Spectrofluorimetric Detection Research Articles

The Application of Pipette-Tip and Magnetic Dummy-Template Molecularly Imprinted Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography with Diode Array and Spectrofluorimetric Detection for the Determination of Coumarins in Cosmetic Samples

In this study, adsorbents based on molecularly imprinted polymers (MIPs) in two solid-phase extraction application forms, pipette tip and magnetic extraction, were used for the selective extraction of coumarins. The pipette-tip solid-phase extraction reduced solvent volumes; the magnetic MIP extraction was simple and effective for phase separation. Parameters affecting extraction, such as the amount of adsorbent, type of washing solvent, volume of the elution solvent, and extraction times for magnetic extraction, were optimized. The MIP-based adsorbents displayed high selectivity and extraction efficiency, resulting in recoveries ranging from 70.3 to 102.0% (RSD % less than 5.5%) for five coumarins under study, 6,7-dihydroxycoumarin-6-β-D-glucoside, coumarin, 7-methoxycoumarin, 6-methylcoumarin, and dicoumarol. The extracts were analyzed by high-performance liquid chromatography with diode array (DAD) and fluorescence (FLD) detectors, reaching limits of quantification of 0.5 and 0.9 µg·mL−1 for coumarin and dicoumarol detected by DAD and 0.001–0.012 µg·mL−1 for the other prohibited simple coumarins when used as a fragrance (detected by FLD). The proposed method was validated and its applicability was shown for the analysis of cosmetic samples like shower gel and perfume.

Surfactant-induced AIE-active tin(IV) micelles for sensing naproxen residues in pharmaceutical effluents

Nonsteroidal anti-inflammatory drugs, including naproxen (NPX), are highly consumed globally and their prolonged presence in the environment has detrimental effects on human health and aquatic ecosystems. In the present study, fluorescent micelles of thiophene appended chromone-based diorganotin(IV) crystalline solid (TBSn) have been obtained for the spectrofluorimetric detection of NPX in aqueous systems. Two diorganotin(IV) compounds, TBSn and TMSn were obtained from 2-thiocarboxaldehyde substituted 3-hydroxy-benzo-γ-pyrone and characterized by using FT-IR spectroscopy, multi-nuclear NMR (1H, 13C, and 119Sn) spectroscopy, mass spectrometry, CHN elemental analyses, and single-crystal X-ray diffraction. TBSn and TMSn molecules form brickwork architecture via C–H·····Sn, C–H·····O, C–H·····S, and π⋯π contacts which make them insoluble in water. However, the compounds form nano-aggregated AIE-active micelles with the aid of Pluronic F-127 in water. The micellar solution undergoes rapid elevation in emission intensity (within 5–7 s) in the presence of NPX, showcasing its effectiveness in analyzing NPX in the aqueous medium with the detection limit of 0.11 μM with a linear range of 0.5 to 9.5 μM. Therefore, the micellar formulation can be used as an effective chemosensor for the analysis of NPX in aqueous and pharmaceutical samples. This study marks a pioneering achievement in the spectrofluorimetric analysis based on turn-on detection of NPX utilizing TBSn micelles.

Enhanced fluorimetric detection of diphenylpyraline HCl using micelle and cyclodextrin mediated approach: Spectrofluorimetric and micellar liquid chromatographic application for either single or combined formulation with caffeine and paracetamol

Highly sensitive micellar spectrofluorimetric method (Method I) has been developed and validated for the determination of diphenylpyraline HCl in pharmaceutical tablets and in plasma. Sodium dodecyl sulfate improves the intensity of fluorescence of diphenylpyraline at 286 nm at pH 5 that allow its determination in plasma at nano-level. the mean percent recovery ± S.D was 99.719 ± 0.338 in plasma. In addition, Green cyclodextrin-modified micellar liquid chromatographic method (Method II) has been developed and validated for simultaneous determination of diphenylpyraline, paracetamol and caffeine using cyclodextrin micellar mobile phase consisted of 30 mM Brij*35, 0.5 mM hydroxypropyl β-cyclodextrin and phosphate buffer pH 4: MeOH (95:5, %v/v) that allows their simultaneous determination with enhanced spectrofluorimetric detection of diphenylpyraline. Method II was effectively applied for the simultaneous determination of diphenylpyraline, paracetamol and caffeine in a ternary laboratory prepared mixture which contained all possible excipients with mean percent recoveries ± S.D of 100.176 ± 1.008, 101.166 ± 0.415 and 100.708 ± 1.836, respectively. Linearity range for Method I was 0.1–1 μg. mL−1 for diphenylpyraline and for Method II was 0.3–50, 25–350, and 0.5–50 for caffeine, paracetamol and diphenylpyraline, respectively. Method I was also applied in spiked human plasma with linearity range 0.2–0.5 μg. mL−1. The methods are verified to have excellent greenness.

