The Reasons for Fluorescence Emitting from the Mixture of Colchicine and H2SO4

Abstract

The reasons for fluorescence emitting from the mixture of colchicine and H₂SO₄ in different concentrations were investigated and confirmed through organic synthesis in this article. The compound N‐deacetylcolchiceine (1) which has native fluorescence at λ_ex/λ_em=272/373 was obtained from the reaction of colchicine with diluted H₂SO₄. When colchicine reacted with concentrated H₂SO₄, another compound 2‐demethylcolchicine (2), which also has native fluorescence at λ_ex/λ_em=294/358 was obtained.     

Spectrofluorimetric determination of titanium,zirconium and hafnium and their binary mixtures with biacetylmonoxime nicotinylhydrazone

The synthesis, characteristics and analytical applications of biacetylmonoxime nicotinylhydrazone are described. This compound forms fluorescent complexes with titanium(IV) (λ_ex = 430, λ_em = 540 nm), zirconium (λ_ex = 415 nm, λ_em = 505 nm) and hafnium (λ_ex = 400, λ_em = 500 nm) in an acidic medium. Titanium forms a 1:2 metal:ligand complex, whereas zirconium and hafnium form 1:2:1 metal:ligand:sulphate ternary complexes. Highly selective spectrofluorimetric methods for titanium (20–100 ng ml^?1), zirconium and hafnium (5–100 ng ml^?1) are proposed, and procedures for the analysis of binary mixtures of these ions are described.     

Determination of Polycyclic Aromatic Hydrocarbons in Airborne Particulate by High Performance Liquid Chromatography

This paper presents a trisolvent ultrasonic extraction and HPLC analysis method for the determination of 11 polycyclic aromatic hydrocarbons in air particulate collected on an air filter by a commercial high volume air sampler. A reverse phase column, Vydac 201 TP, and a gradient mobile phase, acetonitrile/water, were used. The 11 PAHs, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a, h]anthracene, benzo[ghi]perylene, indeno[1,2,3-cd]pyrene, and coronene were completely resolved under experimental conditions. All the PAHs except coronene were monitored by fluorescence with λ_ex=270 nm, λ_em>389 nm. Coronene was monitored by UV with λ=300 nm. The methodology was evaluated by spiking SRM 1649 with a PAH standard and then going through different extraction procedures and analyzing the PAH concentrations without clean-up. An external standard method was used for quantitation. The recovery yields for fluoranthene, benz[a]anthracene, benzo[a]pyrene, benzo[ghi]perylene and indeno[l,2,3-cd]pyrene were above 90%. The detection limits of PAH with fluorescence at λ_ex=270 nm, λ_em>389 nm ranged from 5.7 pg to 69.5 pg.     

Spectrofluorometric determination of zinc with 1,5-bis(2,3-dihydroxyphenylmethylene) thiocarbohydrazone

1,5-Bis(2,3-dihydroxyphenylmethylene)thiocarbohydrazone was synthesized; its ionization constants are reported. A procedure is described for the spectrofluorimetric determination of 5–540 ng ml^?1 zinc in 60/40 (v/v) ethanol/water medium, acetate-buffered to apparent pH 6.5 (λ_ex=400 nm, λ_em=508 nm). Interferences were evaluated and the procedure was applied with good results to the determination of zinc in potable waters (0.3–3 μg ml^?1) and lubricating oils.     

Long-wavelength fluorescent indicators for the determination of oxygen partial pressures

A series of stable heterocyclic indicators with λ_ex = 469–566 nm and λ_em = 511–652 nm allows the fluorimetric determination of ca. 1–100% partial pressures of oxygen by quenching of fluorescnce, especially in toluene solution.     

Hydrolytic degradation behavior of poly(l-lactide)/SiO2 composites

In this work, different contents of nano-silica (SiO₂) particles were introduced into poly(l-lactide) (PLLA) to prepare PLLA/SiO₂ composites though a two-step compounding method, i.e. solution compounding (preparing master batch) and subsequent melt compounding (master batch dilution). The dispersion of SiO₂ was characterized using scanning electron microscope (SEM). The hydrophilicity of the material was evaluated by measuring the contact angle of water on the sample surface. The hydrolytic degradation measurements of the nanocomposites were carried out in alkaline solution at two different temperatures, i.e. 37 and 55 °C. Subsequently, microstructure evolution of PLLA matrix during the hydrolytic degradation process was systematically investigated using wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The results showed that SiO₂ had good dispersion in the PLLA matrix. Largely enhanced hydrolytic degradation ability was achieved for PLLA/SiO₂ composites. Increasing the content of SiO₂ or enhancing the hydrolytic degradation temperature accelerated the hydrolytic degradation of PLLA matrix. Further results showed that SiO₂ promoted the reorganization of microstructure of PLLLA matrix during the hydrolytic degradation process.     

