Fluorescence spectroscopy of mechanical pulps III: Effect of chlorite delignification

1995 ◽  
Vol 73 (11) ◽  
pp. 1955-1959 ◽  
Author(s):  
Jennifer A. Olmstead ◽  
Jian H. Zhu ◽  
Derek G. Gray
Keyword(s):  
Fluorescence Spectroscopy ◽  
Fluorescence Intensity ◽  
Fluorescence Spectra ◽  
Lignin Content ◽  
Emission Spectra ◽  
Thermomechanical Pulp ◽  
Fluorescence Excitation ◽  
Lignin Removal ◽  
Mechanical Pulps ◽  
Almost All

Many paper and wood samples fluoresce, but the sources of the emission are not well understood. Fluorescence excitation and emission spectra of paper sheets prepared from thermomechanical pulp (TMP) and bleached chemithermomechanical pulp (BCTMP) showed that the emission from the BCTMP was significantly higher than that from the TMP. Removing almost all of the lignin from both pulps by means of an acid chlorite treatment did not reduce the fluorescence significantly. By means of an approximate correction for changes in sheet reflectivity caused by the chlorite treatment, the fluorescence intensity was found to increase with lignin removal. Clearly, fluorescence is not simply related to lignin content. Keywords: wood pulp, lignin, cellulose, fluorescence spectra, acid chlorite delignification.

scholarly journals Assisted Interpretation of Laser-Induced Fluorescence Spectra of Egg-Based Binding Media Using Total Emission Fluorescence Spectroscopy

2006 ◽  
Vol 2006 ◽  
pp. 1-5 ◽  
Author(s):  
Austin Nevin ◽  
Demetrios Anglos
Keyword(s):  
Amino Acids ◽  
Fluorescence Spectroscopy ◽  
Fluorescence Spectra ◽  
Emission Spectra ◽  
Egg Yolk ◽  
Laser Induced Fluorescence ◽  
Oxidation Products ◽  
Total Emission ◽  
Binding Media ◽  
Age Related

Laser-induced fluorescence (LIF) spectroscopy can provide nondestructive, qualitative analysis of protein-based binding media found in artworks. Fluorescence emissions from proteins in egg yolk and egg white are due to autofluorescent aromatic amino acids as well as other native and age-related fluorophores, but the potential of fluorescence spectroscopy for the differentiation between binding media is dependent on the choice of a suitable excitation wavelength and limited by problems in interpretation. However, a better understanding of emission spectra associated with LIF can be achieved following comparisons with total emission fluorescence spectra where a series of consecutive emission spectra are recorded over a specific range. Results using nanosecond UV laser sources for LIF of egg-based binding media are presented which are rationalised following comparisons with total emission spectra. Specifically, fluorescence is assigned to tryptophan and oxidation products of amino acids; in the case of egg yolk, fatty-acid polymerisation and age-related degradation products account for the formation of fluorophores.

Fluorescence spectroscopy for chromophore studies on bleached kraft pulps

Holzforschung ◽  
2007 ◽  
Vol 61 (5) ◽  
pp. 509-515 ◽  
Author(s):  
Sirje Liukko ◽  
Ville Tasapuro ◽  
Tiina Liitiä
Keyword(s):  
Fluorescence Spectroscopy ◽  
Fluorescence Spectra ◽  
Lignin Content ◽  
Excitation Wavelength ◽  
Kraft Pulps ◽  
Carbonyl Groups ◽  
Residual Lignin ◽  
Pulp Bleaching ◽  
Peroxide Bleaching ◽  
Brightness Reversion

Abstract Fluorescence techniques are highly sensitive and, since aromatic lignin is the most likely source of natural pulp fluorescence, they are suitable for detailed investigation of residual lignin in bleached pulps. Such investigations are important to our understanding of the bleachability and brightness reversion of pulps. In this study, the effect of bleaching on pulps was evaluated using fluorescence spectra of two softwood kraft pulps bleached in six elemental chlorine-free and totally chlorine-free sequences. Fluorescence spectra were recorded in each bleaching stage using four different instrument settings. In general, pulp fluorescence at excitation wavelengths of 270 and 350 nm increased as bleaching proceeded. Below a certain lignin content, however, pulp fluorescence measured at an excitation wavelength of 430 nm decreased with the residual lignin content. Carbonyl groups have a quenching effect on fluorescence, and the formation of carbonyl groups after oxygen and ozone delignification induced a decrease in pulp fluorescence. The increase in pulp fluorescence after peroxide bleaching stages was due to the removal of carbonyl groups. Reactions of chromophores during brightness reversion also had an effect on pulp fluorescence. These findings demonstrate that fluorescence spectroscopy provides an interesting tool for pulp bleaching studies.

