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Paper des Monats
- ja (1)
The introduction of HR-CS-MAS instrumentation, as it is shown in Fig. 1, provides a new way for the determination of non-metals including fluorine via molecular absorption. We present a sensitive and fluorine-specific method for total fluorine determination in fifteen consume care products in which perfluordecalin were declared (nail polishes, eye shadows and body creams). After pyrohydrolytic digestion of samples, fluorine content was determined by GF-HR-CS-MAS. Calcium was used as a molecule forming element and the molecular absorption of calcium monofluoride (CaF) at the wavelength 606.440 nm was used for its quantification. No matrix effect was observed. Analytical signal depends only on the fluorine concentration and therefore pure sodium fluoride NaF was used as calibration standard. The use of zirconium oxide nanoparticles as permanent modifier improves the limit of detection (from 0.2 to 0.1 ng) and characteristic mass (from 0.10 to 0.05 ng) from a previous reported method. These results were also compared with ISE method (standard DIN 51-084) and no significant difference was found
Currently, two main high speed processes can be investigated: electromagnetic absorption and electromagnetic scattering. At the summer university of the School of Analytical Sciences Adlershof (SALSA-HU), a series of 5 articles were presented to ilustrate the potential of ultrafast spectroscopy, from IR band assignment to monitoring time resolved structural changes. First, by studying light absorption is possible to do assignment and interpretation of IR bands in small molecules and to study the influence of ligands or labeled molecules in protein structures. Second, by studying light scattering is possible to monitoring photoinduced structural changes in solid materials.
This presentation contains a study of photoinduced structural changes monitored by light scattering in condensed matter.
High-Resolution Continuum Source Molecular Absorption Spectrometry (HR-CS-MAS) with graphite furnace atomizers has been successfully used for the analytical determination of non-metals. The use of permanent modifiers (or coatings) for molecule formation is necessary, but their mechanisms of action remain unclear. In order to understand and improve the current analytical methods, we present a comprehensive mechanistic study of molecule formation in graphite furnaces: a key step into the recovery of analytical signals. Therefore, a well-known system for fluorine determination was studied: the molecule formation of CaF, with Zr as permanent modifier. Through a kinetic approach, an Arrhenius plot showed a pseudo first order reaction respect to F-. By spectroscopic methods (XPS, XAS, EDX) it was possible to elucidate an intermediate state. Here a mechanism is proposed, where ZrO2 works as heterogeneous catalyst: after a pyrolytic step, it is activated to the intermediate state of ZrO(OCaF) and at higher temperatures, CaF(g) is released from the zirconium-coated graphite surface. With this analytical information, improved surface modifications and coatings for graphite furnaces can be designed and some of them, for example with Zr nanoparticle and Zr xerogels are here presented.
Heavy alcohol induces several chronic diseases, including cirrhosis. Consequently, cirrhotic patients need liver transplantation. However, alcoholic patients are not suitable for this. How can be physicians sure of non-alcohol consumption of a potential organ receptor? Monitoring of biomarkers by mass spectrometric techniques is today the most suitable option. This subject was discussed at the Graduate School of Analytical Science Adlershof (SALSA) in Berlin, as a part of a lecture series in analytical science.
For the purpose of finding suitable molecules applicable to sulfur determination and to compare their analytical sensitivity systematically, high-resolution overview molecular absorption spectra of sulfides of group 14 elements produced in a graphite furnace were investigated. To that end a modular simultaneous echelle spectrograph (MOSES) was used, which allows recording sub-ranges of spectra out of a total wavelength range from 190 nm to 735 nm. The combined overview spectra show a complex structure with many vibrational bands, each of them consisting of a multitude of sharp rotational lines. The absorption of rotational lines of SiS (282.910 nm), GeS (295.209 nm), SnS (271.578 nm), and PbS (335.085 nm) has been analyzed for optimizing the particular experimental conditions regarding to the sulfur determination. Using the commercial CS AAS instrument contrAA 600 under optimized conditions such as the temperature program, the modification of the platform with Zr and the use of chemical modifiers, the achieved characteristic masses for sulfur are 12 ng (CS), 15.7 ng (SiS), 9.4 ng (GeS), 20 ng (SnS), and 220 ng (PbS). The first four sulfides provide an analytical sensitivity with roughly the same level, but the GeS molecule seems to be the best one with respect to analytical sensitivity and flexibility in molecular formation control. The PbS molecule provides the lowest analytical sensitivity, and together with its low bond strength it is not recommended for sulfur determination.
