Analysis of Thyroidal Amino Acids in Pharmaceutical Preparations. I - Reverse Phase High Pressure Liquid Chromatography Analysis of Sodium Liothyronine from Tablets

Abstract

A simple, sensitive and specific assay method was developed for the assay of sodium liothyronine (T₃Na) from tablets. Sodium liothyrorn'ne was extracted from powdered tablets with a solvent system consisting of butanol and dilute hydrochloric acid. The solvent was removed under vacuum and the residue was dissolved in ammonical methanol. An aliquot of this solution was injected on a μBondapak C₁₈ column and the elution was carried out with a mobile phase consisting of methanol:water:phosphoric acid (55:45: 0.1). The effluent was monitored by U. V. detection at 254 nm. A linear calibration curve was obtained in the range of 10 to 250 ng on column with a precision of ±4% (C. V.). The internal standard consisted of 3, 3′, 5-triiodothyronine (T3′ or RT₃). The usefulness of an alternate compound, 3, 5-diiodo-3′, 5′-dibromothyronine, which is not endogenous, was also demonstrated as an internal standard.     

Determination of Apomorphine in Tablets Using High Performance Liquid Chromatography with Electrochemical Detection

Abstract

A rapid and selective method using high performance liquid chromatography with electrochemical detection is described for the determination of apomorphine in tablets. Tablet mixes were dissolved in a standard volume of mobile phase containing the internal standard, N-n-propylnorapomorphine. Separation was achieved on a μ-phenyl column using methanol-acetonitrile-0.05M KH₂PO₄ (5:15:80) as mobile phase. The eluted compounds were detected with a sandwich-type electrochemical detector employing a glassy carbon working electrode and operated at 0.5V. Satisfactory accuracy and precision were obtained during analyses of tablets containing apomorphine.     

Rapid and Sensitive Determination of Furosemide in Human Plasma by High Pressure Liquid Chromatography

Abstract

A rapid and sensitive determination of furosemide in human plasma by high pressure liquid chromatography is described. The drug is extracted from plasma after addition of the internal standard (2,4-dinitrophenol), the extract is concentrated by means of evaporation and injected on to the liquid chromatograph. Separation is achieved on a reversed-phase column with 50 % methanol in water, containing 0.5 % glacial acetic acid; detection is carried out at 340 nm. The method is linear up to 5 μml and can determine concentrations down to 0.1 μg/ml in a 1ml plasma sample. It is much faster than existing methods and is at least as good with respect to accuracy and sensitivity.     

Determination of Ergotamine Tartarate and Cyclizine Hydrochloride in Pharmaceutical Tablets by Reverse Phase HPLC

Abstract

A high performance liquid chromatographic procedure is presented for the determination of ergotamine tartarate and cyclizine hydrochloride in pharmaceutical tablets. An aliquot of the sample is dissolved in methanol containing ethyl p-hydroxybenzoate as an internal standard and chromatographed on a 5 üm, C₁₈, Hibar pre-packed, Lichrospher (250 mm × 4.0 mm i.d.), column using a mobile phase of 0.01 M ammonium acetate in acetonitrile: water: triethylamine (35:64:1) solution, the pH was adjusted to 3.7 with glacial acetic acid. The method was tested for linearity, recovery, and specificity and was found to be fast, sensitive, accurate and reproducible with a total elution time of six min.     

High Performance Liquid Chromatographic Determination of Amiodarone in Plasma and Tissues

Abstract

A simple and rapid high-performance liquid chromatographic (HPLC) method for the determination of amiodarone (AD) in plasma and tissues was developed. The method involved deproteinization of plasma or homogenized tissue with acetonitrile containing an internal standard (N-Cetylpyridinium chloride) followed by reversed phase chromatography using μ bondapack C₁₈ column (10μm) with a mobile phase consisting of acetonitrile - methanol - sodium dihydrogen phosphate buffer (70:10:20%, v/v), the pH adjusted to 4.0 and pumped at flow rate of 1.0 ml/min. The column effluent was monitored at 242 nm. A linear relationship was obtained between peak height ratios (drug to internal standard) versus drug levels over the concentration range of 50–750 ng/ml. The detection limit of AD in plasma and tissues by this method was 20 ng/ml.     

