Collective dynamics of sub- and supercritical methanol by inelastic X-ray scattering

Inelastic X-ray scattering experiments have been performed on methanol as a function of density from ambient to the supercritical state. Positive dispersion of the sound velocity, as compared to the hydrodynamic values, is 50% in the ambient condition and decreases to zero at 0.50 g cm⁻³ over the momentum transfer Q = 1–10 nm⁻¹ with lowering density; however, it increases again with a further decrease in density down to 0.20 g cm⁻³in the supercritical state only in the Q-range above 5 nm⁻¹. These results have been interpreted as the formation of small oligomers in the low-density supercritical methanol.     

Sinterability enhancement in semicokes obtained by controlled pyrolysis of a petroleum residue

Self-sintering semicokes were prepared by pyrolysis of an aromatic petroleum residue at 460–480 °C and pressures of 0.1–1.0 MPa. The evolution of gases and thermoplasticity from resultant semicokes were monitored by TGA and TMA, respectively. Sintering behaviour of the semicokes is extremely sensitive to pyrolysis conditions which determine contents of volatile matter and binder phase. Semicokes produced at 1.0 MPa have high volatile contents with excessive plasticity. Changes of temperature and soak time, used to reduce volatile matter contents induce reductions to the plasticity and sintering. A lower pyrolysis pressure has a similar effect. Although the operational window is narrow, heat-treated compacts (2500 °C) can be made with high density (1.9 g cm⁻³) and bending strengths >75 MPa. Using high-temperature pyrolysis (460 °C) with a post-treatment at 350–400 °C eliminates light components, without decreasing sintering properties. Compacts from these powders also exhibit high density (1.9 g cm⁻³) with higher bending strengths >90 MPa, comparable or superior to mesocarbon microbeads (MCMB) obtained from the same precursor.     

Simultaneous determination of sugars and organic acids in aged vinegars and chemometric data analysis

Aceto Balsamico Tradizionale of Modena (ABTM) is a typical product (PDO denomination) of the province of Modena produced by cooked grape must which undergoes a long ageing period (at least 12 years) in series of wooden casks (batterie). The study of the transformations of this product during ageing is extremely relevant in order to control the authenticity of ABTM towards succedaneous products and mislabelling of age.

This paper presents the results of the investigation of sugars and fixed organic acids in ABTM samples of different ages, coming from different batterie. The analytes were simultaneously determined by a gas chromatographic method optimised for this peculiar matrix.

The method shows good separation and resolution of the investigated chemical species and allows their determination in the concentration ranges reported in brackets: malic (7.6–15.5 g kg⁻¹), tartaric (4.0–9.7 g kg⁻¹), citric (0.6–1.5 g kg⁻¹) and succinic (0.36–0.62 g kg⁻¹) acid and glucose (153–294 g kg⁻¹), fructose (131–279 g kg⁻¹), xylose (011–0.39 g kg⁻¹), ribose (0.078–0.429 g kg⁻¹), rhamnose (0.061–0.195 g kg⁻¹), galactose (0.136–0.388 g kg⁻¹), mannose (0.41–1.46 g kg⁻¹), arabinose (0.33–1.00 g kg⁻¹) and sucrose (0.46–6.84 g kg⁻¹), with mean associated errors ranging from 5 to 19% depending on the analytes.

Moreover, the recovery values are always satisfactory, being close to one for most of the analytes.

Furthermore, in order to assess the degree of variability of the different analytes content with vinegar ageing and the similarity/dissimilarity among series of casks a three-way data analysis method (Tucker3) is proposed. The chemometric technique applied on the data set shows differences between the samples on the bases of their different ageing period, and between the batterie, which traditionally have an own peculiar production procedure.     

Synthesis and characterization of nanosilica prepared by precipitation method

Nanosilica was prepared by precipitation method and was characterized by various analytical tools. From transmission electron micrograph the silica particles are found to have almost spherical shape with a dimension of 50 nm. The surface area is found to be of 560 m² g⁻¹ and density 2.2 g cm⁻³. From thermogravimetric analysis the total silanol density in the silica is found to be 7.68 nm⁻². A two tier hydration model is proposed from the results of thermogravimetric analysis. The number of reactive silanols that forms hydrogen bond with water molecules is found to be 2.48. The infrared spectral data supports the presence of hydrogen bonded silanol group and the siloxane groups in silica.     