Variations in the isotope amount composition of some elements like lithium, boron, magnesium, calcium and copper have been used as proof of provenance of a sample and to describe geological processes. Routinely, isotope compositions are determinate by mass spectrometry; the working horse of the isotope analysis. However, mass spectrometric methods are expensive, time consuming and they require a high qualified analysist.
Here an alternative faster and low cost optical method for isotope ratio determination is proposed: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Stable isotope amount composition of X= Li, B, Mg, Ca, Cu and Sr have been determined by monitoring the absorption spectrum of their monohydride (XH) in graphite furnace HR-CS-MAS.
Analytical applications of high resolution continuum source molecular absorption spectrometry
(2017)
High-resolution continuum source molecular absorption spectrometry (HR-CS-MAS) has been apply for the determination of non-metals and isotope analysis, extending so the application range of atomic absorption spectrometry (AAS). This seminar is divides in two main parts. First, here is presented a comprehensive mechanistic study of molecule formation in graphite furnaces, a key step into the recovery of analytical signals in AAS and MAS. Therefore, a well-known system for fluorine determination was studied: the molecule formation of CaF, with Zr as permanent modifier. Through a kinetic approach, an Arrhenius behaved pseudo first order reaction respect to F- was observed and by spectroscopic methods (XPS, XAS, EDX) an intermediate state was possible to be elucidated. Here it is proposed a mechanism, where zirconium works as heterogeneous catalyst: after a pyrolytic step, it is activated the intermediate ZrO(OCaF) and at higher temperatures, CaF(g) is released from the zirconium-coated graphite surface. Second, we have developed analytical methods using HR-CS-MAS as detector for quantification of fluorine in consume-care products with declared per-fluorinated ingredients. Ad, the high resolution of the instrumentation allows identify isotopic shifts in some observed molecular spectra. Consequently, the molecular spectra of enriched isotopes of B were investigated and so the potential of HR-CS-MAS for the determination of isotopic ratios is established.
Analysis of stable isotopes has been used as proof of provenance of mineral and biological samples, to estimate a contamination source and to determine geological processes. This kind of analysis needs high accuracy and precision for reliable conclusions. Currently, stable isotope analysis is dominated by mass spectrometric techniques that are time consuming and expensive. Here we present a fast and low cost alternative for isotope analysis of boron and magnesium: high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). Two stable isotope systems were evaluated separately: boron (10B:11B) and magnesium (24Mg:25Mg:26Mg). Their isotope amount ratios were estimated by monitoring their absorption spectra in-situ generated monohydrides. The molecular absorption spectrum of a XH molecule (X= B or Mg) with n isotopes would be a linear combination of n isotopologue spectra and the amount of each component (isotope) could be calculated by a multivariate regression (n= 2 and 3 for B and Mg respectively). For the analysis of boron certified reference materials (CRM), the band 1→1 for the electronic transition X1Σ+ → A1Π was measured around wavelength 437.1 nm. Since boron has a memory effect in graphite furnaces, a combination of 2 % (v/v) hydrogen gas in argon, 1 % trifluoromethane in argon, an acid solution of calcium chloride and mannitol as chemical modifiers were used during the BH vaporization at 2600 °C. Partial least square regression (PLS) for analysis of samples was applied. For this, a spectral library with different isotope ratios for PLS regression was created. Magnesium does not have memory effect. Therefore, only 2 % of hydrogen in argon as gas modifier during vaporization at 2500 °C was employed for analysis of magnesium CRM. Absorption spectra of MgH for the X2Σ→A2Π electronic transition (band 0→0) were recorded around wavelength 513.45 nm. A similar PLS procedure to the BH was applied. Results for B and Mg CRM are metrologically compatible with those reported by mass spectrometric methods. An accuracy of 0.08 ‰ for B and 0.1 ‰ Mg was obtained as the average deviation from the isotope CRM. Expanded uncertainties with a coverage factor of k = 2 range between 0.10 - 0.40 ‰.
Variations in the isotope amount composition of some elements like lithium, boron, magnesium, calcium, copper and strontium have been used as proof of provenance of a sample and to describe geological processes. Routinely, isotope compositions are determinate by mass spectrometry; the working horse of the isotope analysis. However, mass spectrometric methods are expensive, time consuming and they require a high qualified analysist.
Here an alternative faster and low cost optical method for isotope ratio determination is proposed: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Stable isotope amount composition of X= Li, B, Mg, Ca, Cu and Sr have been determined by monitoring the absorption spectrum of their monohydride (XH) in graphite furnace HR-CS-MAS. For example, for the three Mg isotopes (24Mg, 25Mg and 26Mg) band (0→0) for the electronic transition X1Σ+ → A1Π was evaluated around wavelength 513.4 nm (Fig. 1). Partial least square regression (PLS) for analysis of samples and reference materials were applied. For this, a spectral library with different isotopes ratios for PLS regression were built. Results are metrological compatible with those reported by mass spectrometric methods.
