Direct determination of P in biodiesel by high-resolution continuum source graphite furnace atomic absorption spectrometry

The direct determination of P in biodiesel by high-resolution continuum source graphite furnace atomic absorption spectrometry has been investigated. A slow drying stage proved to be essential for good repeatability. Optimization was performed by a D optimal planning. The atomization temperature and modifier composition were the most relevant parameters. Thus, using a mixture of Pd (30 μg) and Mg(NO₃)₂ (20 μg) as the modifier, previously deposited onto the platform of the graphite tube and dried, a five step drying stage, and pyrolysis and atomization temperatures of 1000 and 2700 °C, respectively, a limit of detection of 0.5 μg g^− 1 was obtained. The analysis of biodiesel of different origins confirmed that external calibration with organic P standard solutions, diluted in P-free biodiesel, could be used. In this way, excellent agreement between the found and expected results was observed in the analysis of an ANP interlaboratorial exercise sample.     

The determination of calcium in yttrium oxide by alpha-particle activation analysis

The determination of calcium in yttrium oxide through the⁴⁰Ca(α, p)⁴³Sc reaction was studied, using a post-irradiation radiochemical separation procedure. The half-life of⁴³Sc was determined to be 3.87 hr. The chemical recovery was about 70%. The detection limit was about 10 ppb, for a 30 min irradiation at an alpha-particle beam current of 1 μA (E_α=13.4 MeV) and γ−γ coincidence counting (background counts being<1, cpm), with counting starting at 4 hours after the end of irradiation. Four samples of a batch of yttrium oxide (A.R.) were analyzed, and found to contain 13.9±1.0 ppm of calcium.     

Application of gas chromatography high-resolution mass spectrometry to the determination of trace monobromopolychlorodibenzo-p-dioxins in environmental samples

A capillary column gas chromatographic/high resolution mass spectrometric method was developed for the determination of monobromopolychlorodibenzo-p-dioxins (BPCDDs) in environmental samples. The mass spectrometer was operated at high resolution (> 10,000) in the selected ion monitoring mode with magnet switching among tetra through octa groups to achieve low or subpicogram detection limits. Standard BPCDDs (tetracongener through octacongener groups) were utilized to measure accurately the mass spectrometric relative response factors for these compounds, and linear calibrations were achieved by using these standard compounds at different concentrations. The method detection limit is low or sub-parts-per-trillion levels for BPCDDs, the accuracy better than 80% and the precision better than ± 10%. Quantification of BPCDDs and preliminary identification of some specific BPCDD isomers in fly ash samples are also reported.     

Rapid determination of amino acids in foods by hydrophilic interaction liquid chromatography coupled to high-resolution mass spectrometry

This study describes a rapid and sensitive analytical method for the determination of amino acids in foods and drinks. The method entailed dilution or extraction of amino acids from foods using the mixture of acetonitrile and 0.1% aqueous formic acid (50:50, v/v). Chromatographic separation of underivatized amino acids was performed using a hydrophilic interaction liquid chromatography within a runtime of 6 min. Both hydrophobicity and charge of the side chain played important roles on the elution order of amino acids under the chromatographic conditions. High-resolution mass spectrometry allowed qualitative and quantitative detection of amino acids in complex food matrices. Its response was found linear over a concentration range of 0.25-10 μg/ml. The method could be successfully applied to various foods and drinks to profile individual amino acids. Mean percentage recoveries of amino acids from different matrices were 88.5% or higher with residual standard deviation of less than 5.0%.     

Feasibility of high-resolution continuum source molecular absorption spectrometry in flame and furnace for sulphur determination in petroleum products

