Liquid chromatographic determination of colchicine in pharmaceuticals: collaborative study

A liquid chromatographic (LC) method for the determination of colchicine in pharmaceutical dosage forms and the bulk drug was evaluated in an interlaboratory study which included 13 participating laboratories. The method involves extraction (or dissolution) of the active ingredient with methanol-water (1 + 1), followed by filtration of the extract and reverse phase LC using an octylsilane bonded phase column and UV detection at 254 nm. The mobile phase consists of a methanol-phosphate buffer mixture (pH = 5.5). Three commercial tablet formulations (0.5-0.6 mg colchicine/tablet), 1 synthetic injectable preparation (0.510 mg colchicine/mL), and 1 bulk drug sample were assayed in duplicate by the proposed method. The reproducibility and repeatability standard deviations based on nonpooled results for each sample ranged from 0.0062 mg/mL to 0.0147 mg/tablet and from 0.0037 mg/mL to 0.0127 mg/tablet, respectively; the corresponding coefficients of variation ranged from 1.21 to 2.54% and from 0.73 to 2.19%, respectively. The mean recovery from the synthetic injectable formulation was 100.0%. The method has been adopted official first action.     

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.     

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 dexamethasone acetate and cortisone acetate in bulk drug substance and dosage forms: collaborative study

A reverse-phase liquid chromatographic method for determination of dexamethasone acetate and of cortisone acetate was subjected to an interlaboratory study by 8 collaborators for each steroid acetate. Bulk drug substance, suspensions, and tablets were assayed. Bulk drug or dosage form is dissolved in an acetonitrile-buffer mixture and analyzed by an external standard method. The steroid acetate is resolved from extraneous components by reverse-phase chromatography and detected at 254 nm. The sample solutions are stable for at least 72 h. For dexamethasone acetate, coefficients of variation were 0.9 and less than or equal to 3.1% for the bulk drug substance and the suspensions, respectively. For cortisone acetate, coefficients of variation were 0.7% for bulk material, less than or equal to 2.0% for suspensions, and less than or equal to 2.5% for tablets. All dosage forms were commercial formulations. The 2 methods have been adopted official first action.     

Rapid differential pulse polarographic determination of tiaprofenic acid

Tiaprofenic acid (Surgam) has been determined directly by using differential pulse polarography (DPP) and pH 5.5 acetate buffer as a supporting electrolyte. The differential pulse polarogram was obtained under constant amplitude pulses of 50 mV superimposed on a linearly increasing dc ramp. Peak current was measured at the peak potential of -0.990 V vs Ag/AgCl reference electrode. Under the experimental conditions used, a linear relationship between peak current and concentration was established over the range 0.5-5.0 micrograms/mL. Mean percentage recoveries for tiaprofenic acid in authentic and tablet forms were 100.27 +/- 2.25 and 99.45 +/- 1.44, respectively. The results obtained by the DPP method were compared with those of the spectrophotometric method used by the manufacturer for the analysis of tiaprofenic acid and its tablet form.     

Gas chromatographic determination of histapyrrodine hydrochloride in pharmaceutical preparations

A simple gas chromatographic method is described for the determination of histapyrrodine HCl in marketed formulations. Chlorpheniramine maleate is used as the internal standard. The amount of histapyrrodine HCl found by the proposed method averaged 19.91 mg/tablet, compared with the label claim of 20 mg/tablet. The method was statistically evaluated for accuracy and precision.     

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.     

Liquid chromatographic determination of penicillin V potassium in tablets: collaborative study

A liquid chromatographic method for the determination of penicillin V potassium in tablets was collaboratively studied by 7 laboratories. The method uses an octadecyl silane reverse-phase column, a mobile phase of acetonitrile-methanol-0.01 M potassium phosphate monobasic (21 + 4 + 75 v/v/v), photometric detection at 225 nm, and sulfadimethoxine as an internal standard. Each collaborator received 6 samples: powdered composites of 2 commercial tablet preparations and 1 synthetic tablet powder mixture, each with blind duplicates. The mean repeatability and reproducibility relative standard deviations for commercial samples were, respectively, 1.10 and 1.46% (250 mg dosage), and 0.84 and 2.82% (500 mg dosage). The average standard recovery from the synthetic formulation was 99.1%, with repeatability and reproducibility relative standard deviations of 1.30 and 3.66%, respectively. The method has been adopted official first action.     

