Liquid Sample Flow Research Articles

A Sensitive Fluorescence Analysis Method of Pathogenic Microorganisms Based on Silicon Photomultiplier.

The monitoring of pathogenic microorganisms in water is important for public health and disease outbreaks prediction. Recently, optical detection techniques have drawn much attention due to the advantages of rapid response, security and high sensitivity. In this paper, a fluorescence spectrometer based on 375nm exciting laser and the microchannel liquid sample flow technology is proposed. The 4 × 4 narrowband filter array was coupled to a Silicon Photomultiplier (SiPM) array with single-photon sensitivity. B500 fluorescent microspheres and Escherichia coli were used for performance evaluation of the spectrometer. As a result, it is feasible to use random particle counting method to detect the bacteria concentration level in water even low to several CFU/mL. In addition, based on Python tools and neural network algorithm models, the fluorescence spectra of different kinds of substances (biotic and abiotic) can be classified with an accuracy of more than 97%. The method was successfully applied to tap water samples. The results suggest that the proposed method is applicable for on-site bacteria detection.

Development of a flat jet delivery system for soft X-ray spectroscopy at MAX IV.

One of the most challenging aspects of X-ray research is the delivery of liquid sample flows into the soft X-ray beam. Currently, cylindrical microjets are the most commonly used sample injection systems for soft X-ray liquid spectroscopy. However, they suffer from several drawbacks, such as complicated geometry due to their curved surface. In this study, we propose a novel 3D-printed nozzle design by introducing microscopic flat sheet jets that provide micrometre-thick liquid sheets with high stability, intending to make this technology more widely available to users. Our research is a collaboration between the EuXFEL and MAX IV research facilities. This collaboration aims to develop and refine a 3D-printed flat sheet nozzle design and a versatile jetting platform that is compatible with multiple endstations and measurement techniques. Our flat sheet jet platform improves the stability of the jet and increases its surface area, enabling more precise scanning and differential measurements in X-ray absorption, scattering, and imaging applications. Here, we demonstrate the performance of this new arrangement for a flat sheet jet setup with X-ray photoelectron spectroscopy, photoelectron angular distribution, and soft X-ray absorption spectroscopy experiments performed at the photoemission endstation of the FlexPES beamline at MAX IV Laboratory in Lund, Sweden.

Analysis of Extracellular Vesicles Lysing using Surface Acoustic Wave Resonator

The integration of a Y-channel microfluidic system with an annular SAW device developed using MEMS technology has built an efficient platform for mixing and lysing of extracellular vesicles. The travelling SAW used in this study operating at a frequency of 50 MHz is capable of generating surface acoustic waves stream on a liquid sample inside a Y-chamber. At a height of 80µm the PDMS chamber and a liquid sample flow rate of 10µl/min can produce a mixing method that is able to generate gas bubbles that cause the occurrence of microcavities which are the agents of the extracellular vesicle lysing mechanism. This method of rupturing extracellular vesicles through cavitation techniques results in cell rupture through a combination of shear force and pressure changes without destroying proteins and nucleic acids. The Bradford assay is used to observe the increased presence of proteins resulting from the rupture of extracellular vesicles after exposure to acoustic waves. Based on the results, it can be concluded that the most optimal SAW exposure time and power is at 20dBM and 60 seconds. Through this test it can also be observed that a longer exposure period will generate heat which results in the degradation of the proteins that come out of the extracellular vesicles. It can be concluded that the results of this study prove that mechanical method of integrating an annular -SAW device and a Y-channel PDMS microfluidic chamber for micro-mixing, the analysis of biological cells and lysing mechanism can be achieved more effectively compared to conventional methods.

Surface-Enhanced Raman Scattering-Based Dual-Flow Lateral Flow Assay Sensor for the Ultrasensitive Detection of the Thyroid-Stimulating Hormone.