Determination of Furosemide by Simple Diazotization Method in Pharmaceutical Preparations

A simple and rapid spectrophotometric method has been investigated for the determination of furosemide. The method is based upon simple diazotization reaction. The absorbance was measured at 480 nm. The method is optimized for acidity, amount of reagents required and heating time. The range of linearity was 0.4–10 μg mL^?1 of furosemide with molar absorptivity of 1.0 × 10⁴ l mol^?1 cm^?1. Standard deviation, coefficient of variance, limit of detection and limit of quantification were calculated using authentic standard of furosemide and were found to ± 0.0013,12.7%, 0.16 ppm and 0.52 ppm, respectively. The method was applied to various pharmaceutical preparations containing furosemide. The results of the investigated method for furosemide were compared with available official literature method. The results obtained by the proposed method agree well with the standard established method.     

Spectrophotometric Determination of Furosemide Based on Its Complexation with Fe(III) in Ethanolic Medium Using a Flow Injection Procedure

Abstract

A fast flow injection procedure with spectrophotometric detection based on the furosemide complexation with Fe(III) ions in ethanolic media is described. As carrier the flow single line system configuration used an ethanolic 10^?2 mol L^?1 Fe(III) solution flowing at 1.0 mL min^?1, a 50 cm sample loop (250 µL total sample injection), and a 50 cm long reactor coil, at room temperature. The detection at 513 nm presented a linear dynamic range from 1.00×10^?4 to 1.00×10^?2 mol L^?1, obeying the linear equation Abs=8.9×10^?3+22.3×[furosemide] (r=0.998, n=7). The limit of detection (3σ/slope) was 3.00×10^?5 mol L^?1. The proposed method was applied to four commercial samples from different suppliers, as tablets and ampoules, and a synthetic urine sample spiked with the analyte without an effect from the other substances present in the formulation. The proposed procedure presented an analytical frequency of 95 measurements per hour. The results agreed with those from both the label and those determined by a spectrophotometric comparative procedure. Recoveries close to 100% were found in the commercial formulations and synthetic urine matrixes.     

An Improved HPLC Method for the Determination of Furosemide in Plasma and Urine

Abstract

A sensitive HPLC method with minimal sample preparation and good reproducibility for the determination of furosemide in plasma and urine is described. Acidified plasma samples were extracted using CH₂Cl₂ containing desmethylnaproxen as internal standard (IS). Fresh urine samples were incubated with β-gluc-uronidase for 15 minutes and then treated with CH₃CN containing IS.

Chromatography was performed on a C18 column with 10 mcl sample injection, Mobile phases were: a) for plasma: 0.01 M NaH₂PO₄, pH 3.5 - CH₃OH (65:35), and b) for urine: acetic acid, pH 3.5 - CHS3OH (60:40) at 3 ml/min and fluorescence detection at Ex 235/Em 389 nm. The plasma standard curve was linear from 0.01 to 15.0 mcg/ml and the urine from 0.5 to 200.0 mcg/ml. The within run CV's were 3,2% at 0.74 mcg/ml plasma and 2.0% at 10.7 mcg/ml urine. Recovery from plasma was 69.9% at 2.0 mcg/ml and 98.6% from urine at 5.0 mcg/ml. The stability of furosemide and its glucuronide were studied. Both methods have been applied to the analysis of plasma and urine samples obtained from human volunteers.     

Determination of Nabumetone and Its Major Metabolite in Plasma and Tablet Formulations by Reverse-Phase HPLC

Abstract

A high performance liquid chromatographic procedure is presented for the determination of nabumetone in pharmaceutical tablets and in plasma. An aliquot of the sample is dissolved in 50% acetonitrile (ACN) containing 4-methoxyacetophenone as an internal standard and chromatographed on a Supelcosil LC-8 (5μ) (150 mm × 4.6 mm i.d.) column. The mobile phase was a mixture of acetonitrile (500 mL), triethylamine (1.5 mL) and glacial acetic acid (8 mL) diluted to 1000 mL, with distilled deionized water. The detection was carried at 270 nm. The method was tested for linearity, recovery and specificity.     

High Performance Liquid Chromatographic Assay of Methoclopramide in Plasma Using a Silica Gel Column and An Aqueous Meobile Phase

Abstract

A high performance liquid chromatographic method for quantitating matoclopramide in plasma is presented. Proteins ara precipitated from the plasma sample with acetonitri la containing the internal standard, procainamida. The treated samples ara than analyzad using an Ultrasphere Si column, an aqueous solution at pH 7 of 65% CH³CN and 5.0 mM (NH₄)₂HPO₄ as a mobile phase, and a fluorescence detector. The retention times for drug and intarna1 standard ara 11.2 and 13.2 min, respectively. The caibration curve is Linear from 0.89 to 44.5 ng/ml. The detection limit is 0.89 ng/ml [signaL/hoisa = 31] for 0.2 ml plasma samples Pracision is measured by intraday and intarday coefficients o f variation, which are less than 10%. This method is currently being used for pharmacokinetic studies of methoclopramide.     

