Fourier-transform Instrument Research Articles

Synthesis of Atenolol-Imprinted Polymers with Methyl Methacrylate as Functional Monomer in Propanol Using Bulk and Precipitation Polymerization Method.

Atenolol is one of the beta-1 blocker drugs that is misused by athletes to increase their performance during competition. Therefore, it is important to analyze atenolol levels in blood selectively. The preparation method that can be used in separating atenolol in sample is molecular imprinting solid-phase extraction (MI-SPE) because it has good selectivity and sensitivity. This study aims to examine the characteristics and analytical performance of imprinted polymers synthesized from functional monomer methyl methacrylate. The stages of this study include the determination of association constants, synthesis of sorbent MI-SPE atenolol using the bulk polymerization method, and precipitation with atenolol as the template, methyl methacrylate as the functional monomer, and propanol as the porogen. The template was extracted from a polymer, and then, the adsorption ability, capacity, and selectivity of MI-SPE and finally the application of the best MI-SPE to spiked serum samples were determined. MI-SPE was also characterized by using Fourier-transform instrument infrared (FTIR) and scanning electron microscope (SEM). The result of characterization with FTIR and SEM showed that MIP made by the precipitation polymerization method was completely polymerized, more porous, and produced smaller particle size with an average value of 0.274 μm. It had better analytic performances than MIP made by bulk polymerization, with affinity value 0.3607 mg/g and homogeneity value 1.3246, and good selectivity toward atenolol with imprinting factor value 22.519. Application of MI-SPE to spiked serum samples has an excellent recovery percentage of 95.46% over 0% for the nonimprinting one. Based on the result of study, MIP made by precipitation polymerization could be used to extract atenolol on serum samples toward drug analysis.

Comparative Analysis of Inkjet Printer Inks Extracted from Printed Documents by FT-IR Spectrophotometry

Primary coloured inks i.e. Cyan, Magenta, Yellow, and Black used in inkjet printers were extracted from the printed document and analyzed in order to identify the possible functional groups using Infrared (IR) spectroscopic technique. Experiments were conducted on the all four primary inks and the results are presented. The technique can provide valuable information if an admitted sample is provided for comparison with the suspect printed document. Determination of authenticity of a document is based on many factors. Characterization of writing/printing instruments used to produce the document such as ink; paper etc may be a leading step in the investigation. Many instrumental analytical techniques are available to determine the actual composition of dyes and other compounds present in inkjet printer inks. The IR technique is one of the techniques which can provides important information about the commercially available printer inks (Yuen et al, 2005). IR spectroscopy deals with the infra red region of the electromagnetic spectrum. The IR portion of the electromagnetic spectrum is usually divided into three regions; the near-IR (approximately 14000-4000 cm −1 ), mid-IR (4000-400 cm −1 ) and far- infrared (400-10 cm −1 ). The near-IR can excite overtone or harmonic vibrations, the mid-infrared may be used to study the fundamental vibrations and associated rotational- vibrational structure whereas the far-infrared has low energy and may be used for rotational spectroscopy. IR spectroscopy is based upon the ability of certain compounds to absorb radiation by interaction of IR radiation with the molecular bonds of the sample. Absorption occurs when the molecular bond has a vibrational frequency equal to the IR radiation. The wavelengths at which a measured absorption occurs correspond to specific functional groups. This information can be interpreted to characterize the compounds. Fourier Transform Infrared Spectroscopy (FTIR) is used to obtain an infrared spectrum of a solid, liquid or gas. In the Fourier Transform instrument the whole wavelength range is measured at once and then a transmittance or absorbance spectrum is generated with the help of a computer. Analysis of the position, shape and intensity of peaks in the spectrum reveals details about the molecular structure of the sample. A simple glass tube with length of 5 to 10 cm equipped with infrared windows at the both ends of the tube can be used for concentrations down to several hundred ppm. Sample gas concentrations well below ppm can be measured with a White's cell in which the infrared light is guided with mirrors to travel through the gas. Liquid samples can be sandwiched between two plates of highly polished transparent sodium chloride, potassium bromide or calcium fluoride. These plates are transparent to the infrared light. Solid samples can be prepared in a variety of ways such as by finely mixing the fine powder sample with an oily mulling agent (usually Nujol) in a marble or agate mortar, with a pestle. A thin of the mull is smeared onto salt plates and measured. The second method is to grind a quantity of the sample with potassium bromide finely. This powder mixture is then pressed in a mechanical press to form a translucent pellet through which the beam of the spectrometer can pass. A third technique is the cast film technique mainly used for polymeric materials and most suitable for qualititative analysis. The sample is first dissolved in a suitable, non hygroscopic solvent. A drop of this solution is deposited on surface of KBr or NaCl cell. The solution is then evaporated to dryness and the formed on the cell is analyzed directly. The final method is to use microtomy to cut a thin (20-100 µm) from a solid sample. IR technique can provide valuable information about the chemical composition of a material (Kan, et al., 2000; Wen, 2004; Huang, 2004) with convenient sample analysis.