The surface-enhanced Raman scattering (SERS)-based lateral flow assay (LFA) strip has been considered a high-sensitivity sensor that can overcome the low sensitivity and the difficulty of quantitative analysis problems inherent in the colorimetric LFA sensor. In the SERS-based LFA strip reported so far, a liquid sample flows through the nitrocellulose membrane in a single pathway. In some cases, however, this single-flow approach still has a limitation in detection sensitivity. This study developed a conceptually new SERS-based dual-flow LFA sensor to improve the detection sensitivity in a single-flow LFA sensor. First, a 25 nm Raman reporter-labeled gold nanoparticle (AuNP) solution flowed through one way, and a 45 nm AuNP solution continuously flowed through another path. This sequential flow of two different AuNP solutions enables forming additional bright hot spots between 25 and 45 nm AuNPs in the test line, and the SERS signal is strongly enhanced. Using this SERS-based dual-flow LFA sensor, it was possible to detect thyroid-stimulating hormone less than 0.5 μIU/mL that cannot be measured with a SERS-based single-flow LFA sensor.

A self-driven microfluidic surface-enhanced Raman scattering device for Hg2+ detection fabricated by femtosecond laser.

In this paper, we proposed a novel approach for rapid and flexible fabrication of self-driven microfluidic surface enhanced Raman scattering (SERS) chips for quantitative analysis of Hg2+ by femtosecond laser direct writing. In contrast to traditional microfluidic chips, the microchannels of the device can drive a liquid sample flow without external driving force. The sample flow speed is tunable since the wettability and capillarity properties of the channels, which depend on the roughness and the inner diameter of the microchannels, can be controlled by optimizing the laser processing parameters. The SERS active detection sites, which exhibit high enhancement effects and fine reproducibility, were integrated through the femtosecond laser-induced periodic surface structures (LIPSS), followed by 30 nm Ag deposition. The SERS performance of the as-prepared microfluidic SERS detection chip was studied with R6G as probe molecules. The quantitative analysis of Hg2+ was realized by simply injecting the Hg2+ sample and the probe molecules R6G from the two inlets, separately, and collecting the SERS signal at the detection site. The lowest detection limit for Hg2+ is 10-9 M. It should be mentioned that this study is not only limited to Hg2+ quantitative analysis, but is also mainly aimed to develop a new technique for the design and fabrication of novel self-driven microfluidic devices depending on practical application requirements.

Comparison of Membrane Inlet and Capillary Introduction Miniature Mass Spectrometry for Liquid Analysis.

Membrane inlet mass spectrometry (MIMS) is commonly used for detecting the components in liquid samples. When a liquid sample flows through a membrane, certain analytes will permeate into the vacuum chamber of a mass spectrometer from the solution. The properties of the membrane directly determine the substances that can be detected by MIMS. A capillary introduction (CI) method we previously proposed can also be used to analyze gas and volatile organic compounds (VOCs) dissolved in liquids. When CI analysis is carried out, the sample is drawn into the mass spectrometer with no species discrimination. The performance of these two injection methods was compared in this study, and similar response time and limit of detection (LOD) can be acquired. Specifically, MIMS can provide better detection sensitivity for most inorganic gases and volatile organic compounds. In contrast, capillary introduction shows wider compatibility on analyte types and quantitative range, and it requires less sample consumption. As the two injection methods have comparable characteristics and can be coupled with a miniature mass spectrometer, factors such as cost, pollution, device size, and sample consumption should be comprehensively considered when choosing a satisfactory injection method in practical applications.

An Optical Configuration of Crossed-Beam Photothermal Lens Spectrometer Operating at High Flow Velocities and Its Application for Cysteine Determination in Human Serum and Saliva.