Toward an Electronic Tongue Based on Surfactant-Stabilized Chemosensory Microparticles with a Dual Detection Mode.

We propose a novel type of electronic tongue based on four types of monodispersed chemosensory microparticles (MPs) with a lipophilic core stabilized by a nonionic poloxamer surfactant. The lipophilic core composition was designed to achieve cross-sensitivity toward various ions and to enable spectrophotometric and/or spectrofluorimetric detection. Thus, generic anion-selective MPs, generic cation-selective MPs, as well as two types of metalloporphyrin-based MPs were fabricated and their morphology was characterized. Next, their differential sensing ability toward the discrimination of five l-tyrosine derivatives (dopamine, 3,4-dihydroxyphenylacetic acid, 3,4-dihydroxy-l-phenylalanine, normetanephrine, 4-hydroxy-3-methoxymandelic acid) was assessed. Comparison with the respective ion-selective electrode (ISE) responses was also provided to verify if the results from the potentiometric e-tongue correspond to outputs of the developed MP optode array. The recognition of dietary supplements containing l-tyrosine (l-Tyr) derivatives with the use of the MP-based e-tongue proved the potential of the developed sensing assay in pharmaceutical analysis.

High chitotriosidase and AGE levels in acromegaly: a case-control study.

Acromegaly is associated with oxidative stress and inflammation parameters. Chitotriosidase (CHITO) is a marker of macrophage activation and plays a pivotal role in the activation of inflammatory and immunological responses. Our study aimed to determine CHITO,YKL-40, advanced glycation end product (AGE), and high-sensitivity C-reactive protein (hsCRP) levels to investigate malondialdehyde (MDA), catalase, superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activities and to evaluate any association of these parameters with carotid intima media thickness (cIMT) in patients with controlled acromegaly. Thirty controlled acromegaly patients and 41 age- and sex-matched control cases were studied. We obtained demographic data, hormonal and metabolic parameters, and cIMT. CHITO activity was measured with the fluorometric method of Chamoles et al. YKL-40 and hsCRP levels were measured using ELISA. AGEs were measured based on spectrofluorimetric detection. GSH-Px activity was determined by a colorimetric assay. MDA, SOD, and catalase activities were determined in hemolysis. Higher CHITO, AGE, and hsCRP concentrations were observed in patients with acromegaly compared to controls. SOD levels were non-significantly higher in the acromegaly group, while catalase activities were lower in patients with acromegaly. Correlation analyses of CHITO, AGEs, YKL-40, hsCRP, MDA, catalase, GSH-Px, and SOD with metabolic, anthropometric, and laboratory parameters did not demonstrate any significant correlation (p > 0.05). There was no significant difference between groups with regard to cIMT levels. This is the first study investigating CHITO and AGE levels in patients with acromegaly. Serum CHITO, AGE, and hsCRP levels in acromegalic patients were significantly increased. It may be important to evaluate CHITO, AGE, and hsCRP levels in acromegalic patients who are already under cardiometabolic surveillance due to risk of developing cardiovascular disease.

Highly selective and sensitive spectrofluorimetric method for determination of cypermethrin in different environmental samples.

A sensitive, selective, and simple spectrofluorimetric method for the detection and determination of cypermethrin (CYP) in various samples based on thioglycolic acid-caped Mn-doped ZnS quantum dots (TGA@Mn-ZnS-QDs)is reported. These quantum dots were synthesized using the Gonzalez method. The synthesized quantum dots were structurally characterized with the help of different spectroscopic techniques including X-ray diffraction (XRD) and energy dispersive X-ray (EDX) techniques and fluorescence spectroscopy. The quantum dots were used for spectrofluorimetric detection and determination of CYP. The emission peak of these quantum dots at 632nm showed a linear quenching with increasing the concentration of CYP, noticing an excellent linear relationship between F°/F values and CYP in the range of 0.5-12µgmL-1 with a correlation coefficient (R2) of 0.992. The influence of different physiochemical parameters such as time, pH, the concentration of quantum dots, and other pesticides interference on the fluorescence quenching was investigated. The detection limit was calculated to be 0.132µgmL-1. The developed method was successfully applied for the detection and determination of CYP in various spiked samples (tomato, okra, pea, spinach, soil, and water) using the spike and recovery methods. The percent recoveries of CYP from these samples were found to be 77 ± 0.05% to 95 ± 0.12%at various levels.