For the first time, high-resolution molecular absorption spectrometry with a high-intensity xenon lamp as radiation source has been applied for the determination of sulphur in crude oil and petroleum products. The samples were analysed as xylene solutions using vaporisation in acetylene-air flame or in an electrothermally heated graphite furnace. The sensitive rotational lines of the CS molecule, belonging to the ?ν = 0 vibrational sequence within the electronic transition X¹∑⁺ → A¹П, were applied. For graphite furnace molecular absorption spectrometry, the Pd + Mg organic modifier was selected. Strong interactions with Pd atoms enable easier decomposition of sulphur-containing compounds, likely through the temporal formation of Pd_xS_y molecules. At the 258.056 nm line, with the wavelength range covering central pixel ± 5 pixels and with application of interactive background correction, the detection limit was 14 ng in graphite furnace molecular absorption spectrometry and 18 mg kg⁻¹ in flame molecular absorption spectrometry. Meanwhile, application of 2-points background correction found a characteristic mass of 12 ng in graphite furnace molecular absorption spectrometry and a characteristic concentration of 104 mg kg⁻¹ in flame molecular absorption spectrometry.The range of application of the proposed methods turned out to be significantly limited by the properties of the sulphur compounds of interest. In the case of volatile sulphur compounds, which can be present in light petroleum products, severe difficulties were encountered. On the contrary, heavy oils and residues from distillation as well as crude oil could be analysed using both flame and graphite furnace vaporisation. The good accuracy of the proposed methods for these samples was confirmed by their mutual consistency and the results from analysis of reference samples (certified reference materials and home reference materials with sulphur content determined by X-ray fluorescence spectrometry).     

Lanthanum fluoride coprecipitation technique for the preparation of actinides for alpha-particle spectrometry

A simple and rapid procedure is described by which actinides can be mounted in a form suitable for alpha-particle spectrometry without recourse to electrodeposition. The actinides are coprecipitated as fluorides with 100 g of lanthanum carrier from an acidic solution. The precipitate is mounted on a 0.1 -pore membrane filter containing LaF₃ substrate, also prepared from 100 g of lanthanum. The resolution obtained using samples of pure radiotracers and of frations isolated from lake sediments is generally comparable to that afforded by the conventional electrodeposition technique. The coprecipitation yield is generally quantitative. The entire procedure can be completed in about 90 min.     

Precision of fragmentation patterns in high-resolution mass spectrometry

The effect of controlling the temperature of the ion source of a high-resolution mass spectrometer is to increase the confidence in mass spectral pattern coefficients of saturated molecules. Results are presented for both controlled and uncontrolled ion-source temperatures. Standard deviations have been calculated for selected summations of ion intensities and criteria have been suggested for maintaining meaningful analytical results in the study of petroleum distillates.     

Open-access high-resolution mass spectrometry in early drug discovery

Techniques such as mass spectrometry and NMR spectroscopy form an essential part of the medicinal chemist's toolbox for characterizing and assessing the purity of new molecules. Empowering medicinal chemists to gain early insight into their reaction products has a direct impact on productivity. Devolution of cutting-edge techniques from the specialist to the bench chemist also frees the specialist to concentrate on solving the more demanding of analytical problems. For open-access techniques to be taken up, they must be robust and be able to handle differing sample concentrations and varying sample complexities. This paper details the implementation of high-resolution liquid chromatography/mass spectrometry in open access to aid the medicinal chemist in characterizing desired products and identifying unexpected rearrangements, by-products and complete unknowns.     

Isolation and alpha-particle spectrometric determination of238Pu and239,240Pu in sediments

A simple method is described for the isolation and determination of plutonium isotopes in sediments. The method involves leaching of sample with nitric acid and subsequent separation of plutonium on an anion-exchange column. Major matrix elements and several potential radiochemical interferences are removed during 8M HNO₃ sample loading on the column. Thorium is removed by thorough washing with 10M HCl. Plutonium (IV) is eluted with 4M HCl. Source for alpha-particle spectrometry is prepared by LaF₃ coprecipitation technique at which stage a complete separation from uranium(VI) is also achieved. The entire analytical procedure is completed in about two days.     

Calculation of ion composition in organic high-resolution mass spectrometry

The theory of a method for the calculation of organic ion compositions is described. It is based on concepts of homologous groups and homologous increments of ‘mass defect.’ Unlike the common algorithms usually used for this purpose, the proposed method excludes the analysis and outcome of chemically unreal combinations of atoms. Reduction of the number of alternative compositions is discussed. The possibility of a single (non-alternative) solution is considered in the case of additional information on the presence of functional groups containing nitrogen and/or oxygen and also aromatic fragments easily identified by their infrared spectra. The efficiency of the method is demonstrated with the help of new software for DEC- and IBM-compatible computers.     

