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1.
Molecules ; 25(11)2020 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-32481516

RESUMO

Endohedral metal fullerene are potential nanopharmaceuticals for MRI; thus, it is important to study their effect on reactive oxygen species (ROS) homeostasis. Superoxide anion radical is one of the key ROS. The reactivity of aqueous dispersions of pristine (non-functionalized) fullerenes and Gd@C82 endofullerene have been studied with respect to superoxide in the xanthine/xanthine oxidase chemiluminescence system. It was found that C60 and C70 in aqueous dispersions react with superoxide as scavengers by a similar mechanism; differences in activity are determined by cluster parameters, primarily the concentration of available, acting molecules at the surface. Gd endofullerene is characterized by a significantly (one-and-a-half to two orders of magnitude) higher reactivity with respect to C60 and C70 and is likely to exhibit nanozyme (SOD-mimic) properties, which can be accounted for by the nonuniform distribution of electron density of the fullerene cage due to the presence of the endohedral atom; however, in the cell model, Gd@C82 showed the lowest activity compared to C60 and C70, which can be accounted for by its higher affinity for the lipid phase.

2.
Lab Chip ; 19(15): 2581-2588, 2019 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-31250849

RESUMO

High-throughput fluorescence polarization immunoassays (FPIAs) for mycotoxin were conducted using a portable FP analyzer with a microdevice. Simultaneous FPIA measurements for 8 different deoxynivalenol (DON) concentrations in 12 chambers (total of 96 samples) and high-throughput FPIA measurements for single DON concentrations in more than 500 chambers were conducted. The results indicated that simultaneous FPIAs for 96 independent samples and for 500 samples were possible by FP imaging. The FP analyzer has a size of 65 cm (W 35 cm × D 15 cm × H 15 cm) and costs less than $5000. The sample volume was 1 nL. Furthermore, it is expected that sample reaction and FP detection can be automatically conducted with the analyzer by changing the microdevice and the software. Its features such as low cost and portability will contribute to on-site measurement and point-of-care testing. Additionally, the high-throughput feature will contribute to the study of molecular interactions based on FP measurements.

3.
Lab Chip ; 18(2): 356-361, 2018 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-29264613

RESUMO

We herein report the preparation of a surface that behaves in a hydrophobic manner but does not undergo protein adsorption in an aqueous/organic two-phase system. We found that polyethylene-glycol (PEG)-modified poly(dimethylsiloxane) (PDMS) exhibits hydrophobic properties when the surface is immersed in an organic solution, while the PEG moiety prevents protein adsorption on the PDMS surface in an aqueous solution at high protein concentrations due to the dynamic behaviour of the PEG moiety. As such, we demonstrated the in-well droplet formation of an aqueous solution containing a high protein concentration. In addition, to demonstrate the feasibility of this method in single cell analyses, a droplet array of a liquid medium containing 10% fetal bovine serum and HeLa cells was formed. The preparation of a droplet array using our PDMS-PEG surface to promote in-well droplet formation avoided the use of flow control equipment and complicated microstructures. We therefore expect that the dynamic wettability of our reported surface will be applicable in single cell and biochemical analyses, such as protein characterisation using crystallography or immunoassays.


Assuntos
Dimetilpolisiloxanos/química , Técnicas Analíticas Microfluídicas/instrumentação , Polietilenoglicóis/química , Análise de Célula Única/instrumentação , Molhabilidade , Adsorção , Células HeLa , Humanos , Interações Hidrofóbicas e Hidrofílicas , Técnicas Analíticas Microfluídicas/métodos
4.
Talanta ; 174: 206-213, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-28738569

RESUMO

Determination of chromophores of various classes-rosaniline (fuchsine), cyanidin-3-O-glucoside, tris(1,10-phenanthroline) iron(II), and phenol red - in their concentrated solutions near their solubility limits is performed with the optoacoustic technique for optically dense solutions; light-absorption coefficients of samples range from 0.5 to 500cm-1. The assessment of these substances in organo-aqueous and organic solvents is possible up to ca. 0.1molL-1. Characteristic stability and rate constants of the chelation of iron(II) with 1,10-phenanthroline are determined. It was found that turbidities up to 200 FTU and dynamic viscosities up to 20mPas do not affect the determination. The determination of total anthocyanins (as cyanidin-3-O-glucoside) in bilberry and sweet-cherry juices agrees with the reference spectrophotometric method and demonstrates the possibilities of the optoacoustic technique for the analysis of real samples without dilution and with almost no sample preparation.