Approaches for the complex assessment of polychemical pollution of permafrost-affected soils and the upper layer of permafrost.

The analysis of about 200 samples taken from 42 permafrost-affected soil profiles was carried out on four key sites in different regions of cryolithozone (West Siberia, Central, North, and North-East Yakutia) characterized by different active layer depths and soil lithology. The aim of the study was to determine the influence of different processes of cryogenic mass-exchange on the redistribution and accumulation of major pollutants such as petroleum products, acid-soluble forms of trace elements, polycyclic hydrocarbons, and technogenic radionuclides transferred via atmospheric transport or after the local anthropogenic impact in different soil horizons of Cryosols and in the upper layers of permafrost. Samples were analyzed using modern precise techniques (direct γ-spectrometric measurements with Ge(Li) and NaI(Tl) detectors; fluorometric method; reversed-phase high-performance liquid chromatography; spectrofluorimetric detection; atomic absorption spectrometry with flame atomization). The study has shown that processes (cryoturbations, frost heaving, gelifluction along with fluvial processes) that strongly affect Cryosols' profile structure can also lead to the active migration and accumulation of local and global pollutants in the middle and lowermost suprapermafrost soil horizons. The accumulation of some pollutants in suprapermafrost horizons of cryogenic soils and in the upper layers of permafrost (in particular, petroleum products and mobile forms of trace elements) can be associated with a combination of factors, such as the relatively light particle size distribution, relatively weak manifestation of cryoturbation processes, and low thickness of the active layer (about 40-60cm). The integral calculation of the geoaccumulation index values has shown that all of the groups of human-affected soil horizons are moderately to extremely polluted by petroleum hydrocarbons (and at a relatively lower level by trace elements) and the maximum pollution stands for the suprapermafrost horizons as well as in cryoturbated or buried fragments of organogenic matter in some cases. The maxima of the heavy PAH content in permafrost-affected soils can be confined to horizons enriched with anthropogenic inclusions and artifacts (for example, construction slag, coal) and to individual horizons of soils buried as a result of both cryogenic and alluvial processes. The specific activity of the technogenic radionuclide cesium in cryogenic soils revealed its association mainly with the surface organogenic and organomineral horizons of the studied profiles and rarely observed in the cryoturbated fragments of these horizons in the middle and suprapermafrost layers of soil profiles. The necessity of the complex analytical assessment of the permafrost-affected soils has been revealed especially in case of studying of the ecological state of the anthropogenically affected Cryosols.

Determination of chlorpromazine, levomepromazine, and promethazine by sequential injection analysis with VIS spectrometric or spectrofluorimetric detection

Determination of chlorpromazine, levomepromazine, and promethazine by sequential injection analysis with VIS spectrometric or spectrofluorimetric detection

Chip-Based Spectrofluorimetric Determination of Iodine in a Multi-Syringe Flow Platform with and without In-Line Digestion-Application to Salt, Pharmaceuticals, and Algae Samples.

In this work, a flow-based spectrofluorimetric method for iodine determination was developed. The system consisted of a miniaturized chip-based flow manifold for solutions handling and with integrated spectrofluorimetric detection. A multi-syringe module was used as a liquid driver. Iodide was quantified from its catalytic effect on the redox reaction between Ce(IV) and As(III), based on the Sandell–Kolthoff reaction. The method was applied for the determination of iodine in salt, pharmaceuticals, supplement pills, and seaweed samples without off-line pre-treatment. An in-line oxidation process, aided by UV radiation, was implemented to analyse some samples (supplement pills and seaweed samples) to eliminate interferences and release iodine from organo-iodine compounds. This feature, combined with the fluorometric reaction, makes this method simpler, faster, and more sensitive than the classic approach of the Sandell–Kolthoff reaction. The method allowed iodine to be determined within a range of 0.20–4.0 µmol L−1, with or without the in-line UV digestion, with a limit of detection of 0.028 µmol L−1 and 0.025 µmol L−1, respectively.

