High pressure liquid chromatographic determination of oxazepam dosage forms: collaborative study

A reverse phase high pressure liquid chromatographic method for the determination of oxazepam in tablets and capsules was collaboratively studied by 9 laboratories. Collaborators were supplied with 6 samples that included synthetic and commercial formulations. Tablet and capsule composites are diluted with methanol and filtered. Oxazepam is determined at 254 nm by using a C18 column. Mean recoveries of oxazepam from synthetic tablet and capsule formulations were 97.2 and 99.0%, respectively. Mean coefficients of variation for tablets and capsules ranged from 1.85 to 2.86%. The method has been adopted official first action.     

Proton magnetic resonance spectroscopic determination of bethanechol chloride in tablets

A simple and reliable proton magnetic resonance spectroscopic method was developed for the assay of bethanechol chloride in tablets. The proposed method entails a minimum of procedural steps and reagents. The recovery of bethanechol chloride from synthetic formulations was 99.9 +/- 0.4% (n = 15), CV = 0.4%. Mean assay values for 25 and 10 mg commercial tablets were 100.5% (n = 8) and 99.7% (n = 7) of declared, respectively. A detailed interpretation of the proton magnetic resonance spectrum is also presented.     

Liquid chromatographic determination of organic nitrogenous bases in dosage forms: a progress report

A liquid chromatographic (LC) method has been developed as a general procedure for the assay of the salts of organic nitrogenous bases in a variety of dosage forms. The method uses a nitrile-bonded reverse phase column, a methanol-0.003M ammonium acetate (90 + 10) mobile phase, and photometric detection at 254 nm. The sample is dissolved in the mobile phase and an aliquot is injected through a 20 microL injection loop. Average recovery values for duplicate assays were chlorpheniramine maleate injection 97.8%, chlorpheniramine maleate tablets 99.1%, cyclizine hydrochloride tablets 100.0%, doxylamine succinate tablets 103.3%, mesoridazine besylate tablets 100.4%, pentazocine hydrochloride tablets 103.0%, promethazine hydrochloride injection 98.4%, protriptyline hydrochloride tablets 101.2%, pyrilamine maleate tablets 97.8%, pyrimethamine tablets 100.0%, tripelennamine citrate elixir 100.0%, and tripelennamine hydrochloride tablets 97.2%. Results by this method were in good agreement with those obtained by the USP XX method. This study, which is being continued, will be expanded to include additional drugs.     

Ultraviolet spectrophotometric determination of hydralazine hydrochloride in tablets following derivatization with nitrite

Routine use of the USP XXI spectrophotometric method for the content uniformity determination of hydralazine hydrochloride tablets has shown that tablet excipients can significantly alter the spectral characteristics of the drug and thus cause inaccurate assay values to be obtained. Because of this problem, a simple and reliable alternative spectrophotometric assay method, based on the conversion of hydralazine to tetrazolo [5,1-alpha]phthalazine with nitrite ions under acidic conditions, was developed. The derivative showed an absorption maximum at about 274 nm and obeyed Beer's law over the concentration range 4-40 micrograms/mL. Mean recoveries of hydralazine hydrochloride added to commercial coated and uncoated tablets were 101.0% (n = 10) and 100.8% (n = 8), respectively. The proposed method was found suitable for the assay not only of individual tablets but also of tablet composites.     

Liquid chromatographic determination of methyldopa and methyldopa-thiazide combinations in tablets: collaborative study

A reverse phase liquid chromatographic method for the determination of methyldopa, methyldopa-hydrochlorothiazide, and methyldopachlorothiazide in tablets was collaboratively studied by 8 laboratories. Each collaborator received 20 samples that included drug substance, synthetic and commercial tablet compositions. The overall repeatability and reproducibility standard deviations for commercial tablets were 1.11 and 1.75% for methyldopa, 0.96 and 1.62% for chlorothiazide, and 1.21 and 2.15% for hydrochlorothiazide, respectively. The overall recoveries of methyldopa, chlorothiazide, and hydrochlorothiazide added to synthetic tablets were 100.78, 100.70, and 101.34%, respectively. The method has been adopted official first action.     

