Constant-energy Synchronous Fluorescence Research Articles

Enhanced Detection of Benzo[a]pyrene in Olive Oil through Low Temperature Liquid-Liquid Extraction Coupled with Constant Energy Synchronous Fluorescence Spectroscopy

Refined processed olive oil can indeed become significantly contaminated with polycyclic aromatic hydrocarbons (PAHs). To assess exposure to these contaminants, benzo[a]pyrene (B[a]P) is utilized as a marker due to its known carcinogenicity in humans. The European Commission has established a maximum limit of 2 μg kg-1 for B[a]P in edible oils. However, the analysis of trace amounts of B[a]P in a complex matrix like olive oil poses a persistent challenge. In this study, we have developed a low-temperature liquid-liquid extraction method in combination with constant energy synchronous fluorescence analysis for the determination of B[a]P in olive oil samples. The analyte was extracted from the olive oil using a mixture of acetonitrile and acetone. The performance of fluorescence measurements was evaluated by carefully considering the effects of solvent, temperature, acetone quenching, and slit width for monochromators. The proposed method demonstrates a linear range from 0.8 to 3.2 μg kg-1, with limits of detection and quantification of 0.04 and 0.80 μg kg-1, respectively. Precision and trueness assessments revealed relative standard deviations of less than 10% and recovery rates ranging from 103 to 112%. This method presents an efficient and rapid alternative to sample preparation procedure that minimizes organic solvent consumption.

Machine Learning-Assisted Synchronous Fluorescence Sensing Approach for Rapid and Simultaneous Quantification of Thiabendazole and Fuberidazole in Red Wine.

Rapid analysis of components in complex matrices has always been a major challenge in constructing sensing methods, especially concerning time and cost. The detection of pesticide residues is an important task in food safety monitoring, which needs efficient methods. Here, we constructed a machine learning-assisted synchronous fluorescence sensing approach for the rapid and simultaneous quantitative detection of two important benzimidazole pesticides, thiabendazole (TBZ) and fuberidazole (FBZ), in red wine. First, fluorescence spectra data were collected using a second derivative constant-energy synchronous fluorescence sensor. Next, we established a prediction model through the machine learning approach. With this approach, the recovery rate of TBZ and FBZ detection of pesticide residues in red wine was 101% ± 5% and 101% ± 15%, respectively, without resorting complicated pretreatment procedures. This work provides a new way for the combination of machine learning and fluorescence techniques to solve the complexity in multi-component analysis in practical applications.

Determination of molecular mass 302 polycyclic aromatic hydrocarbons in Standard Reference Material 1597a by reversed-phase liquid chromatography and constant energy synchronous fluorescence spectroscopy

High-performance liquid chromatography with fluorescence detection is often used for the analysis of polycyclic aromatic hydrocarbons (PAHs) in environmental extracts. Since fluorescence chromatograms are usually recorded at a single set of excitation and emission wavelengths, qualitative parameters for PAH identification are restricted to characteristic retention times. The research presented here explores the use of constant energy synchronous fluorescence spectroscopy (CESFS) for the analysis of co-eluting PAHs with similar chromatographic behaviors under normal and reversed-phase conditions. Twenty-one PAH isomers with molecular mass (MM, g/mol) 302 were studied. Synchronous fluorescence spectra were recorded under stop-flow conditions with the aid of a commercial HPLC system. PAHs were extracted from a coal tar sample (Standard Reference Material 1597a) and fractionated by normal-phase liquid chromatography (NPLC). Qualitative and quantitative analysis of NPLC fractions was carried out via reversed-phase liquid chromatography-CESFS (RPLC-CESFS). Of the 21 isomers investigated in the coal tar sample, 16 were spectrally identified in the absence of matrix interference. Three of the remaining isomers were tentatively identified in the presence of moderate spectral interference. Thirteen isomers were used to investigate the accuracy of the RPLC-CESFS approach. Mass fractions statistically equivalent to the NIST reported values (P = 95%; N1 = N2 = 3) were obtained for ten isomers ranging from 2.04 (dibenzo[a,h]pyrene) to 10.41 mg/kg (naphtho[2,1-a]pyrene). The non-destructive nature of CESFS provides an additional layer of selective and accurate information to the analysis of PAH isomers with MM 302.

Determination of human albumin in serum and urine samples by constant-energy synchronous fluorescence method.