Direct determination of cadmium in natural waters by electrothermal atomic absorption spectrometry without matrix modification

A procedure for the determination of cadmium in fresh, coastal and estuarine waters by polarized Zeeman-effect graphite-furnace atomic absorption spectrometry is validated by using lake waters and seawater. The limit of detection for freshwaters is <2 ng l^?1 cadmium. Undiluted seawater can be analyzed directly without the addition of matrix modifiers with the aid of a stabilized temperature platform. The instrument is calibrated with diluted NBS SRM 1643a (Trace Elements in Water). Analytical performance was tested extensively with fresh and brackish water samples and procedures were worked out to ensure that a high degree of accurately is achieved consistently.     

Method development for the determination of nickel in petroleum using line-source and high-resolution continuum-source graphite furnace atomic absorption spectrometry

Several sample preparation methods have been investigated for the direct determination of nickel in crude oil using graphite furnace atomic absorption spectrometry (GF AAS). Xylene was found unsuitable as solvent because of the poor long-term stability of the solutions and the resulting contamination of the equipment. Isobutyl methyl ketone (IBMK) solutions exhibited better stability, but the sensitivity of the organic nickel salt used for the standard solutions showed a high day-to-day variability. An oil-in-water emulsion using Triton X-100 as surfactant gave the best results. Using high-resolution continuum-source (HR-CS) GF AAS, it could be observed that up to 50% of the nickel in crude oil, most likely low molecular weight nickel porphyrins, were lost already at pyrolysis temperatures >400 °C, whereas the rest of the nickel as well as the nickel standard were stable up to 1300 °C. The nickel absorption at a secondary line at 232.138 nm was recorded simultaneously with that at the primary line at 232.003 nm, expanding the dynamic working range by an order of magnitude. The best characteristic mass obtained was m₀=27 pg and the limit of detection was around 0.07 μg g⁻¹ Ni in oil, based on an emulsion of 2 g oil in 10 ml. The accuracy of the procedure was verified by analyzing the certified reference material (CRM) NIST SRM 1634c, Trace Metals in Residual Fuel Oil.     

A practical method for the determination of sulphur in coal samples by high-resolution continuum source flame atomic absorption spectrometry

Sulphur in coal was determined using a high-resolution continuum source flame atomic absorption spectrophotometer (HR-CS-FAAS) with actylene/air flame. The C-S absorption band at 258.056 nm was found the most suitable analytical line with respect to sensitivity and spectral interferences. The instrumental parameters were optimized. The coal samples were dried and dissolved using microwave-assisted digestion technique. The validity of the method was tested using standard reference material and certified values were found in the limits of 95% confidence level. Since the concentrations of matrix elements of coal other than carbon are low enough not to cause any spectral interferences, the linear calibration method was applied in all quantifications without any problem. The calibration standards were prepared in sulphuric acid. The method was accurate, fast, simple and sensitive. The limit of detection (LOD, 3δ, N = 10) and the limit of quantification (LOQ, 10δ, N = 10) were found to be 0.01 and 0.03% (w/w), respectively. The sulphur concentrations of various kinds of the coal samples received around Turkey were determined. The sulphur contents of the coal samples were ranged from ≤LOQ to 1.2%.     

Simultaneous determination of palladium, platinum and rhodium in crude platinum samples by activation analysis and high-resolution gamma spectrometry

Instrumental neutron-activation analysis using a Ge(Li) detector has been investigated for the simultaneous determination of platinum, palladium and rhodium in crude platinum samples contained in lead cupels. This technique proved feasible and appears promising for extension to the determination of most of the noble metals.     