Analysis of stable isotopes has been used as proof of provenance of mineral and biological samples, to estimate a contamination source and to determine geological processes. This kind of analysis needs high accuracy and precision for reliable conclusions. Currently, stable isotope analysis is dominated by mass spectrometric techniques that are time consuming and expensive. Here we present a fast and low cost alternative for isotope analysis of boron and magnesium: high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). Two stable isotope systems were evaluated separately: boron (10B:11B) and magnesium 24Mg:25Mg:26Mg). Their isotope amount ratios were estimated by monitoring their absorption spectra in-situ generated monohydrides. The molecular absorption spectrum of a XH molecule (X= B or Mg) with n isotopes would be a linear combination of n isotopologue spectra and the amount of each component (isotope) could be calculated by a multivariate regression (n= 2 and 3 for B and Mg respectively). For the Analysis of boron certified reference materials (CRM), the band 1→1 for the electronic transition X1Σ+ → A1Π was measured around wavelength 437.1 nm. Since boron has a Memory effect in graphite furnaces, a combination of 2 % (v/v) hydrogen gas in argon, 1 % trifluoromethane in argon, an acid solution of calcium chloride and mannitol as chemical modifiers were used during the BH vaporization at 2600 °C. Partial least square regression (PLS) for analysis of samples was applied. For this, a spectral library with different isotope ratios for PLS regression was created. Magnesium does not have memory effect. Therefore, only 2 % of hydrogen in argon as gas modifier during vaporization at 2500 °C was employed for analysis of magnesium CRM. Absorption spectra of MgH for the X2Σ→A2Π electronic transition (band 0→0) were recorded around wavelength 513.45 nm. A similar PLS procedure to the BH was applied. Results for B and Mg CRM are metrologically compatible with those reported by mass spectrometric methods. An accuracy of 0.08 ‰ for B and 0.1 ‰ Mg was obtained as the average deviation from the isotope CRM. Expanded uncertainties with a coverage factor of k = 2 range between 0.10 - 0.40 ‰.
Boron presents two stable isotopes, 10B and 11B and due to their relatively large mass difference (~ 10%) isotope fractionation leads to considerable isotope amount ratio variations n(10B)/n(11B) in natural occurrence. These have been used as a proof of provenance of mineral and biological samples, to estimate a contamination source and to the determination of geological processes by erosion or subduction. Additionally, boron is employed in the nuclear industry due to the capability of its isotope 10B to thermal-neutron capture and therefore 10B enriched boric acid solutions are used in the cooling system of thermonuclear facilities and in the alloying of steel and carbides for protective shielding. Usually, isotope ratio variations are determined by mass spectroscopic methods.
Here an alternative faster and low cost method for isotope ratio determination is proposed: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Boron isotope amount ratios have been determined by monitoring the absorption spectrum of boron monohydride (BH) in graphite furnace HR-CS-MAS. Bands (0→0) and (1→1) for the electronic transition X1Σ+ → A1Π were evaluated around wavelengths 433.1 nm and 437.1 nm respectively. Partial least square regression (PLS) for analysis of samples and reference materials were applied. For this, a spectral library with different isotopes ratios for PLS regression was built. Results obtained around the 433.1 nm and 437.1 nm spectral regions are metrologically compatible with those reported by mass spectrometric methods. Moreover, a precision and accuracy of the method of ± 0.5 ‰ for the evaluated spectral region around 437.1 nm is reported here. This accuracy and precision is comparable with those obtained by thermal ionization mass spectrometry (TIMS) and multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for boron isotope ratio measurements.
Boron isotope amount ratios n(10B)/n(11B) have been determined by monitoring the absorption spectrum of boron monohydride (BH) in a graphite furnace using high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Bands (0→0) and (1→1) for the electronic transition X1Σ+ → A1Π were evaluated around wavelengths 433.1 nm and 437.1 nm respectively. Clean and free of memory effect molecular spectra of BH were recorded. In order to eliminate the memory effect of boron, a combination of 2% (v/v) hydrogen gas in argon and 1% trifluoromethane in argon, an acid solution of calcium chloride and mannitol as chemical modifiers was used. Partial least square regression (PLS) for analysis of samples and reference materials were applied. For this, a spectral library with different isotopes ratios for PLS regression was built. Results obtained around the 433.1 nm and 437.1 nm spectral regions are metrologically compatible with those reported by mass spectrometric methods. Moreover, for the evaluated region of 437 nm, an accuracy of 0.15‰ is obtained as the average deviation from the isotope reference materials. Expanded uncertainties with a coverage factor of k = 2 range between 0.15 and 0.44‰. This accuracy and precision are compatible with those obtained by mass spectrometry for boron isotope ratio measurements.
