Simple and sensitive method for spectrofluorimetric determination of dodecyl benzene sulfonic acid sodium

The interaction of poly(diallyldimethyl ammonium chloride) (PDDA) with dodecyl benzene sulfonic acid sodium (DBS) has been studied by fluorescence spectra. The fluorescence of DBS can be greatly enhanced by addition of PDDA, owing to the interaction between PDDA and DBS. The enhancement intensity of fluorescence was proportional to the concentration of DBS over the range 2.5x10(-7) to 9.6x10(-5)molL(-1). Its detection limit is 3.5x10(-7)molL(-1). The method has high sensitivity and selectivity and was applied to the determination of trace amounts of DBS in water samples with satisfactory result.     

Stability indicating method for the determination of paracetamol in its pharmaceutical preparations by TLC densitometric method

Simple, sensitive and accurate thin layer procedure was described for a quantitative determination of paracetamol in its bulk powder and in its pharmaceutical dosage forms in the presence of its degradation product. The method consists of dissolving the drug in methanol and then spotting the solution on a thin layer of silica gel G254. Paracetamol was separated on silica gel using the mixture of the mobile phase, ethyl acetate: benzene: acetic acid in a ratio (1:1:0.05 v/v/v).Absorbance measurements (detection of reflectance) of the separated drug were carried out at 250 nm. Calibration curves were established in the concentration range of 5–20 mcg/spot for paracetamol. Quantitation is achieved by comparing the area under the peaks obtained from scanning the thin layer chromatographic plates in a spectrodensitometer. The method has been successfully applied to pharmaceutical preparations (capsules) and the results obtained were statistically compared with those obtained by applying the reference method.     

Flow injection chemiluminescence determination of paracetamol

A simple chemiluminometric method using flow injection has been developed for the determination of paracetamol (acetaminophen), based on the chemiluminescence produced by the reduction of tris(2,2′-bipyridyl)ruthenium(III). The latter is obtained by oxidation of tris(2,2′-bipyridyl)ruthenium(II) by potassium permanganate in dilute sulphuric acid in the presence of paracetamol. A standard or sample solution was injected into the ruthenium(II) stream (flow rate 1.5 ml min⁻¹) which was then merged with potassium permanganate in dilute sulphuric acid stream (flow rate 0.5 ml min⁻¹). The chemiluminescence intensity is enhanced by the presence of manganese(II) ions. Under the optimum conditions, a linear calibration graph was obtained over the range of 0.3-50.0 μg ml⁻¹ and the detection limit was 0.2 μg ml⁻¹ (s/n = 3). The relative standard deviation of the proposed method calculated from 20 replicate injections of 5.0 μg ml⁻¹ paracetamol was 1.1%. The sample throughput was 90 h⁻¹. The method was successfully applied to the determination of paracetamol in commercial pharmaceutical formulations.     

Simultaneous determination of paracetamol and chlorpheniramine in human plasma by liquid chromatography-tandem mass spectrometry

An analytical method for the determination of paracetamol and chlorpheniramine in human plasma has been developed, validated and applied to the analysis of samples from a phase I clinical trial. The analytical method consists in the extraction of paracetamol and chlorpheniramine with diethyl ether, followed by the determination of both drugs by an LC–MS–MS method, using 2-acetamidophenol as internal standard. The intra-assay and inter-assay precision and accuracy of this technique were good and the limit of quantitation was 0.5 μg/ml of plasma for paracetamol and 0.2 ng/ml for chlorpheniramine. The concentration working range was established between 0.5 μg/ml and 25 μg/ml for paracetamol and between 0.2 ng/ml and 50 ng/ml for chlorpheniramine. This method has been used for analyzing more than 1200 human plasma samples from a clinical study with 24 volunteers.     

