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World Congress on Biosensors 2014

World Congress on Biosensors 2014
Biosensors 2014

Monday, 24 December 2012

Just Published: Spectrochimica Acta Part B: Atomic Spectroscopy


A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Spectrochimica Acta Part B: Atomic Spectroscopy
http://rss.sciencedirect.com/publication/science/5287
Selected papers from the latest issue:

A dried urine spot test to simultaneously monitor Mo and Ti levels using solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry

24 December 2012, 09:33:37
Available online 21 December 2012
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy

Home-based collection protocols for clinical specimens are actively pursued as a means of improving life quality of patients that require frequent controls, such as patients with metallic prosthesis, for whom monitoring the evolution of Mo and Ti in biological fluids may play a decisive role to detect prosthesis mal-functioning. The collection of biological fluids on clinical filter papers provides a simple way to implement these protocols. This work explores the potential of solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry for the simultaneous and direct determination of Mo and Ti in urine, after its deposition onto clinical filter paper, giving rise to a dried urine spot. The approach used for depositing the sample was found crucial to develop a quantitative method, since the filter paper acts as a chromatographic support and produces a differential distribution of the target analytes. Furthermore, the high spreading of urine onto a filter paper results in a small amount of urine per surface unit, and thus, ultimately, in lack of sensitivity. In order to circumvent these problems, the use of an alternative approach based on the use of pre-cut 17x19 mm filter paper pieces onto which larger amounts of sample (500 μL) can be retained by single deposition was proposed and evaluated. In this way, an approximately 12-fold increase in sensitivity and a more homogeneous distribution of the target analytes were obtained, permitting the development of a quantification strategy based on the use of matrix-matched urine samples of known analyte concentrations, which were subjected to the same procedure as the samples. Accuracy of this method, which provides LODs of 1.5μgL-1 for Mo and 6.5μgL-1 for Ti, was demonstrated after analysis of urine reference materials. Overall, the performance of the method developed is promising, being likely suitable for determination of other analytes in dried urine spots.

Highlights

► deposition of urine on clinical filters is a simple way to implement home-base collection procedures to monitor patient's evolution ► solid sampling HR CS GFAAS is investigated for the direct determination of Mo and Ti, used as biomarkers to detect prosthesis malfunctioning, in urine dried spots; ► the way in which the sample is deposited in the filter is key to ensure sufficient sensitivity and to avoid chromatographic effects; ► use of matrix-matched urine standards for calibration is proposed, permitting achieving accurate results and LODs of a few μgL-1;

Hydride generation - in-atomizer collection of Pb in a quartz trap-and-atomizer device for atomic absorption spectrometry – an interference study

24 December 2012, 09:33:37
Available online 21 December 2012
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy

Interferences of selected hydride forming elements (As, Sb, Bi, Se and Sn) on lead determination by hydride generation atomic absorption spectrometry were extensively studied in both on-line atomization and preconcentration (collection) modes. The commonly used on-line atomization mode was found free of significant interferences, whereas strong interference from Bi was observed when employing the preconcentration mode with plumbane collection in a quartz trap-and atomizer device. Interference of Bi seems to take place in the preconcentration step. Interference of Bi in the collection mode cannot be reduced by increased hydrogen radical amount in the trap and/or the atomizer.

Highlights

► Interference study on Pb determination by in-atomizer trapping was performed for the first time. ► Bi was found as a severe interferent in the preconcentration mode (Pb:Bi ratio 1:100). ► No interference was found in the on-line atomization (no preconcentration). ► Bi interference occurs during preconcentration.

Atomic and Molecular Emissions in Laser-Induced Breakdown Spectroscopy

24 December 2012, 09:33:37
Available online 20 December 2012
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy

This article summarizes measurements and analysis of hydrogen Balmer series atomic lines following laser-induced optical breakdown. Electron number density on the order of 1 × 1025 m−3 can be measured using H α Stark width and shift in the analysis of breakdown plasma in 1 to 1.3 × 105 Pa, gaseous hydrogen. The H β line can be utilized for electron number density up to 7 × 1023 m−3. The historic significance is elaborated of accurate H β measurements. Electron excitation temperature is inferred utilizing Boltzmann plot techniques that include H γ atomic lines and further members of the Balmer series. Laser ablation of aluminium is discussed in view of limits of application of the Balmer series. H β and H γ lines show presence of molecular carbon in a 2.7 and 6.5 × 105 Pa, expanding methane flow. Diagnostic of such diatomic emission spectra is discussed as well. Laser-induced breakdown spectroscopy historically embraces elemental analysis, or atomic spectroscopy, and to a lesser extent molecular spectroscopy. Yet occurrence of superposition spectra in the plasma decay due to recombination or due to onset of chemical reactions necessitates consideration of both atomic and molecular emissions following laser-induced optical breakdown. Molecular excitation temperature is determined using so-called modified Boltzmann plots and fitting of spectra from selected molecular transitions. The primary interest is micro-plasma characterization during the first few micro-seconds following optical breakdown, including shadowgraph visualizations.