Assuntos
Acústica , Antocianinas/análise , Fenômenos Químicos , Fenômenos Ópticos , Absorção Fisico-Química , Antocianinas/química , Calibragem , Cor , Análise de Alimentos , Soluções
5.
Anal Cell Pathol (Amst) ; 2016: 2642361, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27699143

RESUMO

Control of sickle cell disease (SCD) stage and treatment efficiency are still time-consuming which makes well-timed prevention of SCD crisis difficult. We show here that in vivo photoacoustic (PA) flow cytometry (PAFC) has a potential for real-time monitoring of circulating sickled cells in mouse model. In vivo data were verified by in vitro PAFC and photothermal (PT) and PA spectral imaging of sickle red blood cells (sRBCs) expressing SCD-associated hemoglobin (HbS) compared to normal red blood cells (nRBCs). We discovered that PT and PA signal amplitudes from sRBCs in linear mode were 2-4-fold lower than those from nRBCs. PT and PA imaging revealed more profound spatial hemoglobin heterogeneity in sRBCs than in nRBCs, which can be associated with the presence of HbS clusters with high local absorption. This hypothesis was confirmed in nonlinear mode through nanobubble formation around overheated HbS clusters accompanied by spatially selective signal amplification. More profound differences in absorption of sRBCs than in nRBCs led to notable increase in PA signal fluctuation (fluctuation PAFC mode) as an indicator of SCD. The obtained data suggest that noninvasive label-free fluctuation PAFC has a potential for real-time enumeration of sRBCs both in vitro and in vivo.


Assuntos
Anemia Falciforme/diagnóstico , Técnicas Fotoacústicas/métodos , Análise de Célula Única/métodos , Animais , Eritrócitos/patologia , Hemoglobina Falciforme , Humanos , Camundongos Endogâmicos C57BL , Dinâmica não Linear , Análise Espectral
6.
Anal Sci ; 32(1): 11-21, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26753700

RESUMO

Fundamental aspects of rapidly advancing micro/nanofluidic devices are reviewed from the perspective of liquid interface chemistry and physics, including the influence of capillary pressure in microfluidic two-phase flows and phase transitions related to capillary condensation.

7.
Anal Sci ; 32(1): 23-30, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26753701

RESUMO

Efficient environment protection and human safety require high-throughput analysis techniques for pollutants or toxicants for large sample sets. State-of-the-art HPLC and GC coupled to various detecting strategies offer excellent sensitivity and selectivity, though they are quite time-extensive (2 - 3 samples/h or less when sample preparation is involved). Efforts are made towards screening techniques with high sample throughputs simultaneously providing detection limits below the maximum contaminant levels for the analyte. However, such approaches frequently sacrifice the selectivity or sensitivity (or just give a yes/no response). In this review, we demonstrate thermal-lens spectrometry and microscopy as highly sensitive spectrometric techniques in combination with flow-injection analysis (FIA) and microfluidic FIA along with lab-on-a-chip chemistry for fast screening (several samples/h and up to 20 samples/min) exemplified by organophosphates and carbamates as neurotoxigenic compounds. Various approaches to determining other topical toxicants, like microcystin and cyanopigments as its indicators, allergens, and carcinogenic chromate, are also discussed.


Assuntos
Poluentes Ambientais/análise , Substâncias Perigosas/análise , Dispositivos Lab-On-A-Chip , Técnicas Analíticas Microfluídicas/métodos , Neurotoxinas/análise , Análise Espectral/métodos , Carbamatos/análise , Desenho de Equipamento , Análise de Injeção de Fluxo , Técnicas Analíticas Microfluídicas/instrumentação , Microscopia/instrumentação , Microscopia/métodos , Organofosfatos/análise , Sensibilidade e Especificidade , Análise Espectral/instrumentação , Temperatura
8.
Appl Spectrosc ; 67(7): 709-17, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23816121