Advanced glycation end product: A potential biomarker for risk stratification of non-alcoholic fatty liver disease in ELSA-Brasil study.

BACKGROUNDLiver diseases are associated with the excess formation of advanced glycation end products (AGEs), which induce tissue inflammation and oxidative damage. However, the trend of oxidative marker levels according to the steatosis grade in non-alcoholic fatty liver disease (NAFLD) is unclear.AIMTo compare serum AGE levels between participants with NAFLD accordingly to steatosis severity in the baseline ELSA-Brasil population.METHODSIn 305 individuals at baseline ELSA-Brasil, NAFLD-associated steatosis was classified by ultrasound hepatic attenuation. The participants were grouped according to the severity of steatosis: mild and moderate/severe pooled. The measurement of serum fluorescent AGE concentrations was based on spectrofluorimetric detection. Serum AGE content and clinical and laboratory characteristics of the participants were compared between groups. The correlation between serum AGE levels and the grade of steatosis was analyzed. Logistic regression analysis was used to investigate the relationship between serum AGE levels and steatosis severity. A P value < 0.05 was considered statistically significant.RESULTSAccording to the steatosis severity spectrum in NAFLD, from mild to moderate/severe, individuals with the most severe steatosis grade had a higher incidence of metabolic syndrome (63% vs 34%, P ≤ 0.001), diabetes mellitus (37% vs 14%, P ≤ 0.001), and high cholesterol levels (51% vs 33%, P < 0.001). Moreover, individuals with increasing severity of steatosis presented increasing waist circumference, body mass index, systolic and diastolic blood pressure, fasting blood glucose, glycated hemoglobin, insulin, triglycerides, alanine aminotransferase, gamma-glutamyl transferase, C-reactive protein, and uric acid levels and lower high-density lipoprotein. Higher serum AGE content was present in the moderate/severe group of individuals than in the mild group (P = 0.008). In addition, the serum AGE levels were correlated with the steatosis grade in the overall sample (rho = 0.146, P = 0.010). Logistic regression analysis, after adjusting for confounding variables, showed that subjects with higher serum AGE content had a 4.6-fold increased chance of having moderate or severe steatosis when compared to low levels of serum AGEs. According to the results of the receiver operator characteristic curves analyses (areas under the curve, AUC = 0.83), AGEs could be a good marker of steatosis severity in patients with NAFLD and might be a potential biomarker in predicting NAFLD progression, strengthening the involvement of AGE in NAFLD pathogenesis.CONCLUSIONNAFLD-associated steatosis was associated with serum AGE levels; therefore, plasmatic fluorescent AGE quantification by spectroscopy could be a promising alternative method to monitor progression from mild to severe NAFLD accordingly to steatosis grade.

Danofloxacin pharmacokinetics and tissue residues in Bilgorajska geese

Danofloxacin is a fluoroquinolone developed for veterinary medicine and used in avian species for the treatment of numerous bacterial infections. However, no pharmacokinetic data have been reported in geese. The aim of the study was three-fold: (i) to evaluate the pharmacokinetics of danofloxacin in geese after single oral (PO) and intravenous (IV) administrations; (ii) to define its residue depletion profile in different goose tissues, and (iii) to recreate a multiple-dose simulation in the practical context of large-scale breeding.Twenty-four healthy geese were randomly divided in three groups each composed of eight animals. Group 1 received danofloxacin IV (5 mg/kg) and groups 2 and 3 were treated PO with the same dose. Blood was collected until 24 h (IV; group 1) and 48 h (PO; group 2) after administration. Two animals from group 3 were sacrificed at 6, 10, 24 and 48 h to collect samples of muscle, heart, kidney, liver, and lung. Danofloxacin was quantified in each matrix using a validated high-performance liquid chromatography method with spectrofluorimetric detection and the pharmacokinetic analysis was performed using non-compartmental and compartmental approaches.Danofloxacin showed a moderate elimination half-life (6.61 h), a slow clearance (0.35 mL/g*h) and a large volume of distribution (1.46 mL/g). The peak plasma concentration after PO administration and the time to reach it were 0.96 μg/mL and 1.70 h, respectively. The oral bioavailability was moderate (58%). Higher residue concentration was found in liver and kidney, compared to the other tissues.If the AUC(0–24) value found in the present study is included in the pharmacokinetic/pharmacodynamic index (AUC(0–24)/MIC) for the prediction of fluoroquinolones' efficacy, danofloxacin seems to be effective in geese against gram-negative bacteria with a minimum inhibitory concentration (MIC) < 0.076 μg/mL and against S. pneumoniae with a MIC < 0.29 μg/mL after a single PO dose of 5 mg/kg. Liver and kidney showed the highest drug tissue penetration value, with an explorative withdrawal time of 2.6 and 3.8 days, respectively. A practical multiple-dose regimen simulation does not lead to significant plasma drug accumulation.

