Enhancement in sample collection for the detection of MDMA using a novel planar SPME (PSPME) device coupled to ion mobility spectrometry (IMS).
ABSTRACT Trace detection of illicit drugs challenges the scientific community to develop improved sensitivity and selectivity in sampling and detection techniques. Ion mobility spectrometry (IMS) is one of the prominent trace detectors for illicit drugs and explosives, mostly due to its portability, high sensitivity and fast analysis. Current sampling methods for IMS rely on wiping suspected surfaces or withdrawing air through filters to collect particulates. These methods depend greatly on the particulates being bound onto surfaces or having sufficient vapour pressure to be airborne. Many of these compounds are not readily available in the headspace due to their low vapour pressure. This research presents a novel SPME device for enhanced air sampling and shows the use of optimized IMS by genetic algorithms to target volatile markers and/or odour signatures of illicit substances. The sampling method was based on unique static samplers, planar substrates coated with sol-gel polydimethyl siloxane (PDMS) nanoparticles, also known as planar solid-phase microextraction (PSPME). Due to its surface chemistry, high surface area and capacity, PSPME provides significant increases in sensitivity over conventional fibre SPME. The results show a 50-400 times increase in the detection capacity for piperonal, the odour signature of 3,4-methylenedioxymethamphetamine (MDMA). The PSPME-IMS technique was able to detect 600 ng of piperonal in a 30 s extraction from a quart-sized can containing 5 MDMA tablets, while detection using fibre SPME-IMS was not attainable. In a blind study of six cases suspected to contain varying amounts of MDMA in the tablets, PSPME-IMS successfully detected five positive cases and also produced no false positives or false negatives. One positive case had minimal amounts of MDMA resulting in a false negative response for fibre SPME-IMS.
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ABSTRACT: A simple and fast method for the detection of aldehydes by headspace solid-phase microextraction (HS-SPME) based on nanostructure polypyrrole film coupled to ion mobility spectrometery (IMS) is described. The detection of aldehydes (pentanal, hexanal and heptanal) has been successfully accomplished using in situ chemical derivatization with dibutylamine as the derivatization reagent and IMS. The simultaneous and rapid detection of aldehydes is important, since elevated level of aldehydes is considered as the biomarker of different diseases. The highlight of this method was that it involved an amine nucleophilic addition reaction (which was often considered as Mannich reaction) in gas phase for enhancing IMS sensitivity of aldehydes. Dibutylamine was used as the derivatization reagent driven into the cell by using a syringe pump. The calibration graphs were linear in the range of 2.0–50.0 μg mL−1 with R 2 ≥ 0.99 in aqueous solutions and limit of detections were determined ≤ 1.8 μg mL−1. The RSD% values of the aldehydes determination was ≤ 8 %. Here we have demonstrated that other amine types (butylamine and tributylamine) can derivatize aldehydes and significantly improve the IMS sensitivity of tagged analytes. However, IMS spectrum is complicated by presence of the different product ions in the process.International Journal for Ion Mobility Spectrometry 09/2013; 16(3). DOI:10.1007/s12127-013-0119-3
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ABSTRACT: A preconcentration device that targets the volatile chemical signatures associated with illicit drugs and explosives (high and low) has been designed to fit in the inlet of an ion mobility spectrometer (IMS). This is the first reporting of a fast and sensitive method for dynamic sampling of large volumes of air using planar solid phase microextraction (PSPME) incorporating a high surface area for absorption of analytes onto a sol-gel polydimethylsiloxane (PDMS) coating for direct thermal desorption into an IMS. This device affords high extraction efficiencies due to strong retention properties at ambient temperature, resulting in the detection of analyte concentrations in the parts per trillion range when as low as 3.5 L of air are sampled over the course of 10 s (absolute mass detection of less than a nanogram). Dynamic PSPME was used to sample the headspace over the following: 3,4-methylenedioxymethamphetamine (MDMA) tablets resulting in the detection of 12-40 ng of piperonal, high explosives (Pentolite) resulting in the detection of 0.6 ng of 2,4,6-trinitrotoluene (TNT), and low explosives (several smokeless powders) resulting in the detection of 26-35 ng of 2,4-dinitrotoluene (2,4-DNT) and 11-74 ng of diphenylamine (DPA).Analytical Chemistry 03/2010; 82(7):2826-35. DOI:10.1021/ac902785y
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ABSTRACT: Solid-phase microextraction (SPME) is a widely used sampling technique that has been proved to enable efficient extraction of a broad range of analytes. Generally, SPME achieves non-exhaustive extraction, and therefore the analyte mass transfer distribution in the sampled multiphase system should be considered while developing a calibration method. Here, a new method, aimed at quantifying the extracted analytes without the need to consider their mass distribution, is proposed. This method relies on the generation of mass response curves by loading a known analyte mass onto the absorbent phase of a SPME fiber, and then conducting analysis by the preferred technique. Precise and accurate deposition of analyte over the restricted dimension of a fiber is demonstrated for the first time by utilizing a drop-on-demand microdrop printer. This system enables direct, non-contact deposition of micron-sized drops containing negligible solvent volumes (<1 nL), on the center of the extraction phase of the fiber which enables immediate analysis. Printed fiber response curves were determined herein, with three model compounds of different volatility-2,4-dinitrotoluene (2,4-DNT), diphenylamine (DPA), and 1,3 diethyl-1,3-diphenylurea (ethyl centralite, EC), using two analytical techniques, gas chromatography-mass spectrometry (GC-MS) and ion mobility spectrometry (IMS). Quantification of the absolute amounts extracted by headspace SPME yielded comparable results between the two methods of analysis with only less than 10% variation for 2,4-DNT and EC and less than 30% for DPA. In comparison, quantification by the traditional liquid injection/spike response curves determined by each technique led to mass estimates that were significantly greater by hundreds of percent.Analytical and Bioanalytical Chemistry 09/2010; 398(2):1049-60. DOI:10.1007/s00216-010-3983-2