Simultaneous high-performance liquid chromatographic determination of phenazopyridine and nitrofurantoin in tablets

Summary A reversed-phase, High-performance Liquid chromatographic method for the simultaneous determination of phenazopyridine and nitrofurantoin in tablets is described. An aminopropyl-silica (APS-Hypensil) 5μm column and a mobile phase consisting of Methanol:H₂O: 0.05M sodium dihydrogen phosphate (50∶45∶5) were used. Calibration curves were linear over the concentration range 2–20μg/ml, with minimum detectability of 10ng/ml for both drugs. The method was applied to tablets containing the two species and the results obtained were compared to those given with a published method.     

High-Performance Liquid Chromatographic Determination of Atenolol in Tablets

Abstract

A reversed phase high-performance liquid chromatographic method was developed for the determination of atenolol in four oral 100 mg atenolol preparations.

An aliquot of the sample is dissolved in a mobile phase consisting of 0.0612 M potassium hydrogen phosphate - isopropanol-tetrahydrofuran (84:10:6) v/v). The pH was adjusted to 6.7 with phosphate buffer. Nicotinamide was used as internal standard and chromatographed on a Pinkerton column ISRP (GFF-S5–80) 5 μm, 150 × 4.6 mm i.d. The applied column is convenient for the assay at least 90 samples of atenolol without degrading column performance. The detection was performed at 272 nm. The retention time for atenolol was 5.07 min.

The proposed HPLC method was found to be suitable for the rapid and precise routine analysis of atenolol in tablets.     

Determination of Vitamin B12 in Multivitamin Tablets by High Performance Liquid Chromatography

Abstract

Two procedures for separation and determination of vitamin B₁₂ in multivitamin tablets by reversed phase high performance liquid chromatography are proposed. Sample preparation is very simple: tablets are dissolved in distilled water, centrifuged and filtered. The sample solution is directly applied in the sample loop injector and chromatograms are obtained with gradient elution using water-methanol and water-acetonitrile as solvents. The peak of vitamin B₁₂ from samples of B-complex tablets is well separated with the two procedures. For multivitamin tablets, however, only the procedure with water and methanol as solvents was good for separation and quantification of vitamin B₁₂. Both procedures were verified by the standard addition method and also compared to a previously developed method using electrothermal atomic absorption spectrometry for vitamin B₁₂ determination.     

Quantitative Determination of Nadolol in Tablets by High‐Performance Liquid Chromatography and UV‐Derivative Spectrophotometry

Abstract

High‐performance liquid chromatographic (HPLC) and UV derivative spectrophotometric (UVDS) methods were developed and validated for the quantitative determination of nadolol in tablets. The HPLC method was performed on a C18 column with fluorescence detection. The excitation and emission wavelengths were 230 and 300 nm, respectively. A mobile phase composed by acetonitrile‐water containing 0.1% triethylamine (15∶85 v/v) and pH adjusted to 4.6 with formic acid was used. The UVDS method was performed taken a signal at 279.5 nm. The correlation coefficient (r) obtained for both methods was 0.9999. The proposed methods are simple, precise, accurate, and can be used in routine analysis.     

Simultaneous Analysis of Cimetidine and Ranitidine in Human Plasma by HPLC

Abstract

A rapid method for the simultaneous quantitation of the H₂-receptor antagonist drugs cimetidine and ranitidine in human plasma by isocratic ion-pair reverse-phase HPLC is described. The method involves a simple organic extraction step of the alkalinized plasma containing added internal standard followed by back extraction of the extract with dilute acetic acid and subsequent analysis of the aqueous acidic phase on a reverse-phase (C18) column. The eluting solvent was acetonitrile-water (20:80 v/v) containing 0.005 mole/litre octanesulphonic acid and was monitored at 229 nm. The run time for the assay was 12.5 minutes, with a detection limit for cimetidine of 50 ng/m1/(0.2 μmole/1) and that for ranitidine was 20 ng/ml (0.06 umole/1).     

High Performance Liquid Chromatographic Determination of Pentamidine in Plasma

Abstract

A high performance liquid chromatographic method for quantitating pentamidine in plasma has been developed. Sample clean-up involved precipitating plasma with acetonitrile containing the internal standard, hexamidine. The supernatant was passed through a C₈ Bond Elut column and eluted with a methanolic solution of sodium 1-heptanesulfonate. The eluate was then analyzed on an Altex C₈ column with a mobile phase consisting of 45% CH₈CN, 0.02% detramethylammonium chloride and 0.1% H₃PO₄. Using fluorescence detection (EX: 275 nm and EM: 340 nm), the detection limit was 1.25 ng/ml for 0.5 ml of plasma. The coefficients of variation for interday and intraday were around 10%.     

