Chiral HPLC analysis of formoterol stereoisomers and thermodynamic study of their interconversion in aqueous pharmaceutical formulations.

A chiral HPLC method was validated and successfully applied for the determination of formoterol stereoisomers and their inversion products in an aqueous matrix stored at 5-70 degrees C up to 3 weeks. Analysis was performed on a Chiral-AGP column (100 x 4-mm, 5-microm) using a variable mixture of mobile phase A (50-mM sodium phosphate buffer, pH 7.0) and B (10% v/v IPA) at a flow rate of 1.3 ml min(-1), and UV detection at 242 nm. All four formoterol stereoisomers were adequately resolved with acceptable detection and quantitation limits varying from 0.01-0.04 microg/ml and 0.04-0.1 microg/ml, respectively. The method showed acceptable accuracy (> or = 88%), precision (RSD < or = 8.5%) and good linearity (r(2) > or = 0.9999) over the concentration range investigated. While interconversion at 5+/-3 degrees C and 25+/-2 degrees C/60% RH +/-5% RH was too low to be determined accurately within the study period, chiral inversion of formoterol stereoisomers measured at high temperatures followed the first order rate kinetics and occurred at a single chiral center, resulting in the reversible formation of diastereoisomers, (R,R)<-->(S,R) and (S,S)<-->(R,S). No enantiomerization or diastereomerization occurred. There was no significant difference in inversion of the active components in racemic (R,R/S,S)-formoterol fumarate and the single isomer (R,R)-arformoterol tartrate drug formulations, and both drugs are expected to maintain their stereochemical integrity throughout the proposed shelf-life at the recommended storage condition (5+/-3 degrees C).

Chromatographic and Spectral Analysis of Two Main Extractable Compounds Present in Aqueous Extracts of Laminated Aluminum Foil Used for Protecting LDPE-Filled Drug Vials.

Laminated aluminum foils are increasingly being used to protect drug products packaged in semipermeable containers (e.g., low-density polyethylene (LDPE)) from degradation and/or evaporation. The direct contact of such materials with primary packaging containers may potentially lead to adulteration of the drug product by extractable or leachable compounds present in the closure system. In this paper, we described a simple and reliable HPLC method for analysis of an aqueous extract of laminated aluminum foil overwrap used for packaging LDPE vials filled with aqueous pharmaceutical formulations. By means of combined HPLC-UV, GC/MS, LC/MS/MS, and NMR spectroscopy, the two major compounds detected in the aqueous extracts of the representative commercial overwraps were identified as cyclic oligomers with molecular weights of 452 and 472 and are possibly formed from poly-condensation of the adhesive components, namely, isophthalic acid, adipic acid, and diethylene glycol. Lower molecular weight compounds that might be associated with the "building blocks" of these compounds were not detected in the aqueous extracts.

Compatibility and aerosol characteristics of formoterol fumarate mixed with other nebulizing solutions.

BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) are often given admixtures of nebulizable drugs to minimize the time of administration in treatment regimens. OBJECTIVE: To evaluate the physicochemical compatibility and aerodynamic characteristics of formoterol fumarate 20 microg/2 mL when mixed or sequentially nebulized with budesonide inhalation suspension 0.5 mg/2 mL, ipratropium bromide 0.5 mg/2.5 mL, cromolyn sodium 20 mg/2 mL, or acetylcysteine 10% (100 mg/mL). METHODS: The admixtures were prepared in triplicate and analyzed for physicochemical compatibility at 0, 15, 30, and 60 minutes after mixing at room temperature. Physical compatibility was determined by visual examination and measurements of pH, osmolality, and turbidity. Chemical stability was evaluated using compendial or in-house-validated high-performance liquid chromatography (HPLC) assay methods. The aerodynamic characteristics of the admixtures or sequentially nebulized drugs were determined from aerosols generated from a Pari LC Plus nebulizer, using an 8-stage cascade impactor followed by HPLC analysis of the deposited drug. RESULTS: The admixtures remained clear, colorless solutions with no precipitation, except for cloudiness observed in the formoterol/budesonide combination due to budesonide suspension. The pH, osmolality, and turbidity for all admixtures were within the initial values (< or = 3%), and there were no significant changes (< or = 2%) in potency of the active components throughout the 1-hour study period. Due to increased drug volume or reconcentration in the nebulizer cup, the respirable fraction/delivered dose increased significantly (p < 0.05) for the mixed or sequentially nebulized drug. However, the fine particle fraction (FPF), mass median aerodynamic diameter, and geometric standard deviation generally remained unchanged for all admixtures, with the exception of FPF for the formoterol/budesonide combination. CONCLUSIONS: Our results indicate that admixtures of formoterol with budesonide, ipratropium, cromolyn, or acetylcysteine are physically and chemically compatible. However, admixing or sequential nebulization significantly increased the amount of drug delivered compared with single drug nebulization. The clinical implications of the in vitro data in patients with COPD have not been determined.

SPME-GC determination of potential volatile organic leachables in aqueous-based pharmaceutical formulations packaged in overwrapped LDPE vials.

