Determination of Tetracycline and Related Compounds by High-Performance Liquid Chromatography

Abstract

An isocratic high-performance liquid chromatography method for the determination of tetracycline and its related compounds is described. The method uses a reverse phase (C₁₈) column, a modified acetonitrile/water mobile phase, and banzoic acid as the internal standard. Elution of all compounds of interest is complete within seven minutes. Results are presented for thirteen commercial capsule formulations and are compared with results by microbiological assay and thin-layer chromatographic methods.     

Spectrophotometric Determination of Pyrithioxin in Dosage Forms

Abstract

Two Spectrophotometric methods were developed for the estimation of pyrithioxin dihydrochloride in its formulations. The first method involves the use of 2,6-dichloroquinone-4-chlorimide (DQC) whereby a bluish-green colour is produced with Λ_max at 650. In the second method, pyrithioxin is reduced using Zn[ddot]/HCL, allowed to react with p-phenylenediamine, followed by ferric ammonium sulphate whereby a bluish-violet colour is produced having a Λ_max at 600 nm. The stoichiometric balance of both reactions was assessed and proposals of the reacition pathways were presented. The suggested methods were applied successfully for the determination of pyrithioxin in tablets and syrups.     

Spectrophotometric Study of Acid-Base Equilibrium of a Thienotriazolodiazepine,Brotizolam, Determination in Pharmaceutical Formulations

Abstract

Brotizolam is a psychotropic drug, derived from the Thieno-triazolodiazepine family, which has sedative and hypnotic properties. In this work, a spectrophotometric study has been carried out to determine the acid-base equilibrium, the pk_a value being obtained, as well as to develop a method for the determination of this compound in pharmaceutical formulations.     

A Rapid Spectrophotometric Method to Resolve Ternary Mixtures of Propyphenazone, Caffeine, and Acetaminophen in Tablets

Summary.  A simple and rapid derivative spectrophotometric assay procedure is described for the analysis of caffeine (1), acetaminophen (2), and propyphenazone (3) in tablet formulations. The concentration range of application is 5.0–25.0 μg·cm⁻³ for 2 and 3 and 1.0–5.0 μg·cm⁻³ for 1. The method involves the extraction of the drugs from tablets with 0.1 N H₂SO₄, filtration, appropriate dilution, and measurement of the fourth derivative absorbance values at zero crossing wavelengths of 230.0, 263.2, and 256.6 nm for 1, 2, and 3. As a reference method, a reversed phase HPLC procedure was developed. Commercially available tablets were analyzed; statistical comparison of the results with those obtained from the reference method showed good agreement. The derivative spectrophotometric method has the advantage of being simple, rapid, inexpensive, and easy to perform. Received April 18, 2001. Accepted (revised) June 5, 2001     

A Rapid Spectrophotometric Method to Resolve Ternary Mixtures of Propyphenazone, Caffeine, and Acetaminophen in Tablets

 A simple and rapid derivative spectrophotometric assay procedure is described for the analysis of caffeine (1), acetaminophen (2), and propyphenazone (3) in tablet formulations. The concentration range of application is 5.0–25.0 μg·cm⁻³ for 2 and 3 and 1.0–5.0 μg·cm⁻³ for 1. The method involves the extraction of the drugs from tablets with 0.1 N H₂SO₄, filtration, appropriate dilution, and measurement of the fourth derivative absorbance values at zero crossing wavelengths of 230.0, 263.2, and 256.6 nm for 1, 2, and 3. As a reference method, a reversed phase HPLC procedure was developed. Commercially available tablets were analyzed; statistical comparison of the results with those obtained from the reference method showed good agreement. The derivative spectrophotometric method has the advantage of being simple, rapid, inexpensive, and easy to perform.     