A sensitive spectrofluorimetric method using constant-energy synchronous fluorescence technique is proposed for the determination of human albumin without separation. In this method, no reagent was used for enhancement of the fluorescence signal of albumin in the solution. Effects of some parameters, such as energy difference between excitation and emission monochromators (ΔE), emission and excitation slit widths and scan rate of wavelength were studied and the optimum conditions were established. For this purpose factorial design and response surface method were employed for optimization of the effective parameters on the fluorescence signal. The results showed that the scan rate of the wavelength has no significant effect on the analytical signal. The calibration curve was linear in the range 0.1-220.0 µg mL(-1) of albumin with a detection limit of 7.0 × 10(-3) µg mL(-1). The relative standard deviations (RSD) for six replicate measurements of albumin were calculated as 2.2%, 1.7% and 1.3% for 0.5, 10.0 and 100.0 µg mL(-1) albumin, respectively. Furthermore the proposed method has been employed for the determination of albumin in human serum and urine samples.

A novel method for the rapid detection of benzo(a)pyrene in liquid milk by dimethyl sulfoxide selectively enhanced synchronous fluorescence spectrometry

Based on the high solubility efficiency and strong fluorescence response of benzo(a)pyrene (BaP) in dimethyl sulfoxide in combination with the high-performance derivative constant-energy synchronous fluorescence spectroscopic (DCESFS) technique, a simple, sensitive and economic method was developed for the determination of BaP in liquid milk. This method comprises ultrasound-assisted solvent extraction, solvent replacement and DCESFS detection. No saponification or other tedious clean-up procedures were needed. The recoveries of BaP in different milk samples were greater than 82%. Detection limits in full- and low-fat milk were 0.03 and 0.04 μg kg–1, respectively.

Distribution and Source of Polycyclic Aromatic Hydrocarbons ( PAHs) in Soils of XinLuo District, Longyan City

The analytical method for the determination of trace polycyclic aromatic hydrocarbons (PAHs) in environmental soil by ultrasonic assisted soxhlet extraction coupled with constant energy synchronous fluorescence spectrometry was described.The results indicated that were taken in Longyan City XinLuo District of soil containing 9 components: Benzo(k)fluorathene, Anthracene, Fluorathene, 1,12-benzoperylene, 2,3-benzanthracene, 1,2,5,6-dibenzo-anthracene, Fluorene, 2,3-Benzofluorene, Coronene and that the concentrations of PA Hs are in the range of 9.344~372.986 ng.g-1. Industrial area around the PAHs were relatively higher in concentration in the soil, non-industrial area around the PAHs increased with the increase of human activity increased.

Determination of Migration Level of Benzo(a) Pyrene from Paper Cups into Food Simulants

This paper quantitatively determined the migration level of benzo(a)pyrene (BaP) from paper cups into aqueous food simulants or fatty stimulants, under different conditions by second derivative constant-energy synchronous fluorescence spectrometry (DCESFS), which proved to be a method with high sensitivity and spectral resolution. The influences of food simulants, time and temperature on the relative migration percent(%) of benzo(a) pyrene were discussed. Results showed that the recoveries of this method ranged from 89.2% to 104.3%. The migration percent(%) of fatty stimulants was higher than that of aqueous simulants. Migration into hot water was also observed, while the migration into cool water was almost negligible. The relative migration percent(%) increased with the increase of time and temperature.

Rapid determination of benzo(a)pyrene in processed meat and fish samples by second-derivative constant-energy synchronous fluorescence spectrometry

A simple, rapid and cost-effective method has been established for the determination of the quantity of benzo(a)pyrene (BaP), one of the most carcinogenic polycyclic aromatic hydrocarbons (PAHs), in roasted, smoked and charcoal grilled foods. Second-derivative constant-energy synchronous fluorescence spectrometry (DCESFS) improves the spectral resolution and selectivity of the fluorescence method. By using this method, processed meat, fish and some other food samples were analysed without resorting to complex pre-separation and purification procedures. The method was found to have a recovery of 97.7% ± 4.3%. The limit of detection (LOD) for BaP was 0.14 µg kg–1, far below the regulatory limit (1.0 µg kg–1) for BaP in food samples specified by the European Union. A certified reference material (Coconut oil, BCR®-458) was used to confirm the validity of the proposed method. The results suggest that the measurements are in a good agreement with the certified BaP concentrations (5.4% deviation). The results obtained by the proposed method for analysing BaP in food samples correlated well with those obtained by GC/MS.