Liquid chromatographic determination of levodopa and levodopa-carbidopa in solid dosage forms: collaborative study

A liquid chromatographic method for the determination of levodopa in tablets and capsules and levodopa-carbidopa in tablets was collaboratively studied by 6 laboratories. Collaborators were supplied with duplicate powdered composites of levodopa (1 synthetic formulation, 1 commercial tablet, and 1 commercial capsule) and levodopa-carbidopa (1 synthetic formulation and 2 commercial tablets), along with individual levodopa-carbidopa tablets for content uniformity determinations. The repeatability coefficient of variation (CVo) and reproducibility coefficient of variation (CVx) for levodopa single component were 0.48 and 0.87%; for levodopa in combination, 0.50 and 0.90%; and for carbidopa, 0.77 and 1.20%, respectively. Overall, the recovery values for levodopa and carbidopa from synthetic formulations simulating tablets were 100.4 and 99.5%, respectively. The pooled CVDo and CVDx values for the individual tablet assays were 2.07 and 2.30% for levodopa, and 1.80 and 2.24% for carbidopa, respectively. The method has been adopted official first action for determination of the active ingredients in levodopa tablets and capsules and in levodopa-carbidopa tablets and for content uniformity testing in the combination dosage form.     

Reverse-phase liquid chromatographic determination of clioquinol in cream and ointment preparations: collaborative study

Seven laboratories participated in a collaborative study to analyze, in duplicate, 2 synthetic formulations and 2 commercial preparations, labeled to contain 3% clioquinol. Clioquinol is determined as its nickel (II) complex by reverse-phase liquid chromatography on a phenyl-bonded column with a mobile phase of acetonitrile-methanol-water, containing ammonium acetate and nickel chloride. Detection is at 273 nm and diphenylamine is added as an internal standard. Mean recoveries were 99.1 and 101.1%, respectively, for the ointment and cream synthetic preparations and 96.7 and 99.7%, respectively, for the commercial ointment and cream. All results are consistent with the variability of other methods at this concentration range. The method has been approved interim official first action.     

UV spectrophotometric determination of hydralazine hydrochloride in tablets: collaborative study

A UV spectrophotometric method for the determination of hydralazine hydrochloride in tablets was collaboratively studied by 5 laboratories. The method is based on conversion of hydralazine to a tetrazolo [5,1-alpha]phthalazine derivative which shows an absorption maximum at about 274 nm. Each collaborator received blind duplicate samples of 2 commercial powdered composites from 10 and 100 mg tablets, and 1 synthetic tablet formulation. Each collaborator also received a set of 10 tablets for determination of content uniformity. The pooled mean recovery of hydralazine hydrochloride from the synthetic formulation was 101.2 +/- 0.94%. The mean assay values for 10 and 100 mg tablets were 95.6 +/- 0.98 and 101.0 +/- 0.73% of the declared amounts, respectively, with corresponding CV values of 1.02 and 0.73%. The pooled mean for individual tablet assay was 99.8 +/- 3.26% of the declared value, with a CV of 3.29%. The method has been adopted official first action.     

Ion exchange method for determining mephentermine sulfate in drug formulations: collaborative study

Ion exchange chromatography is used to separate mephentermine sulfate from drug formulations. The drug is subsequently measured by ultraviolet spectrophotometry. Assays on 4 commercial samples of tablets and injectables gave recoveries from 97.6 to 104% of declared. A collaborative study involving 2 tablet and 2 liquid formulations gave mean recoveries ranging from 94.7 to 99.3% and coefficients of variation from 1.39 to 2.00%.     

Liquid chromatographic method for perphenazine and its sulfoxide in pharmaceutical dosage forms for determination of stability

A liquid chromatographic method is described for determination of perphenazine and perphenazine sulfoxide in representative dosage forms. Sulfoxide levels were nondetectable or less than 1% in tablets and in an injectable product. Sulfoxide levels increase with time in some syrup formulations and may be as high as 11% in syrup formulations before their expiration date.     

Gas chromatographic determination of formaldehyde in maple syrup as 2,4-dinitrophenylhydrazone derivative

A procedure is presented for the quantitative extraction and determination of formaldehyde in maple sap and syrup. The method is based on the reaction between formaldehyde and 2,4-dinitrophenylhydrazine and determination of the derivative by gas chromatography. The procedure was used to evaluate formaldehyde in saps and syrups of paraformaldehyde implanted trees. Average recoveries were 101.5 +/- 5.7%. The detection limit was 0.078 mg/kg.     