RESUMO

Procedures for the photothermal lens determination of metals and organic compounds, on the basis of solid-phase mesoporous optical-sensing materials (polymethacrylate [PMA]) matrices with immobilized reagents, were developed. These procedures combine (i) selective and efficient preconcentration of trace substances to be analyzed in specially designed and synthesized transparent mesoporous PMA plates; (ii) sensitive determination with the reliable and traceable photometric reactions previously developed for classical spectrophotometry; and (iii) the sensitivity enhancement of photothermal lens detection in polymers, which provides at least a ten-fold increase in sensitivity compared with solutions due to polymer thermo-optical properties (solid phase-enhanced thermal lensing). It is shown that the overall sensitivity of photothermal lens measurements in PMA matrices is two orders higher than photometric absorbance measurements for the same excitation source power, which is in good agreement with the expected theoretical sensitivity. Changes in the preparation of transparent PMA plates and analytical procedures for photothermal measurements compared with spectrophotometry are discussed. PMA matrices modified with various analytical reagents were applied to trace determination of Hg(II), Fe(II), Ag(I), Cu(II), and ascorbic acid, with subnanomolar to nanomolar limits of detection.


Assuntos
Ácido Ascórbico/análise , Ácido Ascórbico/química , Metais/análise , Metais/química , Microquímica/métodos , Ácidos Polimetacrílicos/química , Espectrofotometria/métodos , Calefação/métodos , Lentes , Luz , Microquímica/instrumentação , Porosidade , Espectrofotometria/instrumentação
9.
Nanoscale ; 5(4): 1529-36, 2013 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-23314800

RESUMO

Detonation nanodiamond (ND) is a suitable source material to produce unique samples consisting of almost uniform diamond nanocrystals (d = 3-5 nm). Such samples exist in the form of long stable aqueous dispersions with narrow size distribution of diamond particles. The material is finding ever increasing application in biomedicine. The major problem in producing monodispersed diamond colloids lies in the necessity of deagglomeration of detonation soot and/or removing of clusters formed by already isolated core particles in dry powders. To do this one must have an effective method to monitor the aggregation state or dispersity of powders and gels prior to the preparation of aqueous dispersions. In the absence of dispersity control at various stages of preparation the reproducibility of properties of existing ND materials is poor. In this paper we introduce differential scanning calorimetry (DSC) as a new tool capable to distinguish the state of aggregation in dry and wetted ND materials and to follow changes in this state under different types of treatment. Samples with identical X-ray diffraction patterns (XRD) and high resolution transmission electron microscopy (HRTEM) images gave visibly different DSC traces. Strong correlation was found between dynamic light scattering (DLS) data for colloids and DSC parameters for gels and powders of the same material. Based on DSC data we improved dispersity of existing ND materials and isolated samples with the best possible DSC parameters. These were true monodispersed easily dispersible fractions of ND particles with diameters of ca. 3 nm.


Assuntos
Varredura Diferencial de Calorimetria/métodos , Cristalização/métodos , Diamante/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Coloides/química , Temperatura Alta , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Pós , Propriedades de Superfície
10.
Photoacoustics ; 1(3-4): 54-61, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25302150

RESUMO

An optoacoustic technique for solutions of strongly light-absorbing analytes at 0.1-0.01 mol l(-1) is proposed. The technique is based on the wide-band forward mode detection of temporal profiles of laser-generated ultrasonic pulses (optoacoustic signals). The leading edge of the signal repeats the distribution of the laser fluence in the medium, which makes it possible to determine its optical absorption and investigate its dynamics during a reaction. The range of light-absorption coefficients starts from 1 to 5 and reaches 10(4) to 10(5) cm(-1). The determination of iron(II) as ferroin shows the possibility of probing 0.1 mol l(-1) of iron(II), which was not previously achieved for this reaction by optical spectroscopy. To further prove the concept, kinetic measurements for ferroin decomposition at the level of 0.1 mol l(-1) and at high pHs are performed. The results are compared with spectrophotometry at lower concentrations and show good reproducibility and accuracy of kinetic constants.

11.
Electrophoresis ; 33(17): 2748-51, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22965721

RESUMO

A new compact near-field desktop-sized diode laser thermal-lens microscope for analysis in microfluidics was proposed. A novel beam-alignment and detection systems provided high signal stability and, along with reduced number of optical elements rendered the instrument portable. The detection of nonfluorescent model species (Fe(II)-bathophenanthroline chelate) in water showed good linearity in the range of 5 × 10(-9) to 1 × 10(-4) M, and the limit of detection was 3.5 × 10(-9) M, which corresponded to 3.5 × 10(-7) absorbance units and provided a 20-fold enhancement in sensitivity compared with existing schematic.


