Laser-induced breakdown spectroscopy analysis of complex silicate minerals—beryl

Beryl (Be₃Al₂Si₆O₁₈) is a chemically complex and highly compositionally variable gem-forming mineral found in a variety of geologic settings worldwide. A methodology and analytical protocol were developed for the analysis of beryl by laser-induced breakdown spectroscopy (LIBS) that minimizes the coefficient of variance for multiple analyses of the same specimen. The parameters considered were laser energy/pulse, time delay and crystallographic orientation. Optimal analytical conditions are a laser energy/pulse of 102 mJ and a time delay of 2 μs. Beryl compositions measured parallel and perpendicular to the c axis were identical within analytical error. LIBS analysis of 96 beryls from 16 countries (Afghanistan, Brazil, Canada, China, Colombia, India, Ireland, Italy, Madagascar, Mexico, Mozambique, Namibia, Norway, Russia, Tanzania and United States), Antarctica, and ten US states (AZ, CA, CO, CT, ID, ME, NC, NH, NM and UT) were undertaken to determine whether or not LIBS analysis can be used to determine the provenance of gem beryl.     

Terahertz time-domain spectroscopy of some pentoses

1 Introduction Terahertz time-domain spectroscopy (THz-TDS) is a new spectral technique based on femto-second laser technology developed since the 1980s[1]. Terahertz (THz) waves lie between the infrared and microwave bands in the electromagnetic spectrum covering the frequency range from 100 GHz to 10 THz. Despite great scientific interest, the THz frequency range re- mains one of the least tapped regions of the electro- magnetic spectrum because there are neither conven- ient high-power…     

Thermal Treatments of Fe—Mn Alkoxide of Glycerol: Infrared absorption and emission spectroscopy

Synthetic Fe—Mn alkoxide of glycerol samples are submitted to controlled heating conditions and examined by IR absorption spectroscopy. On the other hand, the same sample is studied by infrared emission spectroscopy (IRES), upon heating in situ from 100 to 600°C. The spectral techniques employed in this contribution, especially IRES, show that as a result of the thermal treatments ferromagnetic oxides (manganese ferrite) are formed between 350 and 400°C. Some further spectral changes are seen at higher temperatures.This revised version was published online in November 2005 with corrections to the Cover Date.     

New contributions to the field of bead-injection spectroscopy—flow-injection analysis: determination of cobalt

A novel method based on column-switching high-performance liquid chromatography-electrospray mass spectrometry (LC-MS) coupled with an on-line extraction column containing conjugated avidin has been developed for direct injection analysis of di(2-ethylhexyl) phthalate (DEHP) and its metabolite, mono(2-ethylhexyl) phthalate (MEHP), in blood samples. The sample preparation for on-line extraction involved the mixing of blood samples with internal standards, DEHP-d(4) and MEHP-d(4), in LC glass vials. A linear response was found for column-switching LC-MS when tests were conducted within the validated range of 25 to 1000 ng mL(-1) for DEHP and 5 to 1000 ng mL(-1) for MEHP, with correlation coefficients (r) greater than 0.999. In addition, the recoveries of DEHP and MEHP from human plasma were calculated by using this method with on-line extraction, yielding recoveries of up to 91.2% (RSD<5%). We measured the background levels of DEHP and MEHP in six human plasma samples from healthy volunteers and three fetal bovine serum samples for cell-line culture. DEHP and MEHP were not detected in all human plasma samples (N.D. is <25 ng mL(-1) for DEHP, and N.D. is <5.0 ng mL(-1) for MEHP). In contrast, high DEHP contamination of commercially available fetal bovine serum samples was found by this method.     

Applications of Fourier transform Raman spectroscopy in inorganic chemistry—a considered view

A sudy of a wide variety of coloured main group metal, transition metal coordination and transition metal organometallic complexes using Fourier transform Raman (FT-Raman) spectroscopy has demonstrated a high success rate (ca 50%) with good quality spectra obtained in short periods of time. It is suggested that FT-Raman spectroscopy should now be regarded as a routine spectroscopic tool for use in inorganic as well as organic research and teaching laboratories.     