High-temperature behaviour of lithium borates:: Part I: Characterization and thermal stability

Nine compounds, namely Li₃BO₃, -Li₄B₂O₅, β-Li₄B₂O₅, Li₆B₄O₉, -LiBO₂, Li₂B₄O₇, Li₃B₇O₁₂, LiB₃O₅ and Li₂B₈O₁₃ in the Li₂O–B₂O₃ system have been synthesized and characterized. The unit-cell parameters, density and solubility in water at room temperature of all the compounds are reported. The densities of the compounds were found to be in the 1.90–2.50 g cm⁻³ range, while their solubility in water at room temperature was in the 0.91–8.64×10⁻² g cm⁻³ range. Determination of the thermal stability of the compounds by quenching and differential thermal analysis (DTA) showed that only -LiBO₂ and Li₂B₄O₇ retained their original symmetry up to their congruent melting at 1121 and 1188 K, respectively, in air.     

Analysis of acrylamide in coffee and dietary exposure to acrylamide from coffee

An analytical method for analysing acrylamide in coffee was validated. The analysis of prepared coffee includes a comprehensive clean-up using multimode solid-phase extraction (SPE) by automatic SPE equipment and detection by liquid chromatography tandem mass spectrometry using electrospray in the positive mode. The recoveries of acrylamide in ready-to-drink coffee spiked with 5 and 10 μg l⁻¹ were 96±14% and 100±8%, respectively. Within laboratory reproducibility for the same spiking levels were 14% and 9%, respectively. Coffee samples (n = 25) prepared twice by coffee machines and twice by a French Press Cafetière coffee maker contained 8±3 μg l⁻¹ and 9±3 μg l⁻¹ acrylamide. Five ready-to-drink instant coffee prepared twice contained 8±2 μg l⁻¹. Hence, the results do not show significant differences in the acrylamide contents in ready-to-drink coffee prepared by coffee machine, French Press or from instant coffee. Medium roasted coffee contained more acrylamide (10 μg l⁻¹) than dark roasted coffee (5 μg l⁻¹). Males aged 35–45 years, drinking on average 1.1 l coffee per day are exposed to the highest doses of acrylamide from coffee. The dietary intake of acrylamide from coffee comprises, on an average, 10 μg day⁻¹ for males and 9 μg day⁻¹ for females aged 35–45 years. Probabilistic modelling of the exposure of Danish consumers (all adults) to acrylamide from coffee shows a mean exposure of 6.5 μg day⁻¹ and a 95 percentile of 18 μg day⁻¹.     

Rapid determination of aluminum by UV-vis diffuse reflectance spectroscopy with application of suitable adsorbents

Diffuse reflectance spectroscopy (DRS) can be used as a rapid and sensitive method for the quantitative determination of low amounts of aluminum. In this analytical technique, the analyte in samples are extracted onto a solid sorbent matrix loaded with a colorimetric reagent and then quantified directly on the adsorbent surface. Alternatively, colored aluminum complexes formed in solution can also be immobilized onto adsorbent surface and be measured by DRS technique. Octadecyl silica disk, methyltrioctylammonium chloride–naphthalene and MCM-41 were examined as adsorbents. Eriochrome cyanine R and quinalizarin were used as coloring reagents. Optimal sorption conditions were found for each system of analyte–reagent–adsorbent. The concentration of analyte is determined using the appropriate form of the Kubelka–Munk function. We obtained for each of the aluminium–reagent–adsorbent system a calibration curve by plotting the absorbance versus the log 10²[Al³⁺] μg ml⁻¹. The linear dynamic range extends over two orders of magnitude within 0.01–15 μg ml⁻¹ with little differences in the range and in the correlation coefficients among the adsorbents. We consider that for a rapid determination of aluminum a spot-test-DRS combination with a detection limit of 1.0 × 10⁻² μg ml⁻¹ is the more facile and preferred technique.     

