Rapid on-line extraction and quantification of escitalopram from urine using sol-gel columns and mass spectrometric detection

Abstract

A fast and easy way to quantify escitalopram in urine has been developed. A capillary with a silica based monolithic bed inside is used to extract escitalopram from urine and the for mass spectrometry detrimental matrix is washed away by applied pressure. The analyte is eluted by a solution containing organic modifier and directly electrosprayed into a time-of-flight mass spectrometer, ESI-TOF-MS. This method makes it possible to load large volumes of sample onto the column and preconcentrate escitalopram on-line before detection. Standard addition of escitalopram to the urine sample gave a linear calibration curve (R(2)=0.988). The analyzed sample was found to contain an escitalopram concentration of 0.62 ng/ml, well in line with earlier publications. The calculated LOD was 10 pg/ml and LOQ was 34 pg/ml as compared to earlier reports with a LLOQ of 1 ng/ml. The intra day variation of the escitalopram peak area is less than 6.3%.