Synchronous Scanning Research Articles

The characterization of soybean varieties by fluorescence spectroscopy

SummaryFluorescence spectroscopy was used to differentiate between β‐conglycinin (βC) and glycinin (G) fractions that were isolated from four food grade soybean varieties (Glycine max var. K1430, Hutcheson, K93‐90‐29, and KS4997) grown in the same location. The protein fractions were discriminated by using spectroscopic tryptophan fluorescence emission and synchronous scanning techniques that took advantage of the sensitivity of the chromophore to changes in the protein environment. The relative intensities of the βC and glycinin fluorescence ranged from 1.00 to 1.30 and 1.00 to 1.31 respectively. The intensities of the βC and glycinin synchronous fluorescence ranged from 1.00 to 1.45 and 1.00 to 1.30 respectively. The spectroscopic method proved to be an effective technique to differentiate between different soybean varieties.

Characterization ofAnabaena cylindrica solution system using synchronous-scan fluorescence spectroscopy

The characterization of the algaeAnabaena cylindrica solution with Fe (III) was investigated using fluorescence emission and synchronous-scan spectroscopy. The ranges of concentrations of algae and Fe (III) in aqueous solutions were 5.0×108 2.5×108 cell/L and 1060 μmol/L. respectively. The effective characterization method used was synchronous-scan fluorescence spectroscopy (SFS). The wavelength difference (Δλ) of 90 nm, was maintained between excitation wavelength (λen) and emission wavelength (λen). The peak was observed at about (λex) (λem) 326 nm for synchronous scan fluorescence spectroscopy. The fluorescence quenching in system of algae Fe(III)-HA was studied using synchronous-scan spectroscopy for the first time, Fe(III) was clearly the effective quencher. The relationship betweenI I (quenching efficiency) andc (concentration of Fe (III) added) was, a linear correlation for the algae solution with Fe(III). Also, Aldrich humie acid (HA) was found to be an effective quencher.

Performance bounds on synchronous laser line scan systems

In this article a performance bound is derived for feasible image resolution among a class of imaging systems that can be referred to as synchronous laser line scan systems. Most often, these systems use a narrow beam projected source (typically a laser) in conjunction with a very small field of view receiver that is synchronously scanned. Here, a bound on the maximum system resolution is derived when both source and receiver are "delta function like". The bound demonstrates that the best achievable overall system point spread function is the square of the one way point spread function for the medium.

Application of fluorescence spectroscopy in the studies of natural organic matter fractions reactivity with chlorine dioxide and ozone

The composition of natural organic matter (NOM) fractions before and after the reaction with chlorine dioxide as well as ozone was studied by means of total luminescence spectroscopy (TLS) and synchronous scanning fluorescence measurements. The excitation–emission matrices spectra (EEMs) of natural as well as oxidised NOM fractions revealed two well-resolved bands with maxima at Ex/Em of 250–265/422–452nm and at Ex/Em 300–336/414–446nm ascribed to humic and fulvic material. The study of emission and synchronous spectra also confirmed the presence of protein-like constituents in all examined NOM fractions. The study of EEMs proved, that oxidation of all NOM fractions with ClO2 caused mainly the break-up of molecules into smaller fragments and a decrease of the aromaticity. Changes in EEMs after the oxidation of individual NOM fractions with O3 confirmed the formation of a significant amount of ozonation by-products, i.e. carboxylic acids, aldehydes and ketones during the oxidation process. In addition, the fluorescence studies confirmed relatively high reactivity of all NOM fractions with ClO2 as well as with ozone.

Preparation of novel composite nanoclusters and their application in the ultrasensitive detection of proteins

An ultrasensitive method for detecting protein by synchronous fluorescence scan technique with a novel composite nanoclusters has been developed. The novel composite nanoclusters has been prepared by an in situ polymerization method and applied as a protein synchronous fluorescence probe. The surface of the composite nanoclusters was covered with functional groups (−COOH, −CONH−, −OH). These groups may have “synergistic effect” and play a major role in the ultrasensitive method. The nanoclusters are water-soluble, stable and biocompatible. The synchronous fluorescence intensity of the composite nanoclusters is significantly increased in the presence of trace protein at pH 1.09. Based on this, a new synchronous fluorescence scan (SFS) analysis was developed for the determination of proteins including BSA, HSA and human γ-IgG. The liner range is 0.03–2.0μgml−1 for HSA, 0.02–2.2μgml−1 for BSA and 0.02–1.5μgml−1 for human γ-IgG, respectively. Besides high sensitivity, the method is characterized by good reproducibility, excellent accuracy and few interfering substances.