Evaluation of the Compact High-Field Orbitrap for Top-Down Proteomics of Human Cells

Mass spectrometry based proteomics generally seeks to identify and fully characterize protein species with high accuracy and throughput. Recent improvements in protein separation have greatly expanded the capacity of top-down proteomics (TDP) to identify a large number of intact proteins. To date, TDP has been most tightly associated with Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Here, we couple the improved separations to a Fourier-transform instrument based not on ICR but using the Orbitrap Elite mass analyzer. Application of this platform to H1299 human lung cancer cells resulted in the unambiguous identification of 690 unique proteins and over 2000 proteoforms identified from proteins with intact masses<50 kDa. This is an early demonstration of high throughput TDP (>500 identifications) in an Orbitrap mass spectrometer and exemplifies an accessible platform for whole protein mass spectrometry.

Passive Detection of Biological Aerosols in the Atmosphere with a Fourier Transform Instrument (FTIR)—the Results of the Measurements in the Laboratory and in the Field

Fourier Transform Infrared Radiation (FTIR) spectroscopy is one of the most powerful methods for the detection of gaseous constituents, aerosols, and dust in planetary atmospheres. Infrared spectroscopy plays an important role in searching for biomarkers, organics and biological substances in the Universe. The possibility of detection and identifications with FTIR spectrometer of bio-aerosol spores (Bacillus atrophaeus var. globigii=BG) in the atmosphere is discussed in this paper. We describe the results of initial spectral measurements performed in the laboratory and in the field. The purpose of these experiments was to detect and to identify bio-aerosol spores in two conditions: 1) In a closed chamber where the thermal contrast between the background and aerosols was large, and 2) In open air where the thermal contrast between the background and aerosols was small. The extinction spectrum of BG spores was deduced by comparing our measurements with models, and other measurements known from the literature. Our theoretical and experimental studies indicate that, during passive remote sensing measurements, it is difficult—but possible to detect and to identify bio-aerosol clouds by their spectral signatures. The simple spectral analysis described in the paper can be useful for the detection of various kinds of trace aerosols—not only in the Earth’s atmosphere, but also during planetary missions in the environments of other astronomical objects such as planets, comets etc. We expect that the interpretation of data from spectrometric sounding of Venus and Mars during the current missions Mars and Venus Express, and later during the Rosetta mission will benefit from our experimental work and numerical modelling.

Quantitative analysis in alkaline solutions by Raman spectroscopy.

A detailed investigation has been made of the analysis of concentrated alkaline aluminate solutions (synthetic Bayer liquors) by Fourier transform (FT) Raman spectroscopy. Satisfactory determinations of Al(OH)4-, SO42- and CO32- were achieved at industrially-relevant concentrations. Possible extensions to a number of other inorganic and organic anions of interest to the alumina refining industry were demonstrated. No significant interferences were observed except for a small but readily correctable contribution of a minor SO42- mode at ∼615 cm-1 to the Al(OH)4- envelope centred at ∼620 cm-1. Hydroxide (OH-) could not be determined with the present FT instrument, due to the low detector sensitivity at high wavenumbers, but might be possible with other spectrometers. Successful extension of the analyses to industrial Bayer process solutions is briefly discussed.

