and LOD reducing the total time of analysis for each sample to 12.5 min. The comparison between the developed method and the classical radiochemical method shows a good agreement when taking into account the associated uncertainties.

Decoration of Fe3O4@SiO2@ZnO as a high performance nanosorbent on a stir bar microextraction device for preconcentration and determination of cadmium in real water samples

In this work, a novel, fast and simple method that so called stir bar sorptive–dispersive microextraction (SBSDµE) applied for preconcentration and determination of trace amounts of Cd (II) ions in real water samples. For this purpose, Fe3O4@SiO2@ZnO core–shell microspheres were coated on a neodymium stir bar magnetically, and dispersed in the sample solution at high stirring rate, while adsorbing Cadmium target ions. The effective factors on extraction of Cd (II) (pH, stirring rate, salt effect and extraction time) were investigated and optimized using response surface methodology (RSM) as a powerful statistical technique. Under the optimal conditions, linear dynamic range (LDR) of SBSDµE method was 1–150 ng mL−1, the intra-day and inter-day relative standard deviations (RSD%) at 80 ng mL−1 concentration level were 3.7% and 8.4% (n = 5), respectively. The limit of detection (LOD) was 0.37 ng mL−1 and the limit of quantification (LOQ) was 1.23 ng mL−1. The proposed microextraction analytical method was successfully used for determination of ultra trace amounts of cadmium in some real water samples.

On-site Colorimetric Determination of Trace Arsenic in Water Using a Syringe Filter as a Separation and Pre-concentration Device

On-site Colorimetric Determination of Trace Arsenic in Water Using a Syringe Filter as a Separation and Pre-concentration Device

Determination of Stable Nitrogen and Oxygen Isotope Ratios in Atmospheric Aerosol Nitrates

Abstract Several conditions of two-step chemical reduction method for simultaneously determination of stable nitrogen and oxygen isotope compositions in atmospheric nitrate (NO3−) particles, such as the pH, reaction time, type of cadmium powder and concentration of NaCl, were optimized. The nitrite (NO3−) in the samples was reduced to nitrous oxide (N2O) through the improved method and the produced N2O was measured for their isotope compositions (δ15N and δ18O) by coupling an autosampler and a pre-concentration device with the MAT253 isotope ratio mass spectrometer. The standard curves of the nitrogen (R2 = 0.9999) and oxygen (R2 = 0.9996) isotope ratios of N2O and NO3− were established by measuring the international standards with known isotope ratios, and the nitrogen and oxygen isotope ratio of nitrates of the sample could be therefore converted. The principle of this method was clear, and only required very small amounts of samples (i.e., 0.8 μg of N). The standard deviations of δ15N and δ18O were 0.08‰ and 0.24‰, respectively. This method was not only suitable for atmospheric aerosol samples, but also for the other environmental samples such as rainwater and snow samples with low concentrations. This study provided a novel method for better understanding emission sources and transformation pathways of atmospheric nitrate.

Development of a titanium dioxide-assisted preconcentration/on-site vapor-generation chip hyphenated with inductively coupled plasma-mass spectrometry for online determination of mercuric ions in urine samples

In this study, a novel automatic analytical methodology using a titanium dioxide (TiO2)-assisted preconcentration/on-site vapor-generation (VG) chip hyphenated with inductively coupled plasma-mass spectrometry (ICP-MS) for online determination of mercuric ions (Hg2+) was developed. Interestingly, the TiO2 nanoparticle (nano-TiO2) coating on the channel surface acted not only as a sorbent for preconcentration but also as a catalyst for photocatalyst-assisted VG. Under optimum operation conditions, the developed method was validated by analyzing the certified reference material (CRM) Seronorm™ Trace Elements Urine L-2 (freeze-dried human urine). Based on the obtained results, the dramatic reduction of “hands-on” manipulation and the elimination of hazardous materials (e.g., sodium borohydride (NaBH4) and stannous chloride (SnCl2)) from the process enabled a simple and ultraclean procedure with an extremely low detection limit of 0.75 ng L−1 for Hg2+ in urine samples. To the best of our knowledge, this is the first study to report the direct exploitation of a nano-TiO2-coated microfluidic device for online sample preconcentration and on-site VG prior to ICP-MS measurement.

A three-dimensional printed electromembrane extraction device for capillary electrophoresis

A concentric electromembrane extraction preconcentration device was designed and fabricated using fused deposition modelling 3D printing. The device consisted of a hemispherical electrode sample vial printed from a filament of conductive polylactic acid (PLA), into which sat a smaller hemispherical 3D printed porous membrane acceptor vial. Application of voltage between a point-electrode placed in the center of 20 μL solution inside the acceptor vial and the electrode vial containing 1 mL of sample, enabled anion migration through the 3D printed porous material into the acceptor solution. Electromembrane extraction was proved using fluorescein for imaging of the extraction process, with preconcentration rates of 0.833 μM/sec at 120 V with close to 95% recovery. The performance of the fabricated porous 3D printed device was evaluated for the preconcentration of anions from water prior to capillary electrophoresis detection. Preconcentration factors ranging between 36–44 were obtained for chloride, nitrate, perchlorate and sulfate, while a lower performance was observed for weaker acids as fluoride and phosphate (3–4). The limit of detection (LOD) was determined to be 0.16 μM, 0.18 μM and 0.18 μM for NO3−, ClO4− and SO42- respectively. The extraction and quantitation of ions from a soil slurry without filtration, namely NO3− and SO42- content was determined to be 0.24 and 0.03 mmol/100 g of soil, respectively which are values in the range of those typically reported in soil samples.

Continuous, quantifiable, and simple osmotic preconcentration and sensing within microfluidic devices

Insurmountable detection challenges will impede the development of many of the next-generation of lab-on-a-chip devices (e.g., point-of-care and real-time health monitors). Here we present the first membrane-based, microfluidic sample preconcentration method that is continuous, quantifiable, simple, and capable of working with any analyte. Forward osmosis rapidly concentrates analytes by removing water from a stream of sample fluid. 10-100X preconcentration is possible in mere minutes. This requires careful selection of the semi-permeable membrane and draw molecule; therefore, the osmosis performance of several classes of membranes and draw molecules were systematically optimized. Proof-of-concept preconcentration devices were characterized based on their concentration ability and fouling resistance. In-silico theoretical modeling predicts the experimental findings and provides an engineering toolkit for future designs. With this toolkit, inexpensive ready-for-manufacturing prototypes were also developed. These devices provide broad-spectrum detection improvements across many analytes and sensing modalities, enabling next-generation lab-on-a-chip devices.