Benzo (a) pyrene residue surveillance in retail food in the city of Xiamen, China: report from 121 samples

To investigate Benzo (a) pyrene (BaP) residue in retail food of Xiamen. BaP residue in 121 retail food samples collected from Xiamen were determined by a rapid BaP detector based on derivative constant-energy synchronous fluorescence technique. BaP was detected in 84.3% samples and the concentration were ranged from 0.17 to 59.0 microg/kg. There were 49.6% samples exceeding 5.00 microg/kg, and most of them were roasting food (1.44 - 54.10 microg/kg), processed meat products (0.17 - 59.00 microg/kg) and aquatic products (2.79 - 36.80 microg/kg). The BaP concentration in 34 samples collected from roadside stands were 1.78 - 49.60 microg/kg, of which the rate of the samples exceeding 5.00 microg/kg was 88.2%. The BaP contamination in retail food samples from Xiamen is serious.

Identification of polycyclic aromatic hydrocarbons (PAHs) in soil by constant energy synchronous fluorescence detection

In this paper, a novel method of constant energy synchronous fluorescence (CESF) was proposed to the simultaneous determination of different polycyclic aromatic hydrocarbons (PAHs) in a mixture of 16 components. When different appropriate intervals of the constant energy (Δ ν = 1400 or 4800 cm −1) were chosen during constant energy synchronous scanning, 13 PAHs could be identified and quantified by the corresponding synchronous spectra. Results show that their linear relations are fine and the limits of detection (LODs) were between 0.2 and 7.6 ng ml −1. Then the application of CESF method proposed in the analysis of the real soil samples under the optimum conditions indicated that 11 PAHs could be identified and the total concentration of PAHs in a real soil sample is 5.1 μg g −1, most of PAHs in the soil samples had three or four rings. Recoveries of these PAHs were from 70.9 to 121.4% in most cases. This CESF method is a simple, rapid, sensitive method with high resolution and also suitable to analyze the complex mixtures of PAHs in other environmental samples.

Micelle-Sensitized Constant-Energy Synchronous Fluorescence Spectrometry for the Simultaneous Determination of Pyrene, Benzo[a]pyrene and Perylene

The use of micellar media in constant-energy synchronous fluorescence spectrometry has been proposed. The influence of some aqueous micellar systems on the determination of pyrene, perylene and benzo[a]pyrene has been investigated. The presence of these micellar systems allows their determination in aqueous media, thus avoiding the use of an organic solvent, and greatly enhances the fluorescence signals. The combination of a constant-energy synchronous scanning technique and a micellar system provided a single spectrum for the simultaneous identification and quantitative determination of the three polycyclic aromatic hydrocarbons (PAHs). Further there was no energy transfer among them, making the measurement simple and fast. A constant-energy difference of 2800 cm(-1) was selected. The analytical characteristics of the proposed method in the presence of anionic micelles of sodium dodecylsulfate (SDS) were studied. The detection limits were at a level of ng ml(-1). Analysis of water samples from two different origins spiked with known amount of pyrene, perylene and benzo[a]pyrene also gave satisfactory results, and total average recoveries were greater than 97.1%.

Determination of polycyclic aromatic hydrocarbons (PAHs) in a complex mixture by second-derivative constant-energy synchronous spectrofluorimetry

In this work, the combination of the excellent band narrowing features of derivative spectrometry with constant-energy synchronous fluorescence spectrometry for the simultaneous determination of different polycyclic aromatic hydrocarbons (PAHs) in a mixture of 18 is assessed. This mode of scanning allowed for the identification and quantification of 10 PAHs and the grouping of some of these.

Fluorescence Spectroscopic Analysis of Tars from the Pyrolysis of a Victorian Brown Coal in a Wire-Mesh Reactor

Constant-energy synchronous fluorescence spectroscopy was used to examine the aromatic structural features of the tars from the pyrolysis of Loy Yang brown coal in a wire-mesh reactor. Tars from the pyrolysis of the raw coal and its H-form and Ca-form coal samples at various heating rates, peak temperatures, and holding times at the peak temperature were analyzed. The synchronous spectra of all of the tars showed two characteristic peaks with centers at ca. 335−340 and 385−390 nm. Synchronous fluorescence intensity per unit absorbance was found to be a useful parameter to examine the changes in the intramolecular energy transfer due to the changes in tar structural features. The degree of intramolecular energy transfer is considered a measure of the relative amounts of aromatic ring systems in oligomeric structures. Increasing heating rate during pyrolysis was found to enhance the release of larger (3 or more fused rings) aromatic ring systems. The introduction of ion-exchangeable cations (e.g., Ca2+) int...

