Ion-Pairing High-Performance Liquid Chromatographic Determintation of Pyridoxine and Pyrithioxine in Dosage Forms

Abstract

An ion-pairing High-performance liquid chromatographic method is described for the simultaneous determination of pyridoxine HCI and pyrithioxine 2HCI in dosage forms. A reversed-phase chromatography using tetrabutylammonium hydroxide as the counter-ion was employed. the analysis was carried out utilizing an Aminopropylsilicon-(APS-Hypersil) 5 μm column. Calibration curves were rectilinear over the concentration range 5–40 μg/ml for pyridoxine HCI and 10–100 μg/ml for pyrithioxine 2HCi with minimum detectability (S/N=2) of 0.02 and 0.08 μg/ml respectively. the proposed method was applied to tablets containing the two species, and the results obtained were accurate and precise.     

Spectrophotometric Determination of Gadolinium(III) With O-Hydroxyhydroqoinonephthalein in Mixed Micelles of N-Hexadecylpyridinilm Chloride and Brij 35

Abstract

A sensitive, simple and selective spectrophotometric method for the determination of gadolinium(III) is proposed using o-hydroxyhydroquinonephthalein(Qnph), by analogy with phenylfl-uorone(Phfl), in the presence of N-hexadecylpyridinium chlo-ride(HPC)-Brij 35 mixed surfactants. The calibration curve is rectilinear in the range of 0 – 16.0 μg per 10 ml at 590 nm with an apparent absorption coefficient(?) of 1.2 × 10⁵ 1 cm^?1 mol^?1 and Sandell sensitivity of 0.0013 μg/cm² gado-linium(III).     

Bioanalysis of Naproxen by High Performance Reversed Phase Liquid Chromatography with Photometric and Fluorimetric Detection

Abstract

Methods for the quantitative determination of NAPROXEN and its main metabolite in plasma and urine are described. The separation is based on reversed phase liquid chromatography with LiChrosorb RP 8 (5 μm) as the support and methanol/phosphate buffer pH 7 as mobile phase, in some cases with addition of tetrabutyl ammonium ion as ion-pairing agent to improve the chromatographic selectivity. With UV-detector and a simple filter fluorometer an extraction-evaporation procedure is used for both plasma and urine determinations, while the high selectivity and sensitivity of a sophisticated fluorescence detector permits the direct injection of diluted samples on to the column. Use of an internal standard improves the within-run precision (s_rel%), which for plasma determinations of NAPROXEN are - with UV-detection, 0.2 – 1.7% (range 10 – 40 μg/ml), with filter fluorometer, 2.4 – 5.9% (range 12 – 58 μg/ml), and with fluorescence detector, 0.8 – 4.1% (range 5 – 20 μg/ml).     

Second Derivative Ultraviolet Spectrophotometry and High Performance Liquid Chromatography with Fluorometric Detection of Cycloserine Using 9-Chloro-10-methyl Acridinium Triflate as a New UV and Fluorescent Labeling Agent

Abstract

Sensitive and simple second derivative UV spectrophotometric and HPLC with fluorometric detection methods were developed for cycloserine based on derivatization with 9-chloro-10-methyl acridinium triflate (CMAT) to yield a reaction product which absorbs in the UV at 361 nm and is fluorescent using excitation and emission wavelengths of 257 nm and 475 nm, respectively. The CMAT derivatization reaction takes 30 minutes at 70°C. Cycloserine was linear in the 0.3 – 5.0 μg/ml range (r=0.999, n=5) for the second derivative UV method and the 0.8 – 5 μg/ml range for the HPLC method (r=0.999, n=5). The limit of detection for cycloserine in the HPLC method can be improved to 0.15 μg/ml with the addition of glacial acetic acid to the analytical sample. The HPLC assay was applied to the determination of cycloserine in spiked human urine samples. The correlation coefficient (r) was in the 0.999 range and sensitivity was at the low pg/ml level.     

