Non-destructive NIR-FT-Raman spectroscopy of plant and animal tissues, of food and works of art

Just after the discovery of Raman spectroscopy in 1928, it became evident that fluorescence with a quantum yield of several orders of magnitude higher than that of the Raman effect was a great and apparently unbeatable competitor. Raman spectroscopy could therefore, in spite of many exciting advantages during the last 60 years, not be applied as an analytical routine method: for nearly every sample, fluorescing impurities had to be removed by distillation or crystallisation. Purification, however, is not possible for cells and tissues, since the removal of the fluorescing enzymes and coenzymes would destroy the cells. There is fortunately one alternative solution. When excited with the radiation of the Nd:YAG laser at 1064 nm Raman spectra are practically free of fluorescence. Raman spectra can now be recorded with minimal sample preparation. In order to facilitate non-destructive Raman spectroscopy of any sample, cells and tissues, food, textiles and works of art, a new entrance optics for Raman spectrometers is used. Typical results from several fields are demonstrated.     

Diagnosis of inflammatory lesions by high-wavenumber FT-Raman spectroscopy

The Raman spectroscopy technique has been extensively used for biological sample characterization. In particular, the fingerprint spectral region (800?C1,800?cm^?1) has been shown to be very promising for optical biopsy purposes. However, limitations for the widespread use of Raman-based optical biopsy technique still persist. For example, fluorescence when one uses visible light (400?C700?nm) spectral sources is often present and appears to affect the mid-IR/Raman region more than the high-wavenumber region (2,800?C3,600?cm^?1). But, both the higher wavenumber spectral region and the mid-IR/Raman region can be fluorescence-free when one uses lasers sources, which do not cause fluorescence, for example, 1,064, 830 or 785?nm sources. In addition, the Raman spectral signal of inflammatory infiltrates can influence the biopsy diagnoses and is one important source of misdiagnosis of normal versus pathological tissues. The present work seeks to evaluate whether the Raman spectra in the high-wavenumber spectral region can be used to distinguish between oral inflammatory fibrous hyperplasia (IFH) lesions and normal (NM) tissues and hence be used as a new diagnostic tool. Thirty spectra of oral IFH lesions and NM tissues from biopsies of 12 patients were analyzed using both principal components analysis (PCA) and a binary logistic regression (BLR) model. It was found that the high-wavenumber region Raman spectra can be used to discriminate between NM tissue and oral IFH tissues by analyzing the 2,800?C3,050?cm^?1 (CH₂ and CH₃ vibrations of lipids and proteins) and 3,050?C3,600?cm^?1 (CH, OH, and NH vibrations of proteins and water) spectral intensities. A simple classification model based on the relative areas of the above cited regions resulted in concordant pairs of 95.3%. Considering the standard errors in the model parameters, it was found that the sensitivity (Se) and specificity (Sp) fall in the interval 87%?<?Se?<?100% and 73%?<?Sp?<?93%, respectively. In addition, it has been found that the Raman scattering cross-sections in the NH, OH, and CH stretching region are more intense than in the mid-IR/Raman (fingerprint) region.     

Investigation of azlactones and azlactams by IR spectroscopy

The IR spectra of a number of azlactones and their structural analogs, viz., azlactams, in solutions in carbon tetrachloride and in chloroform and in the solid phase were obtained. The character of the interaction of the carbonyl group of the heteroring with substituents with different electronic natures has a substantial effect on the frequencies of the stretching vibrations of the carbonyl group and the azomethine and ethylene bonds. The carbonyl frequencies were subjected to correlation analysis, and high conductivity of the electronic effects of substituents in the 2-phenyl-4-arylideneoxazol-5-one series was ascertained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 171–174, February, 1984.     

Identification of secondary metabolites in medicinal and spice plants by NIR-FT-Raman microspectroscopic mapping

This paper demonstrates the special potential of vibrational NIR FT Raman microspectroscopy for the study of fennel fruits, chamomile inflorescence and curcuma roots to obtain detailed information about their microstructure and chemical composition. Microscopic Raman maps of fennel fruits demonstrate that anethole, which is the main essential oil component, is present in the whole mericarp with highest concentration at the top of the fruit. In situ measurements obtained of the essential oil cells are dominated by two bands observed at 1657 cm(-1) and 1609 cm(-1) which are characteristic for anethole. Raman images of chamomile inflorescence show that spiroethers, identified by significant bands between 2150 and 2250 cm(-1), are accumulated in the middle part of the flower head. Due to the intense curcumin bands in the Raman spectrum of curcuma root, the distribution of this dyeing substance can be clearly determined; highest concentration of curcumin was observed on the core of the root.     

