Constant-wavelength Synchronous Spectrofluorimetry Research Articles

Two different synchronous spectrofluorimetric approaches for simultaneous determination of febuxostat and ibuprofen.

Two green, simple and sensitive synchronous spectrofluorimetric methods were developed for the first time for the simultaneous estimation of febuxostat (FEB) and ibuprofen (IBU). Method I is constant-wavelength synchronous spectrofluorimetry where FEB and IBU were recorded at 329 and 258 nm, respectively, using Δλ of 40 nm. Method II is constant-energy synchronous spectrofluorimetry using a wavenumber interval of −4000 cm−1. All measurements were carried out in a borate buffer of pH 7 and distilled water for dilution which increased the methods' greenness. The two methods were rectilinear over concentration ranges of 30.0–700.0 ng ml−1 and 0.5–9.0 µg ml−1 in the first method and 20.0–500.0 ng ml−1 and 0.1–8.0 µg ml−1 in the second method for FEB and IBU, respectively. High sensitivity was attained for the two drugs with limits of quantitations (LODs) down to 0.41 and 5.51 ng ml−1 in the first method and 0.25 and 3.32 ng ml−1 in the second method for FEB and IBU, respectively. Recovery percentages were in the range of 97.3–101.9% after extraction from spiked human plasma samples, demonstrating high bioanalytical applicability. The two methods were further applied to tablet dosage forms with good recovery results. The methods' greenness was assessed according to the analytical Eco-Scale and Green Analytical Procedure Index guidelines.

Comparison of Analytical Methods for the Rapid Determination of Melatonin in Food Supplements

Melatonin is a hormone produced by the pineal gland and extra-pineal tissues with chronobiotic effects that can alter the circadian rhythms, among other health benefits. This study intended to compare two different methods, high-performance liquid chromatography coupled to a variable wavelength detector plus a fluorescence detector (HPLC-VWD-FLD) and constant-wavelength synchronous spectrofluorimetry, to determine melatonin in food supplements. HPLC-MS/MS was used as a confirmatory technique. The data showed that both analytical methodologies were valid for the determination of melatonin with correlation between the datasets obtained (99% confidence level). Constant-wavelength synchronous spectrofluorimetry is a fast, simple, and economical method that can be used for a rapid and precise determination of melatonin in supplements, in the absence of other compounds that could interfere in the analysis. On the other hand, the HPLC-VWD-FLD method showed to be more suitable for the determination of melatonin in complex samples because of its high sensitivity and separation efficiency. Finally, all supplements analyzed from the Spanish market comply with the melatonin content declared on the label and with the claim “contributes to the alleviation of subjective feelings of the jet lag of jet lag” (0.5 mg/day). Also, 7 out of 10 complain about the claim “contributes to the reduction of time taken to fall asleep” (1 mg/day).

Comparison of Methods for the Study of Ellagic Acid in Pomegranate Juice Beverages

The present study aims to compare two kinds of methods to detect and quantify ellagic acid in commercial pomegranate beverages. Constant-wavelength synchronous spectrofluorimetry and high-performance liquid chromatography have been used for the study, and high-performance liquid chromatography photo diode array mass spectrometry has been used as a confirmatory technique. Ellagic acid is a polyphenol with strong antioxidant capacity which confers its numerous health benefits. Spectroflurometric is the most sensitive method (LOD = 0.021 μg/mL; LOQ = 0.024 μg/mL) in comparison with high-performance liquid chromatography (HPLC) (LOD = 0.079 and LOQ = 0.097 μg/mL), and it takes also less time to perform. The obtained results for ellagic acid concentration differ in the two studied methods; the reason could be that other compounds are detected at the same wavelength (λ ex = 383 nm) than the ellagic acid in the constant-wavelength synchronous spectrofluorometry. Among these compounds was the punicalagin which is the most important ellagitanin present in the pomegranate beverages and the hydroxicinnamic acids. Therefore, it was concluded that the most suitable method to quantify ellagic acid was HPLC-UV, and the confirmation by HPLC-MS/MS. On the other hand, constant-wavelength synchronous spectrofluorimetry is considered as a good alternative method in the ellagitannins detection in juices and beverages, since it give us an idea of the juice antioxidant power.

Comparison of methods for rapid analysis of quercetin.

Quercetin is a polyphenol of growing interest that is present in many foods. In this study, we compared two methods for its determination in samples of drinks made of juice and in dietary supplements, one chromatographic (HPLC) and other spectrofluorimetric (constant-wavelength synchronous spectrofluorimetry). To confirm the identification of the quercetin in the samples an HPLC-PDA-MS/MS system was used. It was concluded that both methods are suitable for dietary supplements and the choice of one or the other depends on the type of sample, time available for the analysis as well as the available resources. For juice beverages only HPLC is suitable.