Combustion properties of reduced-lignin black liquors

TAPPI Journal ◽  
2014 ◽  
Vol 13 (8) ◽  
pp. 81-90 ◽  
Author(s):  
NIKLAS VÄHÄ-SAVO ◽  
NIKOLAI DEMARTINI ◽  
RUFUS ZIESIG ◽  
PER TOMANI ◽  
HANS THELIANDER ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Lignin Content ◽  
Black Liquor ◽  
Nitrogen Atmosphere ◽  
Pulp Mills ◽  
Lignin Removal ◽  
Nitric Oxide Formation ◽  
Combustion Properties ◽  
Black Liquors ◽  
Almost All

The growing interest in production of green chemicals and biofuels from biomass provides an incentive for pulp mills to identify new possibilities in recovering more wood components from the pulping process. One possibility is to use lignin, separated from black liquor. We undertook this work to determine the combustion properties of reduced-lignin black liquors—two kraft liquors and one soda liquor—in a laboratory-scale, singleparticle furnace. The combustion times, maximum swollen volume, nitric oxide formation, cyanate formation, and sulfur release were measured for the original liquors, the filtrates, and intermediate levels of lignin reduction. Combustion experiments were conducted at 900°C in 10% oxygen. Cyanate formation experiments were carried out by pyrolyzing the droplets at 800°C in 100% nitrogen to form a char. The chars were then gasified at 800°C in a 13% carbon dioxide/87% nitrogen atmosphere to obtain the smelt. Sulfur release was studied by pyrolyzing the samples at temperatures ranging from 300°C to 900°C. Liquors with the lowest lignin content had a smaller maximum swollen volume than the original sample. The devolatilization time was not affected by the lignin removal to any great extent, but lignin removal did have a clear effect on the char burning time. The amount of formed nitric oxide (g N/kg black liquor solids) remained constant or decreased slightly with increasing lignin removal in the kraft liquor samples, while for the soda samples the amount of nitric oxide formed increased. The amount of cyanate decreased clearly when comparing the samples with lowest lignin content to the original liquor samples. The peak sulfur release occurred at 500°C for both kraft liquors. In almost all experiments, the share of sulfur released was highest for the original samples and lowest for the sample with lowest lignin content. These results provide new data on combustion properties for reduced-lignin black liquors and indicate that for lignin removal levels up to about 20%, no significant changes are expected in the combustion behavior.

scholarly journals Optically Dilute, Absorbing, and Turbid Phantoms for Fluorescence Spectroscopy of Homogeneous and Inhomogeneous Samples

1993 ◽  
Vol 47 (12) ◽  
pp. 2114-2121 ◽  
Author(s):  
A. J. Durkin ◽  
S. Jaikumar ◽  
R. Richards-Kortum
Keyword(s):  
Optical Properties ◽  
Fluorescence Spectra ◽  
Flavin Adenine Dinucleotide ◽  
Emission Spectra ◽  
Hemoglobin Concentration ◽  
Scattering Coefficient ◽  
Polystyrene Microspheres ◽  
Fluorescence Excitation ◽  
Structure Boundary ◽  
Optical Properties Of Tissue

This paper presents a phantom which simulates the optical properties of tissue. The phantom absorption coefficient, scattering coefficient, anisotropy factor, and fluorescence quantum yield can be independently varied to investigate the effects of these parameters on fluorescence excitation and emission spectra from 300 to 650 nm. Phantom fluorophores include Flavin Adenine Dinucleotide (FAD) and Rhodamine B. Absorption is controlled by adjusting phantom hemoglobin concentration. On the basis of their smoothly varying scattering coefficient and the relatively low amount of fluorescence contributed to the mixture in comparison to other available scatterers, 1.05-µm-diameter polystyrene microspheres were selected as a scatterer. Sample inhomogeneities are simulated by preparing the phantom in a gelatin substrate. The optical properties of turbid phantoms determined with the use of indirect techniques agree well with known values as long as µs(l – g) > µa. Data are presented from dilute, absorbing, and turbid phantoms and inhomogeneous phantoms to qualitatively illustrate the effects of optical properties and sample geometry on fluorescence spectra. The phantom provides the framework for detailed quantitative investigations of the effects of optical properties, sample size, shape, and structure, boundary conditions, and collection geometry on fluorescence spectra.

scholarly journals Determination of the Degree of Consumption (DoC) of Lube Engine Oils Using Fluorescence Spectroscopy