Investigation of 2,5-disubstituted silylfurans by PMR spectroscopy

The¹H,¹³C, and²⁹Si NMR spectra of S-substituted furfurals and the corresponding diethyl acetals containing various alkylsilyl substituents at position S of the furan ring were studied in comparison with the carbon- and sulfur-containing analogs and also with a series of monosubstituted silylfurans. In cases where the substituent was conjugated with the residue of the furan molecule the effect of the substituent at position S of the furan was transmitted to C of the aldehyde group. The reverse effect was also observed. It was determined that the contribution from the aldehyde group and the substituents at position S of the furan to the screening of the carbon nuclei of the furan ring was not additive.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 449457, April, 1996.     

Investigation of micelle formation by fluorescence correlation spectroscopy

We show that noncovalently bound dye molecules can be used as labels in single-molecule fluorescence experiments for the determination of aggregate formation in standard surfactant systems. Aqueous solutions of sulfosuccinic acid bis(2-ethylhexyl) ester sodium salt, hexadecyltrimethylammonium chloride, and pentaethylene glycol monododecyl ether have been studied by fluorescence correlation spectroscopy using commercially available dyes. The translational diffusion coefficient and the critical micelle concentrations have been determined and compare well to values reported in the literature. The respective charges of the surfactant and of the dye molecule are crucial for the effectiveness of the presented method.     

Zinc analysis in human skin by laser induced-breakdown spectroscopy

The feasibility of using laser induced-breakdown spectroscopy (LIBS) as a quick and simple method to analyze trace elemental concentrations in the stratum corneum of human skin was investigated. A 60 mJ pulse(-1) Nd:YAG laser operating at 1064 nm was used to form the laser induced plasma. Zinc was chosen for this study. By using poly-(methyl methacrylate) (PMMA) solution to coat the slides, zinc standard solutions were dispersed on the slides with the help of a centrifuge. The percent of R.S.D. of the dispersed area size obtained from 17 measurements was 6%. The precision from intra-measurements (precision on one slide) and inter-measurements (precision between slides) was 4-8% and less than 1%, respectively. A calibration curve with a linear correlation coefficient of 0.998 and a detection limit of 0.3 ng cm(-2) were obtained. An aqueous zinc solution or zinc ointment was deposited on the biceps area of the forearms of several volunteers for a time period of 30 min and 2.75 h. Six skin layers of 2-3 mum each in thickness were then removed using cyanoacrylate glue without causing any pain for the volunteers. The results indicated that Zn was absorbed through the skin and the concentration decreased exponentially with depth into the skin. The results indicate that LIBS is a useful tool for trace elemental analysis in human skin.     

Investigation of the conformation of epoxychalcones by IR spectroscopy

Molecules of ketone oxides in the solid phase exist exclusively in the gauche form, whereas compounds of the open type form a mixture of cis and gauche conformers in solution. The effect of temperature on the conformational equilibrium was investigated.     

某些芳香族羟肟一过渡金属配合物的红外光谱

The preparation and infrared spectroscopic studies of coordination compounds of salicylaldoxime, 2-hydroxy-acetophenone oxime, 2-hydroxy-benzophenone oxime and 2-hydroxy-4-methoxy-benzophenone oxime with copper (II), nickel (II), cobalt (II) and iron (II) have been described. The frquency of the C=N stretching vibration is usually higher in the complex than that in the ligand. The higher the frequency of the C=N vibration is, the larger the stability constant of the complex will be, but there is no quantitative relationship. In the case of complexes of salicylaldoxime with Cu, Ni, Co and Fe, &CC=N values are correlated linearly with the ionization potentials of the central metal ions. The frequency of the OH stretching vibration is closely related to the geometric configuration of the complex. Thus aromatic hydroxyoximes form coordination compound with Co (II) and Fe (II) with cis configuration possessing six membered stronger hydrogen bonding ring. This is indicated in the infrared spectra by the complete absence of the absorption band due to the OH stretching vibration, or by the appearance of an extremely broad and flat band of very low intensity. However, Cu (II) or Ni (II) complex possesses trans configuration with five membered hydrogen-bonding bridge showing characteristic OH absorption band in the infrared region. The &COH of complex investigated is closely related to the polar nature of the substituents on the benzene ring. By examining the spectra of Cu-63 and Cu-65 complexes with 2-hydroxy-4(5)-substituted benzophenone oximes, the characteristic frequencies of M -- O and M -- N in the far infrared region were assigned for a series of aromatic hydroxyoxime-transition metal complexes.     

