Showing papers on "Fluorescence spectrometry published in 1996"
TL;DR: A new multiway regression method called N‐way partial least squares (N‐PLS) is presented, which is superior to unfolding methods, primarily owing to a stabilization of the decomposition.
Abstract: A new multiway regression method called N-way partial least squares (N-PLS) is presented. The emphasis is on the three-way PLS version (tri-PLS), but it is shown how to extend the algorithm to higher orders. The developed algorithm is superior to unfolding methods, primarily owing to a stabilization of the decomposition. This stabilization potentially gives increased interpretability and better predictions. The algorithm is fast compared with e.g. PARAFAC, because it consists of solving eigenvalue problems.
An example of the developed algorithm taken from the sugar industry is shown and compared with unfold-PLS. Fluorescence excitation—emission matrices (EEMs) are measured on white sugar solutions and used to predict the ash content of the sugar. The predictions are comparable by the two methods, but there is a clear difference in the interpretability of the two solutions. Also shown is a simulated example of EEMs with very noisy measurements and a low relative signal from the analyte of interest. The predictions from unfold-PLS are almost twice as bad as from tri-PLS despite the large number of samples (125) used in the calibration.
The algorithms are available from World Wide Web: hhtp:\
ewton.foodsci.kvl.dk\foodtech.
660 citations
TL;DR: In this article, total luminescence spectra, represented as excitation−emission matrices (EEMs), were used to discriminate between soil-derived and aquatic-derived IHSS humic substances and between humic and fulvic acids derived from the same source.
Abstract: Total luminescence spectroscopy was applied to the fluorescence characterization of humic substances obtained from the International Humic Substances Society (IHSS). Results show that total luminescence spectra, represented as excitation−emission matrices (EEMs), may be used to discriminate between soil-derived and aquatic-derived IHSS humic substances and between humic and fulvic acids derived from the same source (soil or aquatic). Ionic strength in the range of 0−1 M KCl and humic substance concentration in the range of 5−100 mg/L had little effect on the fluorescence spectral characteristics of the humic substances, while pH had significant effects as expected. Absorbance correction was shown to be essential for accurate representation and comparison of the EEMs of the humic substances at high concentrations.
400 citations
TL;DR: The resonance light-scattering technique, using a spectrofluorometer, was first developed as a sensitive instrumental analysis method as mentioned in this paper, and linear relationships between the enhanced extents of lightscattering and the concentrations of nucleic acids in the range of 1.8 × 10-7−10.
Abstract: The resonance light-scattering technique, using a spectrofluorometer, was first developed as a sensitive instrumental analysis method. At pH 7.48 and ionic strength 0.004, the extent of light-scattering of α,β,γ,δ-tetrakis[4-(trimethylammoniumyl)phenyl]porphine (TAPP) is enhanced by nucleic acids near 432 nm. There are linear relationships between the enhanced extents of light-scattering and the concentrations of nucleic acids in the range of 1.8 × 10-7−10.8 × 10-7 M for calf thymus and fish sperm DNA and in the range of 1.8 × 10-7−1.8 × 10-6 M for yeast RNA. The limit of determination (3σ) is 4.1 × 10-8 M for calf thymus DNA, 4.6 × 10-8 M for fish sperm DNA, and 6.7 × 10-8 M for yeast RNA. Mechanism study indicates that nucleic acids react with the title porphyrin in two modes, depending on the concentrations of nucleic acids. When the molar ratio of nucleic acids to TAPP is smaller than 4:1, the hypochromicity and fluorescence quenching of TAPP by nucleic acids appear, and the enhancement of resonance l...
324 citations
TL;DR: A morphological model of colon tissue fluorescence is developed which connects the clinically observed spectra with their underlying microscopic origins and quantitated these spectral features in terms of the intrinsic fluorescence properties of tissue and its general histological characteristics.