Liquid chromatographic determination of six sympathomimetic drugs in dosage forms

A simple and rapid stability-indicating liquid chromatographic method is described for quantitative determination of 6 sympathomimetic drugs in various liquid and solid formulations. Analyses were carried out on a C18 reverse phase column using 0.01M 1-octanesulfonic acid, sodium salt in 0.2% acetic acid-methanol (70 + 30) as the mobile phase with photometric detection at 220 nm. Coefficients of variation for 5 consecutive injections of a mixed standards solution ranged from 0.62% for metaraminol to 1.40% for epinephrine. Standard recoveries ranged from 98.8% for metaraminol to 100.8% for epinephrine. The method was linear between 0.2 and 10 micrograms of drug injected and was used successfully to analyze 17 commercial products in a variety of dosage forms.     

Liquid chromatographic determination of pentaerythritol tetranitrate in pharmaceuticals: collaborative study

A liquid chromatographic (LC) method for the determination of pentaerythritol tetranitrate (PETN) in pharmaceutical formulations and the bulk drug triturate was evaluated in an interlaboratory study that included 12 participating laboratories. The procedure involves extraction of the active ingredient with mobile phase, followed by filtration of the extract and reverse-phase liquid chromatography using an octadecylsiliane bonded phase column and UV detection at 230 nm. The mobile phase composition is 35% water in acetonitrile (v/v). Three bulk drug samples (20, 20, and 35% PETN), 2 commercial tablet formulations (20 and 80 mg PETN/tablet), and 1 commercial capsule formulation (45 mg PETN/capsule) were analyzed in duplicate by the proposed method. Repeatability (sr, RSDr) and reproducibility (SR, RSDR) based on peak height measurement for these samples ranged from 0.0066 to 0.1806 (0.53-3.36%) and 0.0165 to 0.2075 (0.76-3.86%), respectively. Results for peak area measurements ranged from 0.0145 to 0.2011 (0.93-3.74%) and 0.0231 to 0.2091 (1.28-3.89%), respectively. The method has been approved interim official first action by AOAC.     

High pressure liquid chromatographic determination of antihistamine-adrenergic combination products: collaborative study

A reverse phase high pressure liquid chromatographic method in which ion-pairing is used for the determination of combinations of pseudoephedrine hydrochloride with triprolidine hydrochloride or chlorpheniramine maleate in syrups and tablets was collaboratively studied by 8 laboratories. Collaborators were supplied with 12 samples including synthetic and commercial syrup formulations and commercial tablet composites. Mean recoveries of pseudoephedrine hydrochloride and triprolidine hydrochloride from synthetic syrup formulations were 100.5 and 99.6%, respectively. Mean recoveries of pseudoephedrine hydrochloride and chlorpheniramine maleate from synthetic syrups were 98.8 and 100.5%, respectively. Mean coefficients of variation for syrups and tablets ranged from 1.68 to 3.07% for pseudoephedrine hydrochloride, from 2.92 to 3.85% for triprolidine hydrochloride, and from 1.34 to 2.15% for chlorpheniramine maleate. The method has been adopted official first action.     

Determination of carotenoid stereoisomers in commercial dietary supplements by high-performance liquid chromatography

A method for the determination of beta-carotene, lutein, and zeaxanthin including their cis-isomers and alpha-carotene in commercial dietary supplements by HPLC has been developed. The study comprises 11 oral dosage forms, including 9 soft gelatin capsules, 1 dragée, and 1 effervescent tablet formulation. The capsule content was extracted with an acetone-hexane mixture, and the gelatin shell was digested with papain to release carotenoids that had migrated into the coat. Sample preparation for tablets and dragées was carried out as described for the capsule content. Extraction recoveries exemplified for all-trans-beta-carotene and all-trans-lutein were 95 +/- 5% and 93 +/- 2%, and 95 +/- 2% and 79 +/- 5% after enzymatic treatment, respectively. Apart from all-trans-beta-carotene, its 9-cis- and 13-cis-isomers were detected in all samples, whereas no evidence for cis-isomerization of lutein and zeaxanthin could be obtained. Migration of carotenoids into the shells was only observed in the case of beta-carotene. With the exception of one preparation, the beta-carotene contents determined exceeded the dosage specified on the label by up to 48%, which results from stability overages necessary to compensate for losses during storage.     

Determination of fluoride in fluoride tablets and solutions by ion-selective electrode: collaborative study

A proposed method using the fluoride (F) ion-selective electrode has been developed for determining the fluoride ion concentration in tablets and solutions containing sodium fluoride. The method has been subjected to collaborative study. Eight samples consisting of 2 authentic fluoride solutions, 2 commercial fluoride solutions, and 4 commercial fluoride tablets were sent to each of 11 collaborators together with a copy of the method. Single assays on the authentic fluoride solutions known to contain 1 mg F/5 mL were performed with average recoveries of 99.5 and 99.6% and relative coefficients of variation (CV) of 2.11 and 1.91%, respectively. Single assays of 2 commercial fluoride solutions declared at 1 mg F/5 mL gave mean values of 0.994 and 0.990 mg and relative CV values of 1.88 and 2.36%, respectively. Single assays of 2 commercial fluoride tablet preparations declared at 0.5 mg F gave mean values of 0.485 and 0.478 mg and relative CV values of 3.12 and 3.71%, respectively. Single assays of 2 commercial fluoride tablet preparations declared at 1 mg F gave mean values of 0.991 and 0.981 mg and relative CV values of 2.99 and 2.85%, respectively. The method has been adopted official first action.     