A direct liquid immersion solid-phase microextraction-gas chromatographic (SPME-GC) method was developed and validated for the determination of 11 potential volatile organic compounds that may leach from preprinted foil laminate overwrap into aqueous pharmaceutical formulations filled in low-density polyethylene (LDPE) vials. The target compounds namely, ethanol, acetone, isopropyl alcohol, ethyl acetate, 2-butanone, n-heptane, isopropyl acetate, n-propyl acetate, toluene, diacetone alcohol and 1-propoxy-2-propanol, were suitably extracted from aqueous sample solutions by SPME using a 100-microm PDMS fiber, desorbed inside the GC inlet port, and analyzed using a J&W Scientific DB-1701 (86% polydimethylsiloxane/14% cyanopropylphenyl, 30 m x 0.53 mm i.d., 1.5-microm film thickness) capillary column with FID detection. The variables affecting the SPME absorption and desorption conditions were optimized and discussed. The average recoveries for all analytes varied from about 97.9 to 116.7% with the exception of n-heptane and toluene where the mean recoveries ranged from about 73.6 to 100.0% presumably due to their poor solubility in the aqueous sample matrix. The standard curves for all compounds were linear over the concentration range investigated with coefficient of correlations, r(2)> or =0.98. The detection and quantitation limits ranged from approximately 0.6 ng/ml to 1.7 microg/ml and 5 ng/ml to 4.2 microg/ml, respectively, and the intra- and inter-day precision was considered adequate (R.S.D.< or =16%) for low-level determination of the target analytes in the sample matrix. The method was successfully applied for determination of the target compounds from preprinted foil laminate overwrap in selected aqueous-based pharmaceutical formulations.

Optimization and validation of a gas chromatographic method for analysis of (RS,SR)-diastereoisomeric impurity in formoterol fumarate.

A gas chromatographic method for the determination of formoterol (RS,SR)-diastereoisomer, a process impurity, in formoterol fumarate was optimized and validated. The method involves silylation of formoterol fumarate with N-(trimethylsilyl)imidazole in N,N-dimethylformamide at room temperature in an autosampler vial to produce trimethylsilyl derivatives of the enantiomers prior to GC analysis. The optimized silylation and separation conditions, respectively, produced good yield and resolution of the analytes. The method appears to be convenient and fast, and permits accurate determination of (RS,SR)-diastereoisomer in formoterol fumarate with adequate precision (R.S.D. = 3.0%, n = 9) and sensitivity (DL < 0.01%) when compared with the official liquid chromatographic limit test method of Pharmeuropa. The method was successfully applied to quality control of commercial formoterol fumarate for their (RS,SR)-diastereoisomer contents.

Validation of a RP-HPLC method for the assay of formoterol and its related substances in formoterol fumarate dihydrate drug substance.

A stability-indicating reversed-phase high performance liquid chromatographic (HPLC) method has been developed and validated for the assay of formoterol fumarate and the related substances, namely, formoterol fumarate desformyl and formoterol fumarate acetamide analogs, in the active pharmaceutical ingredient. The separation was achieved by isocratic elution using an Alltech Alltima C18 (150 x 4.6 mm) column, a mobile phase consisting of ammonium acetate (50 mM; pH 5.0)-ethanol (65:35, v/v), a flow rate of 1.0 ml/min and UV detection at 242 nm. The detection and quantitation limits were 0.03 and 08 microg/ml, respectively, while the linear range of detection was between 0.03 and 255 microg/ml. Comparative determinations of formoterol fumarate in three lots of bulk drugs using the proposed HPLC method and the standard potentiometric titration method of pharmacopoeia show that both methods are equivalent for pure drug substance assay. However, the HPLC method allowed the separation and quantitation of the impurities not achievable with the official methods in the bulk drugs. This study shows that the proposed method is accurate, linear, and sensitive as stability indicating assay method for formoterol fumarate in the bulk drug.

Diisocyanate emission from a paint product: a preliminary analysis.

Exposure of workers to diisocyanates in the polyurethane foam manufacturing industry is well documented. However, very little quantitative data have been published on exposure to diisocyanates from the use of paints and coatings. The purpose of this study was to evaluate emission of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate (2,6-TDI), and isophorone diisocyanate from a commercially available two-stage concrete coating and sealant. A laboratory model of an outdoor deck coating process was developed and diisocyanate concentrations determined by derivatization with 1-(2-methoxyphenol)-piperazine and subsequent high performance liquid chromatographic analysis with UV detection. The detection limit for 2,4-toluene diisocyanate and 2,6-toluene diisocyanate urea derivatives was 0.6 microg TDI/gm wet product, and 0.54 microg IPDI/gm wet product for the isophorone diisocyanate urea derivative. No 2,4-toluene diisocyanate or isophorone diisocyanate was detected in the mixed product. A maximum mean 2,6-TDI emission rate of 0.32 microg of 2,6-TDI/gram of wet product applied/hour was observed for the 1-hour sampling time, 0.38 microg of 2,6-TDI/gram of wet product applied/hour was observed for the 5-hour sampling time, and 0.02 micrpg of 2,6-TDI/gram of wet product applied/hour was observed for the 15-hour sampling time. The decrease in rate of 2,6-TDI emission over the 15-hour period indicates that emission of 2,6-TDI is virtually complete after 5 hours. These emission rates should allow industrial hygienists to calculate exposures to isocyanates emitted from at least one curing sealant.