Fluorometric Determination of Cellulase

Abstract

A fluorometric procedure is described for the determination of the enzyme cellulase. The method is based upon the hydrolysis of the nonfluorescent substrate, resorufin acetate, by the enzyme to give the highly fluorescent resorufin (λ_ex = 540 mμ;, λ_em = 580 mμ). By this procedure from 0.00010 to 0.060 units per ml. of cellulase can be determined with an accuracy and deviation of about 1.5%. Evidence is offered to demonstrate cellulase, and not esterase, activity.     

Stopped-flow injection determination of copper(II) at the ng ml−1 level

A stopped-flow injection method for the determination of copper(II) in the range 0.2–300 ng ml^?1 is proposed, based on the catalytic effect of this ion on the 2,2'-dipyridylketone hydrazone/hydrogen peroxide reaction. The oxidation product shows an intense blue fluorescence that is monitored at λ_ex = 350 nm, λ_em = 427 nm. The sampling rate (72 h^?1), r.s.d. (1.4%) and the lack of interference from most foreign ions, allowed application of the method to the determination of copper in foods and blood serum.     

Syntheses,Crystal Structures and Photophysical Properties of a Series of Cadmium(II) Coordination Polymers

Three cadmium(II) coordination polymers [Cd(NA)₂(H₂O)₂]_n ( 1 ), {[Cd(NA)(phen)(NO₃)]·(H₂O)_1/2}_n ( 2 ), {[Cd(NA)(CH₃C₆H₄COO)(H₂O)₂]·(CH₃C₆H₄COOH)}_n ( 3 ) (HNA = nicotinic acid, phen = 1, 10‐phenanthroline) have been synthesized by hydrothermal method. Their single‐crystal structures were determined by X‐ray diffractometry. The absorption, excitation and emission spectra were investigated and all the complexes emit strong fluorescence: λ^em_max = 544 nm (λ^ex = 492 nm), 1 ; λ^em_max = 466 nm (λ^ex = 393 nm), 2 ; λ^em_max = 430 nm (λ^ex = 313 nm), 3 . At room temperature in the solid state the fluorescence lifetimes of the complexes were investigated and the relationships between the spectra were discussed as well as the connections of luminescence and crystal structures.     

Determination of metoprolol in human plasma and urine by high‐performance liquid chromatography with fluorescence detection

A simple, specific and sensitive HPLC method has been developed for the determination of metoprolol in human plasma and urine. Separation of metoprolol and atenolol (internal standard) was achieved on an Ace C₁₈ column (5 μm, 250 mm×4.6 mm id) using fluorescence detection with λ_ex=276 nm and λ_em=296 nm. The mobile phase consists of methanol–water (50:50, v/v) containing 0.1% TFA. The analysis was performed in less than 10 min with a flow rate of 1 mL/min. The assay was linear over the concentration range of 3 – 200 and 5 – 300 ng/mL for plasma and urine, respectively. The LOD were 1.0 and 1.5 ng/mL for plasma and urine, respectively. The LOQ were 3.0 and 5.0 ng/mL for plasma and urine, respectively. The extraction recoveries were found to be 95.6 ± 1.53 and 96.4 ± 1.75% for plasma and urine, respectively. Also, the method was successfully applied to three patients with hypertension who had been given an oral tablet of 100 mg metoprolol.     

