Unambiguous characterization of analytical markers in complex, seized opiate samples using an enhanced ion mobility trace detector-mass spectrometer.

Ion mobility spectroscopy (IMS)-based trace-compound detectors (TCDs) are powerful and widely implemented tools for the detection of illicit substances. They combine high sensitivity, reproducibility, rapid analysis time, and resistance to dirt with an acceptable false alarm rate. The analytical specificity of TCD-IMS instruments for a given analyte depends strongly on a detailed knowledge of the ion chemistry involved, as well as the ability to translate this knowledge into field-robust analytical methods. In this work, we introduce an enhanced hybrid TCD-IMS/mass spectrometer (TCD-IMS/MS) that combines the strengths of ion-mobility-based target compound detection with unambiguous identification by tandem MS. Building on earlier efforts along these lines (Kozole et al., Anal. Chem. 2011, 83, 8596-8603), the current instrument is capable of positive and negative-mode analyses with tightly controlled gating between the IMS and MS modules and direct measurement of ion mobility profiles. We demonstrate the unique capabilities of this instrument using four samples of opium seized by the Canada Border Services Agency (CBSA), consisting of a mixture of opioid alkaloids and other naturally occurring compounds typically found in these samples. Although many analytical methods have been developed for analyzing naturally occurring opiates, this is the first detailed ion mobility study on seized opium samples. This work demonstrates all available analytical modes for the new IMS-MS system including "single-gate", "dual-gate", MS/MS, and precursor ion scan methods. Using a combination of these modes, we unambiguously identify all signals in the IMS spectra, including previously uncharacterized minor peaks arising from compounds that are common in raw opium.

Design considerations for high speed quantitative mass spectrometry with MALDI ionization.

A MALDI ion source on a triple quadrupole mass spectrometer constructed for the purpose of obtaining high speed quantitative measurements on drugs and other low molecular weight compounds is described. Particular attention is given to the ion generation and transport phenomena that affect analysis speed, throughput, and practical instrument robustness. In this regard parameters that affect desorption speed, beam spreading, ion flight times, sensitivity, signal-to-noise, ion fragmentation, sample carry-over, and instrument contamination are examined and experimental results are provided. MALDI and electrospray sensitivity is compared, to provide a practical frame of reference.