High‐Performance Liquid Chromatography Determination of Latanoprost in Pharmaceutical Formulations using UV Detection

Abstract

A simple, fast, and accurate high‐performance liquid chromatography (HPLC) method was developed to determine latanoprost in pharmaceutical formulations. The drug was chromatographed on a C₁₈ column. Eluents were monitored at a wavelength of 210 nm using a mixture of acetonitrile and 0.05 M potassium phosphate buffer pH 3.0 (70:30, (v/v). A linear response (r>0.9998) was observed in the range of 10.0–90.0 µg mL^?1. The method showed good recoveries (average 100.4%) and the relative standard deviations intra‐ and inter‐day were ≤1.0%. The method can be used for quality control assay of latanoprost in raw materials as well as in pharmaceutical formulations.     

Spectrophotometric Determination of Certain Local Anaesthetics in Pharmaceutical Preparations

Abstract

A direct colorimetric method was described for the rapid, sensitive and accurate determination of dibucaine, lidocaine, bupivacaine, procaine and tetracaine in pharmaceutical preparations. The method involves the use of haematoxylin reagent in the presence of boric acid to give a reddish-violet chromogen (λ_max = 555 nm). Beer's law was obeyed in the range from 2–60 μg/ml. No interference was observed from the commonly present additives or agents in pharmaceutical formulations.     

Simultaneous Determination of Atenolol and Chlorthalidone in Pharmaceutical Preparations by Capillary-Zone Electrophoresis

Abstract

A capillary zone electrophoresis (CZE) method for the simultaneous determination of the β-blocker drugs atenolol and chlorthalidone in pharmaceutical formulations has been developed. The CZE separation was performed under the following conditions: capillary temperature, 25°C; applied voltage, 25 kV; 20 mM H₃PO₄–NaOH running buffer (pH 9.0); and detection wavelength, 198 nm. Phenobarbital was used as internal standard. The method was validated and showed not only good precision and accuracy but also good robustness. The method has been successfully applied to the simultaneous determination of both atenolol and chlorthalidone in pharmaceutical tablets.     

High Performance Liquid Chromatogrphy of Fat-Soluble Vitamins. III. Determination of Vitamin D3 in Pharmaceutical Preparations and in Blood

Abstract

A reversed phase high-performance liquid chromatographic method (HPLC) is described for separation and determination of colecalciferol (Vitamin D₃) in Vitamin preparations and in biological materials. Vitamin D₃ is extracted from the formulations and from the blood in a fully automated electronically controlled extraction apparatus. For HPLC a column of lichrosorb RP18 and methanol as eluent are used. The extraction, separation and determination of vitamin D₃ needs about 10–20 minutes. The described extraction and HPLC methods allow the detection of 1–2 ng per injection and are well reproduced with a maximum coefficient of variation of < 3,5%. Vitamin A-acetate is used as internal standard.     

Reversed-Phase High-Performance Liquid Chromatographic Determination of Nicotine in Pesticide Formulations

Abstract

A simple and rapid reversed-phase high-performance liquid chromatographic procedure is described for the determination of nicotine in liquid formulations. Samples are diluted with methanol, and naphthalene is added as the internal standard. Peak height ratios obtained from injections of standard and sample filtrates are used for quanti-tation. An eluting solvent of 0.05M (NH₄)₂ HPO4 (pH 7.5) -methanol (40/60, v/v) at a flow of 2 mL/min gives retention times of 3.13 and 6.88 min respectively for nicotine and naphthalene. Sample analysis can be completed in approximately one hour by the method described as compared to 1.5 days required by the Official AOAC gravimetric method (6.176–6.177).     

Simple UV and visible spectrophotometric methods for the determination of doxycycline hyclate in pharmaceuticals

