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: 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. · 3.66 Impact Factor
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ABSTRACT: A simple and sensitive headspace (HS) solid phase microextraction (SPME) coupled with ion mobility spectrometry (IMS) method is presented for analysis of urea in dialysis human serum samples. A dodecylbenzenesulfonate-doped polypyrrole coating was used as a fiber for SPME. The HS-SPME-IMS method exhibits good repeatability (relative standard deviation of 3 % or less), simplicity, and good sensitivity. The influence of various analytical parameters such as pH, ionic strength, extraction time and temperature was investigated and the parameters were optimized. The calibration graph was linear in the range from 5 to 50 μg mL(-1), and the detection limit was 2 μg mL(-1). The method was applied successfully for determination of urea in human serum and with acceptable recovery (more than 98 %). Finally, a standard addition calibration method was applied to the HS-SPME-IMS method for the analysis of human serum samples before and at the end of dialysis. The proposed method appears to be suitable for the analysis of urea in serum samples as it is not time-consuming and requires only small quantities of the sample without any derivatization process.Analytical and Bioanalytical Chemistry 04/2013; · 3.66 Impact Factor
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ABSTRACT: The general principles and the technical implementations of traditional time-of-flight ion mobility spectrometers and analyzers with field dependent mobilities were reviewed in our last article in this journal. Recent advances in instrumentation and new applications since 2006 are highlighted in this review. In addition to traditional applications as military chemical-agent detector, ion mobility techniques became more and more popular for different purposes. While ion mobility spectrometry was solely used as vapor sensor in the past decades, further developments in ionization techniques (especially electrospray ionization) permit now the routine use for the analysis of liquid samples. The coupling of ion mobility spectrometry with selective sample preparation techniques such as molecular imprinted polymers, the coupling with chromatographic techniques, the use of dopants and the application of selective ionization sources led to an expanded number of applications in industrial and environmental analysis with complex sample matrices due to an improved selectivity in comparison with traditional stand-alone spectrometers. Furthermore, new developments in hyphenated techniques, especially ion mobility—mass spectrometry couplings, resulted in an increased number of new applications for the analysis of biomolecules, pharmaceutical samples and in clinical diagnostics.Applied Spectroscopy Reviews 01/2011; 46:472-521. · 2.92 Impact Factor