Spectroscopic and structural analysis of Ca substituted La orthoferrite

Samples of orthoferrites La_1−xCa_xFeO₃ (0.15≤x≤0.45) were synthesized by double sintering ceramic technique. X-ray diffraction and infrared spectroscopy experiments were carried out and discussed for the investigated samples. The data showed the formation of single-phase orthorhombic structure of space group Pbnm. The FTIR spectra were performed in the region (1200–200 cm⁻¹). Four main absorption bands were present with some side bands and shoulders in the range (1200–400 cm⁻¹). Another four bands were appeared in the range (400–200 cm⁻¹). The positions, intensities and values of the absorptions bands vary depending on the Ca content in the samples. The first absorption band appeared at about 920 cm⁻¹ was assigned to the La–O stretching vibration.     

Continuous flow system for lead determination by faas in spirituous beverages with solid phase extraction and on-line copper removal

A continuous flow system for the determination of lead in home made spirituous beverages was developed. The determination was based on the formation of a neutral chelate of the element with ammonium pyrrolidine dithiocarbamate, its adsorption onto a minicolumn packed with sodium faujasite type Y synthetic zeolite, followed by elution with methyl isobutyl ketone and determination by flame atomic absorption spectrometry. Ethanol and copper interfere strongly in the determination and therefore, must be separated prior to the analysis. Copper is removed by precipitation with rubeanic acid, while ethanol is eliminated by rotaevaporation. Sample solutions containing Pb²⁺ in the concentration range from 5 to 120 μg l⁻¹ at pH 2.5 could be analyzed, by using a preconcentration time of 3 min. Preconcentration factors from 80 to 140 were achieved for a sample volume of 6 ml and the detection limit varied from 1.4 to 3.5 μg l⁻¹, depending on the matrix composition. The relative standard deviations for 60 μg l⁻¹ Pb was 3.2% (n = 10) and the recovery of spikes (20, 40, 60 and 80 μg l⁻¹) added to the samples was estimated within 92–105% range, suggesting that lead can be quantitatively determined in such samples. Determining lead in several samples by an alternative technique further checked the accuracy. Finally, the concentrations of Pb²⁺ determined in 28 samples of Venezuelan spirituous beverages were in 12.6–370.0 μg l⁻¹ range, depending on the fermenting material based on different mixtures of agave, raw sugar cane and white sugar.     

Monoclonal antibody-based ELISA for the quantification of nitrofuran metabolite 3-amino-2-oxazolidinone in tissues using a simplified sample preparation

A sensitive and specific monoclonal ELISA for the determination of tissue bound furazolidone metabolite 3-amino-2-oxazolidinone (AOZ) is described. The procedure enables the detection of AOZ in matrix supernatant after homogenisation, protease treatment, acid hydrolysis and derivatisation of AOZ released from the tissue by o-nitrobenzaldehyde. The formed p-nitrophenyl 3-amino-2-oxazolidinone (NPAOZ) is determined by ELISA calibrated with matrix-matched standards in the concentration range of 0.05–5.0 μg I⁻¹. The assay was validated according to criteria set down by Commission Decision 2002/657/EC for the performance and validation of analytical methods for chemical residues. Detection capability, set on the basis of acceptance of no false negative results, was 0.4 μg kg⁻¹ for shrimp, poultry, beef and pork muscle. This sensitivity approaches the established confirmatory LC–MS/MS able to quantify tissue-bound AOZ at levels as low as 0.3 μg kg⁻¹. An excellent correlation of results obtained by ELISA and LC/MS–MS within the concentration range 0–32.1 μg kg⁻¹ was found in the naturally contaminated shrimp samples (r = 0.999, n = 8). A similar correlation was found for the incurred poultry samples within the concentration range of 0–10.5 μg kg⁻¹ (r = 0.99, n = 8).     

