High-performance liquid chromatographic determination of phenylephrine and tropicamide in human aqueous humor

Validated Liquid Chromatography-Tandem Mass Spectroscopic Method for Simultaneous Determination of Certain Drugs Used in Cataract Surgery in Rabbit Aqueous Humor

A sensitive, selective, accurate and precise ultra-high performance liquid chromatography-Tandem mass spectrometry (MS/MS) method was developed and validated for the simultaneous determination of drugs used as eye drops in cataract surgery in aqueous humor. Cataract surgery requires a powerful mydriatic eye drops combination such as cyclopentolate hydrochloride and phenylephrine hydrochloride to dilate the pupil and facilitate eye lens replacement and also requires strong fluoroquinolone antibiotic such as lomefloxacin hydrochloride. The method was performed with positive ion electrospray ionization and the analytes were quantified and monitored on a triple quadrupole mass spectrometer using multiple reaction monitoring scanning mode. Liquid-liquid extraction was used for the purification and preconcentration of analytes from rabbit aqueous humor matrix. Chromatographic elution was performed using an Phenomenex Luna® C18 (150 mm × 2.1 mm, 1.6 μm) column and moxifloxacin hydrochloride as internal standard with a mobile phase consisting of methanol:water:formic acid (70:29:1, by volume) at flow rate of 0.2 mL/min. Satisfactory results regarding linearity, recovery, stability, accuracy and precision of the analytes were obtained. Full validation of the procedure was performed according to the US Food and Drug Administration guidance for industry: bioanalytical method validation and European Medicines Agency (EMA) guideline on bioanalytical method validation.

Mydriatics release from solid and semi-solid ophthalmic formulations using different in vitro methods

The aim of the present paper was the development of semi-solid (hydrogels) and solid (film) ophthalmic formulations for the controlled release of two mydriatics: phenylephrine and tropicamide. The formulations - based on polyvinylalcohol and hyaluronic acid - were characterized, and release studies were performed with three different in vitro set-ups, i.e. Franz-type diffusion cell, vial method and inclined plane; for comparison, a solution and a commercial insert, both clinically used to induce mydriasis, were evaluated. Both gels and film allowed for a controlled release of drugs, appearing a useful alternative for mydriatics administration. However, the release kinetic was significantly influenced by the method used, highlighting the need for optimization and standardization of in vitro models for the evaluation of drug release from ophthalmic dosage forms.

Quantitative estimation of trimazolin hydrochloride in pharmaceutical preparation by RP-HPLC method

A sensitive and selective RP-HPLC method was developed and validated for the quantitative determination of trimazolin hydrochloride in nasal drops formulations. The mobile phase composition was water-acetonitrile (50:50, v/v) and the UV detection was carried out at 270 nm. Linearity range in the concentration range of 10 to 110 ?g cm-3. The method was tested and validated for various parameters according to ICH guidelines. The detection and quantization limits were found to be 1.45 and 4.8 ?g cm-3, respectively. The results demonstrated that the procedure for estimation of trimazolin hydrochloride in nasal drops formulations was accurate, precise and reproducible.

Evaluation of volatile ion-pair reagents for the liquid chromatography–mass spectrometry analysis of polar compounds and its application to the determination of methadone in human plasma

A liquid chromatography method using volatile ion-pairing reagents and tandem mass spectrometry was developed to obviate observed matrix effect for ionizable polar compounds. The present study investigated the addition of volatile ion-pair reagents to the reconstitution solution instead of the mobile phase to enhance the efficiency of chromatographic separation and minimize the sensitivity loss due to the formation of ion-pairs. The volatile ion-pair reagents used were perfluorinated carboxylic acids with n-alkyl chains: heptafluorobutanoic acid (HFBA), nonafluoropentanoic acid (NFPA), tridecafluoroheptanoic acid (TDFHA) and pentadecafluorooctanoic acid (PDFOA). The model analytes evaluated were N-methylnicotinamide (MNA) chloride, N-methyl 2-pyridone 5-carboxamide (2PY) and phenylephrine. The effects of alkyl chain length and the concentrations of the ion-pair reagents on the retention of analytes were studied, as well as the effect of pH on the retention of phenylephrine. The volatile ion-pair reagents in the reconstitution solution showed significant effect on the retention of the ionizable polar compounds, and the sensitivity of detection was improved for plasma samples through decreasing the matrix effect. This methodology was successfully applied to establish a quantitative assay for the polar drug substance methadone in human plasma with a concentration range from 0.1 to 50 ng/mL. Ion-pair reagents not only shifted the retention time but also reduced the carry-over peak for methadone.

Determination of tropicamide in pharmaceutical formulations using high-performance liquid chromatography

An isocratic, reversed-phase liquid chromatographic method was developed for determination of tropicamide using atropine as an internal standard in a pharmaceutical dosage form. Tropicamide and atropine sulfate were separated using a microBondapak ODS (C18) column by isocratic elution of mobile phase with flow rate of 2.0 ml/min. The mobile phase composition was methanol-50 mM phosphate buffer (pH 4; 30:70, v/v). The eluate was monitored at 257 nm with detector range setting fixed at 0.01 AUFS. Under these conditions, the retention times were 4.81 min for atropine and 11.89 min for tropicamide. The standard calibration curve was linear over a sample concentration range from 2 to 300 microg/ml, with limit of detection of 0.15 microg/ml. The assay linearity was good (typically r2 = 0.9992) and the standard curves were linear in the detection range. The precision of the method (expressed by relative standard deviation) and the accuracy (mean error in percent) were <5% for both intra- and inter-day assays. Recovery at 80-120% of labeled claim ranged from 98.4 to 100.7% for tropicamide. The proposed method was satisfactorily applied to the determination of tropicamide in pharmaceutical preparation and stability indicating studies.