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1.
A miniaturized fluorescence detector utilizing a three-dimensional windowless flow cell has been constructed and evaluated. The inlet and outlet liquid channels are collinear and are located in the same plane as the excitation paths, while the optical fiber used to collect the emission light is perpendicular to this plane. The straightforward arrangement of the flow path minimizes band dispersion and eliminates bubble formation or accumulation inside the cell. The use of high-brightness light-emitting diodes (LEDs) as the excitation source and a miniaturized metal package photomultiplier tube (PMT) results in a compact and sensitive fluorescence detector. The detection limit obtained from the system for fluorescein isothiocyanate (FITC) in flow injection mode is 2.6 nmol/L. The analysis of riboflavin and FITC by packed capillary liquid chromatography is demonstrated.
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2.
Laser-induced breakdown spectroscopy (LIBS) in liquids using a double-pulse Q-switched Nd:YAG laser system has provided reliable
results that give trace detection limits in water. Resonant laser excitation has been added to enhance detection sensitivity.
A primary laser pulse (at 532 nm), transmitted via an optical fiber, induces a cavitation bubble and shockwave at a target
immersed in a 10 mg l−1–100 mg l−1 indium (In) water suspension. The low-pressure rear of the shockwave induces bubble expansion and a resulting reduction in
cavity pressure as it extends away from the target. Shortly before the maximum diameter is expected, a secondary laser pulse
(also at 532 nm) is fed into the bubble in order to reduce quenching processes. The plasma field generated is then resonantly
excited by a fiber-guided dye laser beam to increase detection selectivity. The resulting resonance fluorescence emission
is optically detected and processed by an intensified optical multichannel analyzer system.
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3.
Thin nanoporous alumina obtained by anodization of aluminum films offers promising advantages for application in fluorescence-based biological sensors including convenient preparation, increased density of binding sites, and improved collection efficiency of fluorescence. These advantages are illustrated in the detection of streptavidin using biotin covalently bound to the surface of alumina nanopores. Fluorescence intensity enhancement as high as 7 times is observed in nanopores in comparison to flat glass surface.
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4.
The paper reviews the state-of-art for micro optical fluidic systems (MOFS), or optofluidics, which employs optics and fluidics
in a microsystem environment to perform novel functionalities and in-depth analysis in the biophysical area. Various topics,
which include the introduction of MOFS in biomedical engineering, the implementation of near-field optics and also the applications
of MOFS to biophysical studies, are discussed. Different optical detection techniques, such as evanescent wave, surface plasmon
resonance, surface enhanced Raman scattering, resonators and transistors, have been studied extensively and integrated into
MOFS. In addition, MOFS also provides a platform for various studies of cell biophysics, such as cell mass determination and
cell Young’s modulus measurement.
Figure Cell encapsulation and trapping for refractive index measurement in MOFS 相似文献
5.
Because variability exists within populations of cells, single-cell analysis has become increasingly important for probing
complex cellular environments. Capillary electrophoresis (CE) is an excellent technique for identifying and quantifying the
contents of single cells owing to its small volume requirements and fast, efficient separations with highly sensitive detection.
Recent progress in both whole-cell and subcellular sampling has allowed researchers to study cellular function in the areas
of neuroscience, oncology, enzymology, immunology, and gene expression.
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6.
7.