Determination of small quantities of atropine in commercial preparations by liquid chromatography with fluorescence detection

A method is presented for the determination of small quantities of atropine in commercial preparations by liquid chromatography (LC) with fluorescence detection. The sample is extracted with CHCl3 from basic suspension, the CHCl3 is evaporated on the steam bath, and the dry residue is dissolved in a small volume of CH3OH. A reverse phase column is used for the LC analysis; the eluting solvent is prepared by mixing 950 mL CH3OH with 50 mL water containing 1 g of the sodium salt of 1-pentanesulfonic acid. The fluorescence detector is set at an excitation wavelength of 255 nm and an emission wavelength of 285 nm. Several commercial tablets and injections containing atropine in combination with other ingredients and a commercial sample of belladonna extract were analyzed by the proposed method. Recoveries of atropine sulfate from aqueous solutions averaged 100.7% with a relative standard deviation (RSD) of 3.35% for atropine sulfate levels of 0.12 mg. Recoveries of atropine sulfate from synthetic injection formulations were 99.8 and 100.0% with RSDs of 2.03 and 2.35%, respectively; the atropine sulfate concentrations of commercial injections with the same formulations were found to be 97.0 and 100.0% of the labeled amounts with RSDs of 0.53 and 1.46%, respectively.     

Semiautomated method for the analysis of formulations of chlorpheniramine maleate and brompheniramine maleate.

The determination of chlorpheniramine maleate and brompheniramine maleate in tablets, capsules, injections, and elixirs has been automated. The active ingredient is dissolved in dilute HCl. The dilute acid solution is sampled, made basic with dilute NaOH, and extracted with isooctane. The isooctane phase is resampled and the drug is re-extracted into dilute HCl. The absorbance of the acidic aqueous layer is monitored at 265 nm. The method is an automated version of the general USP XIX assay for salts of organic nitrogenous bases. The results from the semiautomated procedure agree well with the USP XIX and NF XIV official methods. Recoveries were 100% from an authentic tablet material. The system is linear from 0 to 300% of declared potency. The procedure is free from common excipient and dye interferences. Precision data are included for both the automated and official methods.     

Major Carbohydrate, Polyol, and Oligosaccharide Profiles of Agave Syrup. Application of this Data to Authenticity Analysis

Nineteen pure agave syrups representing the three major production regions and four processing facilities in Mexico were analyzed for their major carbohydrate, polyol, and oligosaccharide profiles, as well as their physicochemical properties (pH, °Brix, total acidity, percent total titratable acidity, and color). Additionally, the detection of intentional debasing of agave syrup with four commercial nutritive sweeteners (HFCS 55 and 90, DE 42 and sucrose) was afforded by oligosaccharide profiling employing both high performance anion exchange liquid chromatography with pulsed amperometric detection (HPAE-PAD) and capillary gas chromatography with flame ionization detection (CGC-FID). Results showed that the major carbohydrate and polyol in agave syrups were fructose and inositol with mean concentrations of 84.29% and 0.38%, respectively. Oligosaccharide profiling was extremely successful for adulteration detection with detection limits ranging from 0.5 to 2.0% for the aforementioned debasing agents. Also, all four of these possible adulterants could be detected within a single chromatographic analysis.     

Second derivative spectrophotometric determination of acetaminophen and phenacetin in presence of their degradation products

A rapid and accurate method for determining acetaminophen and phenacetin in presence of their degradation products is presented. Solutions of these drugs in 0.1N HCl were analyzed by measuring their second derivative spectral response at 295 nm where the degradation products do not interfere. The mean percent recoveries for mixtures of acetaminophen and/or phenacetin with the corresponding degradation products were 100.2 +/- 0.6 and 100.6 +/- 1.1, respectively. The method can be used for assessing the stability of the 2 drugs. The proposed method is also applied to the determination of acetaminophen in tablets and syrups.     

Application of 1H-nuclear magnetic resonance spectroscopic method for quinidine to simultaneous determination of quinidine and dihydroquinidine in quinidine sulfate tablets

Based on the structural differences between quinidine and dihydroquinidine, a 1H-nuclear magnetic resonance spectroscopic method previously reported for quinidine drug substance was modified and shown to be applicable to the quantitative determination of both compounds in quinidine sulfate tablets. Deuterated chloroform was used as the solvent and hexamethylcyclotrisiloxane served as an internal standard. The average recovery and standard deviation of quinidine sulfate (calculated as the sum of quinidine sulfate plus dihydroquinidine sulfate) from synthetic formulations was 98.94 +/- 0.43% (n = 10). Five lots of 200 mg tablets of quinidine sulfate from one commercial source were found to contain from 92.9 to 95.8% quinidine sulfate, and from 1.1 to 7.0% dihydroquinidine sulfate.     

