Rapid detection of explosive vapors by thermal desorption atmospheric pressure photoionization differential mobility analysis tandem mass spectrometry.

Rationale: The increased frequency in the number of international terror threats has led to a corresponding increase in demand for fast, sensitive and reliable screening methods suitable for the detection of airborne explosive vapors. We demonstrate herein a workflow suitable for the determination of nitrogen-based explosives at the picogram level in just minutes.

Methods: A method is described that combines Thermal Desorption (TD) sample introduction with Differential Mobility Analysis (DMA) Tandem Mass Spectrometry (MS/MS), enabling a sensitive and accurate workflow suitable for the rapid detection of trace nitroaromatic, nitroester and nitramine explosive vapors.

Field-Free Atmospheric Pressure Photoionization-Liquid Chromatography-Mass Spectrometry for the Analysis of Steroids within Complex Biological Matrices.

A comparison study is presented in which the relative performance of a new orthogonal geometry field-free atmospheric pressure photoionization (FF-APPI) source was evaluated against both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) for the analysis of a small panel of clinically relevant steroids, spiked within various complex biological matrices. Critical performance factors like sensitivity and susceptibility to matrix effects were assessed using a simple, isocratic, high-throughput LC-MS workflow. FF-APPI was found to provide the best performance in terms of both sensitivity and detection limit for all of the steroids included in the survey.

Development of a next-generation field-free atmospheric pressure photoionization source for liquid chromatography/mass spectrometry.

Rationale: Atmospheric pressure photoionization (APPI) is considered a candidate ionization method suitable for a broad range of liquid chromatography/mass spectrometry (LC/MS) applications. Questions remain, however, regarding the ultimate potential of the technique. We propose that sensitivity and thus detection limits may be restricted by geometric source design, limiting widespread acceptance of the technique.

A dopant introduction device for atmospheric pressure photoionization with liquid chromatography/mass spectrometry.

This technical note describes in detail the fabrication, operation and characterization of a pneumatically driven dopant introduction device, with a solvent reservoir capacity of 300 mL. Dopant flow rates and stability for this device are governed by the simple regulation of gas pressure rather than the progression of a stepper motor and syringe diameter, as is the case for typical infusion pumps. The device has the potential to provide days or even weeks of continuous, uninterrupted dopant flow at rates commonly adopted for atmospheric pressure photoionization (APPI) experiments without the need to replenish the dopant supply.