Portable nanoelectrospray periodic focusing differential ion mobility spectrometer for the rapid screening of illicit drugs

The spread of illicit drug abuse is a major public health issue in most countries. Law enforcement personnel on drug abuse need a tool to confiscate and block illicit trade of illicit drug or monitoring drug impaired driving. Therefore, affordable and portable instruments for illegal drug detection are in critical need. In this study, we developed a portable periodic focusing differential ion mobility (PFDMA) spectrometer for in situ motoring illicit drugs. The device comprised an ionization source, drift cell, air blower, voltage divider board and electronic control board. In general, an ion mobility spectrometer (IMS) is able to work with air as a buffer gas at atmospheric pressure. There is no need to install heavy mechanical and/or expensive turbo molecular pumps. For our instrument, a small air blower was used to generate laminar counterflow. The whole device is compact with a size of 150 × 200 × 280 (WLH, mm) and a weight of 2.5 kg. In general, most commercial drift tube ion mobility spectrometers use radioactive or corona discharge ionization. In this work, we utilized a different approach to analyze liquid samples. The device was equipped with a nanoelectrospray ionization source. To avoid memory effects, a disposable micropipette was used. An aluminum-coated tip with an ID of 2 μm was applied with a high voltage to achieve nanoelectrospray ionization without sheath gas. Advantages of PFDMA are to isomer separation and better sensitivity compared to other types of ion mobility spectrometers. Most illicit drugs could be detected by this homemade device. The detection limit is lower than the level allowed by law. With our device, the detection limit of methamphetamine is ∼10 ng/ml.