Photothermal lens spectrometry (TLS) is a high sensitive technique for trace determination of nonfluorescent materials. Previous photothermal lens spectrometers suffer from operating limitations at high flow velocities, arising from taking the heated element off the probe beam direction, which results in a decrease in the thermal lens (TL) signal. Herein, we describe an optical configuration of the crossed-beam photothermal lens in transversal flow mode in which the propagating direction of the probe beam and liquid sample flow azimuth are concentric (CBTC). The system consists of a microfluidic cell with a volume of lower than 3 μL. In the current optical configuration, using 1-(2-pyridylazo)-2-naphthol (PAN) in ethanol as a test solution, by increasing the sample flow velocity and without increasing chopping frequency, the reduction in sensitivity is less pronounced. Under a 15 Hz chopping frequency, the optimum sample flow velocity is about 2 cm s-1, which is among the highest reported values achieved to date for photothermal lens spectrometers. Although the system operates at higher flow velocities and lower chopping frequencies compared to the collinear configuration, it provides a comparable analytical limit of detection. This optical configuration has been successfully employed for highly sensitive and selective determination of cysteine in human serum and saliva samples through a competitive complexation reaction with Cu-PAN as a colorimetric probe. The detection limit of this method (9.5 nM) shows a significant enhancement (726-times) in comparison to UV-vis measurements.

Optimized detection of particulates from liquid samples in the aerosol phase: Focus on black carbon

ABSTRACTOperational parameters for a single particle soot photometer (SP2) and a CETAC Marin-5 nebulizer were optimized for detection of particulates aerosolized from liquid samples. The sensitivity of nebulization efficiency on nebulizer input gas pressure, liquid sample flow rate, and alcohol doping of the sample were explored. The nebulization efficiency of the Marin-5 was found to be roughly independent of applied gas pressure once above a minimum pressure. The nebulization efficiency changed by ∼50% for an order of magnitude change in liquid sample flow. Doping the sample with isopropyl alcohol at a 1:1 ratio results in a ∼50% relative increase in nebulization efficiency over a broad range of liquid flows. These results should apply to all particulate materials in the size range studied. SP2 operational parameters including sheath and sample flow were explored to optimize detection of refractory black carbon (rBC) specifically via coupling to the nebulizer. The SP2 tested samples up to 5 cc s−1 with ...

Estimation of scattering phase function utilizing laser Doppler power density spectra

A new method for the estimation of the light scattering phase function of particles is presented. The method allows us to measure the light scattering phase function of particles of any shape in the full angular range (0°–180°) and is based on the analysis of laser Doppler (LD) power density spectra. The theoretical background of the method and results of its validation using data from Monte Carlo simulations will be presented. For the estimation of the scattering phase function, a phantom measurement setup is proposed containing a LD measurement system and a simple model in which a liquid sample flows through a glass tube fixed in an optically turbid material. The scattering phase function estimation error was thoroughly investigated in relation to the light scattering anisotropy factor g. The error of g estimation is lower than 10% for anisotropy factors larger than 0.5 and decreases with increase of the anisotropy factor (e.g. for g = 0.98, the error of estimation is 0.01%). The analysis of influence of the noise in the measured LD spectrum showed that the g estimation error is lower than 1% for signal to noise ratio higher than 50 dB.

Effect of liquid droplet impact velocity on liquid wicking kinetics in surface V-grooves

The liquid droplet inertia effect on liquid wicking in V-groove has direct implications to the liquid sample flow in microfluidic devices using V-groove channels and to the ink wicking along the inter-fibre gaps on uncoated paper surfaces, which is critical to the ink jet print quality. In this study liquid droplet inertia and the V-groove geometry is systematically varied to understand the effect of droplet impact, V-groove apex angle and groove width on the liquid wicking rate in the groove. Our results show that both the apex angle and the groove width influence the rate of liquid wicking in V-grooves forced by liquid droplet inertia. The inertia effect lasts for only a short time and its influence to the sample delivery accuracy in V-groove microfluidic devices can be minimised or eliminated by improving microfluidic channel design. On improving ink jet printing quality of uncoated papers, this work shows that applying surface sizing to uncoated ink jet papers is likely to be an effective way to change the geometry of the inter-fibre gaps and therefore can reduce the feathering effect in ink jet printing.