Assuntos
Técnicas Analíticas Microfluídicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Microscopia/instrumentação , Análise Espectral/instrumentação , Corantes/química , Desenho de Equipamento , Lasers Semicondutores , Modelos Químicos
12.
Appl Spectrosc ; 65(11): 1275-80, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22054087

RESUMO

This paper reports simultaneous photoinduced precipitation-based online preconcentration of target analytes at the inner walls in capillary zone electrophoresis (CZE) and surface-enhanced near-field crossed-beam photothermal-lens detection of the preconcentrated analytes. A simple technique using online readjustment of the optical scheme of the thermal-lens detector in the course of the separation for gaining optimum sensitivity for both water-soluble and precipitated analytes is proposed. It provides a considerable decrease in the limits of detection (LOD) with good concordance with the previously developed theoretical approach to this combination (D. A. Nedosekin, W. Faubel, M. A. Proskurnin, and U. Pyell, Talanta, 78, 682-690 (2009)). As a result, an enhancement of more than an order of magnitude in the limit of detection of the photoactive 4-aminoazobenzene compared to conventional thermal-lens detection in CZE is achieved while retaining very good sensitivity for unabsorbed analyte (Mordant Yellow 7). The application of the thermal-lens detector to the investigation of laser-induced reactions in flow in capillaries is discussed.


Assuntos
Compostos Azo/química , Precipitação Química , Corantes/química , Eletroforese Capilar/métodos , Lasers , Compostos Azo/isolamento & purificação , Corantes/isolamento & purificação , Limite de Detecção , Espectrofotometria Ultravioleta
13.
Cytometry A ; 79(10): 834-47, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21905207

RESUMO

Recently, photoacoustic (PA) flow cytometry (PAFC) has been developed for in vivo detection of circulating tumor cells and bacteria targeted by nanoparticles. Here, we propose multispectral PAFC with multiple dyes having distinctive absorption spectra as multicolor PA contrast agents. As a first step of our proof-of-concept, we characterized high-speed PAFC capability to monitor the clearance of three dyes (Indocyanine Green [ICG], Methylene Blue [MB], and Trypan Blue [TB]) in an animal model in vivo and in real time. We observed strong dynamic PA signal fluctuations, which can be associated with interactions of dyes with circulating blood cells and plasma proteins. PAFC demonstrated enumeration of circulating red and white blood cells labeled with ICG and MB, respectively, and detection of rare dead cells uptaking TB directly in bloodstream. The possibility for accurate measurements of various dye concentrations including Crystal Violet and Brilliant Green were verified in vitro using complementary to PAFC photothermal (PT) technique and spectrophotometry under batch and flow conditions. We further analyze the potential of integrated PAFC/PT spectroscopy with multiple dyes for rapid and accurate measurements of circulating blood volume without a priori information on hemoglobin content, which is impossible with existing optical techniques. This is important in many medical conditions including surgery and trauma with extensive blood loss, rapid fluid administration, and transfusion of red blood cells. The potential for developing a robust clinical PAFC prototype that is safe for human, and its applications for studying the liver function are further highlighted.


Assuntos
Volume Sanguíneo , Meios de Contraste/análise , Eritrócitos/metabolismo , Citometria de Fluxo/métodos , Corantes Fluorescentes/análise , Imagem Molecular/métodos , Técnicas Fotoacústicas/métodos , Animais , Perda Sanguínea Cirúrgica , Meios de Contraste/metabolismo , Meios de Contraste/farmacocinética , Eritrócitos/citologia , Citometria de Fluxo/instrumentação , Corantes Fluorescentes/metabolismo , Corantes Fluorescentes/farmacocinética , Violeta Genciana/análise , Violeta Genciana/metabolismo , Violeta Genciana/farmacocinética , Hemorreologia/fisiologia , Humanos , Verde de Indocianina/análise , Verde de Indocianina/metabolismo , Verde de Indocianina/farmacocinética , Injeções Intravenosas , Cinética , Azul de Metileno/análise , Azul de Metileno/metabolismo , Azul de Metileno/farmacocinética , Camundongos , Camundongos Nus , Imagem Molecular/instrumentação , Técnicas Fotoacústicas/instrumentação , Análise Espectral , Azul Tripano/análise , Azul Tripano/metabolismo , Azul Tripano/farmacocinética
14.
Anal Sci ; 27(4): 381, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21478613