Direct determination of recombinant bovine somatotropin in plasma from a treated goat by liquid chromatography/high-resolution mass spectrometry

Recombinant bovine somatotropin (rbST) is used in dairy cattle to enhance milk production. Despite the ban on this hormone in some countries, especially in Europe, there is so far no method available for the direct detection of rbST either in milk or in plasma. An analytical strategy has been developed to analyze rbST in plasma, including a purification procedure based on a precipitation with ammonium sulphate, followed by a solid-phase extraction (SPE)-based clean-up on C4 sorbent and precipitation with cold methanol. The hormone was then digested with trypsin and analyzed by liquid chromatography/high-resolution mass spectrometry (LC/HRMSn) on a linear ion trap coupled with an Orbitrap. The tryptic N-terminal peptide, specific to the difference between the endogenous and recombinant form of the somatotropin, was fragmented and product ions were analyzed at high mass resolution. Applying this approach to goat plasma allowed the direct detection of 10 ng mL(-1) of rbST in fortified samples. It also showed the presence of rbST in plasma collected from a goat treated with the hormone, even 2 days after administration. These results are of a great interest in the field of somatotropin control and undoubtedly constitute a first step in the development of a method for the detection of rbST not only in bovine plasma, but also in other biological matrices such as milk.     

Quantitative determination of DNA adducts using liquid chromatography/electrospray ionization mass spectrometry and liquid chromatography/high-resolution inductively coupled plasma mass spectrometry

The quantitative determination of nucleotides from DNA modified by styrene oxide is described using a combination of inductively coupled plasma high-resolution mass spectrometry (ICP-HRMS) and electrospray ionization mass spectrometry (ESI-MS), both interfaced to reversed-phase high-performance liquid chromatography (HPLC). LC/ICP-MS (resolution > 1500 to discriminate against 15N16O+ and 14N16OH+) was employed to determine quantitatively the content of modified nucleotides in standard solutions based on the signal of phosphorus; phosphoric acid served as an internal standard. By means of the standard addition technique the sensitivity of the LC/ESI-MS approach was subsequently determined. Since a comparison of UV, ICP and ESI-MS data suggested that in ESI-MS the ionization efficiency of the adducts is identical within the error limits, quantitative determination of all adducts is possible. For LC/ESI-MS with single ion monitoring, the detection limit for styrene oxide adducts of nucleotides was determined to be 20 pg absolute or 14 modified in 10(8) unmodified nucleotides in a 5 micrograms DNA sample, which comes close to the best methods available for the detection of chemical modifications in DNA.     

Characterization of polysiloxanes by high-resolution pyrolysis-gas chromatography-mass spectrometry

Summary Thermal degradation of various polysiloxanes was studied by pyrolysis-gas chromatography with a fused silica capillary column. The peak identification was carried out by a directly coupled gas chromatography-mass spectrometry system. Generally, polysiloxanes were thermally degraded to cyclic oligomers along with a small amount of the compounds formed through elimination and/or recombination of the pendent substituents. Most of the degradation products including possible stereo- and structural isomers were completely separated in the high-resolution pyrograms which reflect the original stereoregularities and sequence distributions in the polysiloxane chains. Furthermore, relative peak intensities of the characteristic cyclic oligomers observed were successfully interpreted in terms of the compositions of some kinds of siloxane copolymers.

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Charakterisierung von Polysiloxanen durch hochauflösende Pyrolyse-GC-MS

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Dedicated to Prof. Dr. W. Fresenius on the occasion of his 75th birthday     

无探针荧光光谱法测定十二烷基硫酸钠的临界胶束浓度

建立了无探针荧光光谱法测定表面活性剂临界胶束浓度(CMC)的新方法,测定了典型阴离子表面活性剂十二烷基硫酸钠(SDS)在水溶液中的CMC,并与表面张力法和电导率法的测定结果进行了对比。结果表明,荧光光谱法样品用量少,测定的SDS的CMC与传统方法一致,说明采用无探针荧光光谱法能够测定一些物质的临界浓度。     

Pyrolysis—high-resolution mass spectrometry of biological materials

In a diseased state in man or animals a change at eh molecular level might occur. A pyrolysis-high-resolution mass spectrometric method has been developed to measure these changes. The mass spectra are used as fingerprints. A similar approach is reported using low-resolution mass spectrometry. The difference between low resolution and high resolution is that the number of mass spectral lines is strongly increased and therefore also the information content. As a result, a change at the molecular level will be more pronounced in high-resolution mass spectra. As an application, the results of toxicity studies on Daphnia magna are given. The experiments were performed with paraoxon, parathion and malathion. The changes at the molecular level in Daphnia magna appear to be substance-dependent.