Abstract: Fluorescence spectroscopy of tissue is a promising technique for early detection of precancerous changes in the human body. Investigation of the microscopic origin of the clinically observed tissue fluorescence can provide valuable information about the tissue's histology. The objective of this study was the development of a morphological model of colon tissue fluorescence which connects the clinically observed spectra with their underlying microscopic origins. Clinical colon tissue fluorescence spectra were modeled by measuring the intrinsic fluorescence properties of colon tissue on a microscopic level and by simulating light propagation in tissue using the Monte-Carlo method. The computed spectra were in good agreement with the clinical spectra acquired during colonoscopy, and exhibited the characteristic spectral features of the in vivo collected spectra. The authors' analysis quantitated these spectral features in terms of the intrinsic fluorescence properties of tissue and its general histological characteristics. The fluorescence intensity difference between normal and adenoma observed in vivo was found to be due to the increased hemoglobin absorption, the reduced mucosal fluorescence intensity, and the absence of submucosal fluorescence in adenomatous polyps. The increased red fluorescence in adenoma was found to be associated with the dysplastic crypt cell fluorescence.
190 citations
TL;DR: Dysplasia was detected in vivo using fluorescence spectroscopy and a probability-based algorithm and may form the basis for a new surveillance technique for patients with increased risk for dysplastic transformation.
162 citations
TL;DR: The diagnostic contribution of cervical tissue fluorescence spectra acquired in vivo at 380 and 460 nm excitation were analyzed using a general multivariate statistical algorithm.
Abstract: Background and Objective
The diagnostic contribution of cervical tissue fluorescence spectra acquired in vivo at 380 and 460 nm excitation were analyzed using a general multivariate statistical algorithm.
Materials and Methods
The primary steps of the algorithm are to: (1) preprocess data to reduce interpatient and intrapatient variation of tissue spectra from the same diagnostic category, without a priori information, (2) dimensionally reduce the preprocessed spectral data using Principal Component Analysis, and (3) develop a probability based classification scheme based on logistic discrimination using the diagnostically useful principal components. The algorithm was tested on cervical tissue spectra acquired from 165 sites at 380 nm excitation and from 147 sites at 460 nm excitation. A retrospective and prospective estimate of the algorithm's performance was determined.
Results
At 460 nm excitation, (1) SILs can be differentiated from normal squamous tissues with an average sensitivity and specificity of 91% ± 1.3 and 75.5% ± 1, respectively; furthermore, (2) high grade SILs can be differentiated from low grade SILs with an average sensitivity and specificity of 80% ± 4 and 76% ± 5, respectively. In addition, using tissue spectra at 380 nm excitation, SILs can be differentiated from normal columnar epithelia and inflammation with an average sensitivity and specificity of 77% ± 1 and 72% ± 9, respectively.
Conclusions
Fluorescence spectra at multiple excitation wavelengths are essential for the detection and differential diagnosis of SILs at colposcopy. © 1996 Wiley-Liss, Inc.
159 citations
TL;DR: A general multivariate statistical algorithm has been developed to analyze the diagnostic content of cervical tissue fluorescence spectra acquired in vivo.
Abstract: Background and Objective
A general multivariate statistical algorithm has been developed to analyze the diagnostic content of cervical tissue fluorescence spectra acquired in vivo.
Materials and Methods
The primary steps of the algorithm are to: (1) preprocess the data to reduce inter-patient and intra-patient variation of tissue spectra within a diagnostic category, without a priori information, (2) dimensionally reduce the preprocessed fluorescence emission spectrum with minimal information loss and use it to select the minimum number of the original emission variables of the fluorescence spectrum required to achieve classification with negligible decrease in predictive ability, and (3) assign a posterior probability to the diagnosis of each sample, so that samples with relative uncertain diagnosis can be reevaluated by a clinician. The algorithm was tested retrospectively and prospectively on cervical tissue spectra acquired from 476 sites from 92 patients at 337 nm excitation.
Results
The algorithm based on the entire fluorescence spectrum differentiates squamous intraepithelial lesions (SILs) from normal squamous epithelia and inflammation with an average sensitivity and specificity of 88% ± 1.4 and 70% ± 1, respectively. The average sensitivity and specificity of the identical algorithm based on intensity selected at only two emission wavelengths is 88% ± 1.4 and 71% ±1.4, respectively.
Conclusion
The multivariate statistical algorithm based on both types of spectral inputs at 337 nm excitation has a similar sensitivity and significantly improved specificity relative to colposcopy in expert hands. © 1996 Wiley-Liss, Inc.
