A discharge adaptor interface for use in liquid chromatography/mass spectrometry

Area of Science:

• Analytical Chemistry
• Mass Spectrometry

Background:

• Electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) are common mass spectrometry techniques.
• Adapting ionization sources can improve analytical performance for specific applications.

Purpose of the Study:

• To develop and evaluate a novel discharge adaptor (DA) for converting ESI into APCI.
• To assess the DA interface's performance for analyzing generic drugs compared to commercial interfaces.

Main Methods:

• A discharge adaptor (DA) was constructed using a metal casing and platinum (Pt) wire needle, attached to an ESI probe.
• Six generic drugs were analyzed using the DA interface, ESI, and two commercial APCI interfaces.
• Analyte response, ion formation (radical anions, adducts), and matrix effects were compared.

Main Results:

• The DA interface produced more intense radical anions ([M]˙⁻) and fewer sodium adduct ions ([M + Na]⁺) than ESI.
• Molecular ion detection with DA was comparable to commercial APCI.
• The DA interface demonstrated higher sensitivity for tested drugs than a commercial APCI interface.
• The DA interface exhibited good linearity (r² > 0.99), ruggedness, and plasma matrix tolerance.

Conclusions:

• The developed discharge adaptor effectively converts ESI to APCI, offering advantages in ion formation and sensitivity.
• This DA interface is a viable alternative for generic drug analysis, particularly in complex matrices like human plasma.