Colorimetric Determination of Propofol in Bulk form,Dosage Form and Biological Fluids

ABSTRACT

Propofol is coupled with 2, 6-dichloroquinone-4-chlorimide (DCQ) in a reaction buffered at pH 9.6 to give a colored product having an analytically useful maximum at 635 nm. The factors affecting the color generation were optimized and incorporated in the procedure. The reacted propofol has a molar absorptivity of 3.9 × 10^?4 L mol^?1 cm^?1, and Beer's law is obeyed for concentrations 1-5 μg ml^?1 with detection limit 0.25 μg ml^?1. The method was found applicable to biological fluids (plasma and urine) spiked with propofol at concentration levels 1-5 μg ml^?1 for plasma and 1-5 μg 0.5 ml^?1 urine (less sensitivity is obtained with urine volumes above 0.5 ml) with detection limits 0.28 μg ml^?1 for plasma and 0.4 μg 0.5 ml^?1 urine. The average recovery for the commercial preparation (1% w/v propofol emulsion intravenous injection for infusion) was 99.54% with an RSD of 1.05%. The method was validated by an adopted HPLC method. The results obtained by the HPLC method for the commercial preparation were statistically compared with the proposed method and evaluated at the 95% confidence limits.     

Absorption Spectra of 4f Electron Transitions of Neodymium and Erbium with 8-Hydroxyquinoline-5-sulphonic Acid and Diethylamine Systems and Its Analytical Application

Abstract

In this paper the absorption spectra of 4f electron transitions of the systems of neodymium and erbium with 8-hydroxyquino-line-5-sulphonic acid and diethylamine have been studied by normal and third-derivative spectrophotometry. Their molar absorptivities are 80 l.mol^?1.cm^?1 for neodymium and 65 l.mol^?1.cm^?1 for erbium. Use of the third-derivative spectra, eliminates the interference by other rare earths and increases the sensitivity for Nd and Er. The derivative molar absorptivities are 390 1.mol^?1.cm^?1 for Nd and 367 1.mol^?1.cm^?1 for Er. The calibration graphs were linear up to 11.8 μg/ml of Nd and 12.3 μg/ml of Er, respectively. The relative standard deviations evaluated from eleven independent determinations of 7.2 μg/ml (for Nd) and 8.3 μg/ml (for Er) are 1.3% and 1.4%, respectively. The detection limits (signal to noise ratio = 2) are 0.2 μg/ml for Nd and 0.3 μg/ml for Er. The method has been developed for determining those two elements in mixture of lanthanides by means of the third-derivative spectra and the analytical results obtained are satisfactory.     

Color Reaction Between 4-(2-Pyridylazo)Resorcinol and Mercury (II) in the Presence of Surfactant,and Improved Spectrophotometric Determinations of Mercury(II) and Cyanide Ion with its Coloring

Abstract

The reactions among 4-(2-pyridylazo)resorcinol (PAR), mercury(II) and/or cyanide ion in the presence of water soluble surfactants alone or combination were systematically investigated at about pH 9. The spectrophotometric determinations of mercury(II) and cyanide ion were investigated by using the PAR-mercury(II)-HPC complex (3:2:2 molar ratio) in the presence of N-hexadecylpyridinium chloride (HPC) alone; calibration graphs were rectilinear in the ranges of 0 – 40 μg mercury(II) and 0 –10 μg cyanide ion in a final 10 ml with the apparent molar absorptivities of 5.9 × 10⁴ for mercury(II) and 2.5 × 10⁴ 1 mol^?1 cm^?1 for cyanide ion at 590 nm. The proposed method had advantages—rapidity, simplicity without solvent extraction, and sensitivity in comparison with reported solvent extraction methods. The interference of foreign ions decreased 1/2–l//4-fold compared with that in the presence of non-ionic surfactant alone.     

