Cocaine determination in saliva; using molecularly imprinted polymers as selectivity enhancers in ion mobility spectrometry

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  • Published: Mar 19, 2018
  • Author: Rafael Lucena
  • Channels: Electrophoresis / Gas Chromatography / Laboratory Informatics / Detectors / HPLC / Ion Chromatography / Sample Preparation / Proteomics & Genomics / Raman / Chemometrics & Informatics / Atomic / Infrared Spectroscopy / UV/Vis Spectroscopy / Proteomics / NMR Knowledge Base / MRI Spectroscopy / X-ray Spectrometry / Base Peak

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Drug abuse is a problem of public concern worldwide and the detection and determination of these substances in biological fluids is of interest in different fields. The development of rapid methods, able to process many samples while providing appropriate selectivity and sensitivity levels, is required. In a recent article, accepted for publication in Journal of Chromatography A, researchers from the University of Valencia (Spain) have developed a simple method which uses ion mobility spectrometry (IMS) as instrumental technique. IMS is a powerful technique that separates ions in the gas phase by their charge, size, and shape. Its selectivity, which is limited for the resolution of complex matrixes, is usually complemented by a previous chromatographic separation or coupling it to mass spectrometry.

Chromatographic separations, however, increases the time of analysis reducing the sample throughput. In this approach, molecularly imprinted polymers (MIPs) are used as selectivity enhancers eliminating the need for chromatography. The final eluate is thermally desorbed before its introduction in the IMS. This workflow, based on the direct coupling of microextraction with instrumental techniques, is a promising research line. The use of MS in this context that will be commented on this blog shortly is exciting.

MIPs are synthesized around Fe3O4 nanoparticles (NPs) providing a magnetic composite that can be dispersed into the sample and quickly recovered by using an external magnet. The magnetic MIPs are synthesized in two different ways:

  1. The NPs are no covalently coated by PEG, and the resulting material is introduced in the polymerization media. In this case, the simple embedding of the NPs in the polymeric network is intended. The resulting composite is shown in Figure 1A
  2. The NPs are covalently coated with γ-MPS, thus introducing vinyl groups on the surface that can participate in the polymerization. In this case, the NPs are covalently bonded (copolymerized) to the polymer. The resulting material is shown in Figure 1B


SEM pictures of the composites obtained with a) PEG-modified NPs and b) MPS-modified NPs


The discussion of the synthesis is rich and interested readers on the topic can find it in the original article.

Concerning the results, the magnetic MIPs provides a rapid (only 10 min are required), efficient (extraction recoveries close to 100 %) and selective (the non-imprinted material offers a negligible extraction) isolation of cocaine from saliva samples. The sensitivity (in the low μg/L range) and the precision (relative standard deviations smaller than 2.5%) are also remarkable. The accuracy of the proposal is successfully evaluated not only with spiked samples but also comparing the results with other reference methods.


We would like to thank the authors of the article for providing the picture of the magnetic MIPs.


  1. Magnetic molecularly imprinted polymers for the selective determination of cocaine by ion mobility spectrometry.

Blog post by: Rafael Lucena



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