A study of the Raman spectra of alkanes in the Fermi-resonance region

The experimental and theoretically predicted Raman spectra for the first few alkanes in the homologous series: methane, ethane, propane and butane are presented for the region 2700–3100 cm⁻¹. The structure of the spectra is rather complex. Analysis of the results obtained shows that Fermi resonance occurs between the CH stretching vibrations in the 3000 cm⁻¹ region and the 2ν overtones of deformation vibrations in the low frequency (1450–1500 cm⁻¹) region.     

Interference from arsenate when determining phosphate by the malachite green spectrophotometric method

The effect of arsenate on phosphate determination by the malachite green spectrophotometric method was investigated. The molar absorptivities of the molybdophosphate and malachite green–molybdoarsenate species at 625 nm and a final acidity of 0.38 M were calculated as 10.4±0.13×10⁴ and 7.2±0.17×10⁴ l mol⁻¹ cm⁻¹ respectively, indicating that arsenate could interfere in phosphate measurement. Arsenate concentrations as low as 23 μg l⁻¹ caused increase in colour development in phosphate solutions. However, the extent of colour development for both anions depended on the final acid concentration of the solution. An acidified sodium sulphite solution (0.83 M NaSO₃, 0.83 M H₂SO₄) quantitatively prevented arsenate colour development up to 300 μg l⁻¹ As(V). It was also demonstrated that the method removed As(V) interferences in mixed As/P solutions and therefore can be used to treat natural water samples with elevated arsenate concentrations before phosphate measurement.     

Spectrophotometric simultaneous determination of nitrite, nitrate and ammonium in soils by flow injection analysis

A new rapid flow injection procedure for the simultaneous determination of nitrate, nitrite and ammonium in single flow injection analysis system is proposed. The procedure combines on-line reduction of nitrate to nitrite and oxidation of ammonium to nitrite with spectrophotometric detection of nitrite by using the Griess-llosvay reaction. The formed azo dye was measured at 543 nm. The influence of reagent concentration and manifold parameters were studied. Nitrite, nitrate and ammonium can be determined within the range of 0.02–1.60 μg mL⁻¹, 0.02–1.60 μg mL⁻¹ and 0.05–1.40 μg mL⁻¹, respectively. R.S.D. values (n = 10) were 2.66; 1.41 and 3.58 for nitrate, nitrite and ammonium, respectively. This procedure allows the determination and speciation of inorganic nitrogen species in soils with a single injection in a simple way, and high sampling rate (18 h⁻¹). Detection limits of 0.013, 0.046 and 0.047 μg mL⁻¹were achieved for nitrate, nitrite and ammonium, respectively. In comparison with others methods, the proposed one is more simple, it uses as single chromogenic reagent less injection volume (250 mL in stead of 350 mL) and it has a higher sampling rate.     

Simultaneous determination of total arsenic and total selenium in Chinese medicinal herbs by hydride generation atomic fluorescence spectrometry in tartaric acid medium

By HG-AFS, a new method was proposed for simultaneous determination of total arsenic and total selenium existed in the Chinese medicinal herbs in tartaric acid medium. The effects of analytical conditions and coexisting ions on the fluorescence signal intensity of analytes were investigated. The proposed method was provided with linear response ranges above 22 μg l⁻¹ for As and 44 μg l⁻¹ for Se, and the detection limits of 0.13 and 0.12 μg l⁻¹ were obtained for As and Se respectively. The recoveries of 93.8–96.1% for As and 95.3–99.1% for Se, and the precision of 1.2–3.8% and 2.4–5.3% (R.S.D., n = 8) respectively, were obtained via simultaneous determined four samples of Chinese medicinal herbs and three certified botanic reference materials successfully. The proposed method has the advantages of simple operation, high sensitivity and high efficiency.     