Lapainis T Scanlan C Rubakhin SS Sweedler JV 《Analytical and bioanalytical chemistry》2007,387(1):97-105
A laser-induced native fluorescence detection system optimized for analysis of indolamines and catecholamines by capillary
electrophoresis is described. A hollow-cathode metal vapor laser emitting at 224 nm is used for fluorescence excitation, and
the emitted fluorescence is spectrally distributed by a series of dichroic beam-splitters into three wavelength channels:
250–310 nm, 310–400 nm, and >400 nm. A separate photomultiplier tube is used for detection of the fluorescence in each of
the three wavelength ranges. The instrument provides more information than a single-channel system, without the complexity
associfated with a spectrograph/charge-coupled device-based detector. With this instrument, analytes can be separated and
identified not only on the basis of their electrophoretic migration time but also on the basis of their multichannel signature,
which consists of the ratios of relative fluorescence intensities detected in each wavelength channel. The 224-nm excitation
channel resulted in a detection limit of 40 nmol L−1 for dopamine. The utility of this instrument for single-cell analysis was demonstrated by the detection and identification
of the neurotransmitters in serotonergic LPeD1 and dopaminergic RPeD1 neurons, isolated from the central nervous system of
the well-established neurobiological model Lymnaea stagnalis. Not only can this system detect neurotransmitters in these individual neurons with S/N>50, but analyte identity is confirmed on the basis of spectral characteristics.
Lapainis and Scanlan contributed equally to this work. 相似文献
8.
A novel quartz device has been designed to trap arsine and selenium hydride and subsequently to volatilize the collected analyte
and atomize it for atomic-absorption spectrometric detection. The device is actually the multiple microflame quartz-tube atomizer
(multiatomizer) with inlet arm modified to serve as the trap and to accommodate the oxygen-delivery capillary used to combust
hydrogen during the trapping step. The effect of relevant experimental conditions (trap temperature during trapping and hydrogen
flow rate and trap temperature during volatilization) on collection and volatilization efficiency was investigated. Under
the optimum conditions collection and volatilization efficiency for arsenic and selenium were 50 and 70%, respectively.
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9.
Towards biochips using microstructured optical fiber sensors 总被引:2,自引:0,他引:2
Rindorf L Høiby PE Jensen JB Pedersen LH Bang O Geschke O 《Analytical and bioanalytical chemistry》2006,385(8):1370-1375
In this paper we present the first incorporation of a microstructured optical fiber (MOF) into biochip applications. A 16-mm-long
piece of MOF is incorporated into an optic-fluidic coupler chip, which is fabricated in PMMA polymer using a CO2 laser. The developed chip configuration allows the continuous control of liquid flow through the MOF and simultaneous optical
characterization. While integrated in the chip, the MOF is functionalized towards the capture of a specific single-stranded
DNA string by immobilizing a sensing layer on the microstructured internal surfaces of the fiber. The sensing layer contains
the DNA string complementary to the target DNA sequence and thus operates through the highly selective DNA hybridization process.
Optical detection of the captured DNA was carried out using the evanescent-wave-sensing principle. Owing to the small size
of the chip, the presented technique allows for analysis of sample volumes down to 300 nL and the fabrication of miniaturized
portable devices.
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10.
An X-ray fluorescence method (XRF) is presented that allowed low detection limits (at the 0.1–23 ng mL−1 level) to be obtained for Cr, Mn, Fe, Ni, Zn, Sr, Pb, Bi and Br in water. The samples were prepared using a thin layer method. Trace elements were determined via the calibration curve and standard addition. Absorption effects and inhomogenities in prepared samples were checked for using the emission–transmission method and internal standards, respectively. The results from the XRF method were compared with the results from the inductively coupled plasma atomic emission spectrometry method.
相似文献
11.
The objective of this research was to investigate nanoindentation-induced residual stresses in human enamel using Raman microspectroscopy
and establish if this approach can be used as a stress meter. Healthy human premolars and sintered hydroxyapatite samples
were embedded, cut, and the surfaces were polished finely with a 0.05 μm polishing paste before Berkovich and spherical indentations
were made with a force of 100 mN. Spectra were collected using a Renishaw Raman InVia reflex microscope equipped with an air-cooled
charge-coupled device (CCD) camera. Sample excitation was achieved using either an argon ion laser emitting at 514.5-nm or
a NIR diode laser emitting at 830-nm. The residual micro stresses within and surrounding the indentation impressions were
monitored by mapping the position of the ν1(PO4) band of (crystalline) hydroxyapatite. The Raman maps coincided well with the optical micrographs of the samples. Despite
the presence of a fluorescence background from the organic component of human enamel, spectra collected using 514.5-nm excitation
exhibited more significant shifts in the position of the ν1(PO4) band than spectra collected using 830-nm excitation. This implies that the former excitation may be a more appropriate excitation
for stress detection. It was concluded that Raman microspectroscopy provides a novel high-resolution and non-destructive method
for exploring the role of microstructure on the residual stress distribution within natural biocomposites.