Vibrational spectroscopy of D—Glucose: the CH stretching region

We recorded the infrared and Raman spectra of α- and β-D-Glucose and five deuterated derivatives, in the solid. A rule is proposed for the interpretation of the behaviour of the principal force constants of the CH bonds in the various positions, taking into account the interaction of each CH with the vicinal oxygen atom.     

Negative ion photoelectron spectroscopy of teo−

We have recorded the photoelectron spectrum of Te0⁻ using a hot-cathode discharge ion source and a negative ion photoelectron spectrometer. The adiabatic electron affinity of TeO is determined to be 1.697±0.022 eV. The negative ion parameters determined in this work are: (w_e″(TeO⁻) = 690 ± 80 cm⁻¹, r_e″(TeO⁻) = 1.884 ± 0.028 Å. and D_o     

Determination of sub—ppm levels of boron in ground water samples by laser induced breakdown spectroscopy

Laser induced breakdown spectroscopy (LIBS) was applied to the determination of sub-ppm levels of boron in ground water samples using spectroscopically pure graphite planchets as solid support. The data obtained by LIBS agreed well with those from ICP-AES. No spectral interference due to the possibly interfering elements Fe, Cr, Al and Mo was observed. The detection limit was 0.01 µg.g^?1 for boron using the B(I) 249.773 nm emission line. The method is considered to be promising for the rapid determination of boron, with an acceptable degree of accuracy and without the need for elaborate sample treatment, preconcentration and purification steps.     

Intermolecular vibrations and dynamics of the anisole—benzene complex studied by multi-resonance spectroscopy

The intermolecular vibrations of the anisole—benzene complex in the ground and excited electronic states have been observed by the LIF (laser-induced fluorescence) and fluorescence-dip techniques. Short progressions due to the intermolecular vibrations suggest a small structure change of the complex upon electronic excitation. The LIF excitation spectrum shows predominant progressions of 27 cm⁻¹, which is tentatively assigned to one of the intermolecular bending modes in the excited electronic state. On the other hand, the fluorescence-dip spectrum shows only a series of bands with irregular intervals due to the intermolecular modes in the ground electronic state. The decay rates of the vibrationally excited complex in the ground electronic state have also been measured with the SEP-LIF (stimulated emission pumping-laser-induced fluorescence) technique, where the complex vibrationally excited by SEP is probed by the delayed LIF measurements. The complex excited to its purely intermolecular mode stays in the initially prepared state after a delay time of 1 μs. On the other hand, the complex excited to the intramolecular vibrational states above 500 cm⁻¹ does not seem to stay in the prepared states. Neither the relaxed complex nor the dissociated monomer was detected. A possible reason for this observation is discussed.     

Raman spectroscopy in the near infrared – a most capable method of vibrational spectroscopy

Raman spectroscopy has enjoyed a dramatic improvement during the last years: The interference by the fluorescence of impurities is virtually eliminated, the sample preparation is considerably easier as for infrared spectroscopy and many applications in routine analytics, quality control and process control in various branches of industry are now possible. It is shown that the up-to-date near-infrared Raman spectrometers now meet most demands for a modern analytical instrument concerning applicability, analytical information and convenience. It can be anticipated that Raman spectroscopy will catch up infrared spectroscopy, the current workhorse of vibrational spectroscopy.     

Study of ε-caprolactone polymerization by NIR spectroscopy

Near-infrared (NIR) spectroscopy is proposed for the in-line quantitative and kinetic study of the polymerization of ε-caprolactone and eventually to facilitate real-time control of the manufacturing process. Spectra were acquired with a fibre-optic probe operating in transflectance mode immersed in the reactor. The NIR data acquired were processed using a multivariate curve resolution alternating least squares (MCR-ALS) algorithm. The proposed method allows calculation of the concentration and spectral profiles of the species involved in the reaction. The key point of this method is the lack of reference concentrations needed to perform the MCR-ALS method. The use of an extended spectral matrix using both process and pure analyte spectra solves the rank deficiency. The concentration profiles obtained were used to calculate a kinetic fitting of the reaction, but the method was improved by applying kinetic constraints (hard modelling). The rate constants of batches at different temperatures and the energy of activation for this reaction were calculated. Whenever possible, the hard modelling combined with the MCR-ALS method improves the fit of the experimental data: the results show good correlation between the NIR and reference data and allow the collection of high-quality kinetic information on the reaction (rate constants and energy of activation).     