152 citations
TL;DR: In this paper, the influence of fluidized bed combustion (FBC) temperature and coal rank on polycyclic aromatic hydrocarbon (PAH) emissions was assessed, and the results showed that the total PAH emission depends mainly on the pyrolytic process and to a lesser degree on the combustion efficiency.
147 citations
TL;DR: A high concentrated glass bead, with a flux to sample ratio of two to one, was prepared to evaluate the potential for major and trace element analyses of various silicate rocks by X-ray fluorescence spectrometry.
Abstract: A high concentrated glass bead, with a flux to sample ratio of two to one, was prepared to evaluate the potential for major and trace element analyses of various silicate rocks by X-ray fluorescence spectrometry Careful instrument set up, matrix effect and peak overlap corrections allowed enhanced accuracy of analysis The accuracy reached a level comparable to that of using five to one glass beads for major elements and pressed powder pellets for trace elements Using this method, major and trace element analyses were possible using one single glass bead
141 citations
TL;DR: In this article, multi-wavelength molecular fluorescence spectrometry is evaluated prototypically as a method for the determination of stability constants and binding capacities for Cu(II) and Al(III) complexation by dissolved organic matter in a juniper leaf litter extract.
Abstract: Conditional stability constants and binding capacities are important parameters with which to estimate the biological availability of metal ions in aqueous solution in the presence of dissolved natural organic matter (fulvic acid, organic matter in natural waters or in aqueous extracts of forest litter). Determination of these parameters depends on analytical methods that can distinguish between free and organically bound metal ions. This speciation is difficult, mainly because natural organic matter typically is a complex mixture. In this paper, multi-wavelength molecular fluorescence spectrometry is evaluated prototypically as a method for the determination of stability constants and binding capacities for Cu(II) and Al(III) complexation by dissolved organic matter in a juniper leaf litter extract. Equilibrium ion exchange quantitation and electron spin resonance spectroscopy served as quantitative and qualitative reference methods, respectively. Three types of binding site for Cu and Al could be differ...
136 citations
TL;DR: In this article, the binding of DTAC (dodecyltrimethylammonium chloride) to two polyelectrolytes of differing hydrophobicity, the alternated copolymers poly(maleic acid-co-methyl vinyl ether) referred to as PS1 and PS4, respectively, has been investigated by potentiometry with a surfactant ion-specific electrode, by time-resolved fluorescence quenching, by fluorescence anisotropy, and by viscosimetry.
Abstract: The binding of DTAC (dodecyltrimethylammonium chloride) to two polyelectrolytes of differing hydrophobicity, the alternated copolymers poly(maleic acid-co-methyl vinyl ether) and poly(maleic acid-co-butyl vinyl ether) referred to as PS1 and PS4, respectively, has been investigated by potentiometry with a surfactant ion-specific electrode, by time-resolved fluorescence quenching, by fluorescence anisotropy, and by viscosimetry. The surfactant binding isotherms, the number of surfactants (N) making up polymer-bound aggregates, the lifetime of pyrene (τ2) in these aggregates, and their microviscosity (ηi) were thus obtained as a function of the surfactant concentration and copolymer neutralization degree α, which determines its electrical charge density. As observed in other studies, the binding is cooperative in the whole range of α for PS1 and for α ⩾ 0.5 for PS4. Aggregation numbers, pyrene lifetimes, and aggregate microviscosities were all found to be independent of the surfactant concentration but to de...
Book•
02 Dec 1996
TL;DR: A critical review of published papers as discussed by the authors presents theoretical and fundamental aspects of FIA-pharmaceutical analyses, divided the material into chapters based on measurement technique or type of detector, each chapter provides
Abstract: A critical review of published papers, this volume presents theoretical and fundamental aspects of FIA-pharmaceutical analyses. Dividing the material into chapters based on measurement technique or type of detector, each chapter provides
TL;DR: In this article, a new method based on capillary gas chromatography-atomic fluorescence spectrometry (GC/AFS) was described for the determination of methylmercury (MeHg) and ethylmercure (EtHg), in water samples.
TL;DR: The partition coefficient of paclitaxel partitioning into small unilamellar lipid vesicles composed of 1-palmitoyl-2-oleoyl -sn-glycero-3-phosphocholine is determined using two different methods, namely high-sensitivity titration calorimetry and fluorescence spectrometry.