Using Near-Infrared Spectrophotometry for the Identification of Pharmaceuticals and Drugs

The near infrared range (NIR) of the electromagnetic spectrum extends from 800 to 2500 nm, being confined between the middle IR and visible spectral regions. The method of NIR spectroscopy is based on a combination of spectrophotometry and statistical methods of multifactor analysis, which provides excellent possibilities for drug identification and quality control even without opening the package. We have studied a series of drugs including cefazolin sodium and generic drugs based on enalapril maleate. True and falsified variants of a given drug X were classified into groups according to “drug name,” “drug manufacturer,” and “falsified product” by means of NIR spectroscopic analyses performed using the NIR Fourier-transform instruments Multi Purpose Analyzer (Bruker, Germany) and Antaris (Thermo Electron Corporation, USA). The potential of this method for the identification of drugs without violation of their packing shows good prospects for introducing it into the drug quality control system. This method should be recommended for introduction into the future Russian State Pharmacopoeia as a general method of drug analysis.

Evaluation of basic algorithms for transferring quantitative multivariate calibrations between scanning grating and FT NIR spectrometers

A key issue in near infrared spectroscopy (NIR) is the possibility to use calibrations generated on one instrument for predictions on others. A number of methods for calibration transfer have been proposed, but which method to choose is typically not straightforward. An evaluation of a number of methods for transferring quantitative calibrations between different instruments was carried out on near infrared diffuse-reflectance data from a pharmaceutical formulation. Six instruments were included in the study, five of which were scanning grating instruments, both with and without fibre-optic probe configuration, and one of which was a Fourier-transform instrument, equipped with a fibre-optic probe. The results show that it is possible to transfer calibrations between different instruments, provided that a structured procedure is used. Simple techniques for calibration transfer, such as slope/bias correction on the predicted results, as well as standard normal variate transformation and local centring of the raw spectra, gave considerably lower prediction errors on transfer than did standardisation with a certified diffuse-reflectance standard, or direct transfer without any transfer function. Notably, including more than one instrument in the calibration also improved the prediction ability of the models on calibration transfer. No significant differences in wavelength scale were found when a certified diffuse-reflectance wavelength standard was measured on the instruments studied. Nor did simulated wavelength scale differences below ±0.3 nm cause any significant change in the prediction errors.

Birefringent Fourier-transform imaging spectrometer

Fourier-transform imaging spectrometers offer important advantages over other spectral imaging modalities, such as, a wider free spectral range, higher spectral resolutions and, in low-photon-flux conditions, higher signal-to-noise ratios can be achieved. Unfortunately, for application in harsh environments, deployment of Fourier-transform instruments based on traditional moving-mirror interferometers is problematic due to their inherent sensitivity to vibration. We describe a new Fourier-transform imaging spectrometer, based on a scanning birefringent interferometer. This system retains the advantages of traditional Fourier transform instruments, but is inherently compact and insensitive to vibration. Furthermore, the precision requirements of the movement can be relaxed by typically two orders of magnitude in comparison to a traditional two-beam interferometer. The instrument promises to enable application of Fourier-transform imaging spectrometry to applications, such as airborne reconnaissance and industrial inspection, for the first time. Example spectral images are presented.

