A Fluorimetric Method for the Determination of Cyanide with Fluorescein and Iodine∗

Abstract

A rapid, simple and sensitive fluorimetric method has been developed for the determination of cyanide with fluorescein as fluorogenic reagent (λ_ex = 494 nm, λ_em = 514 nm) at pH 6.0–7.0. A linear calibration curve was obtained in the range 0.004–2.0 μg CN^?/25 ml. The detection limit is 0.004 μg CN^-/25 ml. The method was successfully applied to the determination of cyanide in waste water.

     

Extract-Photometric Determination of Vanadium with Isophthaldihydroxamic Acid

Abstract

The spectrophotometric study of violet complex isophthaldihydroxamic acid-vanadium extracted into solution of trioctylmethylammonium chloride in ethylacetate was made (λ_max = 380 nm, ? = 7500 l.mol^?1.cm^?1; λ_max = 510 nm, ? = 5510 l.mol^?1 .cm^?1; stoichiometries, 1:1 and 1:2, V:reagent). A new method for the extract-spectrophotometric determination of V(V) in the range 14–80 μg of vanadium is proposed.     

Flow Injection Chemiluminescence Determination Of Tetracyclines

Abstract

A fast and simple flow injection chemiluminescence method for the determination of trace amounts of tetracyclines is proposed based on the chemiluminescence of the KMnO₄ - TCs redox reaction in acidic medium in the presence of a sensitizer, OP. The response to the concentration of tetracyclines is linear in the range of 1.00 to 1000 μg mL^?1 with a relative standard deviation < 2.3 % for determination of 50.0 μg mL^?1 of each antibiotic (n = 11). The detection limits for tetracycline, oxytetracycline and chlortetracycline are 0.40, 0.52 and 0.60 μg mL^?1, respectively. The recommended method is suitable for automatic and continuous analysis and has been successfully tested for determination of tetracyclines in commercial formulations. The chemiluminescence intensity was found to be remarkably enhanced when in the presence of OP micellar system; possible reasons for this observed micellar induced enhanced chemiluminescence is given.     

A Fluorimetric Method for the Determination of Atmospheric Sulphur Dioxide With 2′, 7′—Dichlorofluorescein∗

Abstract

A rapid, simple and sensitive fluorimetric method has been developed for the determination of atmospheric sulphur dioxide with dichlorofluorescein as fluorogenic reagent (λ_ex = 505 nm, λ_em = 520 nm) at pH 4.0–6.0. A linear calibration curve was obtained in the range 0.01–0.40 μg SO₂/25 ml. The detection limit is 0.01 μg SO₂/25 ml. Nitrogen dioxide does not interfere with the method. The method was successfully applied to the determination of atmospheric sulphur dioxide.

     

Spectrofluorimetric Determination of Nitrite with Pyridoxal-5-Phosphate-2-Pyridylhydrazone

Abstract

The nitrite ion oxidizes pyridoxal-5-phosphate-2-pyridyl-hydrazone in acid medium giving a fluorescent product (λ_ex 325 nm, λ_em 420 nm). This redox reaction is used to developed a spectrofluorimetric method for the determination of nitrite. The calibration graph is liner in the 0.1 ? 1.0 μg mL^?1 range. The interference levels, stoichiometry and nature of the reaction have been studied. The method is applied to determine nitrite in water and soil samples     

Development and Validation of Derivative Spectrophotometric Method for Determination of Rabeprazole Sodium in Pharmaceutical Formulation

Abstract

The aim of this work is to develop and validate the derivative spectrophotometric method for determination of the proton pump inhibitor rabeprazole sodium in pharmaceutical formulations. The technique was applied using water (pH 10.0) as diluent. The first‐order derivative spectra were obtained at N=5, Δλ=4.0 nm, and determinations were made at 304 nm. The method showed high specificity in the presence of formulation excipients and good linearity in the concentration range of 6.0 to 18.0 µg/mL^?1. The intra‐ and interday precision data demonstrated the method has good reproducibility [Relative Standard Deviation ((RSD)=1.0 interdays)]. Accuracy was also evaluated and results were satisfactory (mean recovery of 99.15%). The detection and quantitation limits were 0.055 and 0.17 µg/mL^?1, respectively. The method was demonstrated to be adequate for routine analysis in quality control.     