Analysis of acrylamide in different foodstuffs using liquid chromatography–tandem mass spectrometry and gas chromatography–tandem mass spectrometry

Acrylamide levels over a wide range of different food products were analysed using both liquid chromatography–tandem mass spectrometry (HPLC–MS–MS) and gas chromatography–tandem mass spectrometry (GC–MS–MS). Two different sample preparation methods for HPLC–MS–MS analysis were developed and optimised with respect to a high sample throughput on the one hand, and a robust and reliable analysis of difficult matrices on the other hand. The first method is applicable to various foods like potato chips, French fries, cereals, bread, and roasted coffee, allowing the analysis of up to 60 samples per technician and day. The second preparation method is not as simple and fast but enables analysis of difficult matrices like cacao, soluble coffee, molasses, or malt. In addition, this method produces extracts which are also well suited for GC–MS–MS analysis. GC–MS–MS has proven to be a sensitive and selective method offering two transitions for acrylamide even at low levels up to 1 μg kg⁻¹. For the respective methods the repeatability (n=10), given as coefficient of variation, ranged from 3% (acrylamide content of 550 μg kg⁻¹) to 12% (acrylamide content of 8 μg kg⁻¹) depending on the food matrix. The repeatability (n=3) for different food samples spiked with acrylamide (5–1500 μg kg⁻¹) ranged from 1 to 20% depending on the spiking level and the food matrix. The limit of quantification (referred to a signal-to-noise ratio of 9:1) was 30 μg kg⁻¹ for HPLC–MS–MS and 5 μg kg⁻¹ for GC–MS–MS. It could be demonstrated that measurement uncertainties were not only a result of analytical variability but also of inhomogeneity and stability of the acrylamide in food.     

Multi-elemental analysis of non-food packaging materials by inductively coupled plasma-time of flight-mass spectrometry

Commercial non-food packaging materials of four different matrices (paper, low density polyethylene (LDPE), polyethylene-polypropylene (PE-PP) and high density polyethylene (HDPE)) were examined for the content of Cr, Ni, Cu, Zn, As, Mo, Cd, Sb, Ba, Hg, Tl, Pb and U. The examined samples (0.17–0.35 g) were digested in HNO₃ and H₂O₂ (papers, LDPE and PE-PP) and in HNO₃, H₂SO₄ and H₂O₂ (HDPE) using microwave assisted high pressure system. The inductively coupled plasma-time of flight-mass spectrometry (ICP-TOFMS) has been employed as the detection technique. All measurements were carried out using internal standardization. Yttrium and rhodium (50 ng g⁻¹) were used as internal standards. The detection and quantification limits obtained were in the range of 0.005 ng g⁻¹ (⁵²Cr) to 0.51 ng g⁻¹ (⁶⁶Zn) and 0.015 μg g⁻¹ (⁵²Cr) to 2.02 μg g⁻¹ (⁶⁶Zn) of dry mass, respectively. The evaluated contents (mg kg⁻¹) of particular elements in the examined materials were as follows: 0.22–219; <1.05–9.03; 1.25–112; <2.02–449; <0.98–<1.30; <0.36–2.06; <0.29–113; <0.22–44.1; <0.06–57.4; <0.66–<0.88; <0.08–0.24; <0.13–1222 and <0.08–0.44 for Cr, Ni, Cu, Zn, As, Mo, Cd, Sb, Ba, Hg, Tl, Pb and U, respectively.     

On-line sample treatment and FT-IR determination of doxylamine succinate in pharmaceuticals

A low solvent consumption method for Fourier transform infrared spectroscopy (FT-IR) determination of doxylamine succinate in pharmaceuticals has been developed. The analyte was continuous and selectively extracted with a 13% (v/v) ethanol:chloroform solvent mixture, recirculating the solvent through the sample and monitoring the process by FT-IR. Doxylamine succinate was determined by on-line standard addition measuring the peak area in the regions 1730–1710 and 1485–1462 cm⁻¹ corrected with a two-point baseline established between 2000 and 1800 cm⁻¹. This new method implies low volumes of chloroformic solvent mixture, only 2.6 mL per sample, in front of classical batch FT-IR methods, improving analytical efficiency and reducing waste generation. The on-line extraction and standard addition determination of doxylamine succinate allowed a throughput of 10 h⁻¹.     