Determination of proteins at nanogram levels by synchronous fluorescence scan technique with a novel composite nanoparticle as a fluorescence probe

A novel composite nanoparticle has been prepared by an in situ polymerization method and applied as a protein fluorescence probe. The nano-CdS has been prepared, then the polymerization of acrylic acid (AA) was carried out by initiator potassium persulfate (KPS) under ultrasonic irradiation. The surface of the composite nanoparticles was covered with abundant carboxylic groups (COOH). The nanoparticles are water-soluble, stable, and biocompatible. The synchronous fluorescence intensity of the composite nanoparticles is significantly increased in the presence of trace protein at pH 6.90. Based on this, a new synchronous fluorescence scan (SFS) analysis was developed for the determination of proteins including BSA, HSA, and human γ-IgG. When Δ λ=280 nm, maximum synchronous fluorescence is produced at 290 nm. Under the optimum conditions, the response is linearly proportional to the concentration of proteins. The linear range is 0.1–10 μg ml −1 for HSA, 0.09–8.0 μg ml −1 for BSA, and 0.08–15 μg ml −1 for human γ-IgG, respectively. The method has been applied to the determination of the total protein in human serum samples collected from the hospital and the results are satisfactory.

Synchronous Scan and Excitation-Emission Matrix Fluorescence Spectroscopy of Water-Soluble Organic Compounds in Atmospheric Aerosols

Three-dimensional excitation–emission matrix (EEM) fluorescence spectra of water-soluble organic compounds (WSOC) from aerosol samples were measured and compared with those reported in the literature for natural dissolved organic matter. The EEM profiles of the WSOC presented three characteristic excitation/emission (λExc/λEm) peaks: 240/405 nm, 310/405 nm and 280/340 nm. The fluorescence intensities at λExc/λEm≈240/405 nm and λExc/λEm≈310/405 nm are located at wavelengths shorter than those reported for aquatic humic substances, indicating a smaller content of both aromatic structures and condensed unsaturated bond systems in the WSOC fraction. The EEM profiles of fractions obtained by the isolation procedure of the WSOC by the XAD resins showed that a fractionation has occurred and the XAD-8 eluate is highly representative of the total WSOC of collected aerosol. Synchronous scan spectra were more detailed than conventional fluorescence emission spectra, appearing more suitable for studying multicomponent samples such as the WSOC from atmospheric aerosols.

Classification of edible oils using synchronous scanning fluorescence spectroscopy

Total luminescence and synchronous scanning fluorescence spectroscopy techniques were tested as regards their ability to characterize and differentiate edible oils, including soybean, sunflower, rapeseed, peanut, olive, grapeseed, linseed and corn oils. Total luminescence spectra of all oils studied as n-hexane solutions exhibit an intense peak, which appears at 290 nm in excitation and 320 nm in emission, attributed to tocopherols. Some of the oils exhibit a second long-wavelength peak, appearing at 405 nm in excitation and 670 nm in emission, belonging to pigments of the chlorophyll group. Additional bands were present in the intermediate range of excitation and emission wavelengths in some oils, arising from unidentified compounds. Similarly, bands attributed to tocopherols, chlorophylls and unidentified fluorescent components were detected in the synchronous-scanning fluorescence spectra. Classification of oils based on their synchronous fluorescence spectra was performed using a non-parametrical k nearest neighbours method and linear discriminant analysis. Both methods provided very good discrimination between the oil classes with low classification error. The results presented demonstrate the capability of the fluorescence techniques for characterizing and differentiating vegetable oils.

Comparison of Laurentian Fulvic Acid luminescence with that of the hydroquinone/quinone model system: Evidence from low temperature fluorescence studies and EPR spectroscopy

Fluorescence techniques have been used to identify humic substances, (e.g. aquatic fulvic acids from different origins). Synchronous scans have proven adequate for distinguishing detail and differentiating samples. As well, fluorescence has often been used to probe humic interactions with metals and xenobiotic organics. In this study, the fluorescence of a well-characterized material, Laurentian fulvic acid (LFA) was compared with that of a simple hydroquinone/quinone (H2Q/Q) model system. Synchronous fluorescence (room T) and laser-excited fluorescence experiments at 10°K were carried out to characterize the fluorophore. The synchronous fluorescence behavior of LFA displayed similarities to that of an equilibrated, aerated, H2Q/Q system, but only at higher pH. (Higher pH favours a shift of the redox equilibrium towards quinone.) In contrast, the spectra of LFA suggest the role of “quinone” groups, even at lower pH. A significant feature of these spectra is a lowest energy band. At low temperature this band was more selectively excited at 470 nm, but vibrationally resolved line narrowed spectra were not observed. Fluorescence lifetimes were very short compared to the laser pulse width of ca. 10 ns. Under the low T condition the spectra of LFA and the model are essentially identical. We suggest that the principal luminophore in LFA is a quinone-hydroquinone type, perhaps a charge transfer complex consistent with the absence of the fluorescence line-narrowing phenomenon. The spectra imply a lowest energy component of LFA emission from a fluorophore very similar to that of the simplest H2Q/Q. The significant similarities of the model system to LFA are underscored by striking parallels in the radicals in the two systems seen in well-resolved electron paramagnetic resonance (EPR) spectra that could be obtained at pH = 6.

