Hand-Held Diode Laser for On-Site Analysis Using Transportable Mass Spectrometry

Area of Science:

• Analytical Chemistry
• Forensic Science

Background:

• Rapid screening of illicit substances in solid matrices is crucial for forensic and security applications.
• Existing methods often require complex instrumentation and sample preparation, limiting on-site applicability.

Purpose of the Study:

• To develop a simplified, portable, and cost-effective hand-held laser diode thermal desorption electrospray ionization mass spectrometry (LDTD-ESI-MS) method.
• To demonstrate its capability for rapid screening and identification of organic compounds in solid samples.

Main Methods:

• Utilized a 940 nm surgical laser diode for thermal desorption of solid samples.
• Investigated the use of a black polytetrafluoroethylene substrate to enhance analyte desorption.
• Optimized electrospray ionization (ESI) parameters, including solvent composition (methanol/water, 50:50 v/v) and flow rate (50 μL h⁻¹).
• Coupled the hand-held LDTD-ESI system with time-of-flight MS and a transportable single quadrupole MS.

Main Results:

• Successfully demonstrated the enhanced desorption of analytes using the specialized substrate.
• Achieved optimal sensitivity with specific solvent and flow rate conditions.
• Identified selective androgen receptor modulators (SARMs) in pills and powders using accurate mass measurements.
• Confirmed SARM identification via in-source fragmentation patterns with a portable single quadrupole MS.

Conclusions:

• The developed simplified LDTD-ESI-MS method is effective for rapid screening of organic compounds in solid samples.
• The portable and cost-effective nature of the system holds promise for future on-site testing applications.
• This technique offers a viable alternative for field analysis of illicit substances.