Monitoring of technical oils in supercritical CO(2) under continuous flow conditions by NIR spectroscopy and multivariate calibration

Metal parts and residues from machining processes are usually polluted with cutting or grinding oil and have to be cleaned before further use. Supercritical carbon dioxide can be used for extraction processes and precision cleaning of metal parts, as developed at Forschungszentrum Karlsruhe. For optimizing and efficiently conducting the extraction process, in-line analysis of oil concentration is desirable. Therefore, a monitoring method using fiber-optic NIR spectroscopy in combination with PLS calibration has been developed. In an earlier paper we have described the instrumental set-up and a calibration model using the model compound squalane in the spectral range of the CH combination bands from 4900 to 4200 cm⁻¹. With this model only poor prediction results were obtained if applied to technical oil samples in supercritical CO₂. In this paper we describe a new calibration model, which was set up for the squalane/carbon dioxide system covering the 323–353 K temperature and the 16–35.6 MPa pressure range. Here, calibration data in the spectral range from 6100 to 5030 cm⁻¹ have been used. This range includes the 5100 cm⁻¹ CO₂ band of the Fermi triad as well as the hydrocarbon 1st overtone CH stretching bands, where spectral features of oil compounds and squalane are more similar to each other.

The root mean-squared error of prediction obtained with this model is 4 mg cm⁻³ for carbon dioxide and 0.4 mg cm⁻³ for squalane, respectively. The utilizability of the newly developed PLS calibration model for predicting the oil concentration and CO₂ density of solutions of technical oils in supercritical carbon dioxide has been tested. Three types of “real world” cutting and grinding oil formulations were used in these experiments. The calibration proved to be suitable for determining the technical oil concentration with an error of 1.1 mg cm⁻³ and the CO₂ density with an error of 6 mg cm⁻³. Therefore, it seems possible to apply this in-line analytical approach on the basis of a cost-effective and time-saving model compound calibration for the surveillance of real world de-oiling and other extraction process based on supercritical carbon dioxide, and furthermore to establish an automated process termination criterion based on this technique.     

Enhancement of the chemiluminescence of penicillamine and ephedrine after derivatization with aldehydes using tris(bipyridyl)ruthenium(II) peroxydisulfate system and its analytical application

A novel sequential injection (SI) method was developed for the determination of penicillamine (PA) and ephedrine (EP) based on the reaction of these drugs with tris(bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) and peroxydisulfate (S₂O₈²⁻) in the presence of light. Derivatization of PA and EP with aldehydes has resulted in a significant enhancement of the chemiluminescence emission signal by at least 25 times for PA and 12 times for EP, leading to better sensitivities and lower detection limits for both drugs. The instrumental setup utilized a syringe pump and a multiposition valve to aspirate the reagents, (Ru(bpy)₃²⁺ and S₂O₈²⁻), and a peristaltic pump to propel the sample. The experimental conditions affecting the derivatization reaction and the chemiluminescence reaction were systematically optimized using the univariate approach. Under the optimum conditions linear calibration curves between 0.2–24 μg mL⁻¹ for PA and 0.2–20 μg mL⁻¹ for EP were obtained. The detection limits were 0.1 μg mL⁻¹ for PA and 0.03 μg mL⁻¹ for EP. The procedure was applied to the analysis of PA and EP in pharmaceutical products and was found to be free from interferences from concomitants usually present in these preparations.     

Fabrication of hollow silica spheres using droplet templates derived from a miniemulsion technique

Hollow silica spheres have been successfully fabricated by means of a miniemulsion technique, in which miniemulsion droplets of tetraethoxysilane (TEOS) and octane were prepared with cetyltrimethylammonium bromide as a surfactant and hexadecane as a costabilizer and used as templates. As the TEOS diffused out from the droplets, it was hydrolyzed and condensed to form a silica shell at the oil/water interface. In this way, hollow silica spheres could be obtained directly since the miniemulsion droplets of octane could be evaporated very easily during the reaction process or the drying process; neither an additional dissolution nor a calcination process or additional surface modification of the templates were needed.