Kinetic Analysis of Cobalt in Veterinary Products

A novel kinetic method for the determination of trace amounts of Co(II) has been developed. The proposed method based on the catalytic effect of Co(II) on the oxidation of xylenol orange tetra sodium salt by H₂O₂ in the presence of cationic surfactant (N‐dodecylpyridinium chloride). Co(II) at μg.mL^?1 was determined spectrophotometrically by measuring the decrease in the absorbance of xylenol orange at 577 nm by the differential method. The method is precise, selective, and sensitive. The detection limit of the procedure was 0.058 μg.mL^?1. The relative standard deviation for the replicate determination (n = 6) of 0.7 μg.mL^?1 was 1.285%. The results compared satisfactorily with those of atomic absorption spectrometry. The method was successful for the analysis of Co(II) in veterinary and synthetic samples.     

Flow injection spectrophotometric determination of ascorbic acid in soft drinks and beer

Two spectrophotometric methods, a photochemical and a non-photochemical, for the determination of ascorbic acid in soft drinks and beer using a flow-injection system are proposed. The non-photochemical method is based on the redox reaction that takes place between ascorbic acid and Fe(III), yielding dehydroascorbic acid and Fe(II). Fe(II) reacts with 1,10-phenantroline, originating the reddish orange Fe(phen)₃ ²⁺ complex (ferroin). This complex is spectrophotometrically monitored at 512 nm, and the signal is directly related to the concentration of ascorbic acid in the sample. The photochemical method has the same basis, nevertheless, uses the irradiation with visible light to enhance the redox reaction and so achieve higher sensitivities in the analysis. The non-photochemical method shows a linear range between 5 and 80 μg mL^?1, with a relative standard deviation of 1.6% (n = 11), a detection limit of 2.7 μg mL^?1 and a sample throughput of ¶60 samples h^?1. The photochemical method shows a linear range between 1 and 80 μg mL^?1, with a relative standard deviation of 1.0% (n = 11), a detection limit of 0.5 μg mL^?1 and a sample throughput of 40 samples h^?1.     

A Fluorescence Quenching Method for the Determination of Iodide Ion with Salicylfluorone and Hydrogen Peroxide

Abstract

A highly sensitive and selective fluorescence quenching method has been developed for rapid determination of iodide ion with salicylfluorone (SAF) as fluorogenic reagent (λ_ex = 495 nm, λ_em = 520 nm) at pH 2.5-3.0. The calibration graph is linear over the range 0.05-300 μg/25 ml. The detection limit is 0.05 μ/25 ml iodide. Other halide ions do not interfere with the determination even when present in large excess. The method is rapid and was successfully applied for the determination of iodide ion in sodium chloride, table salt and low sodium salt.     

Voltammetric sensing of triclosan in the presence of cetyltrimethylammonium bromide using a cathodically pretreated boron-doped diamond electrode

ABSTRACT

In the present study, a simple, cheap and sensitive electrochemical method based on a cathodically pretreated boron-doped diamond (CPT-BDD) electrode is described for the detection of triclosan with the cationic surfactant (cetyltrimethylammonium bromide, CTAB) media. The oxidation of triclosan was irreversible and exhibited an adsorption controlled process. The sensitivity of the adsorptive stripping voltammetric measurements was significantly improved with addition of CTAB. Using square-wave stripping mode, a linear response was obtained for triclosan determination in Britton-Robinson buffer solution at pH 9.0 containing 2.5 × 10^?4 M CTAB at around + 0.67 V (vs. Ag/AgCl) (after 30 s accumulation at open-circuit condition). The method could be used in the range of 0.01–1.0 μg mL^?1 (3.5 × 10^?8–3.5 × 10^?6 M), with a detection limit of 0.0023 μg mL^?1 (7.9 × 10^?9 M). The feasibility of the proposed method for the determination of triclosan in water samples was checked in spiked tap water.     

Determination of Procaine Penicillin G and Penicillin G by Second Derivative Spectrophotometry in Pharmaceutical Products

Abstract

“Zero-crossing” derivative spectrophotometry has been used for determining binary mixtures of penicillin G and procaine penicillin G.

The procedure is rapid, simple, nondestructive, and does not require resolutions of equations.

Calibration graphs are linear between 2.0 and 50.0 μg mL^?1 of the penicillin G at 226.0 nm, and between 2.0 and 100.0 μg mL^?1 of procaine penicillin G at 319.0 nm, in the presence of each other. A complete and exhausive statistical analysis of the experimental data was realized to demonstrate the validity of method. The method was successfully applied to assay commercial injections of these drugs.     

