共查询到20条相似文献,搜索用时 15 毫秒
1.
A. A. Zhirkov O. V. Razvazhnaya T. A. Kazakova D. B. Petrenko M. A. Proskurnin Yu. M. Dedkov B. K. Zuev 《Journal of Analytical Chemistry》2011,66(12):1180-1185
The conditions for the thermal lens quantification of boron in aqueous solutions with a detection limit of 0.3 ng/mL are found (λ = 532 nm, laser power 40 mW); this value of the detection limit is an order of magnitude lower than that attainable in conventional spectrophotometry. A 1: 1 composition of an aqueous ethylene glycol mixture is proposed, using which as a medium the detection limit for boron was reduced to 0.1 ng/mL. Using spectrophotometry and thermal lens spectrometry, boron was quantified in mineral water; the results agree with the data acquired by the reference method of inductively coupled plasma atomic emission spectrometry. 相似文献
2.
A tunable thermal lens spectrometry system was developed for microchip analysis. The system utilized a Xe lamp as an excitation source, instead of a laser. The system can measure the absorption spectrum of a turbid solution without disturbance of the light scattering background. 相似文献
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This review considers the advantages and the limitations that thermal lens spectrometry has over conventional spectrophotometry for the measurement of optical absorption in specific applications. The photothermal method is characterized by its intrinsic sensitivity resulting from the indirect nature of the measurement and amplified by physical and thermo-optical parameters which are not effective in absorbance measurements. Other advantages include a weak dependence on light scattering and the complementary nature of photothermal spectra with respect to absorption and emission spectra for speciation studies at very low concentrations. The main drawbacks are the convective noise, the background absorbance and the complexity of the experimental set-up, especially when differential or wavelength scanning measurements are required. 相似文献
4.
The concentration gradient (Soret effect) induced in cw-laser thermal lens spectrometry subsequently to the formation of the thermal gradient (thermal lens effect) has been investigated in aqueous solutions of various macromolecular species including micelles, mixed micelles and polymers. It is shown that the build-up of the concentration gradient is much shorter than that in classical Soret experiments, reaching steady-state values in less than 1 min. The time evolution of the Soret signal has been used to derive mass-diffusion times from which mass-diffusion coefficients were calculated. Our data are in agreement with previous results obtained from quasi-elastic light scattering studies for the micellar solutions and calculated from a known molecular weight-dependent power law for polymer solutions. 相似文献
5.
B. K. Zuev P. A. Gorkin M. A. Proskurnin A. A. Zhirkov 《Journal of Analytical Chemistry》2009,64(4):379-385
A new technique for the generation of a thermal lens effect is considered. In this technique, the action of focused radiation from an inducing laser is replaced by an analogous action of electric current, which forms a thermal lens at a certain site of a liquid by the generation of a high local current density in a small liquid volume. The main regularities of this technique for thermal lens signal generation are considered, and an expression is derived to relate the detected signal (a relative change in probing radiation intensity at the detector) and the electrolyte concentration. A cell is proposed for electroinduced thermal lens detection. The dependence of the thermal lens signal on the applied voltage and on the concentration of the test electrolyte is determined for a model electrolyte (NaCl), and sensitivity characteristics are found to be consistent with theoretical estimations made in this work. 相似文献
6.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1991,47(11):1505-1510
It is shown that the thermal lens signal of fluorescein in aqueous solutions depends on the molecular form of the solute even after correction for fluorescence. Possible factors that may affect the thermal lens response are photochemical reactions and vibration-to-translation energy transfer from the solute to the solvent. These are considered in relation to the existence of excited-state proton transfer reactions. 相似文献
7.
Manuel Caetano Leonardo Padrino T Hector Gutiérrez Alberto J. Fernández Jimmy Castillo 《Mikrochimica acta》1998,128(3-4):169-175
Trace level vanadium determination is reported using a dual beam thermal lens spectrometer. The thermal lens was generated using an argon ion beam laser (pump beam) which was focused into a sample cuvette. The thermal lens signal (TLs) was monitored with a He-Ne laser beam and a photodiode detector. Multichannel averager software was developed for processing the transient TLs. The optimal set up, ensuring maximum sensitivity and linear calibration graphs was obtained using experimental design techniques. Under optimized conditions, the detection limits for aqueous and ethanol-water (2+3 v/v) and (4+1 v/v) vanadium complex solutions were, respectively, 0.0071 mg/l, 0.0065 and 0.0039 mg/l. 相似文献
8.