Cucurbit[6]uril nanocavity as an enhanced spectrofluorimetric method for the determination of pyrene

The effect of the addition of macrocyclic host cucurbit[6]uril (CB6) on the photophysical properties of polycyclic aromatic hydrocarbon pyrene (PYR) was analyzed. The fluorescence emission spectra of the aromatic compound were determined at 25.0 °C in different acidic media (HCl 18%, w/v, or HCOOH 55%, w/v) with and without CB6. A significant enhancement in the fluorescence signals in the presence of CB6 was observed. The average values of the association constant (K_A) for the 1:1 stoichiometry complex and the relative fluorescence quantum yield ratio between the complexed and free PYR (?^PYR–CB6/?^PYR) in acidic media were (4.0 ± 0.5) × 10² M⁻¹ and (5.7 ± 0.2), respectively.The analytical parameters improved in the presence of CB6. The relative decrease in the limit of detection was 92%. The matrix effect was evaluated in fortified samples of tap water and tea extracts. Apparent recoveries obtained by the proposed method in tap water and tea extracts were (82–103)% and (89–99)%, respectively. Selectivity studies with inorganic and organic species were performed. The method is rapid, direct, selective and simple.     

Simultaneous determination of ibuprofen and paracetamol using derivatives of the ratio spectra method

Simple, rapid and accurate new method is described for the simultaneous determination of ibuprofen (IB) and paracetamol (PA) in two components mixture and Cetofen tablets. The method depends on the derivative of the ratio spectra DD by measurement of the amplitude of ¹DD at 225.6 nm and the amplitude of ²DD at 238.9 nm for IB and PA. Calibration graphs are linear in the range 2–32 (LOD 0.53) and 2–24 (LOD 0.57) μg/ml IB and PA, respectively. The proposed method is successfully applied for simultaneous determining IB and PA in authentic mixtures and Cetofen tablets.     

RP-HPLC-DAD method for the determination of phenylepherine,paracetamol, caffeine and chlorpheniramine in bulk and marketed formulation

A simple, specific and accurate isocratic RP-HPLC-DAD method was developed for the simultaneous determination of phenylephrine, paracetamol, caffeine and chlorpheniramine in bulk and tablet dosage form. The four contents are present in variable concentrations and have variable chromatographic behavior making the process of analysis very difficult. For present studies a reversed-phase C-18 column (150 mm × 4.5 mm i.d., particle size 5 μm) with mobile phase consisting of acetonitrile, methanol and 10 Mm phosphate buffer 16:22:62 (v/v) (pH of buffer 2.5 ± 0.02, adjusted with ortho phosphoric acid) was used. The flow rate was 1.0 ml/min and eluents were monitored at 280 nm. The mean retention times of phenylephrine, paracetamol, caffeine and chlorpheniramine were found to be 1.8, 3.1, 5.2 and 10.9 min, respectively. The method was validated in terms of linearity, range, specificity, accuracy, precision and robustness. The proposed method was successfully applied to the estimation of phenylephrine, paracetamol, caffeine and chlorpheniramine in combined tablet dosage form.     

A novel spectrofluorimetric method for the determination of DNA

A new simple, selective and sensitive fluorescence quenching method was developed to determine nucleic acids (DNA) with the 9-anthracenecarboxylic acid (ACA)-cetyl trimethyl-ammonium bromide (CTAB) system. The fluorescence intensity of ACA was decreased by the addition (CTAB). However, the fluorescence intensity of the system increased dramatically when DNA was added to the solution. The fluorescence enhancement is probably based on the DNA interaction with CTAB. Under the optimum conditions, the changes of fluorescence intensity in the absence and presence of nucleic acids was proportional to the concentration of nucleic acids over the range 0.08-1.0 microg mL(-1) for CT (calf thymus) DNA or FS (fish sperm) DNA. Its detection limits are 0.02 microg mL(-1) for CT DNA and 0.019 microg mL(-1) for FS DNA. Based on this approach, a new quantitative method for DNA assay is presented in this paper.     