Determination of Ketoconazole in Plasma and Dosage Forms by High-Performance Liquid Chromatography and a Microbiological Method

Abstract

A simple and rapid high-performance liquid chromatographic (HPLC) method for the determination of ketoconazole in plasma and in tablets was developed. the method employs benzafibrate as internal standard and is sufficiently rapid and sensitive for use in pharmacokinetic studies. Separation of the drug from plasma was achieved by extraction with acetonitrile followed by a reversed phase chromatography on a μ Bondapak column using the isocratic mobile phase of methanol-water-glacial acetic acid (67.5:32:0.5). With this eluting solvent ketoconazole and the internal standard. were well separated from the components of plasma. A linear relationship was obtained between the ratio of the area under the peak of drug to that of the internal standard versus the concentration of the drug. Data comparing the microbiological assay with the HPLC procedure, which was developed, are shown. In the microbiological assay, Candida albicans, was the test organism, using the agar diffusion technique. Both methods were applied to the assay of ketoconazole in plasma and in tablets. Excellent agreement was observed between the results from the two methods.     

Simultaneous Determination of Hydrochlorothiazide and Valsartan in Human Plasma by Liquid Chromatography/Tandem Mass Spectrometry

Abstract

A rapid and specific liquid chromatography/tandem mass spectrometry method was described for the simultaneous determination of hydrochlorothiazide and valsartan in human plasma. After extracted from plasma using methanol, hydrochlorothiazide, valsartan and hydroflumethiazide, irbesartan, used as the internal standard, respectively, were chromatographically analyzed on a Phenomenex Kromasil C₈ column with water and methanol (27:73, v/v) as the mobile phase. Selected reaction monitoring was specific for mass detection employing negative electrospray ionization. The calibration standards were linear over the concentration range (3.13–800 ng/ml for hydrochlorothiazide and 11.72–3000 ng/ml for valsartan). The method was found to be suitable for application to a pharmacokinetic study after oral administration of dispersible tablet containing 12.5 mg hydrochlorothiazide and 80 mg valsartan to 20 healthy volunteers.     

Determination and Validation of an LC Method for Fluvoxamine in Tablets

A new, simple, rapid and specific reversed-phase high-performance liquid chromatography (HPLC) method was developed and validated for the determination of fluvoxamine in pharmaceutical dosage forms. The HPLC separation was achieved on a C₁₈ μ-Bondapack column (250 mm × 4.6 mm) using a mobile phase of acetonitrile–water (80:20, v/v) at a flow rate of 1 mL min⁻¹. Proposed method is based on the derivatization of fluvoxamine with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS) in borate buffer of pH 8.5 to yield a orange product. The HPLC method is based on measurement of the derivatized product using UV-visible absorbance detection at 450 nm. The method was validated for specificity, linearity, precision, accuracy, robustness. The degree of linearity of the calibration curves, the percent recoveries of fluvoxamine, the limit of detection and quantification, for the HPLC method were determined. The assay was linear over the concentration range of 45–145 ng mL⁻¹ (r = 0.9999). Limit of detection and quantification for fluvoxamine were 15 and 50 ng mL⁻¹, respectively. The results of the developed procedure (proposed method) for fluvoxamine content in tablets were compared with those by the official method. The method was found to be simple, specific, precise, accurate, reproducible and robust.     

LC Determination of Gemfibrozil in Tablets

A simple, selective, precise and accurate reversed phase-HPLC assay for analysis of gemfibrozil in tablets was developed and validated. Separation and quantification were achieved on a Phenomenex C₁₈ column under isocratic conditions using a mobile phase (methanol:water, 80:20, v/v) maintained at 1.1 mL min⁻¹. UV-detection was at 280 nm. Atorvastatin was selected as an internal standard. The standard curves were linear over the range of 0.5–3.0 μg mL⁻¹ (r > 0.999). The limits of detection and quantification were 0.20 and 0.51 μg mL⁻¹, respectively. The recoveries for gemfibrozil were above 99.01%. The intra-day and inter-day precision (RSD) for gemfibrozil were below 1.74 and 1.83%, respectively. No chromatographic interferences from the tablet excipients were found. The results of the developed procedure in tablets were compared with those of the reference method to assess gemfibrozil content. Statistical comparison of the results with the reference method using spectrofluorimetric method showed excellent agreement and proved no significant difference in accuracy and precision. This HPLC method is fast and simple for the analysis of gemfibrozil in pharmaceutical preparations.