Iron speciation in human cancer cells by K-edge total reflection X-ray fluorescence–X-ray absorption near edge structure analysis

X-ray absorption near edge structure (XANES) analysis in combination with synchrotron radiation induced total reflection X-ray fluorescence (SR-TXRF) acquisition was used to determine the oxidation state of Fe in human cancer cells and simultaneously their elemental composition by applying a simple sample preparation procedure consisting of pipetting the cell suspension onto the quartz reflectors.XANES spectra of several inorganic and organic iron compounds were recorded and compared to that of different cell lines. The XANES spectra of cells, independently from the phase of cell growth and cell type were very similar to that of ferritin, the main Fe store within the cell. The spectra obtained after CoCl₂ or NiCl₂ treatment, which could mimic a hypoxic state of cells, did not differ noticeably from that of the ferritin standard. After 5-fluorouracil administration, which could also induce an oxidative-stress in cells, the absorption edge position was shifted toward higher energies representing a higher oxidation state of Fe. Intense treatment with antimycin A, which inhibits electron transfer in the respiratory chain, resulted in minor changes in the spectrum, resembling rather the N-donor Fe-α,α′-dipyridyl complex at the oxidation energy of Fe(III), than ferritin. The incorporation of Co and Ni in the cells was followed by SR-TXRF measurements.     

Spectrofluorometric method for determination of the total mercury content in environmental samples — Waste waters

A highly selective spectrofluorometric method for the determination of total mercury (Hg) in waste waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, is the basis of this sensitive method. All forms of mercury, including organic compounds, are pre-oxidized to ionic mercury by acidic potassium permanganate. The final and complete oxidation is achieved by adding potassium persulphate and heating. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. The recoveries were done by adding 3.0 g Hg/100 ml to each sample before the digestion. It was indicated that the recoveries for determining mercury in waste waters were 98.3%–102.7%. The method gives reliable results down to a concentration of 10 ng Hg/ml waste water.     

Development of a gas chromatography — mass spectrometry method for the determination of carbon disulfide in the atmosphere

Carbon disulfide (CS₂), a relevant reduced sulfur compound in air, is well-known for its malodor and its significant effect on global atmospheric chemistry. Therefore, a reliable method for determining CS₂ in atmospheric samples has been developed based on solid-phase sampling and gas chromatography–mass spectrometry (GC–MS). Two types of solid-phase sampling supports (Orbo-32 and SKC) and the elution with organic solvents — hexane and toluene — were evaluated for low-volume outdoor sampling. Recovery studies and the standard addition method were carried out to demonstrate the proper determination of CS₂ in the absence of the influence of interferences such as ozone, hydrogen sulfide or water — important atmospheric pollutants —. The proposed methodology was validated by performing experiments in a high-volume smog chamber and by comparison with two reference optical methods, Fourier Transform Infrared (FTIR) and Differential Optical Absorption Spectroscopy (DOAS) installed in these facilities. Satisfactory analytical parameters were reported: fast analysis, a correct repeatability of 6 ± 1% and reproducibility of 14 ± 3%, and low detection limits of 0.3–0.9 pg m^? 3. Finally, the method was successfully applied to industrial samples near a pulp factory area, where a high correlation between industrial emissions and reported carbon disulfide concentrations were observed.     

Substitution–dilution method to correct the matrix effect in multi-element quantitative analysis by X-ray fluorescence

A mathematical model based on the dilution–addition method (DAM) for multi-elemental analysis using an X-ray fluorescence technique is proposed. The conditions for sample preparation do not require both the unknown and standard samples to be similar in composition and mineralogy, and the unknown sample is replaced quantitatively by the standard sample, hence the denomination substitution–dilution method (SDM). This method makes it possible to correct the matrix effect in multi-elemental quantitative analysis by X-ray fluorescence for each analyte. The proposed model presents hyperbolic behaviour of the experimental data when the X-ray fluorescence intensities are represented versus the substitution factor (h) for each analyte. After calculating the A/B parameter relations, which depend on the X-ray fluorescence intensity of each analyte (I_i^ns) and the substitution factor (h) and determining the analyte concentration in the multi-element standard sample (C_i^p), it is possible to calculate the analyte concentration in the multi-element unknown using an algorithm suggested for this purpose. This work studies the substitution–dilution phase proposed in the method, and the factors arising from incorporation of the standard and diluent are established according to the nature of the samples and the modifications. These factors make it possible to establish the experimental interval of analyte concentration, generally narrow, which corresponds to a section of the hyperbolic function which is so short that it can be accepted as linear. This linear model can be accepted for a wide variety of samples with a diluent/sample ratio greater than 10. The proposed linear method provides satisfactory results which are comparable to those calculated by applying the hyperbolic method. The proposed method (SDM) has been applied to two different types of matrices, a binary alloy (without diluent, using the hyperbolic model) and a geological sample (with diluent, using both hyperbolic and linear models). In all cases the results were satisfactory.     