Ternary ion-association complexes between the indium(III) - 4-(2-pyridylazo)resorcinol anionic chelate and some tetrazolium cations

Complex formation and liquid-liquid extraction were studied in systems containing indium(III), 4-(2-pyridylazo)resorcinol (PAR), tetrazolium salt (TZS), water and chloroform. Two different TZS were used: 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT). The optimum conditions for extraction of In(III) as a ternary complex, (TT⁺)[In(PAR)₂] or (MTT⁺)[In(PAR)₂], were found: pH, extraction time, concentration of PAR and concentration of TZS. The constants of extraction (K_ex), constants of association (β), constants of distribution (K_D) and recovery factors (R%) were determined. The apparent molar absorptivities in chloroform were calculated to be ɛ′₅₂₀=6.6×10⁴ L mol⁻¹ cm⁻¹ and ɛ′₅₁₅=7.1×10⁴ L mol⁻¹ cm⁻¹ for the systems with TTC (I) and MTT (II), respectively. Beer’s law was obeyed for In(III) concentrations up to 3.4 μg mL⁻¹ in both the cases. The limits of detection (LOD=0.07 μg mL⁻¹ I and LOD=0.12 μg mL⁻¹ II), limits of quantification (LOQ=0.24 μg mL⁻¹ I and LOQ=0.41 μg mL⁻¹ II) and Sandell’s sensitivities (SS) were estimated as well.      

Determination of Palmatine in Rabbit Plasma by RP-HPLC with Solid-Phase Extraction

A rapid and specific reversed-phase high performance liquid chromatography (RP-HPLC) method for the determination of palmatine in rabbit plasma has been developed and validated. The chromatographic separation was performed on a C₁₈ column at 40 °C. The mobile phase, delivered at 1.0 mL min^?1, consisted of acetonitrile/phosphate buffer (pH 3.0) 40:60 (v/v). The detection wavelength was set at 345 nm. Palmatine and internal standard (IS) berberine were extracted from plasma by solid-phase extraction using C18 cartridges. Linearity was confirmed in the concentration range of 0.01 to 5 μg mL^?1, the inter-day and intra-day RSDs were within 10.0, the recoveries of palmatine ranged from 93.1 to 110.3, and the limit of detection (LOD, S/N > 3) was 0.002 μg mL^?1. The method is applicable to the determination of palmatine in rabbit plasma after intravenous administration of palmatine.     

Analysis of Metal Ions in Environmental Samples - III Synergistic Determination of Vanadium (V) As its Mixed Complex with N-0-Methoxyphenyl-2-Thenohydroxamic Acid and 3-(0-Carboxyphenyl)-1-Phenyltriazine-N-0Xide

Abstract

A highly sensitive, selective, and rapid method for the spectrophotometry determination of vanadium(V) at trace levels is described. The method is based on the selective extraction of vanadium(v) from strongly acidic (3–6 M hydrochloric acid) met ium with solution of N-0-methoxyphenyl-2- thenohydroxamic acid (0MTHA) in chloroform. The extract is then equilibrated with 3-(0-carboxyohenyl)-1-phenyltriazine-N-oxide(CPPTNO) at pH ? 1.5 and the resulting colour is measured at 445 nm. The colour system obeys Beer's law over the range 0–20 -μg/ml of vanadium; the molar absorptivityat the wavelength of maximum absorption (445 nm), and the Sandell sensitivity of the method are 1.1 × 10⁴1. mole^?1 cm^?1 and 0.005 μg/ml respectively.     

Determination of Vanadium by Solid-Phase Spectrophotometry in a Continuous Flow System

Abstract

A flow analysis method based on direct absorptiometric measurement in solid phase of the violet complex formed between V(V) and 5-Bromosalicylhydroxamic acid has been developed. The measurement is continuously performed at 555 nm, while the coloured species is being concentrated on-line on the beads of an anion exchanger packed into a flow-through cell. The sensing solid phase is regenerated after each measurement achieving a sampling frequency ranged between 10 to 15 h^?1 depending on the working conditions. The sensitivity of the method depended on the sample volume injected, being the detection limit 0.024 and 0.014 μg mL^?1 for 2 and 5 mL, respectively. The method shows a good selectivity and has been applied to determination of V(V) in many different sample matrices namely mussel, oyster and toadstool tissues, petroleum crudes and water samples.     

Fluorescent Complexes of Nucleic Acids/8-Hydroxyquinoline/Lanthanum(III) and the Fluorometry of Nucleic Acids

Abstract

The ternary fluorescent complexes of nucleic acids/8-hydroxyquinoline/ lanthanum (III) were studied. Nucleic acids in the study involve natured and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of pH 8.0–8.4 (controlled by NH₃-NH₄Cl buffer) ternary fluorescent complexes are formed which emit at 485.0 nm for calf thymus DNA and at 480.0 nm for yeast RNA (when excited at 267.0 nm) and emits at 483.0 nm for fish sperm DNA when excited at 265.0 nm. Based on the fluorescence reactions sensitive fluorometric methods for nucleic acids were proposed. Using optimal conditions, the calibration curves were linear in the range of 0.4–3.6 μg˙ml^?1 for calf thymus DNA, 0.4–4.0 μg-ml^?1 for fish sperm DNA and 0.4–4.0 μg˙ml^?1 for yeast RNA, respectively. The limits of determination (3σ) were 0.076 μg˙ml^?1 for calf thymus DNA, 0.068 μg˙ml^?1 for fish sperm DNA and 0.329 μg˙ml^?1 for yeast RNA, respectively. Five synthetic samples were determined with satisfaction.