Levofloxacin pharmacokinetics and tissue residue concentrations after oral administration in Bilgorajska geese

ABSTRACT 1. The aim of this study was to assess the pharmacokinetics of levofloxacin, a third-generation fluoro-quinolone antimicrobial drug, in geese (n = 26) after either single intravenous or oral administration, and to evaluate the depletion profile in goose muscle, heart, liver, kidney and lung after a single oral dose. 2. The pharmacokinetic study involved 16 geese which were randomly divided into two groups (n = 8/group), the first received levofloxacin (2 mg/kg) intravenously while the second was treated with orally (5 mg/kg). The tissue depletion study involved 10 geese which were dosed orally (5 mg/kg) and two animals were killed at different time-points in order to collect the selected tissues. Levofloxacin was quantified in all the matrices tested by a validated high-performance liquid chromatography (HPLC) method, using a spectrofluorimetric detector. The pharmacokinetics were analysed using a non-compartmental model. 3. Plasma concentrations were quantified after up to 24 h in animals administered intravenously and up to 48 h after oral treatment. Levofloxacin was rapidly absorbed after oral administration (Tmax = 0.38 h) showing high bioavailability (95.57 ± 20.61%). The drug showed a moderate volume of distribution (1.40 ± 0.28 ml/g) and rapid clearance (0.28 ± 0.06 ml/g/h). No statistical differences in estimates were found between the two different administration methods (P > 0.05). Drug residues were highest at 6 h and decreased constantly up to 48 h in all the selected tissues. Liver and kidney had the highest levofloxacin concentrations. 4. According to the pharmacokinetic/pharmacodynamic surrogate index (AUC/MIC) the levofloxacin dose regimen (after oral administration) used in the present study could be active against bacteria at a minimum inhibitory concentration (MIC) > 0.24 μg/ml in geese. In addition, drug accumulation in the liver might be controlled using an estimated preliminary withdrawal time of 90 h.

A novel fluorescent sensor for fast and highly selective turn-off detection of Fe3+ in water and pharmaceutical samples using synthesized azopyrazole-benzenesulfonamide derivative

Highly selective spectrofluorimetric detection of Fe3+ ions in acidic medium is developed using novel fluorescent sensor, namely 4-(2-(3-Methyl-5-oxo-1-tosyl-1H-pyrazol-4(5H)-ylidene) hydrazinyl)-N-(pyrimidin-2-yl) benzenesulfonamide (PHBS-sensor), which gives an selective fluorescence quenching response at λEmission 379 nm. The factors affecting fluorescence detection process, such as the pH, solvent type, buffer type, probe concentration, reaction time and co-existing ions were systematically studied and optimized. Theoretical modeling of Fe3+ monitoring through DFT calculation was investigated to display the mechanism of PHBS-Fe3+ complexation. The proposed PHBS-sensor can detect Fe3+ ions at ultra-trace levels with limit of detection 1.7 × 10−5 M. Moreover, this applied method was effectively utilized for the monitoring/detection of Fe3+ ions in real water, such as ground, tap and Nile river water, and pharmaceutical samples, such as hard gelatin capsule and syrup.

Studies on analytical method for determination of fluorescent whitening agents in paper containers for food

The method of determination of fluorescent whitening agents (FWA) in paper containers for food was studied. Samples were assessed in accordance with official procedures. The treated gauze was extracted by dimethylformamide, evaporated to dryness, and then analyzed by HPLC. The extracted FWAs were separated with Prodigy 5 μm ODS (2) column using acetonitrile: 0.01 M sodium dihydrogen phosphate (35:65) as solvent. For spectrofluorimetric detection, an excitation wavelength of 340 nm and emission wavelength of 430 nm were used. Applying the above HPLC method, fifty samples of paper containers for food were analyzed. No residue of FWA was detected in any sample.