The rotational spectrum of thiophene⋯HBr and a comparison of the geometries of the complexes B⋯HX, where B is benzene, furan or thiophene and X is F, Cl or Br

The ground-state rotational spectra of three isotopomers C4H4S⋯H79Br, C4H4S⋯H81Br and C4H4S⋯D79Br of a weakly bound complex formed by thiophene and hydrogen bromide have been observed in the gas phase by means of a pulsed-jet, Fourier-transform instrument. Each spectrum was analysed and fitted to give rotational constants A0, B0 and C0, centrifugal distortion constants ΔJ, ΔJK, ΔK, δJ and δJK and the components χaa, χbb − χcc and χab of the bromine nuclear quadrupole coupling tensor. A detailed analysis of the spectroscopic constants established that the geometry of the complex is of the face-on type. The Br atom of HBr is located close to the perpendicular drawn through the centre of mass of the thiophene ring and the H atom of HBr lies between the Br atom and the ring. The angle αaz made by the HBr internuclear axis z with the a-axis has the two possible values ±9.83°. The preferred structure is that generated when the positive value of the angle is chosen and has the HBr sub-unit pointing in the direction of the S atom of thiophene. The determined geometrical parameters are r(S⋯H) = 2.728(3) A, ϕ = 116.0(2)° and θ = 7.08(4)°, where ϕ is the angle made by the S⋯H internuclear line with the local C2 axis of thiophene and θ is the angular deviation of the S⋯H–Br nuclei from collinearity.

Observation of Fourier transform near-infrared vibrational circular dichroism to 6150 cm-1.

We report here the first measurement of near-infrared (NIR) vibrational circular dichroism (VCD) with Fourier transform (FT) instrumentation. The measurements were carried out using a commercial rapid-scan FT-IR VCD spectrometer modified for operation in the NIR region between 3750 and 6150 cm-1. Overtone and combination band VCD intensities, first reported by Keiderling and Stephens using dispersive VCD instrumentation in 1976, were reproduced with equivalent signal quality and spectral resolution using collection times of only a few minutes. These results offer substantial promise for the routine use of rapid-scan FT instrumentation for the measurement of overtone and combination band VCD spectra in the NIR region.

Are members of the family of hydrogen-bonded complexes formed by furan with the hydrogen halides isostructural? An answer from the rotational spectrum of furan⋯HBr

The ground-state rotational spectra of the five isotopomers C4H4O⋯H79Br, C4H4O⋯H81Br, C4D4O⋯H79Br, C4H4O⋯D79Br, and C4H4O⋯D81Br of a weakly bound complex formed by furan with hydrogen bromide in the gas phase have been observed with a pulsed-jet, Fourier-transform instrument. Each spectrum was analyzed and fitted to give rotational constants A0, B0, and C0, centrifugal distortion constants ΔJ and ΔJK, and components χaa, χbb-χcc, and χab (or χac in the case of C4D4O⋯H79Br) of the bromine nuclear quadrupole coupling tensor. A detailed analysis of the spectroscopic constants reveals that the observed complex does not have C2v symmetry, with HBr lying along the C2 axis of furan. Instead, the geometry is of the face-on type, with the Br atom of HBr lying close to the perpendicular drawn through the center of the mass of the furan ring. The H atom of HBr lies between the Br atom and the face of the furan ring. The angles αaz made by the HBr internuclear axis z with the a axis has the two possible values ±11.929°. The preferred structure is that generated when the positive value of the angle is chosen and has the HBr subunit pointing in the direction of the O atom of furan. The determined geometrical parameters are r(O⋯H)=2.599(3) Å, φ=112.90(14)°, and θ=6.05(4)°, where φ is the angle made by the O⋯H internuclear line with the local C2 axis of furan and θ is the angular deviation of the O⋯H–Br nuclei from collinearity. Reasons why furan⋯HCl, but not furan⋯HBr, obeys some simple rules for predicting angular geometries are discussed.

QUANTITATIVE NMR SPECTROSCOPY

In this review the theoretical and practical factors that govern the suitability and accuracy of NMR measurements for quantitative analysis purposes are discussed. The review is limited to factors important for spectra acquired by modern Fourier Transform instruments.