TL;DR: In this article, an excitation/emission matrix imaging spectrofluorometer was employed for quantitation of two fluorescent compounds, naphthalene and styrene, contained in ocean water exposed to gasoline.
Abstract: An excitation/emission matrix imaging spectrofluorometer was employed for quantitation of two fluorescent compounds, naphthalene and styrene, contained in ocean water exposed to gasoline. Multidimensional parallel factor (PARAFAC) analysis models were used to resolve the naphthalene and styrene fluorescence spectra from a complex background signal and overlapping spectral interferents not included in the calibration set. Linearity was demonstrated over 2 orders of magnitude for determination of naphthalene with a detection limit of 8 parts per billion. Similarly, nearly 2 orders of magnitude of linearity was demonstrated in the determination of styrene with an 11 ppb limit of detection. Furthermore, the synthesis of the EEM spectrofluorometer and the PARAFAC analysis for unbiased prediction of naphthalene and styrene concentration in mixture samples containing uncalibrated spectral interferents was demonstrated.
TL;DR: In this article, the effect of metal cation codopants (Sr2+, La3+, Gd3+, Y3+, Lu3+, Sc3+, and Ga3+) on the state of aggregation of Eu3+ in sol−gel silica was investigated.
Abstract: Fluorescence line-narrowing spectroscopy is used to characterize the effect of metal cation codopants (Sr2+, La3+, Gd3+, Y3+, Lu3+, Sc3+, and Ga3+) on the state of aggregation of Eu3+ in sol−gel silica. Significant Eu3+ clustering occurs in samples doped only with Eu3+. The addition of codopants inhibits the clustering of Eu3+ and promotes better dispersion of Eu3+ in the glasses. The extent of the inhibition of clustering increases with field strength of the codopant and levels off at high field strength. The inhibition of clustering is correlated with the generation of strong crystal field bonding sites for Eu3+ in the presence of codopants. Characteristics of these sites include the presence of Eu−O−M (M = codopant) linkages and stronger interactions with the network-forming regions of the glass. Supporting luminescence decay and Raman spectroscopy measurements are also presented.
TL;DR: In this article, a highly sensitive laser-induced fluorescence (LIF) measurement instrument has been developed, which is based on the A²Σ+v′ = 0-X²Π v″ = 0 transition at 308.15 nm at low pressure.
Abstract: A highly sensitive OH measurement instrument has been developed. It is based on laser-induced fluorescence (LIF) detection of OH using the A²Σ+v′ = 0-X²Π v″ = 0 transition at 308.15 nm at low pressure. The LIF instrument detects OH directly and with high specificity, a fact that was demonstrated by recording laser excitation spectra (Q1(3), Q21(3) and P1(1) lines) of ambient OH. For high time resolution (typ. 60–100 s), the laser wavelength was modulated on-/off- resonance with the P1(1) line. Here, we report some of the OH measurements obtained by this technique during its first application in a tropospheric field campaign (“POPCORN”), which was conducted in August 1994 in a rural environment in the North-East of Germany. These include diurnal OH concentration profiles with maximum OH concentrations up to 1.4×107cm−3at noon. Minimum OH concentrations were measured in the morning and evening down to the detection limit of (3–6) × 105cm−3(SNR=2, measurement time 1 min.). During the day, OH fluctuations were observed on a time scale of minutes and hours. These were highly correlated to the flux of the solar UV radiation which is responsible for the primary OH production by photolysis.
Journal Article•
TL;DR: The oral administration of the thiol N-acetylcysteine, one of the most promising cancer chemopreventive agents endowed with nucleophilic and antioxidant properties, produced a significant decrease of mtDNA adducts in the liver of 2-acetylaminofluorene-treated rats and, sharply, in the lung and liver of rats exposed to cigarette smoke.
Abstract: Damage to mitochondrial DNA (mtDNA) has been postulated to be associated with aging, cancer, and other chronic degenerative diseases which are the predominant causes of death in the population. We used molecular dosimetry techniques, i.e., 32P postlabeling and synchronous fluorescence spectrophotometry, in order to evaluate the formation of adducts to both mtDNA and nuclear DNA (nDNA) in different organs of rats exposed to genotoxic carcinogens. Adducts to mtDNA were detected following administration of benzo(a)pyrene i.p. or 2-acetylaminofluorene by gavage as well as following exposure of animals to cigarette smoke. mtDNA adduct levels were consistently higher than those to nDNA in the same cells, and qualitative differences were also pointed out in the case of the aromatic amine. The oral administration of the thiol N-acetylcysteine, one of the most promising cancer chemopreventive agents endowed with nucleophilic and antioxidant properties, produced a significant decrease of mtDNA adducts in the liver of 2-acetylaminofluorene-treated rats and, sharply, in the lung and liver of rats exposed to cigarette smoke.