Characterization of “oil on copper” paintings by energy dispersive X-ray fluorescence spectrometry

Energy dispersive X-ray fluorescence is a common analytical tool for layer thickness measurements in quality control processes in the coating industry, but there are scarce microanalytical applications in order to ascertain semi-quantitative or quantitative information of painted layers. “Oil on copper” painting becomes a suitable material to be analysed by means of X-ray fluorescence spectrometry, due to the metallic nature of substrate and the possibility of applying layered models as used in coating industry. The aim of this work is to study the suitability of a quantitative energy dispersive X-ray fluorescence methodology for the assessment of the areal distribution of pigments and the characterization of painting methods on such kind of pictorial artworks. The method was calibrated using standard reference materials: dried droplets of monoelemental standard solutions laid on a metallic plate of copper. As an example of application, we estimated pigment mass distribution of two “oil on copper” paintings from the sixteenth and eighteenth centuries. Pictorial layers have been complementarily analysed by X-ray diffraction. Apart of the supporting media made of copper or brass, we could identify two different superimposed layers: (a) a preparation layer mainly composed by white lead and (b) the pictorial layer of variable composition depending on the pigments used by the artist on small areas of the painting surface. The areal mass distribution of the different elements identified in the painting pigments (Ca, Cr, Mn, Fe, Zn, Cd, Hg and Pb) have been determined by elemental mapping of some parts of the artworks.     

Ultra-high-pressure liquid chromatography–tandem mass spectrometry method for the determination of alkylphenols in soil

A novel method has been developed for the determination of alkylphenols in soil by ultra-high-pressure liquid chromatography employing small particle sizes, combined with tandem mass spectrometry. Soil samples were extracted with pressurized liquid extraction (PLE) and then cleaned with solid-phase extraction (SPE). The extracts were separated on C18 column (1.7 μm, 50 mm × 2.1 mm) with a gradient elution and a mobile phase consisting of water and acetonitrile, and then detected by an electrospray ionization tandem mass spectrometry in negative ion mode with multiple reaction monitoring (MRM). Compared with traditional liquid chromatography, it took ultra-high-pressure liquid chromatography much less time to analyze alkylphenols. Additionally, the ultra-high-pressure liquid chromatography/tandem mass spectrometry method produces satisfactory reliability, sensitivity, and accuracy. The average recoveries of the three target analytes were 74.0–103.4%, with the RSD < 15%. The calibration curves for alkylphenols were linear within the range of 0.01–0.4 μg/ml, with the correlation coefficients greater than 0.99. When 10 g soil sample was used for analysis, the limits of quantification (LOQs) of the three alkylphenols were all 1.0 μg/kg.     

Synchrotron radiation total reflection X-ray fluorescence and energy dispersive X-ray fluorescence analysis on AP1™ films applied to the analysis of trace elements in metal alloys for the construction of nuclear reactor core components: a comparison

Synchrotron radiation induced total reflection X-ray fluorescence and conventional 45° energy dispersive X-ray fluorescence analysis using a 150-nm-thick AP1™ film as sample carrier have been exploited for the elemental analysis of traces in alloys used for the construction of reactor core components of nuclear power plants. Both techniques are well suited for the analysis since they require a low amount of sample (μl), important on one hand because of the limited disposal and on the other hand because of its high specific activity. The methods provide a very low background due to the total reflection phenomenon in TXRF and the thin AP1™ film sample support, respectively. The employment of synchrotron radiation was necessary since there are no laboratory sources which can deliver a collimated beam of the energy and intensity needed to excite the K-shell of the rare earth elements, allowing the achievement of minimum detection limits relevant for the proposed purpose (ng/g range). Moreover, the linear polarization of synchrotron radiation combined with a side-looking detection geometry manages to reduce the scattering due to the remaining matrix of the analyzed samples. Detection limits for Nb and for some of the rare earth elements (pg range for absolute detection limits and ng–μg/g range for concentration detection limits) obtained with the two techniques are presented and the two approaches are compared.     