RESUMO

The main types of analytical procedures used in thermal-lens spectroscopy and microscopy, which are based on photometric reactions in (i) aqueous solutions, (ii) organo-aqueous mixtures, (iii) polymer-containing (nonionic surfactants or polyethylene glycol) aqueous solutions, (iv) water-organic extraction systems, and (v) two-phase aqueous extraction systems, were compared from the viewpoint of both reproducibility and sensitivity. This comparison was made by examples of the determination of cobalt and iron for batch conditions, flow determination, and detection in HPLC, flow-injection analysis (FIA), and µFIA. It was revealed that for all five types, the real analytical efficiency (a decrease in the limit of detection (LOD) as compared to spectrophotometry) is primarily determined by the reaction conditions, provided that excitation of the thermal lens is the same. Aqueous solutions provide more efficient optimization of reaction conditions than do those in organo-aqueous solutions and solvent-extraction water-organic mixtures. The best results are achieved when shifting to polymer-containing aqueous solutions and two-phase aqueous extraction systems, which decreases in the LODs by a factor of 20 - 100%.

15.
Appl Spectrosc ; 64(8): 942-8, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20719060

RESUMO

4-Aminophenol was selected as a model hapten for thermal-lens detection in a heterogeneous indirect immunoassay for small organic compounds. The assay is based on the competition of the free hapten and 4-aminophenol labeled with tetramethyl rhodamine isothiocyanate (TRITC) for rabbit anti-4-aminophenol antibodies (4-AP-GA-BSA) immobilized on a transparent poly(ethylene terephthalate) plate. The amount of the colored analyte was directly measured by thermal lensing at the plate surface. The developed method is specific for 4-aminophenol. The limit of detection is 2 x 10(-7) M, which corresponds to the absolute amount of 3 x 10(-11) mol of 4-aminophenol. The sensitivities of the developed thermal-lens and fluorescence-based measurements of the immunoassay under the same conditions are in good agreement with the expected and discussed theoretical sensitivities of photothermal and fluorescence measurements.

16.
J Biophotonics ; 3(12): 791-806, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20572284

RESUMO

Light-absorbing endogenous cellular proteins, in particular cytochrome c, are used as intrinsic biomarkers for studies of cell biology and environment impacts. To sense cytochrome c against real biological backgrounds, we combined photothermal (PT) thermal-lens single-channel schematic in a back-synchronized measurement mode and a multiplex thermal-lens schematic in a transient high resolution (ca. 350 nm) imaging mode. These multifunctional PT techniques using continuous-wave (cw) Ar+ laser and a nanosecond pulsed optical parametric oscillator in the visible range demonstrated the capability for label-free spectral identification and quantification of trace amounts of cytochrome c in a single mitochondrion alone or within a single live cell. PT imaging data were verified in parallel by molecular targeting and fluorescent imaging of cellular cytochrome c. The detection limit of cytochrome c in a cw mode was 5 x 10(-9) mol/L (80 attomols in the signal-generation zone); that is ca. 10³ lower than conventional absorption spectroscopy. Pulsed fast PT microscopy provided the detection limit for cytochrome c at the level of 13 zmol (13 x 10(-21) mol) in the ultrasmall irradiated volumes limited by optical diffraction effects. For the first time, we demonstrate a combination of high resolution PT imaging with PT spectral identification and ultrasensitive quantitative PT characterization of cytochrome c within individual mitochondria in single live cells. A potential of far-field PT microscopy to sub-zeptomol detection thresholds, resolution beyond diffraction limit, PT Raman spectroscopy, and 3D imaging are further highlighted.


