Aspirin--a national survey II: Determination of salicylic acid in bulk aspirin and aspirin formulations by high-pressure liquid chromatography using a fluorescence detector

Comparison of three new spectrophotometric methods for simultaneous determination of aspirin and salicylic acid in tablets without separation of pharmaceutical excipients

Simultaneous analysis of aspirin (ASA) and salicylic acid (SA) in pharmaceutical tablet preparations was performed by two multicomponent UV-spectrophotometric methods utilizing principal component regression and classical least square algorithm. Additionally, an assay procedure based on second-derivative spectroscopy was developed. The analysis was performed in turbid solutions without separation of interfering excipients. The range, as determined by the second-derivative methods, was 0.2 to 103.2 micrograms/mL for ASA and 0.07 to 44.5 micrograms/mL for SA. Sensitivity for determination of SA was 0.004% of ASA content for the second-derivative method and 0.2% of ASA content for both multicomponent methods. The methods were applied to laboratory mixtures and commercial tablet formulations containing ASA and SA. The advantage of the second-derivative method in determining small amounts of SA in commercial tablet preparations is shown in comparison with a conventional HPLC method. All UV-spectrophotometric methods are rapid, accurate, and reproducible.

Liquid chromatographic methods validation for pharmaceutical products

The current status of validation in LC methods for the analysis of pharmaceuticals has been reviewed with special reference to compatibility testing methods. Validation data were provided in terms of method linearity, accuracy, precision, system suitability, specificity, use of alternate methods, injection order, application of peak height or area measurements and of internal or external standards.

Automated flow injection determination of salicylates using Trinder reaction for clinical analysis, assays and dissolution studies of formulations

An automated flow-injection technique is described for salicylate (25-250 or 80-800 mg l(-1)), salicylamide (30-300 mg l(-1)), methylsalicylate (100-1000 mg l(-1)) and acetylsalicylic acid (after alkaline hydrolysis), based on their colour reaction with iron (III) in weak acid medium. The method was evaluated for the determination of salicylate in serum, the assay of the drugs in commercial formulations and automated dissolution studies of drug tablets. There were decreased interferences because of the short reaction time. The precision was good with RSD less than 1% in all cases. Recoveries of salicylate from spiked sera (100-1000 mg l(-1)) varied from 96.4-102.5% (mean 99.3%), and from spiked sample solutions of acetylsalicylic acid, 97.8-103.0% (mean 99.6%). The results of the analysis of commercial drug formulations obtained with the proposed method agreed well with the current USP and BP procedures, with differences of 0.4-1.5% (mean 0.8%). High measurement rates of 180 or 95 per hour were achieved using manifolds without and with predilution respectively.

Determination of aspirin by pre-column transacetylation reaction of 3-aminophenol and reversed-phase high-performance liquid chromatography: simultaneous determination of aspirin, acetaminophen, and caffeine

The accuracy of the measurement of aspirin by high-performance liquid chromatography (HPLC) is reduced by its hydrolysis into salicylic and acetic acids during sample preparation. The ready and quantitative transacetylation of 3-aminophenol by aspirin, giving 3-hydroxyacetanilide (which is stable), has been utilized as a pre-column reaction for the determination of aspirin either alone or in the presence of acetaminophen and caffeine by reversed-phase HPLC.

Quantitative determination by high-performance liquid chromatography of acetylsalicylic acid and related substances in tablets

High-performance liquid chromatography on a Zorbax C8 7-micron column (25 cm X 0.46 cm I.D.) with methanol-water-1 M phosphoric acid (59:36:5) as the mobile phase has been used for the analysis of several naturally aged batches of fourteen brands of acetylsalicyclic acid tablets. The extraction solvent is methanol, containing 2% v/v of formic acid. Salicylic acid is the main impurity. Acetylsalicylsalicylic acid is the second most important impurity, and the corresponding salicylsalicylic acid is rarely present. Buffered or dispersible tablets contain relatively more of the latter two impurities and eventually also the corresponding higher oligomers. Acetylsalicylic anhydride is always a minor impurity. Comparison is made with classical spectrophotometric methods, which are observed to be selective for salicylic acid.

Simultaneous high-performance liquid chromatography assay of acetylsalicylic acid and salicylic acid in film-coated aspirin tablets

A reversed-phase high-performance liquid chromatography (HPLC) method has been developed for the simultaneous assay of acetylsalicylic acid (I) and salicylic acid (II) in film-coated aspirin tablets. As little as 0.1% II (relative to I) can be quantitatively determined. Using a 5-microns octadecylsilane column with water-acetonitrile-phosphoric acid (76:24:0.5) as the mobile phase enabled the chromatographic separation to be completed in 4 min. Due to the slow rate of decomposition of I to II in the extraction solvent, acetonitrile-methanol-phosphoric acid (92:8:0.5), the analysis of many samples was routinely performed by means of automated HPLC equipment. Other compounds (non-aspirin salicylates, caffeine and acetaminophen) were also separated by the chromatographic system.