Rapid assessment of polycyclic aromatic hydrocarbon (PAH) exposure in decapod crustaceans by fluorimetric analysis of urine and haemolymph

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and potentially harmful contaminants of the coastal and marine environment. Studies of their bioavailability, disposition and metabolism in marine organisms are therefore important for environmental monitoring purposes. Detecting PAH compounds in the biological fluids of marine organisms provides a measure of their environmental exposure to PAHs. In the present study, the shore crab Carcinus maenas was exposed to waterborne pyrene for 48 h. Urine and haemolymph samples were analysed by direct fluorimetry utilising both fixed wavelength (FF) and synchronous scanning fluorescence (SFS) techniques. Samples from exposed crabs exhibited fluorescence due to 1-OH pyrene equivalents, whilst samples from control crabs did not. Levels of equivalents were exposure dependent. Urine was shown to be a more suitable medium for the analysis of PAH equivalents. In a separate experiment, depuration of pyrene equivalents in urine was monitored over time. Urinary levels reached a maximum 2–4 days after initial exposure and decreased steadily thereafter. No unchanged parent pyrene was detected in samples from exposed crabs. While fluorimetric techniques could discriminate between 1-OH pyrene equivalents and parent pyrene, identification of specific metabolites was only possible with HPLC/F analysis. This revealed crabs had bio-transformed pyrene into 3 major conjugates of 1-OH pyrene, which were excreted in the urine. While such biotransformation of PAH is well documented in fish and several crustaceans, this is the first study to use direct fluorimetry to detect PAH equivalents in exposed crustacean urine. Fluorimetric results correlated well with those obtained by HPLC/F and ELISA techniques. The technique has great potential as a rapid, inexpensive and non-destructive technique for field biomonitoring of PAH exposure in crustaceans.

Characterization of humic substances: implications for trihalomethane formation.

Humic substances are precursors of carcinogenic trihalomethanes (THMs) formed during disinfection by chlorination in water treatment processes. In an effort to understand the relationship between trihalomethane formation potential (THMFP) and physicochemical properties of humic substances, UV-visible absorbance, fluorescence in emission and synchronous scan modes, and NMR spectra were measured for several aquatic fulvic and humic acids. For comparison, a soil fulvic acid was also examined using these methods. The feasibility of the gradient modified spin-echo (GOSE) NMR experiment to selectively measure singlet resonances arising from isolated protons was examined. In addition, diffusion coefficients were measured for DMSO solutions of the fulvic acids using BPPLED and GOSE-edited pulse sequences. Although none of the methods tested produced results that correlated with THMFP, the GOSE intensities determined for different regions of the NMR spectra did reflect the relative abundance of different types of functional groups produced by lignin oxidation. In addition, the GOSE-edited diffusion results suggest that the isolated protons, those most reactive to chlorination, are more likely contained in the larger molecular weight fractions of fulvic acids.

Fluorescence behaviour of Zn and Ni complexes of humic acids from different sources

Conventional fluorescence spectroscopy in the excitation, emission and synchronous scan modes and three-dimensional fluorescence spectroscopy in the form of an excitation–emission matrix (EEM) of fluorescence intensity as a function of excitation and emission wavelengths have been applied to the study of three humic acids (HAs) extracted from soil (SHA), peat (PHA) and compost (CHA) and their interaction products with Zn(II) and Ni(II) ions. Fluorescence spectra of HAs appear to be related to the nature and origin of the sample. A strong reduction of intensity of all peaks is observed in the spectra of HAs–metal complexes as compared to those of untreated HAs. Ni(II) exhibits greater quenching ability than Zn(II). Fluorescence quenching measured for complexes of HAs at increasing Ni(II) concentrations was linearly correlated with metal ion concentration. The different capacity to interact with metal ions showed by various HAs is attributed to their different molecular complexity.