     

Hydroxy Naphthol Blue as a Spectrophotometric and Fluorometric Reagent for the Uranyl Ion

Abstract

The utility of hydroxy naphthol blue (HNB) as a spectrophotometric and fluorometric reagent for the uranyl ion has been investigated. In phthalate buffer (at a pH of 4.0), UO₂ ²⁺ forms a brown complex of low absorptivity with the red form of HNB. By following the decrease in HNB absorbance at 530 nm (which has ε = 4.1 × 10³) uranyl ion can be determined to levels as low as 1.1 × 10^?6 M (0.30 μg/ml). HNB also emits at 460 nm when excited at 365 nm at these pH values, while the UO₂ ²⁺ complex exhibits greatly reduced emission. Examination of the quenching of HNB emission by UO₂ ²⁺ allows the determination of uranyl ion to levels as low as 3.2 × 10^?6 M (0.86 μg/ml). A 1:1 type complex was formed between UO₂ ²⁺ and HNB, and a formation constant of 9.77 × 10³ (log K₁ = 3.99) was measured for the complex.     

Kinetic Flow Injection Spectrophotometric Determination of Nitrite by its Catalytic Effect on the Oxidation of Chlorophosphonazo-pN by Bromate

Abstract

A flow injection kinetic method has been developed for the determination of nitrite, based on its catalytic effect on bromate oxidation of chlorophosphonazo-pN in H₂SO₄ medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance at 551 nm. The sampling frequency was 83 h^?1. The calibration curve was linear between 0.050 and 1.00 μg/ml, and the detection limit was 0.018 μg/ml. The proposed method was applied to the determination of nitrite in waters and soil with satisfactory results.     

Validated LC Determination of the Piroxicam-β-Cyclodextrin Inclusion Complex in Tablets and in Human Plasma

A simple, rapid, specific, sensitive HPLC method has been developed for the determination of piroxicam in the tablet dosage form and in human plasma. The method totally eliminates solvent extraction and time-consuming separation procedures. Plasma proteins were precipitated by addition of 3:1 (v/v) acetonitrile-methanol, ZnSO₄, and MgSO₄ and the supernatant was injected directly on to a 250 mm × 4.6 mm, 5 μm particle Spherisorb analytical column. Acetonitrile-methanol-0.04 mol L^?1 KH₂PO_4, 40:10:50 (v/v); pH 3.8, was used as mobile phase. The drug was detected by UV detection at 330 nm. The response was linear over the range of 0.01–10 μg mL^?1 and 0.025–5 μg mL^?1 in mobile phase and human plasma samples, respectively. The proposed method was used without interference from the endogenous substances, for determination of piroxicam in plasma samples obtained from healthy volunteers. The results revealed that the method would be useful in monitoring plasma levels of the drug during pharmacokinetic studies. Assay of piroxicam in its dosage forms for quality-control purposes could also be performed successfully by use of this method.     

Spectrophotometric Determination of Selected Antibiotics Using Prussian Blue Reaction

A simple, sensitive and accurate spectrophotometric method has been described for the determination of ampicillin(I), amoxicillin trihydrate(II) and cefazolin sodium(III). The procedure is based on the formation of Prussian Blue (PB) complex. The reaction between the acidic hydrolysis products of antibiotics (T = 60 °C) with mixture of Fe³⁺ and hexacyanoferrate(III) ions was evaluated for the spectrophotometric determination of the mentioned drugs. The maximum absorbance of the colored complex occurs at λ = 700 nm and the molar absorptivity is 3.0 × 10⁴ 1 mol^?1cm^?1. The effect of various parameters such as concentration of K₃Fe(CN)₆ and Fe³⁺, nature and amount of acids used, temperature and time of heating were investigated. Under optimum conditions the linear range of calibration graph was 2.0–12.0, 5.0–13.5 and 3.0–12.0 μg mL^?1 for ampicillin, amoxicillin and cefazolin, respectively. The relative standard deviation for the determination of 10 μg mL^?1 of antibiotics was about 0.5–1.5%. The proposed method was successfully applied to the determination of selected antibiotics from pharmaceutical preparations. The validity of the method was tested by the official methods and by the recovery studies of standard addition to pharmaceuticals.