A simple fluorometric method for the determination of salicylic acid in aluminium acetylsalicylate

A simple, rapid fluorometric method for the determination of salicylic acid in aluminium acetylsalicylate is presented. The method is based on the dissolution of aluminium acetylsalicylate in sodium fluoride-hydrochloric acid solution, filtration and dilution with buffer solution pH = 4 followed by the fluorometric determination of the liberated salicylic acid. The method was applied successfully to the determination of salicylic acid in aluminium acetylsalicylate tablets.

Stabilized normal-phase high-performance liquid chromatographic analysis of aspirin and salicylic acid in solid pharmaceutical dosage forms

A simultaneous analysis of aspirin and nonaspirin salicylates in solid pharmaceutical dosage forms is described. Two separate extraction procedures are employed, one for plain aspirin tablets and one for tablets containing aspirin plus buffers or antacids. The analyses of the extracted samples are accomplished by a stabilized normal-phase high-performance liquid chromatographic (HPLC) procedure. Prepared samples and standards are stable for up to 24 h, and the methodology is suitable for an automated HPLC system.

Spectrofluorometric determination of acetylsalicylic acid, salicylamide, and salicyclic acid as an impurity in pharmaceutical preparations

Spectrofluorometry, either direct or in combination with a separation technique, provides a sensitive and accurate method for the determination of certain extent fluorescent analgesic drugs and the determination of impurities in many combination preparations. A critical examination of the UV spectra of common analgesics and related compounds indicates that the fluorescence inner filter effect should be negligible below 10(-5) M and that selective excitation and emission wavelengths should minimize interference from other fluorescent species. Fluorometric procedures are presented for the determination of salicylamide, acetylsalicylic acid, and salicylic acid, as an impurity, in preparations containing salicylamide, acetylsalicylic acid, acetaminophen, caffeine, and phenacetin as major constituents. Inner filtering is the limiting factor only for the direct and indirect determination of salicylamide and the direct determination of acetylsalicylic acid. Results of fluorometric determinations compare favorably with other reference methods. Salicylic acid is determined in the 10(-7) M concentration range after separation from salicylamide, acetaminophen, and caffeine.

Simultaneous determination of aspirin and salicylic acid in bulk aspirin and in plain, buffered, and enteric-coated tablets by high-pressure liquid chromatography with UV and fluorescence detectors

A quantitative high-pressure liquid chromatographic method that uses a reversed-phase column coupled to UV and fluorescence detectors was developed to determine aspirin and salicylic acid in bulk aspirin and in plain, buffered, and enteric-coated tablets. The aspirin was dissolved, filtered, and injected into the chromatograph. The UV absorbance of aspirin was determined at 254 nm, and the fluorescence of salicylic acid was measured at 425 nm. Excipients and impurities did not interfere. Recoveries of 100% were obtained for aspirin and salicylic acid from simulated tablet formulations. Results obtained by the USP XIX procedure and the proposed method were compared. The coefficient of variation for the aspirin analysis was 0.59%; for salicylic acid, it was 1.69%. The rate of hydrolysis of aspirin to salicylic acid in the solvents used was < 0.05%/hr.

Aspirin--a national survey III: Determination of impurities in bulk aspirin and aspirin formulations by high-pressure liquid chromatography and spectrophotometry

A quantitative high-pressure liquid chromatographic method, using a reversed-phase column and an aqueous acetic acid-methanol solution as the mobile phase, was employed for the determination of O-acetyl-O-salicylsalicylic acid and O-salicylsalicylic acid in pharmaceutical aspirin preparations. The aspirin was dissolved, filtered, and injected into the chromatograph. The absorbance of the impurities was measured at 254 nm. Acetylsalicylic anhydridge was determined by a spectrophotometric method. The aspirin was dissolved in pH 11.3 buffer and extracted with benzene. An aliquot of the benzene was evaporated, and the residue was dissolved in alpha-benzamidocinnamate-pyridine reagent. The acetylsalicylic anhydride was measured using the difference between the absorbance at 362 and 372 nm. Possible interference of aspirin with the procedure is discussed. Thirty-four bulk aspirin and 172 tablet formulations were examined. Results for O-acetyl-O-salicylsalicylic acid, O-salicylsalicylic acid and acetylsalicylic anhydride are given.

Aspirin--a national survey I: Semiautomated determination of aspirin in bulk and tablet formulations and salicyclic acid in tablet formulations

A semiautomated assay to determine aspirin (acetylsalicylic acid) in aspirin tablets, powdered tablet composites, and pure drug substances is presented. The sample was dissolved in alcoholic buffer, diluted, and extracted with chloroform. The absorbance of the chloroform solution was read at 280 nm. Results obtained by the USP XIX and semiautomated methods are compared. The proposed method is accurate and precise, and common excipients do not interfere. Recoveries of 100% were obtained. A semiautomated assay for salicylic acid in aspirin tablets also is presented. The sample was dissolved in alcoholic buffer, ferric nitrate was added, and the absorbance of the resulting purple color was read at 532 nm. The method is suitable as a rapid screening procedure for testing the salicylic acid content of aspirin products. Results obtained by the USP XIX and semiautomated methods are compared, and the accuracy and precision of the proposed method are given. One hundred seventy tablet samples and 34 bulk drug substances were analyzed for aspirin and salicylic acid content. Approximately 5% of the tablet samples failed to meet the USP XIX limits for aspirin content, and 10% failed to meet the limits for salicylic acid.