TL;DR: A spectrofluorometer capable of dispersed-spectrum, simultaneous, multiwavelength UV excitation and collection of luminescence has been constructed for the purpose of qualitatively and quantitatively determining aromatic hydrocarbon pollutants dissolved in ocean water.
Abstract: A spectrofluorometer capable of dispersed-spectrum, simultaneous, multiwavelength UV excitation and collection of luminescence has been constructed for the purpose of qualitatively and quantitatively determining aromatic hydrocarbon pollutants dissolved in ocean water Hydrocarbon fluorescence data produced by this instrument were in the form of excitation/emission matrices, which provide more spectral information about these complex mixtures than is available from conventional excitation or emission fluorescence profiles Second-order statistical methods were applied to these data to determine low part-per-billion concentrations of two primary fluorescent compounds, naphthalene and styrene, found in ocean water exposed to gasoline despite the presence of uncalibrated interference from similar aromatic compounds, the ocean water matrix, and the instrumental background
TL;DR: The association of C10-, C12-, and C14 linear alkylbenzenesulfonates (LAS) with natural and spec- imen-grade dissolved humic substances (DHS) was measured with fluorescence quenching and with ultra...
Abstract: The association of C10-, C12-, and C14-linear alkylbenzenesulfonates (LAS) with natural and spec- imen-grade dissolved humic substances (DHS) was measured with fluorescence quenching and with ultra...
TL;DR: In this article, a review of sample preparation methods unique to atomic and X-ray spectroscopic techniques for trace element analysis of biological materials is presented, but no review or book has dealt with them.
TL;DR: It is shown that fluorescence lifetime measurements, with the τ-LIDAR, can be used to perform complex fluorescence quenching analysis in fluorosensing, like the one developed in the laboratory for near-contact measurements with PAM-fluorimetry.
TL;DR: One of these chiral calixarene derivatives, an (S)-di-2-naphthylprolinol tetramer, is shown to exhibit significant ability to discriminate between enantiomers of 1-phenylethylamine (PEA) and norephedrine on the basis of the quenching of the (S-di- 2-nAPHthyl Prolinol fluorescence emission in chloroform.
Abstract: The synthesis of three chiral calixarene derivatives is described. One of these, an (S)-di-2-naphthylprolinol tetramer, is shown to exhibit significant ability to discriminate between enantiomers of 1-phenylethylamine (PEA) and norephedrine on the basis of the quenching of the (S)-di-2-naphthylprolinol fluorescence emission in chloroform. The chiral discrimination appears to arise from preorganization of the four (S)-di-2-naphthylprolinol substituents on the calixarene, which define a three-dimensional chiral space. The ability to measure the enantiomeric composition of PEA and norephedrine to within an error of 4.1% and 2.6%, respectively, on the basis of a single fluorescence measurement is demonstrated.
TL;DR: It was found that adsorbed HSA is not displaced by IgG and/or Fgn to any large extent, and Igg and HSA dominate the adsorption from the ternary protein mixture, although fibrinogen is also present in the adsorsed layer to a smaller extent.
TL;DR: Under standardized conditions (drug and light dose, timing), the result of the photodynamic therapy of carcinomas of the esophagus with tetra(meta‐hydroxy‐phenyl)chlorin (mTHPC) shows large variations between patients.