Determination of terbutaline sulfate in dosage forms by liquid chromatography with electrochemical detection

A liquid chromatographic method with electrochemical detection has been developed for the determination of terbutaline sulfate in dosage forms. A cyanopropyl bonded-phase column is used with a mobile phase consisting of methanol-0.1 M monobasic potassium phosphate containing 0.1M sodium heptanesulfonate and 1mM disodium ethylenediaminetetraacetate (15 + 85). The compound of interest is detected at a glassy carbon electrode held at a potential of +0.9 V vs silver-silver chloride. The response is linear from 0 to 10 micrograms/mL terbutaline sulfate. The method is applicable to tablet composites, individual tablets, dissolution determinations, and injections. Results and supporting data are reported for the above analyses.     

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.     

Ion-pair column chromatographic determination of trimethobenzamide hydrochloride in capsule and injection dosage forms: collaborative study

An ion-pair column chromatographic method was developed for the determination of trimethobenzamide hydrochloride in capsules and injection dosage forms. Detection is by UV spectrophotometry at 261 nm. Recoveries by the Associate Referee ranged from 98.3 to 101.0% for the drug substance. Results by 5 collaborators for capsules averaged 99.1% of labeled or theoretical with coefficients of variation (CVs) of 1.81% (reproducibility) and 1.17% (repeatability); results for injections averaged 100.4% of labeled or theoretical with CVs of 1.91% (reproducibility) and 0.69% (repeatability). The method has been adopted official first action.     

Performance characteristics of methods of analysis used for regulatory purposes. I. Drug dosage forms. B. Gas chromatographic methods

Gas chromatographic methods for the analysis of drug dosage forms consist of a simple extraction, dilution with an internal standard solution, and injection, or, even simpler, dilution with the internal standard solution and injection. These methods were used in 7 collaborative studies of the determination of 12 pharmaceuticals, published in the Journal of the AOAC during 1973-1983. A total of 43 individual materials consisting of various dosage forms were each analyzed, usually in duplicate, by an average of 8 laboratories, with a total of 582 reported determinations. The average within-laboratory coefficient of variation (CVo) was 1.25% and the average among-laboratories coefficient of variation (CVx) was 2.41%, for a CVo/CVx ratio of 0.52, at an average outlier rate of 1.4% of the reported values. The line of best fit for CVx plotted against concentration increases with decreasing concentration, extending from a CVx of approximately 1.8% at 100% concentration to a CVx of approximately 3.2% at 1% concentration. The change in CVx for a 10-fold decrease in concentration is approximately 0.7% CVx, independent of analyte and matrix.     

Liquid chromatographic determination of prednisolone in tablets and bulk drugs: interlaboratory study

A normal phase liquid chromatographic (LC) method for the determination of prednisolone in tablets and bulk drugs was studied by 7 analysts. An LC system, consisting of a methanol-water-ethylene dichloride-acetic acid mobile phase and a silica column, was used to analyze bulk drugs, individual tablets, and composite samples. Analysts were supplied with 16 samples, including simulated formulations, composites of commercial tablets, intact tablets, and bulk drug substances. Results agreed with those obtained by the author. The coefficients of variation of the analysts' results ranged from 1.34% for bulk drugs to 2.14% for tablet composites. The LC method is suggested as an alternative to the official AOAC and USP XX blue tetrazolium colorimetric methods.     

Equivalence of microbiological and hydroxylamine methods of analysis for ampicillin dosage forms.

Ampicillin formulations were assayed by microbiological and hydroxylamine methods to determine whether thehydroxylamine analytical method is a suitable substitute for the microbiological method. Paired assay results by the 2 analytical methods were obtained on different strengths of tablet, capsule, and suspension, formulations containing ampicillin and ampicillin degradation compounds. Several statistical tests were used to assess the equivalence of the paired assay results. The data analyses indicate that the hydroxylamine method is a suitable substitute for the microbiological method for potency assays and stability studies of ampicillin formulations. The hydroxylamine method yielded slightly higher assay results than the microbiological method for severely degraded formulations.     

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%.