Voltammetric Method for the Simultaneous Determination of Melatonin and Pyridoxine in Dietary Supplements Using a Cathodically Pretreated Boron‐doped Diamond Electrode

The simultaneous voltammetric determination of melatonin (MT) and pyridoxine (PY) has been carried out at a cathodically pretreated boron‐doped diamond electrode. By using cyclic voltammetry, a separation of the oxidation peak potentials of both compounds present in mixture was about 0.47 V in Britton‐Robinson buffer, pH 2. The results obtained by square‐wave voltammetry allowed a method to be developed for determination of MT and PY simultaneously in the ranges 1–100 μg mL⁻¹ (4.3×10⁻⁶–4.3×10⁻⁴ mol L⁻¹) and 10–175 μg mL⁻¹ (4.9×10⁻⁵–8.5×10⁻⁴ mol L⁻¹), with detection limits of 0.14 μg mL⁻¹ (6.0×10⁻⁷ mol L⁻¹) and 1.35 μg mL⁻¹ (6.6×10⁻⁶ mol L⁻¹), respectively. The proposed method was successfully to the dietary supplements samples containing these compounds for health‐caring purposes.     

Spectrophotometric Determination of Tetracyclines in Pure Form and in Pharmaceutical Preparations,by a Molybdenum Blue Method

Abstract

A new and sensitive spectrophotometric method has been developed for the determination of tetracyclines either in a pure form or in Pharmaceuticals, by a molybdenum blue method. The procedure is based on the observation that, in sulphuric acid medium, tetracyclines reduce ammonium molybdate to molybdenum blue, the absorbance of which is proportional to the amount of antibiotic present. The variables affecting development of the color have been investigated and the conditions optimized. Beer's law is obeyed for up to 20 μg/ml of tetracycline HCl and oxytetracycline HCl, 28 μg/ml of demeclocycline HCl, 18 μg/ml of chlortetracycline HCl, 32 μg/ml of doxycycline HCl and 40 μ/ml of rolitetracycline. Molar absorptivities (1 mol^?1 cm^?1) and Sandell's sensitivities (μ cm^?2 per 0.001 absorbance unit) are, respectively: tetracycline HCl 4.9×10⁴ and 0.0098, oxytetracycline HCl 5.4×10⁴ and 0.0092, demeclocycline HCl 1.6×10⁴ and 0.0313, chlortetracycline HCl 5.5×10⁴ and 0.0094, doxycycline HCl 3.4×10⁴ and 0.0141, rolitetracycline 2.7×10⁴ and 0.0195.     

Spectrophotometric Determination of Phenols and Cyanides After Distillation from Natural Waters

Abstract

Total phenols were determined by molecular spectrophotometry, after distillation, complexation with 4-aminoantipyrine and extraction into chloroform. Cyanides were also determined spectrophotometrically after distillation from the acidified samples, and complexation in moderate acidic solution with barbituric acid. The dynamic ranges were 0 – 100 μg L^?1 for total phenols and 0 – 30 μg L^?1 for cyanides. The above methods were applied in the analysis of river, lake and stream waters collected from Northern Greece. The seasonal and spatial variation of concentrations was evaluated by two-way ANOVA. Background levels (4 – 12 μg L^?1 for total phenols and 0.3 – 3 μg L^?1 for cyanides), were found in almost all surface waters, with some exceptions.     

Determination of Molybdenum and Tungsten with Iodide Activity Electrode

Abstract

A new method for the determination of molybdenum and tungsten is described based on their catalysis of the hydrogen peroxide-iodide reaction as monitored with an iodide ion-selective electrode. This method yields better results than methods previously used. For example, Yatsimirskii and Afanaseva¹ and Erdey and Svehla² have found a lower limit of 0.02 and 0.1 μ.g/ml for molybdenum. In the present work as little as 0.004 μg/ml of molybdenum and tungsten is determinable.     