Assessing the Maturity of Crude Petroleum Oils Using Total Synchronous Fluorescence Scan Spectra

There have been many applications of fluorescence methods for the analysis of crude petroleum oils down through the years. However, none of these studies has yielded a robust qualitative or quantitative method for quantifying the chemical composition, or assessing the maturity of crude oils. Simple fluorescence parameters such as lifetime, intensity, and intensity ratios do not correlate well with chemical composition particularly for medium weight crude oils [A. G. Ryder, T. J. Glynn, and M. Feely (2003). Proc. SPIE-Int. Soc. Opt. Eng. 4876, 1188-1195.]. A better approach may be to use the Total Synchronous Fluorescence Scan (TSFS) method to fully interrogate the complex chemical composition of the oils [D. Patra and A. K. Mishra (2002). Anal. Bioanal. Chem. 373, 304-309.]. We present TSFS spectra from 18 crude petroleum oils of varying composition, sourced from around the world. The TSFS plots of these oils are very complex, with the contours being spread over the full 250-700 nm wavelength range (lambda(ex)) and 40-200 nm wavelength interval (delta lambda) sampled. The 3-D contour maps tend to two contour concentrations one at lambda(em) < 300 nm, delta lambda = 120-200 nm, and a second near lambda(ex) approximately 380-400 nm, delta lambda = 40-60 nm. The first feature represents fluorescence emission originating mainly from energy transfer processes with the second, longer wavelength feature originating from fluorescence emission generated by a higher proportion of direct excitation as opposed to emission resulting from energy transfer. The topography of the 3D contour plots is therefore influenced by the balance between energy transfer and direct fluorescence emission, which is governed by the chemical composition of the crude oils. We discuss how the gross chemical composition affects TSFS spectra and how TSFS can be used to assess oil maturity with a view to developing quantitative methods.

Fluorescence Spectroscopy for Characterization and Differentiation of Beers

Total luminescence and synchronous scanning fluorescence spectroscopic techniques were applied for characterization of the intrinsic fluorescence of eight different beers. Spectra were measured using different geometries to reveal the presence of similar fluorescent components. The total luminescence and synchronous fluorescence spectra exhibit a relatively intense short-wavelength emission ascribed to aromatic amino acids and less intense emission in the long-wavelength region, which may originate from B vitamins. Classification of beers based on their synchronous fluorescence spectra was performed using non-parametrical k nearest neighbours method and linear discriminant analysis. Very good discrimination was obtained in both methods with a low classification error. The results demonstrate the potential of fluorescence techniques to characterize and differentiate beers.

Simultaneous determination of the pesticides carbaryl and thiabendazole in environmental samples by a three-dimensional derivative variable-angle and a synchronous room-temperature phosphorescence spectroscopy.

A three-dimensional derivative variable-angle synchronous scanning (DVASS) and a synchronous scanning (SS) heavy-atom room-temperature phosphorimetry (HAI-RTP) method are reported, for the first time, to identify and quantify the spectral overlapping phosphorescent pesticides thiabendazole (TBZ) and carbaryl (CBL). These pesticides are widely used in agriculture. The phosphorescence emission of the two compounds was obtained using sodium sulfite as the O2 scavenger and an external heavy atom salt. A careful selection of these experimental variables has been carried out. The increase of selectivity afforded by the DVASS and the SS methodology permitted the demonstration of its applicability to the simultaneous determination of phosphorescent signals of these two pesticides with overlapping spectral profiles. Limits of detection ranged between 1.4 ng/mL for TBZ and 1.7 ng/mL for CBL. The proposed method has been satisfactorily applied to the analysis of both pesticides in different types of water samples.

Simultaneous determination of albumin and immunoglobulin G with fluorescence spectroscopy and multivariate calibration

A method is proposed for the simultaneous determination of albumin and immunoglobulin G (IgG1) with fluorescence spectroscopy and multivariate calibration with partial least squares regression (PLS). The influence of some instrumental parameters were investigated with two experimental designs comprising 19 and 11 experiments, respectively. The investigated parameters were excitation and emission slit, detection voltage and scan rate. When a suitable instrumental setting had been found, a minor calibration and test set were analysed and evaluated. Thereafter, a larger calibration of albumin and IgG1 was made out of 26 samples (0–42 μg ml −1 albumin and 0–12.7 μg ml −1 IgG1). This calibration was validated with a test set consisting of 14 samples in the same concentration range. The precision of the method was estimated by analysing two test set samples for six times each. The scan modes tested were emission scan and synchronous scan Δ60 nm. The results showed that the method could be used for determination of albumin and IgG1 (albumin, root mean square error of prediction (RMSEP) <2, relative standard error of prediction (RSEP) <6% and IgG1, RMSEP <1, RSEP <8%) in spite of the overlapping fluorescence of the two compounds. The estimated precision was relative standard deviation (R.S.D.) <1.7%. The method was finally applied for the analysis of some sample fractions from an albumin standard used in affinity chromatography.

