Evaluation of a differential mobility spectrometer/miniature mass spectrometer system

Abstract

A planar differential mobility spectrometer (DMS) was coupled to a Mini 10 handheld rectilinear ion trap (RIT) mass spectrometer (MS) (total weight 10 kg), and the performance of the instrument was evaluated using illicit drug analysis. Coupling of DMS (which requires a continuous flow of drift gas) with a miniature MS (which operates best using sample introduction via a discontinuous atmospheric pressure interface, DAPI), was achieved with auxiliary pumping using a 5 L/min miniature diaphragm sample pump placed between the two devices. On-line ion mobility filtering showed to be advantageous in reducing the background chemical noise in the analysis of the psychotropic drug diazepam in urine using nanoelectrospray ionization. The combination of a miniature mass spectrometer with simple and rapid gas-phase ion separation by DMS allowed the characteristic fragmentation pattern of diazepam to be distinguished in a simple urine extract at lower limits of detection (50 ng/mL) than that achieved without DMS (200 ng/mL). The additional separation power of DMS facilitated the identification of two drugs of similar molecular weight, morphine (average MW ϭ 285.34) and diazepam (average MW ϭ 284.70), using a miniature mass spectrometer capable of unit resolution. The similarity in the proton affinities of these two compounds resulted in some cross-interference in the MS data due to facile ionization of the neutral form of the compound even when the ionic form had been separated by

Differential mobility spectrometry/mass spectrometry history, theory, design optimization, simulations, and applications

“…History are examples in this area. Coupling of DMS to a field‐portable miniature mass spectrometer to serve as a simple pre‐separation device has been explored (Tadjimukhamedov et al, ). It offers the opportunity to increase the selectivity of the mass spectrometer without the cost and complexity of adding additional pumps, either liquid pumps in the case of LC or additional vacuum pumps if one were to consider a gain in the extra selectivity from tandem mass spectrometry.…”

Radiation metabolomics and its potential in biodosimetry

“…We will list two examples. In Tadjimukhamedov et al (2010) from Prof. R. Graham Cooks lab at Purdue U., a standard Sionex DMS interface has been fitted to their mini-10.5 iontrap mass spectrometer (10 kg weight). Excellent results have been obtained for separation of morphine from diazepam (differing by 1 mass unit), and for measurements from biological samples.…”

Differential mobility spectrometry with nanospray ion source as a compact detector for small organics and inorganics

“…The capillary or skimmer interface can be used effectively only for offline disposable emitter applications, but this method is the most economical in sample usage and among the highest in ionization efficiency. A simple interface of the latter type was used in recent work in the Cooks group at Purdue on interfacing DMS to a small ion trap mass spectrometer with discontinuous sample introduction (Tadjimukhamedov et al 2010); it is likely that a reaction chamber or curtain gas interface could improve the performance and flexibility of DMS interfaces to this type of device, as it does for independent DMS detection.…”