Sensitive and selective determination of metabolically formed trans-dihydrodiols and phenols of benzo[a]pyrene in water and urine samples by HPLC with amperometric detection

A method has been developed to separate hydroxylated metabolites of the carcinogenic polycyclic aromatic hydrocarbon benzo[a]pyrene, i. e. trans-4,5-, 7,8-, 9,10-dihydrodiol and 1-, 3-, 7-, and 9-phenol, by HPLC with amperometric detection employing an isocratic methanol/water eluent (70:30, v/v) containing 0.5 g/L sulfuric acid and 1 g/L lithium perchlorate. Compared with the usually applied fluorescence (λ_ex = 265 nm, λ_em = 460 nm) and ultraviolet (λ = 265 nm) detection, the amperometric technique is about 2–12 times more sensitive for the determination of all metabolites investigated. The method was applied to the determination of the seven metabolites of benzo[a]pyrene in different water samples and in urine after solid-phase extraction (SPE). The results obtained by HPLC with amperometric detection after SPE enrichment from an aqueous extract of a soil sample and from the urine of a rat intragastrically treated with benzo[a]pyrene agreed well with the values determined with fluorescence and/or UV detection.     

Determination of Oxolinic Acid Residues in Gilthead Seabream (Sparus aurata) Muscle Tissue and Plasma by High-Performance Liquid Chromatography

A high-performance liquid chromatographic method for the determination of oxolinic acid (OA) residues in muscle tissue and plasma of the cultured fish gilthead seabream (Sparus aurata L.), is described. OA was extracted with ethyl acetate and after centrifugation the combined extracts were evaporated. To the remaining residue 1 mL of the mobile phase was added and the extract was partitioned with n-pentane which then was rejected by aspiration. OA was chromatographed on a Zorbax^®SB-C₁₈ column at 50^oC and detected by fluorescence detection at λ_ex 327 nm and λ_em 369 nm. The mobile phase was a mixture of 0.1% trifluoroacetic acid (v/v) pH 2.0 and acetonitrile-methanol 3:2 (v/v) in a combination of 50:50 (v/v) and a flow rate of 1.0 mL min^?1, delivered isocratically. Method mean recovery (R%) achieved was 73.7 ± 4.4% (mean ± SD) for blank fortified samples (n=4) range at 50, 100 and 200 μg kg^?1 with a RSD=3.3%. The limit of detection (LOD) was 2.0 μg kg^?1 oxolinic acid in muscle tissue and plasma and the limit of quantification (LOQ) was 5.0 μg kg^?1. The method is fast and suitable to be used with safety and accuracy for the control of OA residues in cultured seabreams and a trained analyst could carry out ready for chromatography more than 50 samples per working day.     

Synthesis and properties of polyaniline doped with iron-substituted silicotungstate isomers with Keggin structure

Four polyaniline hybrid materials doped with iron-substituted silicotungstate isomers α,?β _i - K_5?n H _n [SiW₁₁Fe(H₂O)O₃₉]?·?xH₂O (β_i?=?β₁, β₂, β₃) were prepared. The materials were characterized by elemental analysis, IR spectra, UV-Vis spectra, scanning electron microscopy (SEM), TG-DTA and X-ray diffraction (XRD). The conductivity and fluorescence were determined and thermal stability was studied. The UV-Vis, IR and XRD results confirm the existence of Keggin anions. Thermal analysis indicates that SiW₁₁Fe/PANI has better thermal stability. The images of scanning electron microscopy (SEM) show that the materials are microporous. The materials exhibit excellent proton conductivity of 8.5?×?10^?2?S?cm^?1 at room temperature (20°C). The spectral data indicate that polyaniline doped with α, β_i-SiW₁₁Fe have similar fluorescence, λ_em?=?418–470?nm, and emit blue light.     

Thermomechanical behavior of rubberlike materials

A simple form of nonisothermal free energy function A(λ₁, λ₂, λ₃, T) for rubberlike materials results from postulating that the entropy is a separable symmetric function of the extension ratios λ_i along the principal strain directions and considering the fundamental properties of rubberlike materials, i.e., that rubber elasticity is associated primarily with changes in entropy and the variation of elastic tension with changes in temperature is linear. The explicit representation of A is reduced to the Valanis-Landel strain energy function for isothermal cases.     