Whole blood and oral fluid microsampling for the monitoring of patients under treatment with antidepressant drugs

Patients suffering from major depression and related pathologies (feeding and eating disorders, obsessive-compulsive disorder, post-traumatic stress disorder, anxiety disorders, etc.) are usually treated with antidepressant agents belonging to several pharmacological and chemical classes; the most recent of these agents are collectively known as “new-generation antidepressants”. In these patients, therapeutic drug monitoring (TDM) with the determination of drug and metabolite blood levels is one of the most useful procedures to optimise and personalise the treatment, enhancing both effectiveness and safety. A new approach is proposed in this study, based on microsampling of both blood and oral fluid by means of volumetric absorptive microsampling (VAMS). This approach makes sampling and storage much simpler and even self- and at-home-sampling possible, while retaining reliability, vastly increasing analyte stability and reducing overall expenses. The microsamples were pretreated by means of microextraction by packed sorbent (MEPS) on C2 sorbent and analysed by liquid chromatography with sequential spectrophotometric and spectrofluorimetric detection (HPLC-UV-FL). Method validation results were satisfactory (extraction yield >84%, precision RSD < 8.9%, stability>85.0% after 3 months). Application to blood and oral fluid VAMS from patients treated with four possible different antidepressants (sertraline, fluoxetine, citalopram and vortioxetine) provided results always in good agreement with those obtained from the corresponding fluid matrices, including the levels of drug metabolites.

Schiff base – Zn2+ ion combo as ‘pick and degrade’ probe for selected organophosphorus chemical weapon mimics and flame retardant analog: Detoxification of fruits and vegetables in aqueous media

A hydrazone based Schiff base (SB) has been synthesized and investigated for the detection, quantification and degradation of selective organophosphates (i.e diethyl chlorophosphate, diethyl cyanophosphonate, tris (2-chloroethyl) phosphate and dichlorvos). The organophosphates (OPs) form a covalent bond with –OH groups of SB and form SB-OP which quenches emission signal at 533 nm. Therefore, it can be used for the spectrofluorimetric detection and quantification of OPs upto the detection limits of 10.2, 158.2, 10.3 and 122.7 nM, respectively. Besides, the SB-OP duo undergoes degradation to non-toxic species in the presence of Zn2+ ions. The mechanism of interaction between SB-OP-Zn2+ trio is investigated by spectrofluorometric, spectroscopic, chromatographic and spectrometric experiments. The optimized recognition and degradation protocols were found accurate and precise when applied to fruits, vegetable and soil samples. Overall, the developed protocols prove SB as highly sensitive, selective and recyclable ‘pick and degrade’ probe for the recognition and degradation of OPs.

Phenylalanine Photoinduced Fluorescence and Characterization of the Photoproducts by LC-MS.

Phenylalanine (Phe) is a direct precursor of tyrosine and several neurotransmitters. The accumulation of Phe in the brain generates serious and not recoverable pathologies in children. Early detection in newborns is fundamental to apply the appropriate therapy and avoid irreversible health problems. Although fluorescence is a sensitive and selective technique for the determination of amino acids, the fluorescent analysis of Phe is limited since it exhibits a very low fluorescence quantum yield; however, the fluorescence of Phe increases drastically under UV irradiation when a peroxide medium is used. The aim of this research was to analyze the effect of the UV-radiation on Phe aqueous-peroxide solutions and to study the influence of the chemical environment on the photoinducted fluorescence process. The nature and characteristics of the fluorescent photoproducts generated under off-line UV irradiation in hydrogen peroxide medium were achieved by high performance liquid chromatography (HPLC) using a spectrophotometer detector (DAD) coupled in series with a mass spectrometer (MS) or with a fast scan spectrofluorimetric detector (FSFD). Environmental characteristics such as pH, initial concentration of Phe, hydrogen peroxide amount and irradiation time were studied in order to establish their influence on the formation of each one of the photoproducts. As the formation of several highly fluorescent photoproducts has been confirmed, the possibility of designing a chromatographic system with a post-column on-line photoreactor is open. The measure of the total fluorescence signal generated from Phe at the optimized irradiation time, could be used for the determination, with high sensitivity, of the initial amount of Phe in aqueous media, such as human serum or environmental samples. These aspects are being studied at present. .