Graphical abstract

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Highlights

► Electron density measurements in plasma using H-alpha and H-beta lines; ► Analysis of recorded data using accepted theories; ► Limitations of hydrogen Balmer series in study of laser-induced optical breakdown; ► Analysis of atomic and molecular superposition spectra; ► Computed atomic profiles and diatomic molecular spectra using line-strength-files.

Elemental analysis by surface-enhanced Laser-Induced Breakdown Spectroscopy combined with liquid–liquid microextraction

24 December 2012, 09:33:37
Available online 7 December 2012
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy

In this work, the possibility of using Laser-Induced Breakdown Spectrometry (LIBS) combined with liquid–liquid microextraction techniques is evaluated as a simple and fast method for trace elemental analysis. Two different strategies for LIBS analysis of manganese contained in microdroplets of extraction solvent (Triton X-114) are studied: (i) analysis by direct laser irradiation of microdroplets; and (ii) analysis by laser irradiation of microdroplets dried on metallic substrates (surface-enhanced LIBS — SENLIBS). Experiments were carried out using synthetic samples with different concentrations of manganese in a 10% w/w Triton X-114 matrix. The analysis by direct laser irradiation of microdroplets showed low precision, sensitivity and poor linearity across the concentration range evaluated (R2 <0.95). On the other hand, the SENLIBS method of analysis improved the sensitivity, the precision and the linearity of the calibration curve with respect to the direct analysis of microdroplets. In comparison with experimental results obtained by direct analysis, SENLIBS also allowed several replicate measurements to be carried out in a single microdroplet. The limit of detection obtained was 6μgg−1 of Mn.

Highlights

► LIBS combined with microextraction procedures for trace analysis is proposed. ► The proposed combination depends on LIBS ability to analyze sample microvolumes. ► A surface-enhanced LIBS methodology for microdroplet analysis was evaluated. ► Results indicate this combination to be promising for trace analysis in liquids.

Calculation of elemental columnar density from self-absorbed lines in Laser-Induced Breakdown Spectroscopy: A resource for quantitative analysis

24 December 2012, 09:33:37
Available online 7 December 2012
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy

The presence of self-absorption of emission lines is usually an undesired effect in Laser Induced Breakdown Spectroscopy because it introduces non linear effects in the growth of line intensity versus the concentration of the emitting species. Several methods have been proposed in recent years for identifying and quantifying self-absorption in the emission spectra. After this diagnostic stage, the lines affected by self-absorption are usually disregarded; otherwise, appropriate corrective factors are applied to their intensity before the utilization for analytical purposes. Changing the point of view, this paper remarks as self-absorption can provide useful information for analyzing the composition of laser-induced plasmas and for their characterization. Whenever the extent of self-absorption is quantified, in fact, the optical depth of the line can be rapidly calculated; then, for plasmas in local thermodynamic equilibrium conditions, the columnar density of the emitting species can be derived. Assuming the plasma homogeneity, the concentration ratio between different elements can be obtained. Moreover, in particular cases, the columnar densities can be used to calculate the plasma temperature and the absolute number densities of plasma species. Some applications of the method are reported in the paper and potentialities and limitations are discussed.

Highlights

► A method for LIBS plasma characterization based on self absorption is presented. ► It allows to calculate absolute columnar number densities of plasma species. ► It allows also to calculate plasma temperature and analytical composition. ► The method does not rely on the spectral calibration of the detection apparatus.

Chemical speciation of chlorine in atmospheric aerosol samples by high-resolution proton induced X-ray emission spectroscopy

24 December 2012, 09:33:37
Available online 5 December 2012
Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy

Chlorine is a main elemental component of atmospheric particulate matter (APM). The knowledge of the chemical form of chlorine is of primary importance for source apportionment and for estimation of health effects of APM. In this work the applicability of high-resolution wavelength dispersive proton induced X-ray emission (PIXE) spectroscopy for chemical speciation of chlorine in fine fraction atmospheric aerosols is studied. A Johansson-type crystal spectrometer with energy resolution below the natural linewidth of Cl K lines was used to record the high-resolution Kα and Kβ proton induced spectra of several reference Cl compounds and two atmospheric aerosol samples, which were collected for conventional PIXE analysis. The Kα spectra which refers to the oxidation state, showed very minor differences due to the high electronegativity of Cl. However, the Kβ spectra exhibited pronounced chemical effects which were significant enough to perform chemical speciation. The major chlorine component in two fine fraction aerosol samples collected during a 2010 winter campaign in Budapest was clearly identified as NaCl by comparing the high-resolution Cl Kβ spectra from the aerosol samples with the corresponding reference spectra. This work demonstrates the feasibility of high-resolution PIXE method for chemical speciation of Cl in aerosols.

Highlights

► Chemical specation of Cl in aerosol samples by high resolution PIXE spectroscopy. ► Fine structure of Kα and Kβ lines of reference compounds and APM samples was given. ► Kα spectra were well aligned with each other confirming the same Cl oxidation state. ► Pronounced chemical effects were observed in the Kβ spectra. ► We showed that chemical speciation of Cl was possible on thin aerosol samples.


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