Boron presents two stable isotopes, 10B and 11B and due to their relatively large mass difference (~ 10%) isotope fractionation leads to considerable isotope amount ratio variations n(10B)/n(11B) in natural occurrence. These have been used as a proof of provenance of mineral and biological samples, to estimate a contamination source and to the determination of geological processes by erosion or subduction. Additionally, boron is employed in the nuclear industry due to the capability of its isotope 10B to thermal-neutron capture and therefore 10B enriched boric acid solutions are used in the cooling system of thermonuclear facilities and in the alloying of steel and carbides for protective shielding. Usually, isotope ratio variations are determined by mass spectroscopic methods.
Here an alternative faster and low cost method for isotope ratio determination is proposed: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Boron isotope amount ratios have been determined by monitoring the absorption spectrum of boron monohydride (BH) in graphite furnace HR-CS-MAS. Bands (0→0) and (1→1) for the electronic transition X1Σ+ → A1Π were evaluated around wavelengths 433.1 nm and 437.1 nm respectively. Partial least square regression (PLS) for analysis of samples and reference materials were applied. For this, a spectral library with different isotopes ratios for PLS regression was built. Results obtained around the 433.1 nm and 437.1 nm spectral regions are metrologically compatible with those reported by mass spectrometric methods. Moreover, a precision and accuracy of the method of ± 0.5 ‰ for the evaluated spectral region around 437.1 nm is reported here. This accuracy and precision is comparable with those obtained by thermal ionization mass spectrometry (TIMS) and multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for boron isotope ratio measurements.
The mechanism of action of zirconium permanent modifiers on graphite surfaces was investigated in order to understand its influence on the analytical signal in atomic and molecular absorption spectrometry (AAS/MAS). For this, the molecule formation of CaF was studied, which is used for the indirect analytical determination of fluorine in high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). The kinetics of this reaction was established by monitoring its molecular spectrum at different atomisation temperatures. An Arrhenius plot showed a pseudo-first order reaction with respect to fluorine (n = 1). An intermediate state was isolated, and its structure was elucidated by spectroscopic methods: scanning electron microscopy with energy dispersive X-ray spectroscopy (SEMEDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XANES and EXAFS), and Raman microspectroscopy. We propose here a mechanism, where ZrO2 acts as a heterogeneous catalyst: after a pyrolytic step, an intermediate state of ZrO(OCaF) is activated, and at higher temperatures, CaF(g) is released from the zirconium-coated graphite surface. No evidence of the formation of zirconium carbide was found. Consequently, as the CaF formation is catalysed by a heterogeneous catalyst, surface modifications with ZrO2 nanoparticles and ZrO xerogels were investigated in order to increase the surface area. Their influence was evaluated in the molecule formation of CaF, CaCl, CaBr, and CaI. Graphite furnace modification with zirconium oxide nanoparticles proves to be the best choice for fluorine analysis with a signal enhancement of more than eleven times with respect a non-coated graphite furnace. However, the influence of zirconium modifications in the analytical signals of Cl, and I is lower than the F signals or even negative in case of the Br. Understanding zirconium modifiers as heterogeneous catalysts offers a new perspective to AAS and MAS, and reveals the potential of surface analytical methods for development of improved permanent modifiers and graphite furnace coatings.
Mass spectrometric methods (MC-ICP-MS and TIMS) are without doubt the working horse of stable isotope analysis. However, drawbacks of these methods include the high costs for instruments and their operation, experienced operators and elaborate chromatographic sample preparation which are time consuming.
We propose a lower-cost and faster optical alternative for the analysis of isotope ratios of selected elements: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Stable isotope amount compositions of boron (B) and magnesium (Mg) were determined based on the absorption spectra of in-situ generated mono-hydrides and halide (MH and MX) using graphite furnace HR-CS-MAS. The use of a modular simultaneous echelle spectrograph (MOSES) helps to find the maximal isotope shift in the diatomic molecular spectra produced in a graphite furnace by using isotopic spike solutions. Isotopes of boron (10B and 11B) were studied via their hydrides for the electronic transition X 1Σ+ → A 1Π. The spectrum of a given sample is a linear combination of the 10BH molecule and its isotopologue 11BH. Therefore, the isotopic composition of samples can be calculated by a partial least square regression (PLS). For this, a spectral library was built by using samples and spikes with known isotope composition. Boron isotope ratios measured by HR-CS-MAS are identical with those measured by mass spectrometric methods at the 0.15 ‰ level. Similar results were obtained for a multiple isotope system like Mg (24Mg, 25Mg, and 26Mg), where isotope shifts of their isotopologues can be resolved in the MgF molecule for the electronic transition X 2Σ → A 2 Πi. The extension of this methodology to other elements like Li, Ca, Cu, and Sr is discussed.
