DIRECT ANALYSIS IN REAL TIME/TIME-OF-FLIGHT MASS SPECTROMETRY: INVESTIGATIONS ON PARAMETERS FOR THE COUPLING WITH LIQUID-PHASE SAMPLE INTRODUCTION TECHNIQUES

Abstract

□ Studies for the evaluation of a lab made liquid jet interface designed for the coupling of direct analysis in real time (DART) time-of-flight mass spectrometry (TOF-MS) with liquid-phase sample introduction systems such as flow injection analysis (FIA) or high performance liquid chromatography (HPLC) have been performed. Thereby a substantial influence of parameters like surface/volume ratio (determined by the inner diameter of the capillary employed) of the liquid jet as well as the composition of the eluent (with respect to the concentration of electrolyte and organic solvent) on signal intensities could be detected. Comparison of the developed interface with other more common interface types (based on electrospray ionization, atmospheric pressure chemical ionization, and atmospheric pressure photoionization) was carried out on the example of a test mixture containing four parabens spiked into biological fluid samples. DART ionization proved superior when employed in combination with FIA as it was less affected by matrix effects resulting in ionization suppression. On the other hand if at least partial separation of the matrix/analytes was performed by using short chromatographic columns, the other ionization techniques turned out to be the better choice primarily due to their increased sensitivity.

Keywords:

• biological fluids
• direct analysis in real time
• flow injection analysis
• high performance liquid chromatography
• parabens
• time-of-flight mass spectrometry

ACKNOWLEDGMENT

We are grateful to JEOL Europe BV for the loan of the AccuTOF DART instrument.

Notes

++detection possible; ion suppression/enhancement < 10%;.

+detection possible; ion suppression/enhancement < 20%;.

-detection possible; ion suppression/enhancement < 50%;.

−no detection possible.