Sensitive and Selective Fluorescent Chemosensors Combining Multiple PET Processes for Ag+ Sensing

In this work, a novel fluorescent chemosensor combining multiple photoinduced electron transfer(PET) processes for the detection of Ag⁺ ion was synthesized. The PET processes were derived from the lone electron pair of the selenium donors and the tertiary nitrogen atom of the coumarin fluorophore, which have not yet been used in the fluorescent chemosensor designed for Ag⁺ ion. Interestingly, the chemosensors showed fluorescent responses to Ag⁺ ion with a fluorescence enhancement factor of 3-5-fold by blocking the intramolecular PET quenching pathways. Furthermore, the probe exhibited high selectivity and sensitivity for Ag⁺ ion over other relevant species with detection limit down to 10 nmol/L level. The chemosensors also showed excellent performances in analyzing natural water samples. The chemosensors developed herein represent a new strategy for the PET fluorescent chemosensor design for the detection of Ag⁺ ion.     

Determination of paracetamol (acetaminophen) by HPLC with post-column enzymatic derivatization and fluorescence detection

Summary A novel method is described for the determination of paracetamol (acetaminophen;N-acetyl-4-aminophenol) in urine. After reversed-phase HPLC separation, paracetamol is oxidized by H₂O₂ with horseradish peroxidase catalysis. Detection is performed fluorimetrically at an excitation wavelength of 329 nm and an emission wavelength of 435 nm. Urine samples were spiked with paracetamol, diluted, and injected directly without further pretreatment. Under these conditions, the limit of detection was 2×10⁻⁸ molL⁻¹, and the limit of quantification was 7×10⁻⁸ molL⁻¹. The method was validated by two different approaches based on HPLC with UV-Vis detection.     

Spectrophotometric and spectrodensitometric determination of paracetamol and drotaverine HCl in combination

Thin-layer chromatography, first derivative, ratio spectra derivative spectrophotometry and Vierordt's method have been developed for the simultaneous determination of paracetamol and drotaverine HCl. TLC densitometric method depends on the difference in Rf values using ethyl acetate:methanol:ammonia (100:1:5 v/v/v) as a mobile phase. The spots of the two drugs were scanned at 249 and 308 nm over concentration ranges of 60-1200 microg/ml and 20-400 microg/ml with mean percentage recovery 100.11%+/-1.91 and 100.15%+/-1.87, respectively. The first derivative spectrophotometric method deals with the measurements at zero-crossing points 259 and 325 nm with mean percentage recovery 99.25%+/-1.08 and 99.45%+/-1.14, respectively. The ratio spectra first derivative technique was used at 246 and 305 nm with mean percentage recovery 99.75%+/-1.93 and 99.08%+/-1.22, respectively. Beer's law for first derivative and ratio spectra derivative methods was obeyed in the concentration range 0.8-12.8 and 0.4-6.4 microg/ml of paracetamol and drotaverine HCl, respectively. Vierordt's method was applied to over come the overlapping of paracetamol and drotaverine HCl in zero-order spectra in concentration range 2-26 and 2-40 microg/ml respectively. The suggested methods were successfully applied for the analysis of the two drugs in laboratory prepared mixtures and their pharmaceutical formulation. The validity of the methods was assessed by applying the standard addition technique. The obtained results were statistically agreed with those obtained by the reported method.     

纳米银增敏鲁米诺液相化学发光分析法测定4-乙酰氨基酚的研究

研究发现在碱性条件下,纳米银对鲁米诺-铁氰化钾液相化学发光体系发光信号具有明显的增敏作用,而4-乙酰氨基酚对该体系具有强烈的抑制作用。结合流动注射技术,建立了流动注射化学发光分析法测定对乙酰氨基酚的新方法。该方法测定对乙酰氨基酚的线性范围为9.0×10-12～1.0×10-10g/mL(0.9947)和1.0×10-1...     