Zero-Order and Third-Derivative Spectrophotometric Determination of Iron(III) with 4-(2-Pyridylazo)-Resorcinol in the Presence of N-Hexadecylpyridinium Chloride

Abstract

The complex formation reaction between iron(III) and 4-(2-pyridylazo) resorcinol(PAR) in the presence of various water soluble surfactants((N-hexadecylpyridinium chloride (HPC), poly(vinylalcohol)(PVA), sodium dodecylsulfate(SDS), sodium N-lauroylsarcosine(SL)) alone or in combination at weakly acidic media was systematically investigated. An improved and more sensitive spectrophotometric method for the determination of iron was proposed by zero-order and third-derivative spectrophotometry using the PAR-iron(III)-HPC ternary complex system at about pH 5.2. The calibration curve was rectilinear in the ranges of 0 – 15.0 μg iron(III) in a final 10-ml on the zero-order spectrophotometry. Also, upon the third-derivative spectrophotometry, Beer's law was obeyed in the range of 0 – 8.0 μg iron(III)/10 ml by measuring the distance between the absorbance peak(λ₁ = 527 nm) and the valley (λ₂ = 560 nm). The apparent molar absorptivity was 4.8 × 10⁴ 1 mol^?1 cm^?1 in zero-order spectrophotometry, and 1.36 × 10⁵ mol^?1 cm^?1 in third-derivative spectrophotometry. The effect of foreign ions was decreased within ½ – ¼-fold in comparison with the method in the presence of PVA without HPC. Especially, the third-derivative spectrophotometric method was sensitive and selective, and made possible to assay mixed sample solution containing iron(III) and copper(II), etc.     

Cyclodextrin Enhanced Spectrofluorimetric Determination of Melatonin in Pharmaceuticals and Urine

ABSTRACT

Melatonin forms a 1:1 inclusion complex with methyl-β-cyclodextrin with an association constant of 139 ? 30 M^?1 at 20 °C. The effect of several cyclodextrins and derivatives on the fluorescence spectra of melatonin was studied with a great increase of fluorescence signal when methyl-β-cyclodextrin was employed. Optimal conditions of the method were: [methyl-β-cyclodextrin] = 0.01 M and temperature 20 °C; the pH does not affect the luminescence emission. The linear dynamic range (LDR) was 50-3000 ng ml^?1 and a limit of detection of 10 ng ml^?1 of melatonin was obtained with a relative standard deviation (RSD) of 0.77% (at 0.3 μg ml^?1 level). This simple method was satisfactorily applied to the determination of melatonin in pharmaceutical preparations and urine.     

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.

     

Determination of Molybdenum in Human Urine by Spectrophotometric Method using Thiazolylazo Compounds as Chromogenic Reagents

ABSTRACT

Four azo compounds based on diazotization of 2-aminobenzothiazole have been synthesized and characterized by elemental analysis as well as different spectroscopic techniques. The potentiality of the prepared compounds as new chromogenic reagents for the spectrophotometric determination of Mo⁶⁺ was studied by extensive investigation of optimum conditions favouring the formation of the coloured complexes. Beers law is obeyed in the concentration range 0.2-8.5 μg ml^?1 whereas Ringbom optimum concentration range was 0.8-7.5 μg ml^?1. The detection limit was 0.05 μg ml^?1. The molar absorptivity and Sandell sensitivity of the formed complexes are calculated. The effect of interfering ions on the determination of Mo⁶⁺ was investigated. The relative standard deviations for six replicate determinations of 5.0 μg ml^?1 of Mo⁶⁺ are 1.23, 1.47, 1.05 and 1.38 % using reagents I, II, III and IV, respectively. The proposed method has been applied to investigate the amount of Mo⁶⁺ in human urine samples. The molybdenum levels found between 0.5-2.1 μg/100 ml.     

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.     

Simultaneous Determination of Diazepam,Oxazepam and Temazepam in Spiked Urine By Hplc

ABSTRACT|Oxazepam and temazepam are two minor metabolites of diazepam. These three benzodiazepines may be found in presence of each other in biological fluids.

