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.     

Liquid chromatographic determination of carbamazepine in tablets

A simple and rapid liquid chromatographic method is described for the qualitative and quantitative determination of carbamazepine in tablet composites and individual tablets, using the internal standard technique. Analyses were performed on a C-18 reverse-phase column with tetrahydrofuran-methanol-water (8 + 37 + 55) as the mobile phase. A linear relationship was obtained between detector responses at 254 nm and amounts of carbamazepine injected ranging from 0.2 to 1.7 micrograms. The coefficient of variation for 10 consecutive injections of a standard preparation was 0.4%. Recoveries of carbamazepine from 100 and 200 mg tablets averaged 101.4 and 99.7%, respectively. Assay results for commercial tablets analyzed by the proposed method agreed favorably with those obtained by the method of USP XXI. The assay results for individual tablets indicated that deviations from the average value and the range of individual values are much wider with the compendial method than with the proposed method.     

Semiautomated method for determining ferrous sulfate in pharmaceuticals: collaborative study

A semiautomated colorimetric method is described for determining ferrous sulfate in tablets, capsules, and elixirs. The method involves the formation of an orange-red complex between 1,10-phenanthroline and ferrous ion. Collaborators were supplied with 3 solid composites and one liquid sample. Two of the solid composites were prepared from commerical tablets of different dosage and one from commercial timed-release capsules; the fourth sample was an elixir. The results of the automated analyses for ferrous sulfate agreed well with those of the applicable USP method. No interference was found from ferric iron or from the red and green coloring used on coated tablets. The method has been adopted as official first action.     

Derivative spectrophotometric determination of clotrimazole in single formulations and in combination with other drugs

First (D1) and second (D2) derivative spectrophotometric methods are presented for the determination of clotrimazole after its acid hydrolysis. Mixtures of clotrimazole with azidamfenicol and dexamethasone have been assayed using D2 measurement at 302 nm after acid hydrolysis for clotrimazole, D1 measurement at 288 nm for azidamfenicol, and D1 measurement at 436 nm after reaction with phenylhydrazinium sulfate for dexamethasone. Reproducible results with relative standard deviations of less than 2% are obtained. The proposed method has been successfully applied to the analysis of creams, topical solutions, and vaginal tablets.     

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%.     

Effect of volume of solution per cylinder on estimation of antibiotic potency in diffusion assay

The volume of antibiotic solutions in cylinders used for diffusion assays is assumed to have no significant effect on estimation of potency. The size of zones of inhibition from cylinders containing 0.10, 0.20, and 0.30 mL of sample solution was compared with zones of inhibition from cylinders containing 0.20 mL of standard solutions. For zinc bacitracin, chlortetracycline.HCl, oxytetracycline, lincomycin.HCl, monensin Na, neomycin sulfate, K penicillin, streptomycin sulfate, and tylosin, the percent recovery (95-102) was optimum when both standard and sample cylinders contained the same volume (0.20 mL/cylinder). At 0.30 mL/cylinder for sample and 0.20 mL for standard solutions, there was a positive bias in potency of about 50%. At 0.10 mL/cylinder, there was a negative bias of approximately 25% except for neomycin, monensin, and bacitracin. For these antibiotics, the bias was about -50%. For hygromycin B, variation in volume of solution per cylinder has little effect on assay results. Experiments on commercial feeds and premixes gave essentially the same results as for the standard solutions experiments.     

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 penicillin V potassium in tablets and powders for oral solution

A reverse-phase liquid chromatographic method is described for the assay of penicillin V potassium in tablets and powders for oral solution. Under isocratic conditions, the combined use of an octadecylsilane column, with a mobile phase composed of acetonitrile-methanol-0.01M monobasic potassium phosphate (21 + 4 + 75, v/v), and photometric detection at 225 nm, separated penicillin V potassium from excipients, related compounds, and degradation products. Sulfadimethoxine was used as an internal standard. Detector responses were linearly related to concentrations of penicillin V over the range 25-225 micrograms/mL (r = 0.99997). Standard addition recoveries ranged from 98.8 to 99.9% (mean 99.5%, n = 8) for tablets and from 97.9 to 101.6% (mean 99.8%, n = 8) for powders for oral solution. The liquid chromatographic assay results were compared with those obtained by the official iodometric titration method. The proposed method is simple, selective, stability-indicating, and free from interference by excipients and degradation products.     

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.     

Computerized gas-liquid chromatographic method for content uniformity analysis of dicyclomine hydrochloride capsules and tablets

An automated, computerized method is presented for the content uniformity determination of dicyclomine hydrochloride capsules and tablets, using up to 4 automatic sampler-equipped gas chromatographs interfaced with a minicomputer. A 3% OV-17 column is used with anthracene as an internal standard. Five sample injections are bracketed by standard mixtures containing about 90 and 110% of the labeled dicyclomine hydrochloride. Data are taken on-line simultaneously from each gas chromatograph and a computer-generated report is produced. Calculations use a BASIC program with linear fit of the 90 and 110% standard mixture. Individual tablet or capsule results are printed in milligrams and per cent declared, including summary calculations of average, high, low, standard deviation, and coefficient of variation. The GLC results are comparable (within 1%) to those obtained using the USP procedure.     