Parabolic Concentration of Diffusely Transmitted near Infrared Radiation in an Acousto-Optic Tunable Filter Spectrometer

The research model near infrared (NIR) spectrometer described in this paper, worthy of quantitative use and suited for industrial applications, is the result of stepwise refinement of the acousto-optic tunable filter (AOTF)-based monochromator and other optical components. A sensitive and rapid response extended-range indium gallium arsenide (InGaAs) detector (covering the 1100–2500 nm range) was selected to match the high speed of acousto-optic TFS electronic wavelength switching. Excellent quantitative performance has been demonstrated in comparison with commercial grating monochromator and Fourier transform (FT)-NIR instruments for multi-component liquids, films, pumped fluids and even supercritical fluids. Software-controlled wavelength switching, data acquisition and programmed or interactive time averaging at each wavelength demonstrated analytically-enhanced performance. Throughput is not limited by slits, and exposure of the sample to white light, as with a diode array or an FT instrument, is avoided. Although focusing optics between sample and detector were found to work well for concentrating radiation on a small surface area InGaAs detector, detector size limited performance in the case of optically difficult samples because of the low solid angle of collection. Use of an experimental non-focusing multistage parabolic concentrator immediately after the sample vessel and before the 1 mm2 detector was found to offer an advantage for highly scattering specimens. Although the reflection optics of the locally fabricated concentrator directed a lower intensity of light transmitted by clear specimens than from the standard lens arrangement, successful analysis was extended to include highly scattering samples. The percentage of incident radiation attenuated via scatter was reduced, and for scatter beyond a point, the absolute intensity of radiation falling on the detector was greater, even though the absolute maximum of non-scattered intensity was less, thus establishing proof of principle. We anticipate that further improvement could be attained for highly scattering samples with a commercial optics manufacturer's version of the homemade concentrator.

Fourier-transform instrument for high-resolution Raman spectroscopy of gases

An instrument is described for recording vibrational-rotational Raman spectra of gases with a resolution of 0.02-0.03 cm(-1). The Raman scattered light is collected by near forward scattering within the cavity of a single-mode, long-term, stabilized Ar-ion laser. The Raman light is analyzed in an ordinary step-scanned Michelson interferometer. To compensate for the low intensity of vibrational-rotational Raman spectra, the interferometer has a beam diameter of 160 mm. The movable mirror, weighing 2.7 kg, is mounted on a smoothly moving sledge, the stepwise motion being performed by three piezotranslators and controlled by three independent He-Ne laser beams. It is shown experimentally that it is possible for one to move the mirror with sufficient precision, using only 13% of the scan time in a typical experiment. In a preliminary spectrum of the fundamental vibration of(14) N(2), the width of the lines has been measured to 0.015 cm(-1).

The structure of CO-OCS: a spectroscopic and theoretical investigation

The spectrum of the weakly bound complex CO-OCS has been measured in the infrared using direct absorption diode laser spectroscopy in a supersonic jet, and in the microwave region using a pulsed nozzle Fourier-transform instrument. In addition, microwave spectra of the two isotopomers 13CO-OCS and CO-OC34S were recorded. A T shaped structure has been determined with the carbon atom in CO closest to the OCS (RMS angle ±20·5° with respect to the intermolecular axis) and the sulphur end of OCS pointing away from CO (vibrationally averaged angle 105·7°). The ground state centre of mass separation is 4·17 A. The effective structure is rationalized by a simple potential incorporating a distributed multipole analysis of the electrostatic charge distribution, distributed dispersion contribution and a cylindrical hard core repulsion, with discussion of the implications for the potential of including correlation effects in the CO multipole.

Pre-reactive intermediates in gas-phase chemical reactions: a contribution from rotational spectroscopy

The detection and detailed characterisation of pre-reactive intermediates in gas mixtures through their microwave rotational spectra are described. Spectra were observed by using two special types of nozzle (a fast-mixing nozzle or a glow-discharge nozzle) in a pulsed-nozzle, Fourier-transform instrument. The pre-reactive intermediates are considered for one example of each of the following reaction types: a ring-opening reaction (1), the addition reaction of a halogen to a π bond (2), the abstraction reaction of H from a molecule by fluorine (3), a proton transfer reaction (4), a reaction in which a compound having a dative bond is formed (5), and a prototype unimolecular reaction (6).