HPLC-UV and spectrofluorimetric methods for simultaneous estimation of fluticasone furoate and vilanterol in rabbit plasma: A pharmacokinetic study

Fluticasone furoate (FF) and vilanterol trifenatate (VT) is a widely prescribed combination in the management of asthma and chronic obstructive pulmonary disease. In the present study, two quantitative methods based on HPLC-UV and spectrofluorimetric analysis had been developed and validated for simultaneous estimation of FF and VT in rabbit plasma using baclomethasone as internal standard (ISTD). Analytes and ISTD were separated from plasma using simple step of protein precipitation with acetonitrile. Chromatographic separation was achieved on Spherisorb S5 ODS2 (250 mm × 4.6 mm, 5.0 µm) column using mobile phase that constitute acetonitrile-0.01% glacial acetic acid in water (70:30, v/v) and then detected on a UV detector at 235 nm wavelength. Spectrofluorimetric detection was performed using absorption/emission wavelength (λabs/em) of 286/352 nm and 362/407 nm for FF and VT, respectively. For both analytes, linearity ranged from 4–200 ng/mL to 10–200 ng/mL using HPLC-UV and spectrofluorimetric method, respectively. Methods were validated as per FDA recommendations. Statistical analysis revealed that these detection methods are statistically insignificant difference and can be used interchangeably without any bias. Further, these methods were applied in pharmacokinetic study for simultaneous estimation of FF and VT in rabbit plasma.

A Comparative Study of Procedures for Preparing Samples of Bottom Sediments in the Determination of Petroleum Products by Chromatographic Methods

A method for determining aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) in bottom sediments using gas chromatography–mass spectrometry and HPLC with spectrofluorimetric detection, respectively, was developed. Various methods are studied for extracting PAHs from the matrix of a solid sample: extraction with organic solvents under mechanical stirring, ultrasonic treatment, and in a Soxhlet apparatus. The recovery depends on the method of sample treatment; it is maximum at mechanical stirring and extraction in the Soxhlet apparatus (up to 60–80%). The simplest method including mechanical stirring is optimal. A procedure for the quantitative separation of aliphatic hydrocarbons and PAHs in a wide concentration range is proposed using column chromatography on silica gel. The limits of detection for PAHs were 0.1–3 ng dry weight; RSD = 4% for benzo[a]pyrene at a concentration of 1 ng/g dry weight. The developed procedure was used to determine aliphatic hydrocarbons and PAHs in real samples of bottom sediments. The proposed option of sample preparation enables identifying and quantifying two groups of substances of petroleum components from one sample and thereby expands the possibilities of determining the source of hydrocarbon contamination of a water body.

Application of Butylamine as a Conjugative Reagent to On-Column Derivatization for the Determination of Antioxidant Amino Acids in Brain Tissue, Plasma, and Urine Samples.

(1) Antioxidants are involved in body protection mechanisms against reactive oxygen species. Amino acids such as glutathione (GSH) and N-acetylcysteine (NAC) are known to be involved in providing protection against oxidative lethality. A quick and simple method for the determination of NAC and GSH in various biological matrices such as urine, plasma, and homogenates of brain tissues has been developed and described in this work. (2) The assay is based on reversed phase high performance liquid chromatography with spectrofluorimetric detection and on-column derivatization. Butylamine and o-phthaldialdehyde have been used as derivatization reagents. Since o-phthaldialdehyde constitutes a part of the mobile phase, the derivatization reaction and chromatographic separation occur simultaneously. (3) Linearity in the detector response for NAC in human urine was observed in the range of 5–200 nmol mL−1, and NAC and GSH in the brain tissue homogenates were observed in the range of 0.5–5 nmol mL−1 and 0.5–15 nmol mL−1, respectively. Human plasma linearity ranges covered 0.25–5.00 nmol mL−1 and 0.5–15 nmol mL−1 for NAC and GSH, respectively. The LODs for NAC and GSH were 0.01 and 0.02 nmol mL−1 while the LOQs were 0.02 and 0.05 nmol mL−1, respectively. The usefulness of the proposed method was proven through its application to real samples.