Jan Houka Nagender Reddy Panyala Eladia Maria Pea‐Mndez Josef Havel 《Rapid communications in mass spectrometry : RCM》2009,23(8):1125-1131
Detonation nanodiamonds (NDs) were studied by time‐of‐flight mass spectrometry (TOF MS). The formation of singly charged carbon clusters, C, with groups of clusters at n = 1–35, n ∼160–400 and clusters with n ∼8000 was observed. On applying either high laser energy or ultrasound, the position and intensity of the maxima change and a new group of clusters at n ∼70–80 is formed. High carbon clusters consist of an even number of carbons while the percentage of odd‐numbered clusters is quite low (≤5–10%). On increasing the laser energy, the maximum of ionization (at n ∼200 carbons) is shifted towards the lower m/z values. It is suggested that this is mainly due to the disaggregation of the original NDs. However, the partial destruction of NDs is also possible. The carbon clusters (n ∼2–35) are partially hydrogenated and the average value of the hydrogenation was 10–30%. Trace impurities in NDs like Li, B, Fe, and others were detected at high laser energy. Several matrices for ionizing NDs were examined and NDs themselves can also be used as a matrix for the ionization of various organic compounds. When NDs were used as a matrix for gold nanoparticles, the formation of various gold carbides AumCn was detected and their stoichiometry was determined. It was demonstrated that TOF MS can be used advantageously to analyze NDs, characterize their size distribution, aggregation, presence of trace impurities and surface chemistry. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Arnaud N Georges J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(5):1085-1092
This work investigates the effect of micelles on the time-resolved and steady-state thermal lens signals in aqueous solutions. The temperature gradient produced subsequently to non-radiative relaxation of the sample induces migration of micelles towards the colder region of the irradiated area along with an opposite flow of solute molecules. This phenomenon, known as the Soret effect, produces an additional probe beam signal with a rise time that is much longer than the thermal time constant and depends on the surfactant and solute concentrations. Extrapolation of the mass-diffusion constant at zero solute concentration allowed the determination of diffusion coefficients that are close to those derived by other methods for Brij 35 micelles in water. It is also shown that the surfactant has only a small effect on the thermal lens signal and that the enhancement produced by micelles with respect to pure water originates mainly firom the Soret effect. It follows that interpretation of experimental data without discriminating both components of the probe beam signal can lead to erroneous values of dn/dT. 相似文献
13.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1994,50(5):953-959
This paper describes some limitations of the pulsed-laser thermal lens method in measuring the heat produced by non-radiative relaxation of excited fluorescent molecules. Simultaneous measurements of the fluorescence intensity and thermal lens signal have been carried out for fluorescein dianion in water and perylene in ethanol. It is shown that complete fluorescence quenching of fluorescein and perylene by potassium iodide and nitromethane, respectively, does not result in full recovery of the thermal energy. The results depend on either the operating mode of the excitation laser or the solvent composition. 相似文献
14.
J. Amador-Hern ndez J. M. Fern ndez-Romero G. Ramis-Ramos M. D. Luque de Castro 《Analytica chimica acta》1999,390(1-3):163-173
A dual-beam thermal lens spectrometer (TLS) with a pulse pump–probe coaxial configuration was coupled to commercially available supercritical fluid extraction equipment using a high-pressure flow cell interface. Because of its feasible critical parameters, moderate cost and good thermooptical properties, carbon dioxide was used as supercritical solvent. Using trans-β-carotene as analyte, several factors related with the extraction process under continuos flow conditions were studied in order to establish their influence in the thermal lens signal magnitude. Under the optimum experimental conditions, the relative TLS signal area showed a linear relationship with the concentration of trans-β-carotene from 1.5×10−6 to 8×10−8 M (n=5, r=0.998) in the supercritical phase. Thus, the viability of on-line detection for supercritical fluid extraction with a pulse thermal lens spectrometer was demonstrated. 相似文献
15.
The determination of Al3+ in solution using a continuous-wave mode mismatched thermal lens spectrometer is reported and two spectrophotometric procedures are compared. The reagent investigated were bromopyrogallol red—tetradecyltrimethylammonium bromide (BPR—TDTA) and chrome azurol S—cetylpyridinium chloride (CAS—CPC). The CAS—CPC system gave a superior detection limit (0.17 μg 1?1) to the BPR—TDTA system (1.15 mg 1?1) owing to the higher reagent blanks and concomitant laser noise in the latter system. 相似文献
16.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1990,46(12):1737-1742
Thermal lensing of erythrosine with pulsed laser excitation may exhibit abnormal signals. It is shown that a non-thermal signal is superimposed to the 相似文献
17.
Several organic solvents, including benzene, xylene, toluene, nitrobenzene, chloroform, carbon tetrachloride, chlorobenzene and high molecular-weight pyridines such as 4-(5-nonyl)pyridine, 2-hexyl-pyridine and benzylpyridine have been investigated as components of systems for the extraction and preconcentration of selenium from nitric acid solutions containing iodide. The results are discussed in terms of choice of reagents and the acid and iodide concentrations, and of several other parameters affecting the extraction. The utility of the method for separation of selenium from aqueous solution has been evaluated. The method has been used for preconcentration of trace levels of selenium from water and hair samples for determination by atomic-absorption spectrophotometry. 相似文献
18.
Emiliano Fernández Daniel López Carmen Mijangos Miroslava Duskova‐Smrckova Michal Ilavsky Karel Dusek 《Journal of Polymer Science.Polymer Physics》2008,46(3):322-328
In this article, we report on the rheological properties of agarose aqueous solutions and gels. Viscosity curves were determined for homogeneous agarose aqueous solutions at different temperatures (from 68 to 38 °C) to study the viscosity behavior as the systems undergo gelation. The gelation phenomenon of agarose solutions was also investigated by shear oscillation experiments and differential scanning calorimetry. The gelation and melting temperature as a function of agarose concentration were determined together with the gelation and melting enthalpies. The results obtained were interpreted using the two‐step model describing the gelation of agarose in water. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 322–328, 2008 相似文献
19.
This review summarizes the most recent achievements related to the application of thermal lens spectrometry (TLS) in food analysis and environmental research. All the applications are associated with the use of an appropriate analytical procedure providing sufficient selectivity, that cannot be achieved by TLS itself. Several selective reagents, biosensors and chromatographic separation procedures (IC, HPLC), used for this purpose, and their performance in combination with TLS, are described. Heavy metals and related species, pesticides, carotenoids, fatty acids, and their determination in samples such as water, fruit juices, oils and marine phytoplankton were given most consideration. The main advantages of novel analytical methods include improved sensitivity and selectivity, simplicity, minimized need for sample preparation and handling as well as reduced time of analysis. 相似文献
20.
I. A. Korobeinikova G. B. Pronchev A. N. Ermakov 《Journal of Analytical Chemistry》2011,66(8):740-744
Model aqueous solutions containing micro impurities of iron(III) are studied by secondary-emission mass spectrometry. The possibility of using this method for the analysis of rain deposits and samples of atmospheric aerosols is discussed. 相似文献