2018 ◽  
Vol 31 (1) ◽  
pp. 124
Author(s):  
Rawnaq Qahtan Abdul Kareem ◽  
Khalid W. Salih Al-Janabi
Keyword(s):  
Fluorescence Spectroscopy ◽  
Fluorescence Intensity ◽  
Oil Quality ◽  
Emission Spectra ◽  
Major Effect ◽  
Engine Oil ◽  
Local Market ◽  
Engine Oils ◽  
Used Oil ◽  
Motor Oils

    The accreditation of a fast, inexpensive, and simple way to discriminate between different kinds of oils and their efficacy “degree of consumption (DoC)” has been developed. The fluorescence spectroscopy provides a reliable method for oil inspection without resorting to tedious separation. Different new and used oil samples available in the local Iraqi market were investigated. While the challenge is to build a directory containing data of all the oils available in the local market. This method expected to control the falsified (forged) trademarks of motor oils and to discriminate between different oils. The excitation-emission spectra of oil samples were determined in the range of 200 – 600 nm. The effect of the presence of trace metals on the fluorescence intensity of oils was considered by adding few milligrams of (Cu, Al, Fe) to the diluted oil solution. No major effect noticed on fluorescence intensity. The research suggests installing a simple Spectrofluorometer into vehicles to check the DoC of the oil regularly and to notify the driver exactly when to replace the engine oil. The obtained results indicate the applicability to execute such gadget to be installed in the vehicles for routine detection of the engine oil quality and its degree of consumption DoC. As well as demonstrate the potential of the technique in oil identification and could be further developed.

Factors influencing fluorescence spectra of free porphyrins.

1988 ◽  
Vol 34 (4) ◽  
pp. 757-760 ◽  
Author(s):  
C F Polo ◽  
A L Frisardi ◽  
E R Resnik ◽  
A E Schoua ◽  
A M Batlle
Keyword(s):  
Ionic Strength ◽  
Fluorescence Spectra ◽  
Emission Spectra ◽  
Main Peak ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Experimental Conditions ◽  
Organic Mixture ◽  
Carbonate Buffer ◽  
Factors Influencing

Abstract We recorded fluorescence excitation and emission spectra of uro- and coproporphyrin under different experimental conditions, to see how these conditions influence quantifications based on measurement of fluorescence intensity. We found that, for bands alpha and beta of the emission spectra and the main peak of the excitation spectra, fluorescence depends on pH and is minimal near pH 5 and near pH 7-7.5 for copro- and uroporphyrin, respectively. For band gamma of the emission spectra there was a constant decrease of fluorescence with increasing alkalinity of the solution. The intensity of porphyrin fluorescence also depends on ionic strength, reaching sharp maxima at 0.1 mol/L (for uroporphyrin) and 1 mol/L (for coproporphyrin). The organic mixture ethyl acetate:acetic acid (4:1 by vol), commonly used to extract porphyrins from biological samples, markedly diminishes the fluorescence of both porphyrins as compared with the same concentration of each porphyrin in aqueous acidic solvent. Furthermore, when we measured different ratios of uro:copro mixture at three distinct pHs and buffers, we found that at pH 10.5 (in carbonate buffer) the measured units of fluorescence depend only on total porphyrin concentration and not on the composition of the mixture.

Fluorescence Spectroscopy for Rapid Detection and Classification of Bacterial Pathogens

2009 ◽  
Vol 63 (11) ◽  
pp. 1251-1255 ◽  
Author(s):  
Miryeong Sohn ◽  
David S. Himmelsbach ◽  
Franklin E. Barton ◽  
Paula J. Fedorka-Cray
Keyword(s):  
Fluorescence Spectroscopy ◽  
Rapid Detection ◽  
Fluorescence Spectra ◽  
Pathogenic Bacteria ◽  
Bacterial Pathogens ◽  
Emission Spectra ◽  
Principal Component ◽  
Minimal Sample ◽  
Synchronous Scan