Doxycycline hyclate (DOX), a broad spectrum antibiotic with activity against a wide range of gram-positive and gram-negative bacteria, is widely used as a pharmacological agent and as an effector molecule in inducible gene expression system. Three simple, selective, rapid, accurate, precise and cost-effective spectrophotometric methods for the determination of DOX in bulk drug and in tablets have been developed and validated. First method (method A) is based on the measurement of absorbance of DOX in 0.1 M HCl at 240 nm. The second method (method B) is based on the measurement of yellow chromogen at 375 nm which is formed in 0.1 M NaOH. The third method is based on the measurement of 2: 1 complex formed between DOX and iron(III) in H₂SO₄ medium, the complex peaking at 420 nm (method C). The optimum conditions for all the three methods are optimized. Beer’s law was obeyed over the ranges 2.5–50.0, 1.50–30.0 and 10–100 g/mL for method A, method B and method C, respectively. The apparent molar absorptivity values are calculated to be 1.03 × 10⁴, 1.73 × 10⁴, and 5.21 × 10³ L mol⁻¹ cm⁻¹ for method A, method B, and method C, respectively. The Sandell sensitivity, limit of detection (LOD) and limit quantification (LOQ) values are also reported. All the methods were validated in accordance with current ICH guidelines. The developed methods were employed with high degree of precision and accuracy for the estimation of total drug content in commercial tablet formulations of DOX.     

Simultaneous determination of levofloxacin hemihydrate and ambroxol hydrochloride in tablets by thin-layer chromatography combined with densitometry

This paper describes the application of thin-layer chromatography (TLC) combined with densitometry to simultaneous determination of levofloxacin hemihydrate (LEV) and ambroxol hydrochloride (AMB) in bulk and tablets. The separation was achieved on aluminum sheet of silica gel 60 F ₂₅₄ using chloroform: methanol: toluene: ammonia (10: 6: 3: 0.8 v/v/v/v) as mobile phase. Quantification was carried out densitometrically at 245 nm. This system was found to give compact spots for LEV (R _f value of 0.4) and AMB (R _f value of 0.7). The calibration curves for LEV and AMB was found to be linear between 9960–16600 ng/spot (r ² = 0.999) and 600–1000 ng/spot (r ² = 0.999), respectively. The mean percentage recoveries from tablets for LEV and AMB were 99.45% and 99.58%, respectively. The TLC-densitometry method has many advantages, such as simplicity, reasonable sensitivity, rapidity, and low cost, and it can be successfully used in routine analysis of both these drugs in tablet formulations.     

Spectrophotometric Determination of Chlorzoxazone in pure State and Formulations Through Oxidative Coupling of its Hydrolysis Product

ABSTRACT

Three simple and sensitive procedures (Methods A, B and C) for the assay of chlorzoxazone (CZZ) in pure form and in formulations are described. The methods are based on the oxidative coupling reaction of the hydrolysis product of chlorzoxazone (HCZZ) with 3-methyl-2-benzothiazolinone hydrazone (MBTH) in the presence of Fe (III) (Method A, λ_max 445 nm), N, N-dimethyl-p-phenylene diamine (DMPD) in the presence of periodate (IO₄) (method B, λ_max 605 nm) and 2, 6-dichloroquinone chlorimide (DCQC) (Method C, λ, _max 560 nm). The Beer's law limits were found to be 5.0 to 25.0 μg/ml in the case of methods A and B and 2.0 to 12.0 μg/ml in the case of method C. The results are statistically validated and the reactions involved are presented.     

Application of Difference and Derivative Ultraviolet Spectrometry for the Assay of Some Benzodiazepines

Abstract

Differential (δ A), second derivative (D₂) and differential second derivative (δ D₂) ultraviolet spectrophotometric methods have been described for the quantitiative estimation of clonazepam, diazepam and medazepam in pharmaceutical formulations such as drops, tablets and capsules. Interferences due to excipients and diluents are thereby avoided. Accuracy of the analyses with the proposed procedures is significantly greater than the conventional spectrophotometric and official methods.     

High Pressure Liquid Chromatographic Determination of Parabens in Pharmaceutical Preparations Containing Hydroxyquinolines

Abstract

A high pressure liquid chromatographic (HPLC) procedure for the analysis of methyl paraben (MP) and propyl paraben (PP) in pharmaceutical preparations containing a halogenated hydroxyquinoline (HHQ) is described. The method involves a separation of the phenolic constituents, MP, PP and HHQ with a Bio-Rad AG 1–X8 anion exchange resin, elution of the phenols with methanol after acidification and a reverse phase HPLC separation of the parabens using methanol-pH 6.5 buffer (60/40) mobile phase, a 30 cm × 3.9 mm (i.d.) column packed with Waters μBondapak C₁₈ packing and a guard column packed with Waters Bondapak C₁₈/Corasil packing. Recovery, precision, specificity and interference data along with the application of the proposed method for some commercial formulations both with and without a hydroxyquinoline are described.     