03/01651 Total synchronous fluorescence scan spectra of petroleum products: Patra, D. and Mishra, A. K. Analytical and Bioanalytical Chemistry, 2002, 373, (4–5), 304–309

03/01651 Total synchronous fluorescence scan spectra of petroleum products: Patra, D. and Mishra, A. K. Analytical and Bioanalytical Chemistry, 2002, 373, (4–5), 304–309

Fluorescence analysis of aldolase dissociation from the N-terminal of the cytoplasmic domain of band 3 induced by lanthanide

The cytoplasmic domain of band 3 (CDB3) offers binding sites for several glycolytic enzymes and regulates the glycolysis of erythrocyte. The interaction between recombinant (His) 6-tagged CDB3 and aldolase, one of the key enzymes that participated in erythrocyte glycolysis, was investigated in the presence of lanthanide. The results indicate that trace lanthanide blocks the inhibition of CDB3-(His) 6 to aldolase and leads to enhancement of aldolase activity. In agreement with activity studies, fluorescence spectra reveal that 4 μM lanthanum ions induce the complete dissociation of aldolase from the N-terminal of CDB3-(His) 6. Interestingly, the synchronous scanning fluorescence spectra of proteins in the presence of various concentrations of lanthanum ions suggest that the conformational change of CDB3-(His) 6 is significantly attributed to the alteration of tryptophan cluster microenvironment, while the aldolase conformation change is mainly derived from tyrosine microenvironment changes. Based on the observation that lanthanide ions induce the dissociation of aldolase from CDB3-(His) 6, it is suggested that the existence of trace lanthanide may affect the glycolysis of erythrocyte.

Biodegradation of soil-derived dissolved organic matter as related to its properties

Abstract Quantifying the contribution of dissolved organic matter (DOM) to C sequestration in soils requires knowledge about extent and rate of its biodegradation. Since degradation experiments are time consuming, estimating the biodegradability of DOM by more easily measurable properties seems valuable. Our goal was therefore to investigate the biodegradation of DOM of different origin and to relate its extent and rate to properties such as UV absorbance, synchronous and emission scan fluorescence, XAD-8 sorption chromatography and 1 H-NMR spectroscopy. We extracted DOM from 13 different samples (maize straw, forest floors, peats, agricultural soils) and carried out a 90-day liquid incubation experiment. DOM biodegradation was quantified by CO 2 evolution. Rapidly and slowly mineralizable portions of dissolved organic carbon (DOC) as a measure of labile and stable DOC and the respective mineralization rate constants and half-lives were calculated by a double exponential model. The extent and rate of DOM biodegradation from less humified organic material (straw, litter and fermentation layers of forest floors) were high resulting in 61–93% of DOC being mineralized. The labile fraction comprised 59–88% of total DOC. DOM extracted from agricultural soils was of an intermediate biodegradability with a CO 2 evolution comprising 17–32% of total DOC. Labile DOC represented 14–25% of total DOC. DOM extracted from peats and Oa forest floor layers was relatively stable (mineralization of 4–9% of total DOC, labile DOC: 3–6%). The half-life of the labile DOC pool was short (2–5 days), whereas that of the stable DOC pool ranged from 0.2 years (DOM from less humified material) to 8.6 years (DOM from the Oa layer under spruce). Extent and rate of DOM biodegradation were closely but nonlinearly related to DOM properties. Solutions exceeding a threshold value of UV absorbance, aromaticity, XAD-8 adsorbable C or of humification indices derived from fluorescence spectra or having carbohydrate contents below a certain level were stable against biodegradation. Relatively simple methods like UV spectroscopy, XAD-8 fractionation and fluorescence emission spectroscopy were suitable to estimate the biodegradation of DOM.

Recent developments in multi-component synchronous fluorescence scan analysis

The ability to analyse complex multi-component mixtures without resorting to tedious separation procedures is extremely useful for routine analysis. Single-wavelength fluorescence measurement is limited in its ability to analyse complicated multi-component samples when they have severely overlapping emission and/or excitation spectra. This can be overcome by using synchronous fluorescence scan (SFS), where overlapping of spectra can be minimized. The selectivity of SFS can still be increased by taking derivative spectrum, applying different multivariate methods, selective fluorescence quenching, three-dimensional synchronous measurement or using some of these procedures in combination. Recent developments in various synchronous fluorescence methods for analysis of multi-component systems are discussed in this review.