This study deals with the rapid detection and differentiation of Escherichia coli, Salmonella, and Campylobacter, which are the most commonly identified commensal and pathogenic bacteria in foods, using fluorescence spectroscopy and multivariate analysis. Each bacterial sample cultured under controlled conditions was diluted in physiologic saline for analysis. Fluorescence spectra were collected over a range of 200–700 nm with 0.5 nm intervals on the PerkinElmer Fluorescence Spectrometer. The synchronous scan technique was employed to find the optimum excitation (λex) and emission (λem) wavelengths for individual bacteria with the wavelength interval (Δλ) being varied from 10 to 200 nm. The synchronous spectra and two-dimensional plots showed two maximum λex values at 225 nm and 280 nm and one maximum λem at 335–345 nm (λem=λex + Δλ), which correspond to the λex=225 nm, Δλ=110–120 nm, and λex=280 nm, Δλ=60–65 nm. For all three bacterial genera, the same synchronous scan results were obtained. The emission spectra from the three bacteria groups were very similar, creating difficulty in classification. However, the application of principal component analysis (PCA) to the fluorescence spectra resulted in successful classification of the bacteria by their genus as well as determining their concentration. The detection limit was approximately 103–104 cells/mL for each bacterial sample. These results demonstrated that fluorescence spectroscopy, when coupled with PCA processing, has the potential to detect and to classify bacterial pathogens in liquids. The methology is rapid (<10 min), inexpensive, and requires minimal sample preparation compared to standard analytical methods for bacterial detection.

Qualitative changes in the fluorescence spectra of intact pea leaves after photoinhibition

1991 ◽  
Vol 69 (5-6) ◽  
pp. 399-403 ◽  
Author(s):  
Wiesław I. Gruszecki ◽  
Konka Veeranjaneyulu ◽  
Roger M. Leblanc
Keyword(s):  
Energy Transfer ◽  
Chlorophyll Fluorescence ◽  
Fluorescence Intensity ◽  
Fluorescence Spectra ◽  
Fluorescence Emission ◽  
Heat Emission ◽  
High Light ◽  
Fluorescence Excitation ◽  
As Effects ◽  
Qualitative Changes

In high light (1400 W m−2) treated, intact pea leaves, a decrease in the ratio of fluorescence emission at 685 to 730 nm and an increase in fluorescence intensity between 500 and 600 nm were observed. Furthermore, photoacoustically monitored heat emission increased slightly, and O2 evolution decreased significantly. These findings are interpreted as effects of a photoprotective mechanism separating the carotenoid pool from the chlorophylls. This is supported by fluorescence excitation measurements and the results of a study on the reversibility of the process.Key words: chlorophyll fluorescence, carotenoid fluorescence, photoinhibition, photosynthesis, energy transfer.

The Determination of Fluorescent Whitening Agent VBL by Fluorescence Spectroscopy

2013 ◽  
Vol 401-403 ◽  
pp. 1135-1138
Author(s):  
Jia Yue Sun ◽  
Qiu Mei Di ◽  
Qi Guang Xu
Keyword(s):  
Fluorescence Spectroscopy ◽  
Fluorescence Intensity ◽  
Calibration Curve ◽  
Fluorescence Spectra ◽  
Excitation Wavelength ◽  
Fluorescent Whitening Agent ◽  
Average Percentage ◽  
Comprehensive Method ◽  
Whitening Agent

Comprehensive method for determining the fluorescent agents was studied through studying the fluorescence spectra of different concentration of VBL. The emission and excitation wavelength in the measurement was 275nm, and 434nm, respectively. When the concentrations of VBL are changing from 0 to 1.0 μg/mL, they have a linear relationship with the emitted fluorescence intensity. In this interval, the calibration curve is y= 1 6.713x+0.7879, showing strong correlation (correlation coefficient R2 is 0.9979). The average percentage of recovery is 89.9%, which meets the measuring requirements. The interaction between VBL and CTAB is preliminary studied.

Biophysical characterization of human breast tissues by photoluminescence excitation-emission spectroscopy

2012 ◽  
Vol 36 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Tatjana Dramićanin ◽  
Lea Lenhardt ◽  
Ivana Zeković ◽  
Miroslav D. Dramićanin
Keyword(s):  
Emission Spectroscopy ◽  
Fluorescence Spectra ◽  
Emission Spectra ◽  
Extracellular Proteins ◽  
Human Breast ◽  
Fluorescence Excitation ◽  
Biophysical Characterization ◽  
Malignant Breast ◽  
Breast Tissues

Abstract Fluorescence excitation-emission spectroscopy was used to investigate specimens of normal and malignant human breast tissues. Measurements were performed in two spectral regions: in the excitation range from 335nm to 400nm and emission range from 430nm to 625 nm, and in the excitation range from 400nm to 470nm and emission range from 500nm to 640 nm. It was found that fluorescence spectra are composed mainly of the emissions of extracellular proteins and that the differences in the intensity of their emissions reveal the changes in the tissue structure and morphology. These differences could be best observed in the emission spectra excited with 370 nm, 425nm and 455nm radiation. Statistical analysis revealed several spectral subregions that exhibited extremely significant statistical difference between normal and malignant breast tissues. The origin of these differences was elaborated, and prospects for optical diagnostics of breast cancer was discussed.

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