Copper complexes as chemical nucleases

Redox active mononuclear and binuclear copper(II) complexes have been prepared and structurally characterized. The complexes have planar N-donor heterocyclic bases like 1,10-phenanthroline (phen), dipyridoquinoxaline (dpq) and dipyridophenazine (dppz) ligands that are suitable for intercalation to B-DNA. Complexes studied for nuclease activity have the formulations [Cu(dpq)₂(H₂O)] (ClO₄)₂.H₂O (1), [CuL(H₂O)₂(μ-ox)](ClO₄)₂ (L = bpy,2; phen,3; dpq,4; and dppz,5) and [Cu(L)(salgly)] (L = bpy,6; phen,7; dpq,8; and dppz,9), where salgly is a tridentate Schiff base obtained from the condensation of glycine and salicylaldehyde. The dpq complexes are efficient DNA binding and cleavage active species. The dppz complexes show good binding ability but poor nuclease activity. The cleavage activity of thebis-dpq complex is significantly higher than thebis-phen complex of copper(II). The nuclease activity is found to be dependent on the intercalating nature of the complex and on the redox potential of the copper(II)/copper(I) couple. The ancillary ligand plays a significant role in binding and cleavage activity.     

Atomic and molecular energies as functionals of the electrostatic potential

Starting from the Hohenberg–Kohn theorem, atomic and molecular energies have been expressed rigorously as functionals of the electronic electrostatic potential, V_elec(r). Explicit formulations have been derived for the functionals representing the kinetic energy and electronic interaction contributions to the total energies.Acknowledgements. The assistance of Dr. Jane S. Murray is greatly appreciated.Contribution to the Jacopo Tomasi Honorary Issue     

RP‐HPLC Method for the Determination of Tenofovir in Pharmaceutical Formulations and Spiked Human Plasma

Abstract

A simple reverse‐phase high‐performance liquid chromatographic method for the determination of tenofovir disoproxil fumarate (TDF) in pharmaceutical formulations and human plasma samples has been developed and validated. Piroxicam (PRX) was used as an internal standard. The assay of the drug was performed on a CLC C₁₈ (5 μ, 25 cm×4.6 mm i.d.) with UV detection at 259 nm. The mobile phase consisted of acetonitrile–water mixture in the ratio of 75∶25, and a flow rate of 1 ml/min was maintained. The standard curve was linear over the range of 0.2–10 µg/ml (r ²=0.9966). Analytic parameters have been evaluated. Within‐day and between‐day precision as expressed by relative standard deviation was found to be less than 2%. The method has been applied successfully for the determination of TDF in spiked human plasma samples and pharmaceutical formulations.     

Voltammetric determination of salbutamol on a glassy carbon electrode coated with a nanomaterial thin film

A rapid and convenient electrochemical method is described for the determination of salbutamol based on multi-carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE). The electrochemical behavior of salbutamol at this modified electrode was studied by square wave voltammetry, which indicated that the oxidation peak potential of salbutamol shifted on 40 mV to less positive potential and the peak current increased 4.5 fold, in contrast to that at a bare electrode. Various experimental parameters such as pH value of supporting electrolyte, the amount of modifier, and accumulation time were optimized. Under optimal measurement conditions, there is a good linear relationship between the peak current (I _pa) and salbutamol concentration in the range from 8.0 × 10⁻⁷ to 1.0 × 10⁻⁵ M, and the detection limit is 2.0 × 10⁻⁷ M (S/N = 3) at 2 min accumulation. The method has been successfully employed to detect salbutamol in pharmaceutical formulations.     

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.