Microfluidic actuation and sampling by dehydration of hydrogel

This paper presents novel micropumps that are actuated by hydrogel drying. Gel dehydration by evaporation makes the gel absorbent. This results in the suction of the liquid from the connected microchannel into the gel. Therefore, the liquid sample flows through the microchannel as a result of this negative pressure. Micropumps with simple structures were fabricated using microfabrication techniques with glass, silicone polymer, and agarose or polyacrylamide gel. The average volume flow rate was measured in variations of several to several tens of picoliters per second according to the kind of gel. This gel micropump functioned for several hours without severe flow rate fluctuations. This pump was also able to deliver viscous fluids such as blood. This pump would be useful for microchips that need slow but steady and long-lasting actuation in the addition of sampling proteins from viscous liquids such as blood. Theoretical approach about diffusion movement of liquid into the gel was also described.

Rapid point-of-care concentration of bacteria in a disposable microfluidic device using meniscus dragging effect.

We report a low cost, disposable polymer microfluidic sample preparation device to perform rapid concentration of bacteria from liquid samples using enhanced evaporation targeted at downstream detection using surface enhanced Raman spectroscopy (SERS). The device is composed of a poly(dimethylsiloxane) (PDMS) liquid sample flow layer, a reusable metal airflow layer, and a porous PTFE (Teflon™) membrane sandwiched in between the liquid and air layers. The concentration capacity of the device was successfully demonstrated with fluorescently tagged Escherichia coli (E. coli). The recovery concentration was above 85% for all initial concentrations lower than 1 × 10(4) CFU mL(-1). In the lowest initial concentration cases, 100 µL initial volumes of bacteria solution at 100 CFU mL(-1) were concentrated into 500 nL droplets with greater than 90% efficiency in 15 min. Subsequent tests with SERS on clinically relevant Methicillin-Sensitive Staphylococcus aureus (MSSA) after concentration in this device proved more than 100-fold enhancement in SERS signal intensity compared to the signal obtained from the unconcentrated sample. The concentration device is straightforward to design and use, and as such could be used in conjunction with a number of detection technologies.

Development and characterization of a Flow Focusing multi nebulization system for sample introduction in ICP-based spectrometric techniques

In this work, a new multiple nebulizer for liquid sample introduction in ICP-based spectrometers was developed and characterized on ICP-AES. The association of the Flow Focusing multiple nebulizer (FFMN) and a dedicated spray chamber was called Flow Focusing multi nebulization system (FFMNS). The nebulizer incorporates four nebulization nozzles with independent liquid feeding and a common gas inlet. Four different spray chambers were constructed and evaluated and the geometry of the best performing one was optimized. The FFNMS was characterized at 0.6–0.9 L min−1 nebulizing gas flow and 0.04–0.6 mL min−1 total liquid sample flow. Drop size and velocity distributions of primary and tertiary aerosols were studied together with total solvent and analyte transport rates. The system was characterized on ICP-AES in both axial and radial view modes and compared to a standard sample introduction system consisting in a concentric nebulizer and a cyclonyc spray chamber using model solutions and certified reference materials (CRM). In terms of sensitivity and LOD, the FFMNS showed a similar behavior to the reference system at half of the liquid sample uptake (0.5 mL min−1 for FFMNS vs. 1 mL min−1 for the standard system). The CRM (hard drinking water) analysis recovery results are ranged between 89%–106% for FFMNS, and between 78%–102% for the reference system. Finally, the FFMNS was applied to an “in chamber” standard addition analysis of synthetic samples and CRM (estuarine water). The results of the CRM analysis showed better recoveries with respect to the external calibration for Cd, Mn and Ni, and similar results for Cu and Pb.

Determination of trace concentrations of dissolved nitric oxide in a biological buffer.