A spectrofluorimetric method for the determination of acitretin in pharmaceuticals

A simple, rapid, and highly sensitive spectrofluorimetric method for the determination of acitretin was developed based on the strong green fluorescence of acitretin. Influence of organic solvents on the fluorescence spectra of acitretin was studied. Effects of pH, standing time, and foreign ions on the determination of acitretin were also examined. Under the optimum conditions, linear relationship between the relative fluorescence intensity and the concentration of acitretin in the range of 30.0–1100 ng mL⁻¹ was obtained. Detection limit of this method is 9.56 ng mL⁻¹ for acitretin. Relative standard deviation for the determination of 480 ng mL⁻¹ of acitretin was 1.70 %. This method was used for the determination of acitretin in pharmaceuticals and the results were compared with those obtained by the HPLC method.     

Development and validation of a stability-indicating RP-HPLC method for the determination of paracetamol with dantrolene or/and cetirizine and pseudoephedrine in two pharmaceutical dosage forms

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed which can separate and accurately quantitate paracetamol, dantrolene, cetirizine and pseudoephedrine. The method was successfully validated for the purpose of conducting stability studies of the four analytes in quality control (QC) laboratories. The stability-indicating capability of the method was demonstrated by adequate separation of these four analytes from all the degradant peaks. A gradient mobile phase system consisting of (A) 50 mmol L⁻¹ sodium dihydrogen phosphate, 5 mmol L⁻¹ heptane sulfonic acid sodium salt, pH 4.2 and (B) acetonitrile was used with Discovery reversed-phase HS C₁₈ analytical column (250 mm × 4.6 mm i.d., 5 μm particle size). Quantitation was achieved with UV detection at 214 nm, based on peak area.The proposed method was validated and successfully applied for the analysis of pharmaceutical formulations and laboratory-prepared mixtures containing the two multicomponent combinations.     

Homogeneous liquid-liquid extraction method for spectrofluorimetric determination of chlorophyll a

A new homogeneous liquid-liquid extraction using a fluorocarbon ionic surfactant, Zonyl FSA (FSA), having a diethylthioether group as a spacer between the perfluoroalkyl group and carboxyl group has been developed. In this FSA method, the phase separation phenomena were observed at mild pH (below pH 6). Moreover, by using this extraction method as a preconcentration, a highly sensitive spectrofluorometric determination of chlorophyll a was established. The results for the standard chlorophyll a were as follows. The concentration factor (V(w)/V(o)) was 200 (water phase, V(w), 20 cm(3), water-immiscible phase, V(o), 100 mul), the distribution ratio, log D, was 4.85, the extraction percentage, E, was 99.7%, and the procedure time was approximately 30 min. The calibration curve was linear in the concentration range 2 x 10(-11)-3 x 10(-7) mol dm(-3) and the detection limit (S/N=3) was 1 x 10(-11) mol dm(-3). The relative standard deviation was 0.72% for 10(-8) mol dm(-3) (five determinations).     

Ratiometric fluorescence chemodosimeter for mercuric ions through the Hg(II)-mediated propargyl amide to oxazole transformation

A coumarin-based alkyne was developed as a fluorescent chemodosimeter for the selective detection of mercuric ion. The probe showed a highly selective and ratiometric response toward Hg(II) ion over other metal ions with a micromolar level of limit of detection.     