Determination of free and total sulfur dioxide in wine samples by vapour-generation inductively coupled plasma–optical-emission spectrometry

Sulfur dioxide (SO₂) is used as a preservative and stabilizer in wine production to prevent undesired biochemical processes in the must and the final product. The concentration of SO₂ is restricted by national regulations. There are two main forms of SO₂ in wine—free (inorganic forms) and bound (fixed to organic compounds, e.g. aldehydes). Iodometric titration is commonly employed for determination of SO₂ concentration (either by direct titration or after pre-separation by distillation); other techniques are also used. In this work inductively coupled plasma–optical-emission spectrometry with vapour generation was used for determination of free and total SO₂ in wine. Gaseous SO₂ is released from the sample by addition of acid and swept into the ICP by an argon stream. The intensity of the sulfur atomic emission lines is measured in the vacuum UV region. Determination of total SO₂ is performed after hydrolysis of bound forms with sodium hydroxide (NaOH). Concentrations of acid for vapour generation and NaOH for hydrolysis were optimised. The method was used for determination of free and total SO₂ in red and white wine samples and results were compared with those from iodometric titration.     

Determination of fluorine in solids down to 120 μg/g by wavelength dispersive X-ray fluorescence spectrometry

An X-ray fluorescence spectrometric method is described for the determination of fluorine from percent level down to 120 g/g in fluoropolymers and in fluoride samples. The method is based on the measurement of the intensity of first order line for 30 seconds using a flow proportional counter and a multilayer AXO6 crystal (2d=5.52 nm). The calibration curves of first degree base polynomials are linear over the concentration range of 8000–120 g/g and of 48.92–76% measured. The precision and accuracy obtained for polymer samples in percent level of fluorine are up to ±0.5 and within ±1%, respectively. However, the precision () for trace concentrations is in the range from 8 to 20%. In most cases the accuracy is up to ±7%, ±5% and ±4% in the concentration range of 120–8000 g/g, 801–8000 g/g and of 120–400 g/g, respectively. The time needed to analyze one sample including calibration and regression analysis is about 8 minutes.     

Energy dispersive X-ray fluorescence determination of cadmium in uranium matrix using Cd Kα line excited by continuum

An energy dispersive X-ray fluorescence method for determination of cadmium (Cd) in uranium (U) matrix using continuum source of excitation was developed. Calibration and sample solutions of cadmium, with and without uranium were prepared by mixing different volumes of standard solutions of cadmium and uranyl nitrate, both prepared in suprapure nitric acid. The concentration of Cd in calibration solutions and samples was in the range of 6 to 90 µg/mL whereas the concentration of Cd with respect to U ranged from 90 to 700 µg/g of U. From the calibration solutions and samples containing uranium, the major matrix uranium was selectively extracted using 30% tri-n-butyl phosphate in dodecane. Fixed volumes (1.5 mL) of aqueous phases thus obtained were taken directly in specially designed in-house fabricated leak proof Perspex sample cells for the energy dispersive X-ray fluorescence measurements and calibration plots were made by plotting Cd Kα intensity against respective Cd concentration. For the calibration solutions not having uranium, the energy dispersive X-ray fluorescence spectra were measured without any extraction and Cd calibration plots were made accordingly. The results obtained showed a precision of 2% (1σ) and the results deviated from the expected values by < 4% on average.     

Determination of elemental sulfur in coal by gas chromatography – mass spectrometry

A method for the determination of S⁰ in coal based on the extraction with cyclohexane with subsequent quantitative analysis of elemental sulfur in the extract by GC/MS is described. The quantity of elemental sulfur was determined in four coal samples with different distribution of sulfur forms. The effect of solvent and extraction time on the efficiency of sulfur removal was studied. The elemental sulfur extracted from coal occurred in the form of S₆, S₇ and S₈. Calibration solutions were prepared from freshly recrystalized elemental sulfur. It was found that the injection temperature has a crucial influence on the m/z 64 ion chromatogram.     