Determination of phycobiliproteins by constant-wavelength synchronous spectrofluorimetry method in red algae

Phycobiliproteins are pigment–protein complexes, brilliant-colored and water soluble, existing in cyanobacteria and red algae. They have a great interest in food technology, food supplements, and pharmaceutical applications. Therefore it is important to have a fast, easy, and reliable method to determine the content of phycoerythrin (PE), phycocyanin (PC), and allophycocyanin (APC) in red algae. The samples are ground, extracted in phosphate buffer (pH 6.8), centrifuged, and the fluorescence scan of the supernatant is recorded. Optimum excitation-emission wavelength intervals (Δλ) for synchronous spectrofluorimetric analysis of the three phycobiliproteins were 10 nm for PE (LD = 10.9 × 10−3 mg/l) and APC (LD = 0.5 mg/l) and 40 nm for PC (LD = 0.77 mg/l). Algae analyzed contain PC and PE.

Use of constant wavelength synchronous spectrofluorimetry for identification of polycyclic aromatic hydrocarbons in air particulate samples

We have developed a simple, rapid, inexpensive method for the identification of fluoranthene (Flan), benz(a)anthracene (BaA), benzo(a)pyrene (BaP), benzo(k)fluoranthene (BkF), pyrene (Pyr), benz(ghi)perylene (BghiP) in suspended particulate matter in an urban environment of Delhi. Suspended particulate matter samples of 24h duration were collected on glass fiber filter papers. Polycyclic aromatic hydrocarbons (PAHs) were extracted from the filter papers using dichloromethane (DCM) and hexane with ultrasonication method. Comparison of the characteristic emission of spectra of PAHs with standard spectra indicated the degree of condensation of aromatic compounds present in investigated mixtures. It was also possible to identify some individual compounds. However, this identification could be more effective with the use of the respective values of Δλ parameter for each particular component of the mixture.

Simultaneous Determination of Lomefloxacin and Ciprofloxacin in Dairy Products by First-Derivative Synchronous Spectrofluorimetry

A simple, sensitive and quick assay to simultaneously determine lomefloxacin (LFLX) and ciprofloxacin (CPLX) had been developed by using zero-crossing first derivative constant wavelength synchronous spectrofluorimetry. Due to their similar molecule structures, it was difficult to analysis and determine LFLX and CPLX simultaneously by conventional fluorometry. In order to improve the sensitivity, aluminium ion was used to significantly enhance their endogenous fluorescent intensity. The different experimental parameters affecting the synchronous fluorescence intensity of the two fluoroquinolone drugs were carefully studied and optimized. The proposed method was successfully applied for the determination of the two drugs in milk samples.

Application of the effects of solvent and dissolved oxygen on the determination of benzo[ a]pyrene by constant-wavelength synchronous spectrofluorimetry in smoke-flavouring

This work studies the effects of solvent and of dissolved oxygen in the determination of benzo[ a]pyrene (B aP) by constant-wavelength synchronous spectrofluorimetry in smoke-flavour agents, as confirmation and quantification techniques. The wavelength of the most intense peak at the optimum excitation–emission wavelength interval (20 or 110 nm in most of nine solvents) varied by up to 5 nm, and the detection and quantification limits by a factor of up to 30. The best quantification limit was obtained with DMSO (0.09 μg l −1). The deoxygenation of the analyte solution decreased detection and quantification limits, by a variable factor (8–1.13 in the case of n-hexane and DMSO, respectively).

Constant-wavelength synchronous spectrofluorimetry for determination of riboflavin in anchovies

Constant-wavelength synchronous spectrofluorimetry was used for the analysis of riboflavin in anchovies. Synchronous fluorescence spectra were recorded between 300 and 600 nm at a scan rate of 240 nm min–1 and with excitation and emission slit-widths both set to 5 nm. The excitation-emission wavelength difference was 65 nm. The fluorescence was measured by peak-area base between 430–509 nm. Recovery was higher than 90.8%.

Determination of Benzo[ a]pyrene in smoking-flavour agents (water-soluble liquid smoke) by second derivative constant-wavelength synchronous spectrofluorimetry

We have developed a simple, rapid, inexpensive method for the determination of benzo[ a]pyrene (BP, a known carcinogen) in smoking-flavour agents (water-soluble liquid smoke; WSLS). After purification of the WSLS by a single passage through a Sep Pak C18 Plus cartridge, BP in the hexane eluate was determined by second derivative constant-wavelength synchronous spectrofluorimetry. Method precision (RSD < 6%) and recovery (≈92%) were satisfactory, and the detection and quantification limits (1.05 and 2.28 μg kg −1 respectively) indicated that the current maximum permissible concentration of BP in smoke flavourings (10 μg kg −1) can be monitored by this method.

Determination of polycyclic aromatic hydrocarbons in drinking and surface waters from Galicia (N.W. Spain) by constant-wavelength synchronous spectrofluorimetry

We describe a fast, new method for determination of the joint concentration of the six polycyclic aromatic hydrocarbons (PAHs), designated by current legislation as indicators of the quality of drinking waters and surface waters intended for the abstraction of drinking waters. The limit of detection of the new method was 6 ng l −1, its limit of quantification 20 ng l −1, its precision (CV%) 2.48 and its recovery 94.05%. Its speed allowed rapid PAH screening of 404 samples of surface and drinking water from Galicia (N.W. Spain).

Raman scattering interference in constant-wavelength synchronous spectrofluorimetry

Various aspects of the influence of Raman scattering on constant-wavelength synchronous spectra and means of decreasing the interference are discussed theoreticaly. General rules for dealing with the problem are describe. The observations could provide guidelines for experimental design.