Direct analysis of illicit drugs in urine by cellulose fiber spray ionization mass spectrometry (CFSI-MS)

Abstract

The detection of illicit drugs and their metabolites in human biological samples remains a critical demand in analytical toxicology. The implementation of fast, simple, and selective methods can significantly enhance the efficiency of forensic analyses. In this study, a method was developed for the simultaneous analysis of illicit drugs using an LTQ XL mass spectrometer operated in Selected Ion Monitoring (SIM) and Selected Reaction Monitoring (SRM) modes, coupled with an ambient ionization technique known as Cellulose Fiber Spray Ionization–Mass Spectrometry (CFSI-MS). A fractional factorial design revealed that, in the CFSI(+)LTQ MS mode, voltage and distance were the most influential variables for ionization efficiency. In the CFSI(−)LTQ MS mode, all three tested parameters—substrate mass, voltage, and distance—showed significant effects. Using a central composite design, the optimal experimental conditions were determined: for positively ionizing compounds, the optimal values were 3.367 mm for distance, 5 kV for voltage, and 13.67 mg for substrate mass; for negatively ionizing compounds, the optimal conditions were 6.633 mm, 2 kV, and 13.67 mg, respectively. The findings indicate that the proposed method holds strong potential for the direct and simultaneous analysis of various illicit drugs in biological matrices, with a particular focus on urine.