A sensitive LC/MS/MS method using silica column and aqueous–organic mobile phase for the analysis of loratadine and descarboethoxy-loratadine in human plasma

Abstract

A sensitive method using liquid chromatography with tandem mass spectrometric detection (LC/MS/MS) was developed and validated for the simultaneous analysis of antihistamine drug loratadine (LOR) and its active metabolite descarboethoxy-loratadine (DCL) in human plasma. Deuterated analytes, i.e. LOR-d 3 and DCL-d 3 were used as the internal standards (I.S.). Analytes were extracted from alkalized human plasma by liquid/liquid extraction using hexane. The extract was evaporated to dryness under nitrogen, reconstituted with 0.1% (v/v) of trifluoroacetic acid (TFA) in acetonitrile, and injected onto a 50×3.0 mm I.D. 5 μm, silica column with an aqueous–organic mobile phase consisted of acetonitrile, water, and TFA (90:10:0.1, v/v/v). The chromatographic run time was 3.0 min per injection and flow rate was 0.5 ml/min. The retention time was 1.2 and 2.0 min for LOR and DCL, respectively. The tandem mass spectrometric detection was by monitoring singly charged precursor→product ion transitions: 383→337 ( m/ z) for LOR, 311→259 ( m/ z) for DCL, 388→342 ( m/ z) for LOR-d 3, and 316→262 ( m/ z) for DCL-d 3. The low limit of quantitation (LLOQ) was 10 pg/ml for LOR and 25 pg/ml for DCL. The inter-day precision of the quality control (QC) samples was 3.5–9.4% relative standard deviation (R.S.D.). The inter-day accuracy of the QC samples was 99.0–107.9% of the nominal values.