Figure Stress maps of nanoindentation impressions on both human enamel and hydroxyapatite disk via Raman Microspectroscopy 相似文献
12.
Short oxidized multi-walled carbon nanotubes (CNT) were derivatized with fluorescein isothiocyanate (FITC). Capillary electrophoresis
coupled with laser-induced fluorescence (CE–LIF) was then used to separate and detect the fluorescently labeled carbon-nanotube
probes (CNTP) in multidrug-resistant cells (K562A) and the parent cells (K562S). Greater expression of P-glycoprotein in K562A
cells than in K562S cells was confirmed by use of anti-P-glycoprotein antibody and flow-cytometric analysis. Analyses of CNTP
in both cell lines using both CE–LIF and flow cytometry showed that CNTP could traverse the cellular membrane without being
pumped out by P-glycoprotein. The CNTP distributed in both cell lines was analyzed at the single cell level and the results
were compared with those from analysis of ten cells and of the lysate from bulk cells. The results revealed the CE–LIF method
could be used for quantitative analysis of CNT in single cells in studies of drug delivery and multidrug resistance.
相似文献
13.
Martinez Vazquez R Osellame R Cretich M Chiari M Dongre C Hoekstra HJ Pollnau M van den Vlekkert H Ramponi R Cerullo G 《Analytical and bioanalytical chemistry》2009,393(4):1209-1216
We use direct femtosecond laser writing to integrate optical waveguides into a commercial fused silica capillary electrophoresis
chip. High-quality waveguides crossing the microfluidic channels are fabricated and used to optically address, with high spatial
selectivity, their content. Fluorescence from the optically excited volume is efficiently collected at a 90° angle by a high
numerical aperture fiber, resulting in a highly compact and portable device. To test the platform we performed electrophoresis
and detection of a 23-mer oligonucleotide plug. Our approach is quite powerful because it allows the integration of photonic
functionalities, by simple post-processing, into commercial LOCs fabricated with standard techniques.
Figure Femtosecond laser written waveguides can selectively excite fluorescence in a microfluidic channel of a commercial lab-on-a-chip.
A compact scheme for on-chip detection by laser induced fluorescence is applied to capillary electrophoresis of a 23-mer Cy3-labeled
oligonucleotide 相似文献
14.
This paper reports on an integrated analytical approach for the noninvasive characterization of Chinese nephrite samples,
encompassing both geological reference specimens and museum objects. Natural variations induced by cationic substitutions,
as well as human-induced alterations such as heating, which both affect color, are the focus of this contribution. Totally
noninvasive methods of analysis were used, including X-ray fluorescence spectroscopy, Raman microspectroscopy, visible reflectance
spectroscopy and X-ray diffraction; moreover, the feasibility of using a portable Raman spectrometer for the in-field identification
of jades has been demonstrated. Fe/Fe+Mg (% p.f.u.) ratios of the jades have been calculated based on hydroxyl stretching
Raman bands, which will provide an important addition to similar data that are being collected at major museums in the Western
and Eastern hemispheres.
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15.
Sensor technology and its application in environmental analysis 总被引:1,自引:0,他引:1
Environmental analysis is one of the fundamental applications of chemical sensors. In this review we describe different sensor
systems for the gas and liquid phases that have been tested either with real-life samples or in the field during the last
five years. Most field sensors rely either on electrochemical or optical transducers. In the gas phase, systems have been
proposed for analysis of oxides of nitrogen, carbon, and sulfur in air, and volatile organic compounds. In the liquid phase,
most detection systems used for real-life samples detect heavy-metal ions or organic contamination, for example pesticides,
organic solvents and polycyclic aromatic hydrocarbons.