Investigation of aromatic hydroxyoxime-transition metal complexes by infrared spectroscopy

The preparation and infrared spectroscopic studies of coordination compounds of salicylaldoxime, 2-hydroxy-acetophenone oxime, 2-hydroxy-benzophenone oxime and 2-hydroxy-4-methoxy-benzophenone oxime with copper (II), nickel (II), cobalt (II) and iron (II) are described. The frequency of the C=N stretching vibration is usually higher in the complex than that in the ligand. The higher this frequency is, the larger the stability constant of the complex will be, but there is no quantitative relationship. In the case of complexes of salicylaldoxime with Cu (II), Ni (II), Co (II) and Fe (II), v_O=N values are correlated linearly with the ionization potentials of the central metal ions. The frequency of the OH stretching vibration is closely related to the geometric configuration of the complex. Thus aromatic hydroxyoximes form coordination compounds with Co (II) and Fe (II) with cis configuration possessing six-membered hydrogen-bonded ring. This is indicated in the infrared spectra by the complete absence of the OH stretching band, or by the appearance of an extremely broad and flat band of very low intensity. However, Cu (II) or Ni (II) complex possesses trans configuration with five-membered hydrogen-bonded bridge showing characteristic OH absorption band in the infrared region. The v_oh's of complexes investigated are closely related to the polar nature of substituents on the benzene ring. By examining the spectra of ⁶³Cu and ⁶⁵Cu complexes with 2-hydroxy-4(5)-substituted benzophenone oximes in the far infrared region, the characteristic frequency of M-O and M-N were assigned for a series of aromatic hydroxyoxime-transition metal complexes.     

Investigation of lithium niobate composition by optical spectroscopy methods

Indirect methods of investigation of composition and defect structures of lithium niobate (LiNbO₃) single crystals with different compositions are discussed. The analysis of two methods for the determination of the Li/Nb ratio in the samples is carried out, viz., the fundamental UV absorption edge and IR vibrational spectra of the OH⁻ group defects. Intrinsic defect concentrations in lithium niobate crystals (lithium vacancies, $ V_{Li^ - } $ V_{Li^ - } and defects, $ Nb_{Li^{4 + } } $ Nb_{Li^{4 + } } ) as a function of the Li/Nb ratio in the samples are given. The results obtained can serve as an effective way of express non-destructive composition analysis in a mass production of parallel-plane plates.     

Investigation of carbon catalysts by x-ray photoelectron spectroscopy and thermal analysis

Theoretical and Experimental Chemistry -     

Investigation of solid surfaces modified by Langmuir-Blodgett monolayers using sum-frequency vibrational spectroscopy and X-ray photoelectron spectroscopy

Langmuir-Blodgett (LB) monomolecular layers of alkylhydroxamic acids and alkylphosphonic acids on copper and iron substrates have been studied by X-ray photoelectron spectroscopy (XPS) and sum-frequency vibrational spectroscopy. According to the XPS results, the structures of the hydroxamic acid and phosphonic acid Langmuir-Blodgett films are very similar: the thickness of the layer of the hydrocarbon tails is typically 1.9-2.1 nm, while the layer of headgroups is about 0.3-0.35 nm thick. The tilt angle of the carbon chains is estimated to be 20-30 degrees with respect to the sample surface normal, and the molecules are connected to the substrate via their headgroups. Analysis of the P 2p and N 1s lines indicates the presence of deprotonated headgroups. The substrate Cu 2p line includes a component which can be assigned to Cu(2+) ions in a thin Cu(OH)(2) layer. The deposition of LB layers led to significant decrease of the hydroxide-related signal, which indicates that binding of the headgroups to the surface is accompanied by the elimination of water molecules. The sum-frequency spectra also clearly indicate that well-ordered monolayers can be formed by the Langmuir-Blodgett technique. Since the non-resonant background from the metal substrates renders the analysis of the spectra more difficult, model system samples on glass were prepared. It was found that the alkyl chains of the adsorbed acids predominantly adopt the all-trans conformation and form an ordered structure. Upper limits for the mean tilt angle of the terminal methyl groups are approximately 10-20 degrees.     

Investigation of the surface of Ni-Pd catalysts by IR spectroscopy

The reaction of carbon monoxide with the surface of Ni, Pd, and Ni-Pd catalysts, deposited on -Al₂O₃, was investigated at 25°C by IR spectroscopy in conjunction with an adsorption volumetric technique. The IR spectra contained the following absorption bands (v, cm^–1): 2020–2100 (AB1) (linear and subcarbonyl forms of adsorbed CO); 1945–1985 (AB2) (bridging); 1920–1940 (AB3) with a shoulder at 1870–1885 (AB4) (bridging and many-center). In the spectrum of Ni the absorption band AB5 appears at 1770–1780 (CO-Ni⁺). It appears with surface coverage a 1.3 mole CO/mole M. The optical density (A) of AB1 for Ni₉₇Pd₃ is appreciably higher than for the other investigated samples. In the Ni-Pd catalysts the intensity of AB2 in relation to AB1 is higher than in nickel. The introduction of K⁺ ions into the support of the bimetallic sample reduces the optical density of AB1. In modified Ni-Pd-K the AB3 and AB4 bands disappear.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1276–1282, June, 1992.