Normal phase liquid chromatographic determination of sulfamethoxazole in tablets: collaborative study

A stability-indicating liquid chromatographic method is presented for determining sulfamethoxazole in tablets. The method uses a 10 micron silica column, an isooctane-methylene chloride-2-propanol-acetonitrile-glacial acetic acid (70 + 25 + 5 + 5 + 0.5) mobile phase, and photometric detection at 254 nm. Seven laboratories collaboratively studied this method on powdered composite samples prepared from commercial 500 and 1000 mg tablets and on an authentic tablet mixture containing 83.32% added sulfamethoxazole. Mean assay results for the 500 and 1000 mg tablets were 102.2 and 97.9% of declared, respectively (n = 4). The mean recovery value for the synthetic sample was 99.4% (n = 4). The pooled reproducibility standard deviation (SD) (coefficient of variation (CV)) and pooled repeatability SD (CV) were +/- 1.01 (1.01%) and +/- 0.96 (0.96%), respectively. These results were in good agreement with those obtained by the Associate Referee for the titration method of USP XX. The proposed method can also be used for monitoring the presence of sulfanilamide in sulfamethoxazole by increasing the proportions of both acetonitrile and 2-propanol in the mobile phase. The method has been adopted official first action.     

Derivative spectrophotometric determination of some corticosteroids in combinations with other drugs

Three 2-component mixtures, namely, dexamethazone-chlorpheniramine maleate, prednisolone-chlorpheniramine maleate, and prednisolone-salicylic acid, have been assayed using their first (D1) and second (D2) derivative spectra in methanol, delta absorption (delta A), and second derivative of delta A (delta D2) spectra in methanol-methanolic HCl. In the first 2 mixtures, chlorpheniramine maleate was determined by measuring its delta D2 value at 278 nm, while dexamethazone and prednisolone were analyzed by measuring their D1 values at 248 nm. Prednisolone and salicylic acid were analyzed in combination by using their respective D2 spectral responses at 272 and 314 nm. The results obtained are reasonably reproducible with a relative standard deviation less than 2%. The method has been successfully applied to the analysis of these drugs in their pharmaceutical formulations.     

Use of differential scanning calorimetry (DSC) as a new technique for detection of adulteration in honeys. 1. Study of adulteration effect on honey thermal behavior.

Differential scanning calorimetry (DSC) was used to study the thermal behavior of authentic honeys (Lavandula, Robinia, and Fir honeys) and industrial sugar syrups. Thermal or thermochemical parameters such as the glass transition temperature (Tg), enthalpies of fusion (DeltaH(fus)), and heat capacity variation (DeltaC(p)) were measured. The syrups and honeys showed significant differences in thermal phenomena, as well as in their amplitude and position on the temperature scale. Results showed good reproducibility of the method for all samples studied. The effect of adulteration of honey with different amounts of syrup (5, 10, 20, 40, and 60%) was investigated. A linear relationship was found between the percentage of added syrup and the glass transition temperature. A similar relationship was obtained from the enthalpy of fusion results in the temperature range of 40-90 degrees C. Under applied conditions, the effects of adulteration of honeys by industrial syrups appeared to be detectable from a level as low as 5%.     

Liquid chromatographic determination of coumarin anticoagulants in tablets: collaborative study

A liquid chromatographic method for the determination of coumarin anticoagulants in tablets was collaboratively studied by 7 laboratories. The method uses an octadecylsilane-bonded microparticulate column, tetrahydrofuran-methanol-water-acetic acid mobile phase, and photometric detection at 311 nm. Each collaborator received samples of warfarin sodium, phenprocoumon, and dicumarol as a synthetic composite and as commercial individual and composited tablets. Pooled average assay values for synthetic and commercial tablet samples of warfarin sodium were 101.6 and 99.5%, respectively, with a combined reproducibility SD of 2.38% (CV = 2.37%) and combined repeatability SD of 1.49% (CV = 1.49%). Pooled average (SD) assay values for dicumarol and phenprocoumon commercial samples were 98.0 (2.27) and 101.3% (4.00), respectively. The content uniformity determinations of 2 mg warfarin sodium and 25 mg dicumarol tablets indicated average tablet contents (range) of 99.5% (91.0-116.0) and 98.0% (89.8-108.8), respectively. The method has been approved interim official first action.