Anionenbestimmung in natürlichen wässrigen Lösungen: ein Methodenvergleich von ionenchromatographischen und Continuous-Flow-Verfahren

Analysis of anions in natural waters: a comparison of methods including ionchromatography and continuous-flow-technics Using waters from different compartments of forest ecosystems, standard solutions, moreover samples containing known internal standards, several analytical methods were tested for the comparability of nitrate, sulfate and chloride results in an inter-laboratory study. The analytical instruments were ion chromatographs with and without suppression as well as continuous-flow-analyzers. A cluster analysis showed a strong correlation between the obtained data and the analytical method used for nitrate, and a poorer relation for sulfate. Concerning nitrate-analysis, the IC-systems showed a better detection limit and a higher recovery of standards. Mean standard deviation among all tested analytical methods was calculated to be 15% for nitrate, 10% for sulfate and 14% for chloride. These results represent deviations as they may occur during laboratory routine analyses with a high amount of samples and the need for simultaneous determination of several anions. For the examined anions no significant correlation was obtained between the variation of the analytical results and the dissolved organic carbon concentrations of the samples.     

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.     

Liquid chromatographic determination of diazepam in tablets: collaborative study

A stability indicating liquid chromatographic method for the determination of diazepam in tablets was collaboratively studied by 6 laboratories. The method uses a C18 reverse phase column, a methanol-water mobile phase, p-tolualdehyde as the internal standard, and photometric detection at 254 nm. The collaborators were supplied with a synthetic tablet powder and 3 commercial tablet samples. The mean recovery of diazepam from the synthetic tablet powder was 100.2%. For all samples analyzed, the coefficient of variation was less than 1.5%. The method has been adopted official first action.     

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.     

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.     

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.     

Reverse phase liquid chromatographic determination of bisacodyl in dosage forms

A method is described for the determination of bisacodyl in enteric-coated tablets and suppositories by liquid chromatography (LC). The method will also determine the hydrolysis degradation products monoacetylbisacodyl and desacetylbisacodyl. The sample is dissolved in 2-propanol, and the extract is diluted with the mobile phase and injected into a liquid chromatograph fitted with a mu Bondapak C18 column and an ultraviolet detector set at 254 nm. The column is eluted with methanol-acetonitrile-0.01M citric acid (25 + 25 + 50). The pooled mean recovery value for bisacodyl from commercial enteric-coated tablets and suppositories was 99.7% with a pooled coefficient of variation (CV) of 0.72%. For content uniformity assays, the CVs were 0.7 and 1.0% for groups of 10 individual commercial suppositories and tablets, respectively. Differences between assay values by the LC and USP XX methods were 0.2% of declared for enteric-coated tablets (n = 5) and 1.0% of declared for suppositories (n = 2). The LC method can determine as little as 0.015 microgram of the monoacetyl or desacetyl degradation product.     

Bioavailability of iron from purple laver (Porphyra spp.) estimated in a rat hemoglobin regeneration bioassay

Laver belongs to the genius of Porphyra and is the most valuable seaweed in the aqua-culture industry. It contains higher iron than many other plant foods. The bioavailability of iron from laver was evaluated in a rat hemoglobin regeneration assay. Reagent-grade ferrous sulfate was used as the reference standard, and the relative biological value (RBV) for laver was expressed as a percentage of the response to ferrous sulfate. RBV was calculated by two methods: slope-ratio and ratio of hemoglobin regeneration efficiency, and both yielded RBV of 26 for laver. Amount of available iron from laver estimated from RBV was comparable to many iron-fortified foods.     

Capillary zone electrophoresis method for the determination of inorganic anions and formic acid in honey

A capillary zone electrophoresis method for the determination of inorganic anions and formic acid in honey samples was developed for the first time. The complete separation of chloride, nitrate, sulfate, phosphate, and formic acid was achieved with a simple electrolyte composed by 2 mM potassium dichromate as the carrier solution and background absorbance provider and 0.05 mM tetraethylenepentamine (TEPA) as electro-osmotic flow suppressor (pH 4.00). Injection was performed hydrostatically by elevating the sample at 10 cm for 10 s. The running voltage was -27 kV at 25 degrees C. Indirect UV absorption detection was achieved at 254 nm. The detection limit was in the range between 0.03 and 20 mg/kg, and the quantification limits ranged from 1.52 to 20.6 mg/kg. The calibration graphs were linear in the concentration range from the quantification limit to at least 2.5 g/kg for chloride, 0.25 g/kg for nitrate, 0.75 g/kg for sulfate, 1.50 g/kg for phosphate, and 0.75 g/kg for formic acid. Precision data in the honey samples analyzed showed repeatability and reproducibility relative standard deviations lower than 1.4 and 2.4% for migration time and lower than 1.8 and 4.3% for anion content, respectively. Recoveries of anions in honey samples analyzed ranged from 94.4 to 99.8%. Ten honey samples were analyzed to test the proposed method. Mean contents of 260.5, 3.93, 60.5, 139.4, and 209.3 mg/kg were found, respectively, for chloride, nitrate, sulfate, phosphate, and formic acid in analyzed honeys. These results agreed with literature data.