Assuntos
Citocromos c/metabolismo , Diagnóstico por Imagem/métodos , Células KB/metabolismo , Mitocôndrias/metabolismo , Análise Espectral/métodos , Diagnóstico por Imagem/instrumentação , Humanos , Células KB/citologia , Microscopia de Fluorescência/métodos , Fotometria/instrumentação , Fotometria/métodos , Sensibilidade e Especificidade , Análise Espectral/instrumentação
17.
Talanta ; 81(1-2): 377-84, 2010 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-20188934

RESUMO

As a primary aim, several approaches to photothermal (thermal-lens) and optoacoustic determination of exogenous pyrogens (lipopolysaccharides) based on photometric procedures for their determination at the microgram level and below are compared. The limits of detection of lipopolysaccharides by thermal-lens spectrometry and optoacoustic spectroscopy are at a level of 2-100 ng/mL, and the conditions of optoacoustic and photothermal procedures are the same. Optoacoustic spectroscopy is advantageous in determining suspensions, while thermal lensing is superior in determining lipopolysaccharides from homogenous aqueous solutions. As a secondary aim, photometric procedures for lipopolysaccharides by the formation of their ion pairs with several dyes and by the reaction of 2-keto-3-deoxyoctulosonic acid as a part of a lipopolysaccharide molecule with thiobarbituric acid are optimized. In the case of the 2-keto-3-deoxyoctulosonic acid reaction, the sampling stage time is decreased twofold, and the possibility of substitution of the toxic metaarsenite for sulfite with better sensitivity is shown.


Assuntos
Lentes , Lipopolissacarídeos/análise , Fenômenos Ópticos , Análise Espectral/métodos , Temperatura , Lasers , Ácido Periódico/química , Substâncias Redutoras/química , Açúcares Ácidos/química , Sulfitos/química , Tiobarbitúricos/química
18.
Anal Sci ; 25(5): 611-6, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19430141

RESUMO

The possibility of thermal lensing of dynamically emerging light-absorbing layers at cell surfaces was investigated. Analyte accumulation at a cell surface determines long-term changes in the thermal-lens signal that was used as a source of analytical information to enhance sensitivity of thermal lensing. Considering the rate of accumulation as an additional analytical signal, we achieved a threefold decrease in the limits of detection for 4-aminoazobenzene to the level of 7 microM in a batch mode with the same level of reproducibility. The details of observed thermal-lens signal behavior in cells are discussed. The possibilities to use thermal-lens detection for 4-aminoazobenzene determination in quartz capillaries in flow mode were discussed and a drastic thermal-lens signal enhancement was discovered. The corresponding limit of detection for 4-aminoazobenzene in a flow mode is further decreased to the level of 3 microM.

19.
Opt Lett ; 34(5): 680-2, 2009 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-19252591

RESUMO

A new spectroelectrochemical method using the thermal-lens effect from electrolytes using regular joule heat generation by current focusing in a small-sized channel is proposed. The experimental dependences of the signal on the analyte concentration and applied voltage are in good concordance with the theoretical estimations. A cell design providing good reproducibility and sensitivity of measurements is proposed.

20.
Electrophoresis ; 29(13): 2741-53, 2008 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-18546176

RESUMO

In this paper, we compared the methods of photothermal spectroscopy used in different spatial scales, namely thermal-lens spectrometry (TLS) and thermal-lens microscopy (TLM) to enhance the performance parameters in analytical procedures. All of the experimental results were confirmed by theoretical calculation. It was proven that the design for both TLM and TLS, despite a different scale for the effect, is governed by the same signal-generating and probing conditions (probe beam diameter at the sample should be equal to the diameter of the blooming thermal lens), and almost does not depend on the nature of the solvent. Theoretical and experimental instrumental error curves for thermal lensing were coincident. TLM obeys the same law of instrumental error as TLS and shows better repeatability for the same levels of thermal-lens signals or absorbances. TLS is more advantageous for studying low concentrations in bulk, while TLM shows much lower absolute LODs due to better repeatability for low amounts. The behavior of the thermal-lens signal with different flow rates was studied and optimum conditions, with the minimum contribution to total error, were found. These conditions are reproducible, are in agreement with the existing theory of the thermal response in thermal lensing, and do not significantly affect the design of the optimum scheme for setups. TLM showed low LODs in solvent extraction (down to 10(-8) M) and electrokinetic separation (10(-7) M), which were shown to be governed by discussed instrumental regularities, instead of by microchemistry.


Assuntos
Dispositivos Lab-On-A-Chip , Lentes , Microscopia/instrumentação , Análise Espectral/instrumentação , Técnicas Analíticas Microfluídicas/instrumentação , Óptica e Fotônica/instrumentação , Fotometria/instrumentação , Reprodutibilidade dos Testes , Solventes/química
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