Fourier transform-Raman spectroscopy using pulsed lasers—II

This paper compares and contrasts two signal processing schemes, viz. the fast filter and the gated integrator. It is shown that the use of a gated integrator further increases the SNR advantage over CW excitation, and extends the use of pulsed excitation to allow the recording of Raman spectra samples at significantly higher temperatures. The use of a ratioing circuit to correct for laser pulse-to-pulse energy fluctuations is also demonstrated.     

Thermotropic liquid-crystal polymers—25. A Mössbauer spectroscopy study of molecular mobility

The Mössbauer label variant of the Mössbauer spectroscopy method is employed to study intramolecular mobility in comb-shaped liquid-crystal (LC) polymer, poly{I-[II-(4′-cyano-4-biphenyloxy)undecyloxycarbonyl]ethylene}(CBO-II-PM) and also in the PA-4 (polybutylacrylate) polymer and 4-hexyloxy-4′-cyanodiphenyl (CBO-6), a low-molecular-weight LC compound, as model systems. Ferrocene and ferrocenealdehyde were used as molecular labels. Measurements were taken between 90 and 390 K. Temperature dependences of the dynamic parameters of the Mössbauer spectra of the labels localized in various polymer matrix microregions were analyzed to estimate characteristic Debyc temperatures and mean square vibrational amplitudes of label molecules. These quantities reflect “rigidity” of the corresponding microregions in the vitreous and LC phases.     

Investigation of hydration of α-amino acids by means of absorption millimeter spectroscopy

The hydration indexes for 19 protein -amino acids are measured by means of absorption millimeter spectroscopy (AMS) at 31.42 GHz. The plot of the hydration indexes on the area of surface of aliphatic amino acid molecules accessible for water is a straight line located above the points corresponding to aromatic or polar amino acids. The contribution of nonpolar groups in the hydration index is greater than that of polar groups provided that their accessible surface areas are equal. The contribution to hydration of -OH and-CONH₂ groups in Ser. Gin, and Asn coincides in sign with that of pure hydrophobic hydration but the value of the contribution is significantly smaller. The change in mobility of water molecules, which is the basis of the AMS method, may serve as the physicochemical foundation for the construction of a new hydrophobicity scale for amino acids comparable with the already existing scales.Deceased September 2, 1995.Translated fromIzvestiya Akodemii Nauk. Seriya Khimicheskaya, No. 3, pp. 618–622, March, 1996.     

Complexation of uranium(VI) with protocatechuic acid—application of iterative transformation factor analysis to EXAFS spectroscopy

The speciation of 1 mM uranium(VI) in carbonate-free aqueous solutions of 50 mM protocatechuic acid (PCA, 3,4-dihydroxybenzoic acid) was studied in the pH range of 4.0 to 6.8 using EXAFS spectroscopy. The uranium L_III-edge EXAFS spectra were analyzed using a newly developed computer algorithm for iterative transformation factor analysis (FA). Two structural different uranium(VI) complexes were observed. The speciation in the pH range of 4.0 to 4.8 is dominated by a 1:2 or 1:3 uranium(VI)/PCA complex with bidentate coordination of the carboxyl group to the uranium(VI) moiety. Already at pH 4.6 significant amounts of a second species are formed. This uranium(VI) species contains two PCA ligands that are bound to the uranium via their neighboring phenolic hydroxyl groups under formation of five-member rings.     

The application of Fourier transform Raman spectroscopy to the identification and characterisation of polyamides—II. Double-number nylons

High quality Fourier transform Raman spectra, substantially free from fluorescent background, have been obtained for twelve double-number nylons ranging from nylon 1,3 to nylon 10,10. These spectra, obtainable on a routine basis, prove to be highly characteristic and therefore of considerable value for analytical purposes. The characteristic trends observed in some regions of this series of spectra are investigated and discussed. A less detailed study suggests that Fourier transform Raman spectroscopy should also be of value for the characterisations of nylon co-polymers.