Near Infrared Excited Surface Enhanced Raman Scattering on HNO3Etched Metals by Using Fourier Transform Technique

Abstract Surface enhanced Raman scattering (SERS) has been produced on HNO3 roughened silver and copper foils using near infrared excited Fourier transform (FT) Raman spectroscopy. The FT-SERS spectra obtained from 4-aminophenyl disulfide reveal the S-S bond fission of the molecule upon adsorption both on Ag and Cu surfaces. The spectra of acryl amide on Ag indicate that a relatively complete polymerization has occurred on Ag. The SERS technique on such metal substrates, in combination with FT instrumentation, shows fair simplicity, high sensitivity and great promise as a general analytical tool for surface reaction studies.

Instrumental Aspects of Dynamic Two-Dimensional Infrared Spectroscopy

Dynamic two-dimensional infrared (2D IR) correlation maps are a convenient means of examining the information contained in time-resolved IR spectra. Dynamic 2D IR spectra can be collected with the use of either dispersive or Fourier transform (FT) IR spectrometers. Use of a step-scanning FT-IR spectrometer has advantages over conventional rapid-scan FT-IR spectrometry when one is acquiring time-resolved IR data on time scales faster than about 0.1 s, because the spectral multiplexing is removed from the time domain. Dynamic IR spectra of atactic polystyrene (undergoing a small-amplitude oscillatory strain) collected on both dispersive and FT instrumentation are compared. Although the dispersive approach produces higher signal-to-noise ratios over small spectral regions, the multiplex advantage makes the FT approach attractive when broader spectral coverages are required. The first vibrational circular dichroism (VCD) spectrum [of (–)- α;-pinene] collected on a step-scanning interferometer is also presented.

Infrared emission band spectrum of Si_2

A strong infrared emission band spectrum of Si2 was observed in the region between 4500 and 6500 cm−1. It consists of 21 red-degraded bands, which are transitions between two newly observed low-lying singlet states d1Σg+–b1Πμ. The bands arise from transitions between vibrational levels from 0 to 6 in both electronic states. Rotational lines up to J = 162 were observed. A global fit was made to 2000 spectral lines, and fits were made to individual branches of each band. The source was a King-type furnace charged with SiC, filled with helium at a pressure of 100 Torr, and maintained at a temperature of 2700 K. The spectrometer was the Fourier-transform instrument at the National Solar Observatory (Kitt Peak).

IR-spectroscopy of the atmosphere

The infrared technique of measuring trace gases in the air has been evolving for many years, with rapid progress during the last ten years. Air pollution research requires such measurements for mixing ratios as low as 10−10. This calls for long optical paths, such as the path from a high altitude observing point to a setting sun. At ground level the best way to achieve a long enough path is to use J.U. White's 3-mirror multiple-pass cell. The infrared method has had its greatest success in the study of the upper atmosphere using balloon-borne spectrometers aimed at the sun. Measurements through the upper atmosphere do not have significant interference from water vapor. At ground level, however, the water vapor absorbs nearly everywhere in the spectrum, and it is necessary to detect the trace gases by the small perturbations they make on the water vapor spectrum. The Fourier transform (FT) spectrometer has been responsible for recent progress. For studies in the lower atmosphere one can obtain superb spectra by combining an FT instrument of about 0.1 cm−1 resolution with a White cell made from mirrors of modest size. Nitrogen-cooled detectors should be used. The path may be in the open air. With an FT instrument, signal fluctuations caused by air turbulence do not appear to introduce noise into the spectrum. This is a result of the multiplexing and the high frequency modulation. Pollutants that have been measured by infrared in ambient air have included HNO3, HNO2, NH3, O3, CO, CO2, SO2, NO, NO2, H2CO, HCOOH, hydrocarbons, peroxy nitrates, HCl and HF. Further study should extend this list.