A new real-time method for measuring a trace concentration of nitric oxide (NO) in a complex matrix routinely used in pharmacological studies of its bioactivity is described. NO was quantified as a gas by chemiluminescence after extraction from a continuous liquid sample flow with a limit of detection of 0.042 nmol dm(-3) at a signal to noise ratio of 3. Theories to calculate the concentration of NO in the liquid sample flow from a direct measurement of NO in the extraction carrier gas are presented. The efficiency of extraction is determined by a stopflow experiment. An example is presented of the measurement of the steady-state concentrations of NO in Krebs-bicarbonate buffer at pH 7.4 and 37 degrees C when its liquid surface is sequentially exposed to gases containing various concentrations of NO in O2 plus CO2.

Macromolecule Analysis Based on Electrophoretic Mobility in Air: Globular Proteins

Globular proteins ranging in molecular mass from 5.7 to 669 kDa were separated and analyzed using an aerosol technique based on the electrophoretic mobility of singly-charged molecular ions in air. The ions were produced by electrospraying and drying 100-nm-diameter droplets of a liquid suspension of the proteins, using ionized air to remove the droplet charge due to the spray process. The electrophoretic mobility was measured using a modified commercial continuous-flow differential mobility analyzer operated near atmospheric pressure. An unmodified commercial condensation particle counter was used for detection. The concentrations analyzed ranged from 0.02 to 200 μg of protein/mL of buffer, with a liquid sample flow rate of approximately 50 nL/min. Sampling time of 3 min was used for each complete distribution measured. The electrophoretic mobilities measured were determined entirely from air flow rates, apparatus geometry, and applied potentials. Results were expressed as electrophoretic mobility equivalent diameters using a Millikan formula.

Droplet size measurements of various nebulizers usingdifferential electrical mobility particle sizer

The Differential Electrical Mobility Particle Sizer (DMPS) was used to characterize the primary droplet size of pneumatic, electrospray, and thermospray nebulizers. Some of these nebulizers have been used to process liquid samples for analysis by mass spectrometry and atomic spectrometry. The nebulizer's primary droplet size and monodispersity may significantly affect the detection limits of these techniques.This study presents size distribution measurements of residue particles formed by drying the dropletsfrom these nebulizers In the range of 10 to 1000 nm. Also, we studied the effect of liquid composition and liquid sample flow rate on the nebulizer's primary droplet size.

Paramagnetic Resonance Study of Liquids during Photolysis: Hydrogen Peroxide and Alcohols

Paramagnetic resonance spectra of free radicals in liquids have been studied during the course of intense irradiation with ultraviolet light. Equipment is described in which the liquid sample flows through the microwave cavity of the spectrometer and is photolyzed as it passes the sensitive region of the cavity. In this way the steady-state concentration of short-lived radicals have been observed. Temperatures from about −70° to 60°C have been used. A number of alcohols containing up to 1% H2O2 have been studied. In the absence of dissolved oxygen the main products are the radicals formed by abstraction of a hydrogen from the position alpha to the hydroxyl group. The radicals RĊHOH where R is H, CH3, C2H5, C3H7, (CH3)2CH, and C6H5 have values of aα near room temperature ranging from 14.7 to 17.4 G and g values ranging from 2.00298 to 2.00334. Those radicals with beta hydrogens have values of aβ ranging from 20.0 to 22.2 G. The ring protons of C6H5ĊHOH are inequivalent. When the alpha hydrogen is abstracted from allyl alcohol two radicals are formed that are geometric isomers with the relative abundances depending on temperature. Coupling values for all hydrogens in each isomer are given. All couplings are also given for the radicals formed from ethylene glycol and isopropyl alcohol. In many cases couplings have been measured at several temperatures. Values for hydrogens in hydroxyl groups are strongly temperature dependent and in some cases become zero. Alpha and beta coupling constants are less temperature dependent. The various results are discussed. In the presence of dissolved oxygen, peroxy radicals are formed and their spectra are discussed. Their linewidths are strongly dependent on temperature and on concentration of dissolved oxygen. Radicals have been seen in photolyzed hydrogen peroxide solutions for concentrations ranging from 10% to 45%. In the presence of acid a single absorption line is observed. Without the acid the spectra are complex. These results are also discussed.