Simultaneous determination of 14β-lactam antibiotics in cosmetic products by liquid chromatography tandem mass spectrometry method

In this study,a simple and rapid high-performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) method was established and validated to determine the 14β-lactam antibiotics in cosmetic products,including 1(ceftazidime),2(cefaclor), 3(cefdinir),4(ampicillin),5(cefalexin),6(ceftezole),7(cefotaxim),8(cefradine),9(cefuroxime),10(cephazoline),11 (cefathiamidine),12(cefoperazone),13(cafalotin),14(piperacillin).     

Synchrotron radiation induced total reflection X-ray fluorescence of low Z elements on Si wafer surfaces at SSRL — comparison of excitation geometries and conditions

The analysis of low Z elements, like Na and Al at ultra trace levels (<10¹⁰ atoms/cm²) on Si wafer surfaces is required by the semiconductor industry. Synchrotron radiation induced total reflection X-ray fluorescence analysis (SR-TXRF) is a promising method to fulfill this task, if a special energy dispersive detector with an ultra thin window is used. Synchrotron radiation is the ideal excitation source for TXRF of low Z elements due to its intense, naturally collimated and linearly polarized radiation with a wide spectral range down to low energies even below 1 keV. TXRF offers some advantages for wafer surface analysis such as non-destructive analysis and mapping capabilities. Experiments have been performed at the Stanford Synchrotron Radiation Lab (SSRL) using Beamline 3-4 (BL 3-4), a bending magnet beamline using white (<3 keV) and monochromatic radiation, as well as Beamline 3-3 (BL 3-3), using a crystal monochromator as well as a multilayer monochromator. A comparison of excitation–detection geometry was performed, using a side-looking detector with a vertically positioned wafer as well as a down-looking detector with a horizontally arranged wafer. The advantages and disadvantages of the various geometrical and excitation conditions are presented and the results compared. Detection limits are in the 100-fg range for Na, as determined with droplet samples on Si wafer surfaces.     

Optimization of a method for the determination of a mustard gas biomarker in human blood plasma by liquid chromatography–high-resolution mass spectrometry

A method for the determination of a mustard gas biomarker (an S-hydroxyethylthioethyl adduct with albumin) in blood plasma was optimized with the use of HPLC with high-resolution tandem mass-spectrometric detection. This method is based on the hydrolysis of this adduct by the proteinase K enzyme with the formation of the following stable tripeptide with cysteine, proline, and phenylalanine: S-[HETE]-Cys- Pro-Phe. The conditions of the sample preparation of human plasma artificially contaminated by mustard gas (the selection of an aliquot portion volume and an enzyme for the hydrolysis), the mass-spectrometric detection (the selection of optimum pairs of ion reactions and high-resolution detection modes), and the gradient elution program in the HPLC separation of an analyzed mixture were optimized. The detection limit of mustard gas in human blood plasma was 1 ng/mL. The approach proposed was tested in the analysis of human blood plasma samples by the standard addition technique and also within the framework of the first official biomedical test carried out by the Organization for the Prohibition of Chemical Weapons (OPCW) in 2016, and it exhibited a good accuracy, reproducibility, and specificity of determination.     

Simultaneous determination of germanium,arsenic, tin and antimony with total-reflection X-ray fluorescence spectrometry using the hydride generation technique for matrix separation—first steps in the development of a new application

This paper introduces a new perspective for total-reflection X-ray fluorescence analysis (TXRF), that is the simultaneous determination of Ge, As, Sn and Sb in seawater. As is well known from atomic absorption spectroscopy (AAS) and inductively coupled plasma techniques (ICP) compounds of these elements can be reduced by sodium borohydride to their hydrides and thus separated from the matrix. In this work the hydride generation is used for matrix separation in TXRF measurements. For this purpose the following procedures are considered: (1) Preconcentration of hydrides by absorption in solvents, and evaporation of some μl of this solution on the sample carrier. (2) Decomposition of hydrides in a heated thin silica tube, or at rough and/or catalytically active surfaces, e.g. in adequately prepared columns, eluting of the species by acid and evaporation of some μl of this solution on the sample carrier. (3) Decomposition of hydrides directly on the surface of a heated silica sample carrier as a thin amorphous film. (4) Combustion of hydrides in the hydrogen flame and deposition of an elemental film on the sample carrier. Basically, all four ways have been tested and the results are promising. © 1997 Elsevier Science B.V.     