Simultaneous determination of three banned psychiatric drugs in pig feed and tissue using solid‐phase reactor on‐line oxidizing and HPLC‐fluorescence detection

The banned addition of psychiatric drugs such as phenothiazines to animal feed and foodstuffs increases the risk of human organ lesion. Phenothiazines usually exhibit weak native fluorescence and can be oxidized to strongly fluorescent compounds. In this study, a novel, sensitive and convenient method of HPLC‐fluorescence detection based on post‐column on‐line oxidizing with lead dioxide solid‐phase reactor has been developed for simultaneous determination of three banned psychotropic drugs, promethazine, chlorpromazine and thioridazine. Three compounds were successfully separated on an Agilent TC‐C₁₈ column with mobile phase of acetonitrile (A) and water (B), both containing 0.5% (v/v) formic acid. A gradient elution was programmed and fluorimetric detection was performed at λ_ex/λ_em of 332/373 nm for promethazine, 340/380 nm for chlorpromazine and 352/432 nm for thioridazine. The calibration graphs gave good linearity over the concentration ranges of 30.0–4976.4 µg/L for promethazine, 2.0–2153.2 µg/L for chlorpromazine, and 15.0–3088.0 µg/L for thioridazine, and correlation coefficients (r) were ≥0.995. The method was applied to the determination of phenothiazines in pig feed and pig tissue, and the average spiked recoveries were in the range 69.1–115.4%. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of catecholamines as their N-hydroxy-succinimidyl-3-indolylacetate derivatives by pre-column derivatization HPLC separation and fluorescent detection

N-Hydroxysuccinimidyl-3-indolylacetate (SIIA) is a new fluorescent derivatizing reagent with an indole ring and ¶an N-hydroxysuccinimide ester functionality. It can react with catecholamines under mild conditions to form corresponding amides, which have strong fluorescence at λ_ex/λ_em = 301 nm/¶365 nm. This paper covers the RP-HPLC separation and fluorescent determination of derivatized catecholamines with SIIA. In a mobile phase of methanol-water (36/64, v/v) containing H₃cit-Na₂HPO₄ buffer (pH = 4.00, 10 mmol/L), the derivatives of norepinephrine (NE), epinephrine (E) and dopamine (DA) were eluted within 15 min on a C₁₈ column. The detection limits were 0.043, 0.13 and 0.18 pmol, respectively, when the ratio of signal to noise (S/N) was 3. The excessive reagent is rapidly hydrolyzed to 3-indolylacetic acid (IA) that can be easily separated from derivatives.     

New Rapid Assay for Nafcillin by Spectrofluorimetry in Pharmaceutical Dosage

Abstract

A method for the spectrofluorimetric determination of nafcillin is proposed (λ_ex = 226 nm, λ_em = 366 nm), for concentrations between 0.10 and 1.0 μg mL^?1. The method was performed in ethanol/water medium (30% V/V), at apparent pH 6.0 provided by adding of phosphate buffer solution with pH = 6.20.

The obtained values of detection and determination limits are 0.016 and 0.054 μg mL^?1, respectively.

The method was successfully applied to assay a commercial injection containing nafcillin sodium monohydrate.     

Two new dinuclear complexes with flexible bipyrazole ligand bridged via μ-Cl or μ1,1-N3

Two dinuclear complexes, {[Cd(bdpp)Cl₂](CH₃OH)}₂ (1) and [Cd(bdpp)(N₃)(NO₃)]₂ (2), have been synthesized by reactions of bdpp with cadmium salts (bdpp?=?1,3-bis(3′,5′-dimethylpyrazol-1′-yl)propane), and characterized by IR, element analysis, fluorescence properties and single crystal structural analysis. Cd in 1 has a trigonal bipyramidal coordination geometry and two such units form a dimer through two μ-Cl bridges. Each Cd in 2 has a distorted octahedral coordination geometry and two Cd units form a dimer through μ_1,1-N₃ bridges. The emission spectra show λ_em?=?413?nm for 1 and λ_em?=?338?nm for 2.     

Use of Optically Transparent Membranes for Preconcentration and Direct Phosphorimetric Determination of Pharmaceutical Flumequine

A preconcentration membrane for the retention and phosphorimetric determination of flumequine is proposed. The membrane has a circular zone adhering to the surface of a polyester strip, which constitutes the preconcentration area where the analyte is retained by absorption from a solution that contains it. The phosphorescence intensity emitted by the flumequine can be measured directly in the solid phase, at λ_exc = 358 nm and λ_em = 459 nm. The variables that influence the construction of the membrane have been studied, along with the experimental variables related to the fixation process of the analyte in the membrane. The calibration graph was linear over the range 0.1–2.0 mg/L with a detection limit of 0.03 mg/L and a precision of 0.5%. The method was applied to samples of human urine and cow's milk, with recovery percentages ranging between 100.0 and 102.8%.