Figure Chemical sensors for real-life environmental applications
Dedicated to Professor Ulrich Nickel on the occasion of his 65th birthday. 相似文献
16.
Chen XW Xu ZR Qu BY Wu YF Zhou J Zhang HD Fang J Wang JH 《Analytical and bioanalytical chemistry》2007,388(1):157-163
Bead injection in a lab-on-valve (LOV) system was adopted for DNA purification via micro solid-phase extraction (SPE) with
a renewable silica microcolumn packed in a channel of the LOV unit. The complex matrix components in human whole blood, including
proteins, were well eliminated by choosing properly the sample loading and elution media. The DNA purification process was
monitored on-line by using laser-induced fluorescence in a demountable side part of the LOV unit incorporating optical fibers.
The practical applicability of the entire system was demonstrated by separation/purification of λ-DNA in a simulated matrix
and human blood genetic DNA by performing SPE, in situ monitoring of the purified products, and postcolumn PCR amplification.
When DNAs in a simulated matrix (10.0 ng μl−1 λ-DNA, 50 ng μl−1 bovine serum albumin, 1.0% Triton X-100) were processed in the present system and laser-induced fluorescence was monitored
at 610 nm, an overall extraction/collection efficiency of 70% was achieved by employing identical sample loading and an elution
flow rate of 0.5 μl s−1, along with a precision of 3.8% relative standard deviation. DNA separation and purification from human whole-blood samples
were performed under similar conditions.
Figure Lab-on-valve mesofluidic system employed for DNA separation and purification integrating a demountable fluorescence flow cell
for in-situ laser induced fluorescence detection 相似文献
17.
A method based on use of functionalized gold nanoparticles on polyethylenimine film has been developed for colorimetric detection of immunoglobulin G (IgG). The immunogold nanoparticles were immobilized on quartz slides by recognition between antibody and antigen, with the antigen chemically adsorbed on the polyethylenimine film. By measurement of the UV–visible spectra of the immobilized immunogold, detection of h-IgG was achieved. The detection limit for h-IgG by use of this method can be as low as 0.01 μg mL−1. This method is quite promising for numerous applications in immunoassay.
Figure 相似文献
18.
Amino acids are important targets for metabolic profiling. For decades, amino acid analysis has been accomplished by either
cation-exchange or reversed-phase liquid chromatography coupled to UV absorbance or fluorescence detection of pre-column or
post-column-derivatized amino acids. Recent years have seen great progress in the development of direct-infusion or hyphenated
mass spectrometry in the analysis of free amino acids in physiological fluids, because mass spectrometry not only matches
optical detection in sensitivity, but also offers superior selectivity. The advent of cryo-probes has also brought NMR spectroscopy
within the detection limits required for the analysis of free amino acids. But there is still room for further improvement,
including expansion of the analyte spectrum, reduction of sample preparation and analysis time, automation, and synthesis
of affordable isotope standards.
Figure Fully automated gas chromatography-mass spectrometry analysis of amino acids. 相似文献
19.
We report a simple method that combines dialysis, as a purification method, with the multielement capability of ICP to determine
the titanium-to-transferrin mole ratio at physiological pH, under buffer conditions. The method, by means of which titanium
and transferrin are determined simultaneously, enabled us to assess the binding capacities of different titanocene complexes.
Figure Titanocene dichloride 相似文献
20.
Webb A 《Analytical and bioanalytical chemistry》2007,388(3):525-528
Figure Schematic diagram of a typical arrangement used for hyphenating chemical microseparations (e.g. capillary HPLC, CE, or CEC)
with microcoil NMR detection 相似文献