Sensitive liquid chromatography–tandem mass spectrometry method for the determination of pantoprazole sodium in human urine

A sensitive and selective liquid chromatographic–tandem mass spectrometric (LC–MS–MS) method was developed to determine pantoprazole sodium (PNT) in human urine. After solid-phase extraction with SPE cartridge, the urine sample was analysed on a C₁₈ column (symmetry 3.5 μm; 75 mm × 4.6 mm i.d) interfaced with a triple quadrupole tandem mass spectrometer. Positive electrospray ionization was employed as the ionization source. The mobile phase consisted of acetonitrile–water (90:10, v/v). The method was linear over a concentration range of 1–100 ng mL^?1. The lower limit of quantitation was 1 ng mL^?1. The intra-day and inter-day relative standard deviation across three validation runs over the entire concentration range was <10.5%. The accuracy determined at three concentrations (8.0, 50.0 and 85.0 ng mL^?1 PNT) was within ±1.25% in terms of relative errors.     

Sulfur- and phosphorus-Kβ spectra analyses in sulfite,sulfate and phosphate compounds by X-ray fluorescence spectrometry

Several sulfite, sulfate and phosphate compounds were studied by X-ray fluorescence spectrometry. Sulfur- and phosphorus-Kβ spectral profile modified by the number of bonding hydrogen and oxygen atoms were analyzed. As it could be confirmed, the molecular orbital theory provides a suitable explanation of the origin and properties of the satellite Kβ′ lines. Also, for the compounds analyzed, it was found that sulfur- and phosphorus-Kβ spectra present two main components and two secondary ones which exhibit a different behavior depending on the number of bonding hydrogen and oxygen atoms. Particularly, the peak corresponding to satellite Kβ′ line increases its intensity and moves away from the main peak when the number of oxygen atoms combined with the sulfur atom is increased. The energy differences between the main peak and the satellite peak found in the analyzed compounds were in average 14.2±0.4 eV, thus being demonstrated that such a separation is a characteristic of the bonding atom, in this instance oxygen.     

Development of a fast liquid chromatography–tandem mass spectrometry method for the determination of endocrine-disrupting compounds in waters

A fast liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) method was developed to study five endocrine-disrupting compounds (4-n-nonylphenol, bisphenol A, estrone, 17β-estradiol and 17α-ethinylestradiol) in water. Different columns were tested; the chromatographic separation of the analytes was optimized on a Pinnacle DB biphenylic column with a water–acetonitrile gradient elution, which allowed the separation of the selected endocrine-disrupting compounds (EDCs) in less than 6 min. Quantitative analysis was performed in selected reaction monitoring (SRM) mode; two transitions were chosen for each compound, using the most abundant for quantitation. Calibration curves using bisphenol A-d ₁₆ as internal standard were drawn, showing good correlation coefficients (0.9993–0.9998). All figures of merit of the method were satisfactory; limits of detection were in the low pg range for all analytes. The method was then applied to the determination of the analytes in real water samples: to this aim, polar organic chemical integrative samplers (POCIS) were deployed in the influent and in the effluent of a drinking water treatment plant in Liguria (Italy). The EDC level was rather low in the influent and negligible in the outlet, reflecting the expected function of the treatment plant.     

Microwave-assisted extraction: a simpler and faster method for the determination of ethyl glucuronide in hair by gas chromatography–mass spectrometry

Alcohol is the most frequently abused “addictive substance” that causes serious social problems throughout the world; thus, alcoholism is of particular interest in clinical and forensic medicine. Alcohol biomarkers are physiological indicators of alcohol exposure or ingestion and may reflect the presence of an alcohol use disorder. The glucuronide conjugation is a minor pathway of ethanol metabolism. Ethyl glucuronide (EtG) is a marker of recent alcohol consumption that detects alcohol use reliably over a definite time period. The present paper describes a new method for the determination of EtG in hair. It is based both in the microwave-assisted extraction (MAE), to extract the analyte from hair samples, and gas chromatography–mass spectrometry (GC-MS), to identify and quantify the EtG in selected ion monitoring (SIM) mode. The method was applied to 15 hair samples from occasional alcohol users, obtaining positive results in all cases. It was fully validated, including a linear range (0.3–10 ng/mg) and the main precision parameters. In summary, the use of microwave-assisted extraction turned out to be a substantially simpler, faster, and a more sensitive procedure than any other conventional sample preparations.