Simultaneous determination of pyridoxal and pyridoxamine by different spectrofluorimetric techniques

Binary mixtures of pyridoxal and pyridoxamine can be resolved by using zero-crossing first derivative spectrofluorimetry, first devivative constant wavelength synchronous luminescence spectrometry and first derivative constant energy synchronous luminescence spectrometry. These methods do not require any previous separation steps. The lowest quantization limit is obtained with first derivative constant energy synchronous fluorescence (13.0 and 9.0 μg/1. for pyridoxal and pyridoxamine, respectively). The measurements were performed in aqueous medium at pH 7.0 provided by adding 0.05 M phosphate buffer solution. In order to demonstrate the validity of these methods a complete and exhaustive statistical analysis of the experimental data was performed. Pyridoxal and pyridoxamine were determined by these methods in synthetic and real mixtures with good results.

Derivative constant-energy synchronous fluorescence for simultaneous analysis of polynuclear aromatic hydrocarbon mixtures

Derivative constant-energy synchronous luminescence spectrometry (DCESLS) was evaluated using four-component mixtures of fluorene, carbazole, anthracene and perylene. The results show the effectiveness of DCESLS for the identification and determination of polynuclear aromatic hydrocarbons.

Analytical applications of synchronous fluorescence spectroscopy

A review is presented of the fundamental principles and analytical applications of synchronous excitation fluorescence spectroscopy, constant-energy synchronous fluorescence spectroscopy and variable-separation synchronous excitation fluorescence spectroscopy.

Identification of polyaromatic hydrocarbon mixtures by low-temperature constant energy synchronous fluorescence spectrometry.

A significant enhancement in the spectral resolution of polyaromatic hydrocarbon (PAH) mixtures was obtained with low-temperature constant energy synchronous fluorescence spectrometry (LTCESFS) measurements at 77K. Spectral separation of mixtures of PAH isomers and PAH alkyl homologues were achieved by LTCESFS analysis. Constant energy differences from 1400 cm/sup -1/ to 2000 cm/sup -1/ were used for scanning. LTCESFS provided a simple, selective, and inexpensive method for the evaluation of PAH isomeric mixtures and PAH alkyl homologue mixtures. 23 references, 4 figures, 1 table.

Rapid scanning fluorometer based on constant energy synchronous scanning

A rapid scanning fluorometer based on constant energy synchronous fluorescence scanning at 200 nm/s has been developed. Constant energy synchronous fluorescence spectrometry involves measurement of fluorescence as both excitation and emission monochromators are scanned with a constant energy difference being maintained. Spectral information is collected in the forward to reverse directions and is processed in real time. A discussion of the instrumentation and software is given. A theoretical comparison between the photomultiplier tube (PMT) detection system used with this system and a silicon intensified target vidicon (SIT) detection system has been given. Calculations indicate that the signal-to-noise ratio S/N for the PMT system should be about 5–40× greater than for the SIT system. A comparison of the experimental figures of merit (detection limits, scan speed, analysis time) of the rapid scan constant energy synchronous fluorescence spectrometer with video fluorometers has also been made, again showing the superiority of the rapid scan synchronous system.

Rapid-scanning constant-energy synchronous fluorescence spectrometer as a liquid chromatographic detector

A rapid-scanning fluorimeter based on constant-energy synchronous scanning is described. It is used as a liquid chromatographic detector for polyaromatic hydrocarbons (PAHs). The computerized system scans at a rate of 200 nm s −1 and collects data in the forward and reverse directions. Data are processed in real time. The system is tested for 3-component and 9-component mixtures of PAHs. A synchronous fluorescence spectrum is obtained for each PAH being eluted in the chromatogram. The spectral peaks observed in the rapid scan correspond to the absorption/fluorescence transitions of the PAHs with an overall vibrational energy loss equal to the Δν value chosen. Limits of determination for the PAHs are in the pg to low ng range. The system provides a reduced signal/noise ratio compared to the variable-wavelength fluorescence system for most PAHs examined.

Rapid Scanning Constant Energy Synchronous Fluorescence Spectrometry: A Comparison of Flow Cells

Rapid scanning constant energy synchronous fluorescence spectrometry (RSCESFS) is evaluated for flow cell design, scan speed, and constant energy interval choice. Analytical figures of merit for several polycyclic aromatic hydrocarbons (PAHs) are given for several experimental conditions, for several flow cells, and for both RSCESFS and conventional (nonscanning) fluorescence spectrometry. With RSCESFS, absolute detection limits as low as 700 fg, linear dynamic ranges as great as five orders of magnitude and the time to record a complete 350 nm spectrum as short as 17 s have been obtained.