Validation of an on-line solid-phase extraction method coupled to liquid chromatography–tandem mass spectrometry detection for the determination of Indacaterol in human serum

Indacaterol has been recently approved in Europe for the treatment of chronic obstructive pulmonary disease (COPD). In the present study, we have developed and validated a rapid and sensitive on-line solid phase extraction (SPE) method coupled to liquid chromatography–tandem mass spectrometry (LC–MS/MS) detection for the determination of Indacaterol in human serum. The sample preparation involves the serum dilution with a 0.2% acetic acid solution prior to the on-line SPE on a mixed-mode cationic (MCX) polymer based sorbent. The samples were then eluted on a reversed phase column with a mobile phase made of acidified water and methanol and detection was performed by MS using electrospay ionization in positive mode. The analysis time between 2 samples was 7.0 min. Standard curves were linear over the range of 10.0 pg/mL (LLOQ) to 1000 pg/mL with correlation coefficient (r2) greater than 0.990. The method specificity was demonstrated in six different batches of human serum. Intra-run and inter-run precision and accuracy within ±20% (at the LLOQ) and ±15% (other levels) were achieved during a 3-run validation for quality control samples (QCs). The stability at room temperature (38 h) was determined and reported. In addition, the comparison between an off-line SPE procedure and our method gave equivalent results. The results of the present work demonstrated that our on-line SPE–LC–MS/MS method is rapid, sensitive, specific and could be applied to the quantitative analysis of Indacaterol in human serum samples. Our method effectively eliminated the tedious conditioning and rinsing steps associated with conventional off-line SPE and reduced the analysis time. The on-line SPE approach appears attractive for supporting the analysis of several hundreds of clinical samples.