Liquid chromatographic methods for the determination of albuterol (salbutamol), albuterol sulphate and related compounds in drug raw materials, tablets and inhalers

Determination of albuterol sulfate and its related substances in albuterol sulfate inhalation solution, 0.5% by RP-HPLC

An isocratic reversed-phase high performance liquid chromatographic (RP-HPLC) method has been developed and validated for the determination of albuterol sulfate and six of its related substances in albuterol sulfate inhalation solution, 0.5% (w/v). The separation was achieved using a YMC phenyl column (250 mm x 4.6 mm ID, 5 microm fitted with a direct connect YMC phenyl guard column (20 mm x 4 mm ID) maintained at ambient conditions, and a mobile phase of 25 mM monobasic potassium phosphate (pH 3.0) and methanol (95:5, v/v). The mobile phase flow rate was 1.5 mL/min and the detection wavelength was 225 nm. Albuterol is quantitated versus an external standard. The method was capable of resolving six of the seven known albuterol-related substances. Bis-ether albuterol, a drug substance process related impurity, is retained on the column due to its different hydrophilic character. The related substances are determined by area percent. However, a correction factor of 1.6 is applied for the determination of albuterol aldehyde, a potential impurity and a degradation product, since its molar absorptivity is about 1.6 times that of albuterol. The limits of detection and quantitation for albuterol and six of its related substances ranged between 0.01 and 0.21% of the assay concentration of 0.3 mg/mL as albuterol base. The method was found to be linear for albuterol over the range of 50-150% of the active label claim. The method was also found to be linear for the six related substances over the range 0.05-0.5%. No interferences from the blank, placebo (formulation matrix), related substances or force-degraded placebo samples were observed for the determination of the active or the individual related substances. The method was found to be accurate, precise, linear, specific, sensitive, rugged, robust, and stability-indicating.

Sensitive detection of salbutamol using europium-enhanced fluorescence with trioctylphosphine oxide (TOPO) as coligand

In this work a simple and sensitive fluorimetric method for determination of salbutamol (4-[2-(tert-butylamino)-1-hydroxyethyl]-2-(hydroxymethyl) phenol) using an Eu enhanced signal was developed. The employed methodology is based on the formation of a ternary complex formed with Eu, salbutamol and trioctylphosphine oxide (TOPO). Intermolecular transfer of energy from the excited organic molecule to the lanthanide followed by lanthanide emission is responsible for excitation of the lanthanide ion in complex solutions and fluorescent enhancement. The luminescence properties of the ternary complex formed with TOPO and optimum formation conditions were investigated. The calibration curve is linear in the range between 6.92-180 microg l(-1) of salbutamol. The detection limit was 2.31 microg l(-1). Common excipients for these formulations were not found to interfere. A proposed method for the assay in commercial aerosols and nebulizer solutions containing salbutamol was applied with very good precision.

Formulation and evaluation of albuterol metered dose inhalers containing tetrafluoroethane (P134a), a non-CFC propellant

This study was undertaken to evaluate tetrafluoroethane (P134a) as a possible chlorofluorocarbon (CFC) replacement for albuterol metered dose inhaler (MDI) formulations. Preformulation studies using three conventional (oleic acid, sorbitan trioleate, lecithin) and a nonconventional (oleyl alcohol) surfactant indicated that P134a is a poor solvent for these surfactants. A slight improvement in the solubility of oleic acid and oleyl alcohol was observed by the addition of low concentrations of a nonconventional cosolvent diethyl ether (< or = 0.5% w/w). Formulation screening of the prepared albuterol formulations indicated that suspensions containing oleyl alcohol and diethyl ether had a slower rate of separation. Product performance of four albuterol formulations containing oleyl alcohol, diethyl ether, and P134a was evaluated and compared to a leading commercial formulation containing CFC propellants (Ventolin). Ventolin showed excellent agreement between the emitted dose and the expected dose but only a reasonable agreement was observed with one of the better P134a-containing formulations. P134a formulations showed higher internal pressure in comparison to the CFC formulation. The concentrations of the surfactant, drug, and cosolvent appeared to have a significant impact on the uniformity of the emitted dose. Determination of particle size using the time-of-flight and the laser diffraction analyzer revealed that P134a formulations had equal or smaller particle size than the formulation containing CFC. However, the CFC formulation showed a higher respirable fraction than the P134a formulation when measured by the two inertial impaction methods. The observed particle size distribution of the formulation appeared to depend on the measuring method used.

Metered dose inhalers III: Metaproterenol sulphate; particle size distribution and dose uniformity

Three American products and one Canadian product were examined for content uniformity and particle size distribution. The results showed that not all products performed equally well. Some of the products exhibited high sprays early in the canister lifetime and all products demonstrated loss of prime. The particle size distributions were determined using the Andersen cascade impactor (USP Induction Port) and the fine particle fraction was determined using the twin impinger. The results showed that three of the four products had similar particle size distribution profiles. Both the Andersen cascade impactor and the twin impinger yielded the same trends in the amount of drug substance delivered to the fine particle fraction.

Voltammetric study of salbutamol and application to its determination in a tablet dosage form and dissolution profiles for the dosage form

The oxidative voltammetric behaviour of salbutamol at a glassy carbon electrode surface has been studied using cyclic voltammetry and differential pulse voltammetry. Oxidation of the drug was effected in a single irreversible, adsorption-controlled step in phosphate buffer. The process was found to be dependent on the ionic strength and the pH of the supporting electrolyte. The response was evaluated with respect to accumulation time, scan rate and other variables. Using differential pulse voltammetry following electrochemical pretreatment of the electrode surface, the drug yielded a well-defined voltammetric response in phosphate buffer, pH 5.0, at +0.75 V (vs SCE). This process could be used to determine salbutamol concentrations in the range 8 x 10(-7) M to 8 x 10(-5) M with a detection limit of 2 x 10(-7) M. The method was applied, without any interferences from the excipients, to the determination of the drug in a tablet dosage form and in drug dissolution studies. The absolute recovery for salbutamol was greater than 95% at the concentration levels studied, and reproducible voltammetric signals were obtained with a relative standard deviation of 2.4% for n = 7 at a concentration level of 8 x 10(-5) M.