Electrochemical behavior and differential pulse voltammetric determination of paracetamol at a carbon ionic liquid electrode

The electrochemical behavior of paracetamol in 0.1 M acetate buffer solution (pH 4.6) was investigated at a traditional carbon paste electrode (TCPE) and a carbon ionic liquid electrode (CILE) fabricated by replacing nonconductive organic binders with a conductive hydrophobic room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF₆). The results showed that the CILE exhibited better reversibility for the electrochemical redox of paracetamol. The oxidation potential of paracetamol at the CILE is +0.462 V, which is approximately 232 mV lower than that at the TCPE; the oxidation peak current response is nine times higher than that at the TCPE. The differential pulse voltammetric determination of paracetamol at the CILE was established based on this behavior. After optimizing several important parameters controlling the performance of paracetamol at the CILE, the oxidation peak current versus paracetamol concentration at the CILE showed linearity in the range from 1.0 μM to 2.0 mM (R ²  = 0.9992) with a detection limit of 0.3 μM (S/N = 3). The method has been applied to the determination of paracetamol in tablets and urine samples and the average recovery of paracetamol was 98.5% and 99.3%, respectively. The proposed CILE showed good sensitivity and reproducible response without influence of interferents commonly existing in pharmaceutical and urine samples. Figure CV curves of paracetamol illustrate the enhanced electrochemical behavior of paracetamol at the CILE (b), which forms the basis for the differential pulse voltammetric determination of paracetamol     

A graphene-based electrochemical sensor for sensitive detection of paracetamol

An electrochemical sensor based on the electrocatalytic activity of functionalized graphene for sensitive detection of paracetamol is presented. The electrochemical behaviors of paracetamol on graphene-modified glassy carbon electrodes (GCEs) were investigated by cyclic voltammetry and square-wave voltammetry. The results showed that the graphene-modified electrode exhibited excellent electrocatalytic activity to paracetamol. A quasi-reversible redox process of paracetamol at the modified electrode was obtained, and the over-potential of paracetamol decreased significantly compared with that at the bare GCE. Such electrocatalytic behavior of graphene is attributed to its unique physical and chemical properties, e.g., subtle electronic characteristics, attractive π-π interaction, and strong adsorptive capability. This electrochemical sensor shows an excellent performance for detecting paracetamol with a detection limit of 3.2 × 10⁻⁸ M, a reproducibility of 5.2% relative standard deviation, and a satisfied recovery from 96.4% to 103.3%. The sensor shows great promise for simple, sensitive, and quantitative detection and screening of paracetamol.     

Highly selective and sensitive fluorescence turn-on probe for a catalytic amount of Cu(I) ions in water through the click reaction

A simple azide-functionalized coumarin (1) was utilized as a fluorescence turn-on probe for a catalytic amount of Cu(I) ions in HEPES buffer. The probe has shown a selective and sensitive response to the cuprous ions over other various cations through a Cu(I)-mediated click reaction of 1 to an alkyne. When a catalytic amount of copper sulfates was added in the presence of ascorbate, the prominent fluorescence ‘Off-On’ change of 1 was observed so that submicromolar concentration of copper ions was detectable by the naked eye.     

Simultaneous voltammetric determination of paracetamol and caffeine in pharmaceutical formulations using a boron-doped diamond electrode

A simple and highly selective electrochemical method was developed for the single or simultaneous determination of paracetamol (N-acetyl-p-aminophenol, acetaminophen) and caffeine (3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione) in aqueous media (acetate buffer, pH 4.5) on a boron-doped diamond (BDD) electrode using square wave voltammetry (SWV) or differential pulse voltammetry (DPV). Using DPV with the cathodically pre-treated BDD electrode, a separation of about 550 mV between the peak oxidation potentials of paracetamol and caffeine present in binary mixtures was obtained. The calibration curves for the simultaneous determination of paracetamol and caffeine showed an excellent linear response, ranging from 5.0 × 10⁻⁷ mol L⁻¹ to 8.3 × 10⁻⁵ mol L⁻¹ for both compounds. The detection limits for the simultaneous determination of paracetamol and caffeine were 4.9 × 10⁻⁷ mol L⁻¹ and 3.5 × 10⁻⁸ mol L⁻¹, respectively. The proposed method was successfully applied in the simultaneous determination of paracetamol and caffeine in several pharmaceutical formulations (tablets), with results similar to those obtained using a high-performance liquid chromatography method (at 95% confidence level).