We propose an alternative faster and low-cost optical method for isotope analysis: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS).
Stable isotope amount composition of X = Li, B, Mg, Ca and Sr were determined by monitoring the absorption spectra of their in situ generated mono-hydrides (XH) in graphite furnace HR-CS-MAS. Isotopes of boron (10B and 11B) were studied via their hydrides for the electronic transition X1Σ+ → A1Π (Fig. 1a). The spectrum of a given sample is a linear combination of the 10BH molecule and its isotopologue 11BH. Therefore, the isotopic composition of samples can be calculated by a partial least square regression (PLS). For this, a spectral library is built by using samples with known isotope composition. Results with an accuracy of 0.15 ‰ are metrologically compatible with those reported by mass spectrometric methods. Similar results are obtained for n isotope systems like Mg (24Mg, 25Mg, and 26Mg), where isotope shifts of their isotopologues can be resolved as shown in Fig.1b. The extension of this methodology to other elements like Li, Ca and Sr is discussed.
Small variations in the isotopic composition of some elements have been used as proof of provenance of mineral and biological samples, to describe geological processes, and to estimate a contamination source. Routinely, isotope compositions are measured by mass spectrometry; the working horse of the isotope analysis. However, mass spectrometric methods are expensive, time-consuming and they require a high qualified analyst.
Here, an alternative faster and low-cost optical method for isotope ratio determination is investigated: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Stable isotope amount composition of X = Li, B, Mg, Ca and Sr have been determined by monitoring the absorption spectra of their in situ generated hydrides (XH) in graphite furnace HR-CS-MAS. For example, the system of two stable isotopes of boron (10B and 11B) was studied via its hydride for the electronic transition X1Σ+ → A1Π (Fig. 1a). The spectrum of a given sample is a linear combination of the 10BH molecule and its isotopologue 11BH. Therefore, isotopic composition of samples and reference materials are calculated by a partial least square regression (PLS). For this, a spectral library is built by using samples with known isotope composition. Results are metrologically compatible with those reported by mass spectrometric methods. [1] Similar results are obtained for n isotope systems like Mg (24Mg, 25Mg, and 26Mg), where isotope shift of their isotopologues can be resolved as shown in Fig.1 b. The extension of this methodology to other elements like Li, Ca and Sr is discussed [2].
References:
[1] C. Abad, S. Florek, H. Becker-Ross, M.-D. Huang, H.-J. Heinrich, S. Recknagel, J. Vogl, N. Jakubowski, U. Panne, Determination of boron isotope ratios by high-resolution continuum source molecular absorption spectrometry using graphite furnace vaporizers, Spectrochim. Acta, Part B, 136 (2017) 116-122.
[2] C. Abad et al., unpublished results, 2018.
Following fluorinated drugs by molecular absorption spectrometry – from cancer cells to body fluids
(2018)
Fluorine has been widely introduced into pharmaceutical drugs. Due to the high C-F bond strength, a single atom substitution with fluorine produces drastic desirable and tunable changes in the molecular properties. However, the clinical monitoring of these drugs is not straightforward.
Organofluorine compounds are elusive for a non-targeted analysis; a significant problem in fluorine determination is the lack of suitable detection techniques. Standard atomic absorption and emission spectrometers cannot access fluorine, because their resonance lines lie in the VUV spectral range below 100 nm. In the case of conventional inductively coupled argon plasmas (ICP), the plasma energy is too low to generate a significant population of excited fluorine atoms. Recently, our group introduces high-resolution continuum source absorption spectrometry (HR-CS MAS) as a new way for the indirect monitoring of fluorinated compounds. Main benefits of HR-CS-MAS includes low limits of detection, complete analyte recovery, simple to no sample preparation, and short time analysis.
Is it a parmesan cheese from Italy? Who painted the Mona Lisa? The determination of the place of origin is essential for consumer protection, detection of falsifications, and also to bring justice.
All the tangible possess an isotopic fingerprint. However, current technologies are too expensive. We work on the development of fast and low-cost optical instruments and methods for isotope analysis.