Quantitative determination of cytisine by laser desorption/ionization mass spectrometry methods

Quantitative determination of the alkaloid cytisine was performed using laser desorption/ionization mass spectrometry with two ionization approaches: surface-assisted LDI employing a gold nanoparticle-enhanced target (AuNPET SALDI MS) and conventional matrix-assisted laser desorption/ionization (MALDI MS) using 2,5-dihydroxybenzoic acid (DHB) as the organic matrix. In both techniques cytisine was detected predominantly as the protonated molecular ion [C11H14N2O+H]⁺, accompanied by minor alkali-metal adducts. The AuNPET-based SALDI approach generated spectra with very low chemical background, limited mainly to gold cluster signals, which improved spectral clarity in the low-mass region. The detectable concentration range for cytisine extended from 0.25 to 100 μg/mL for SALDI MS, whereas MALDI MS enabled reliable detection only in the range of 2.5–100 μg/mL. The limits of detection and quantification obtained for SALDI MS were 0.169 μg/mL and 0.175 μg/mL, respectively, compared with 1.39 μg/mL and 2.32 μg/mL for MALDI MS. These results demonstrate that AuNPET-based SALDI MS provides improved sensitivity and constitutes a rapid alternative approach for cytisine determination.