Therefore, in this study an HPLC method was developed to separate and analyze them. Benzodiazepines have ability to form inclusion complexes with p-cyclodextrin (β-CyD). According to the degree of binding constant with β-CyD, these compounds can be separated by β-CyD bound to silica (cyclobond column) as the stationary phase using HPLC.

The development and validation of the HPLC procedure for the separation and determination of these compounds in mixtures were studied. The mobile-phase system consisted of phosphate buffer (pH 7): methanol [75:25], with flow rate 0.8 ml min^?1 and UV detection at 240 nm was used.

The calibration graphs were rectilinear from 0.1-2.5 μg/ml and coefficients of variation were <2% for the three compounds in bulk forms.

The method was used to analyse these bezodiazepines in spiked urine containing all three compounds in combination. Recoveries were 97-99.8%

The limit of detection and limit of quantitation were 0.05 μg/ml and 0.1 μg/ml, respectively.

The described method is selective, rapid, simple, reproducible and accurate.     

A Stability-Indicating Spectrophotometric Method for the Determination of Fenoterol in Pharmaceutical Preparations.

ABSTRACT

A simple and highly sensitive spectrophotometric method was developed for the determination of fenoterol hydrobromide in pharmaceutical formulations. The method is based on measurement of the orange-yellow color peaking at 436 nm, produced when the drug is coupled with diazotized benzocaine in triethylamine medium. The method is applicable over the range of 0.5 – 10 μg/ml, with minimum detectability of 3.6 ng/ml (≈ 9.4×10^?9 M). The molar absorptivity is 4.61×10⁴ L. mol^?1. cm^?1. with relative standard error of 0.196%. The proposed method was successfully applied to the determination of fenoterol in its dosage forms; the mean recoveries of 99.61 ± 1.59 and 98.97 ± 1.52 for tablets and aerosols, respectively, were obtained. The results of the proposed method were favorably compared to those obtained by the official and reference methods. No i8543168 was encountered from the co-formulated drug ipratropium bromide, common excipients and alkaline induced degradation product. A proposal of the reaction pathway is presented.     

Spectrophotometric Determination of Trimethoprim in Pure Form and in Pharmaceutical Preparations using Bromothymol Blue,Bromocresol Green and Alizarin Red S

ABSTRACT

Simple, sensitive and selective methods for the determination of trimethoprim (TMP) in pure form and in pharmaceutical formulations are described. The methods are based on the reaction of TMP as a π-electron donor with bromothymol blue (BTB), bromocresol green (BCG) and alizarin red S (ARS) as electron acceptors. The coloured products are quantified spectrophotometrically at their corresponding λ_max.

Beer's law is obeyed in case of BTB in the range 2.9-23.2 μg/ml (CHCl₃), 2.9-20.0 μg/ml (CH₂Cl₂) and 5.0-29.0 μg/ml (ClC₆H₅), in the case of BCG 2.9-27.5 μg/ml (H₂O/alc.), 2.9-18.3 μg/ml (CHCl₃) and 2.9-20.3 μg/ml (CH₂Cl₂) and for ARS in the range 3.0-12.0 μg/ml in H₂O/alc medium.

The specific absorptivities, molar absorptivities, Sandell sensitivities, standard deviations and percent recoveries are evaluated. Application of the suggested methods to dosage forms is presented and compared with the pharmacopoeial method. The interference from additives and sulfa compounds, especially sulfamethoxazole, has been overcome by extraction into chloroform or methylene chloride.     

Kinetic Spectrophotometric Determination of Acetaldehyde

ABSTRACT

A method for determination of trace quantities of acetaldehyde based on its inhibition effect on the malachite green-sulfite reaction is described. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance at 613 nm by a fixed time method of 60 seconds. The method allows the determination of acetaldehyde in the range of 0.2-10 μg/ml. The limit of detection was 0.1 μg/ml and the relative standard deviation for ten determinations of 2 μg/ml acetaldehyde was 1.8%. The method is applied to the determination of acetaldehyde in chemical industrial waste water with satisfactory results.