Abstract: BACKGROUND AND OBJECTIVE: Under standardized conditions (drug and light dose, timing), the result of the photodynamic therapy (PDT) of carcinomas of the esophagus with tetra(meta-hydroxyphenyl)chlorin (mTHPC) shows large variations between patients. STUDY DESIGN/MATERIALS AND METHODS: Before patients underwent PDT treatment, the mTHPC level was measured in the lesion, the normal surrounding tissue, and the oral cavity, with an apparatus based on fluorescence spectroscopy. RESULTS: The fluctuations in degree of tumor destruction between patients can be explained by individual variations in the mTHPC level in the mucosa of the esophagus. The patients showing the highest mTHPC fluorescence signal had also the highest response to PDT. Also, a correlation between the mTHPC level in the oral cavity and esophagus mucosa has been found. CONCLUSION: PDT can be improved by measuring the mTHPC level in the esophagus or the oral cavity before treatment by fluorescence spectroscopy, and then by adjusting the light dose to be applied to the observed mTHPC level.
TL;DR: The aim of this work was to find a variety of Cucurbita pepo which has a high oil yield and a high vitamin E content and a total of 100 breeding lines were tested for their tocopherol content.
Abstract: Pumpkin (Cucurbita pepo L.) seed oil is a common salad oil which is produced in the southern parts of Austria, Slovenia and Hungary. It is dark green and has a high content of free fatty acids. Due to its colour, the oil cannot be used for cooking. The content of vitamin E, especiallyγ-tocopherol, is very high. The oil content of the pumpkin seed is about 50%. The seed itself can be eaten. Therefore a pumpkin variety with high vitamin E content is desirable. The aim of this work was to find a variety ofCucurbita pepo which has a high oil yield and a high vitamin E content. A total of 100 breeding lines were tested for their tocopherol content. The tocopherols and tocotrienols are extracted with hexane and analysed by NP-HPLC/FLD with hexane/dioxan (96/4) as eluent, with fluorescence detection at 292/335 nm. The/gg-tocopherol content, which is about 5–10 times as much as that of α-tocopherol varies over a broad range (41–620 mg/kg dry pumpkin seeds).β- andδ-tocopherol are found at low levels.
TL;DR: In this article, a novel experimental approach involving fluorescence nonradiative energy transfer (NRET) is employed to study the Fickian diffusion of small molecules in rubbery polymer films near the glass transition.
Abstract: A novel experimental approach involving fluorescence nonradiative energy transfer (NRET) is employed to study the Fickian diffusion of small molecules in rubbery polymer films near the glass transition. A theoretical formalism has been developed which directly relates the small molecule translational diffusion coefficient, 𝒟, to changes in the energy transfer efficiency, E. Values of 𝒟 as low as 5 × 10-16 cm2/s have been measured. In this approach, two thin polymer films are sandwiched together, one labeled with either NRET donor or acceptor chromophores and the second doped with the complementary chromophore. Upon annealing for a time t, dopant chromophore diffusion occurs in which E is proportional to (𝒟t)1/2/w, where w is the donor film thickness. Values of 𝒟 for pyrene, N-(2-hydroxyethyl)-N-ethyl-4-(tricyanovinyl)aniline (TC1), bis(phenylethynylanthracene) (BPEA), and decacyclene in poly(isobutyl methacrylate) (PiBMA) and for BPEA in poly(ethyl methacrylate) (PEMA) have been measured over temperatures...
TL;DR: In this paper, the authors used total reflection X-ray fluorescence spectrometry (TXRF) and radioisotope excited X-rays (XRF) to determine whether the elemental content of bee honey correlates with any useful information about the environment.
TL;DR: Fluorescent whitening agents (FWAs) used in laundry detergents were determined in aqueous samples from sewage treatment plants and rivers using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with post-column UV irradiation and fluorescence detection as discussed by the authors.
Abstract: Fluorescent whitening agents (FWAs) used in laundry detergents were determined in aqueous samples from sewage treatment plants and rivers using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with post-column UV irradiation and fluorescence detection. FWAs were extracted from 10−200-mL water samples with C18 bonded- phase silica extraction disks and eluted with methanol-containing tetrabutylammonium ion-pairing reagent. No further sample cleanup steps were necessary due to the sensitive and selective fluorescence detection. Recovery of FWAs from raw sewage, primary effluent, secondary effluent, and river water ranged from 76 to 96%. The overall precision of the method, indicated by the relative standard deviation, ranged from 1 to 11%. The limit of quantification was less than 30 ng/L. The concentrations of the two most frequently used FWAs ranged from 7 to 21 μg/L in primary effluent, from 2.6 to 8.9 μg/L in secondary effluent, and from 0.04 to 0.57 μg/L in river water. FWA...