We report the use of a chiral Cu(II) 3D metal-organic framework (MOF) based on the tripeptide Gly-l-His-Gly (GHG) for the enantioselective separation of metamphetamine and ephedrine. Monte Carlo simulations suggest that chiral recognition is linked to preferential binding of one of the enantiomers as a result of either stronger or additional H-bonds with the framework that lead to energetically more stable diastereomeric adducts. Solid-phase extraction of a racemic mixture by using Cu(GHG) as the extractive phase permits isolating >50% of the (+)-ephedrine enantiomer as target compound in only 4 min. To our knowledge, this represents the first example of a MOF capable of separating chiral polar drugs.

A procedure for supporting silver nanoparticles (AgNPs) on nylon is proposed. Besides, the membrane has been developed as a solid-phase colorimetric plasmonic sensor for volatile sulfide compounds (VSCs) like H 2 S, CH 3 SH, and (CH 3 ) 2 S. AgNP behavior in the membrane has been studied by UV−vis diffuse reflectance spectrometry, Raman spectrometry, High-resolution transmission electron microscopy (HR-TEM), and Scanning electron microscopy (SEM). The sensor responded by changing its color from yellow in absence of VSCs to several orange/brown colors in the function of VSC concentration as occurs in solution; an increase in the hydrodynamic diameter, estimated by both asymmetrical flow field-flow fractionation (AF4) coupled on line to Dynamic light scattering (DLS) detector and batch DLS, is achieved when sulfide is added to the citrate-capped AgNPs. Diffuse reflectance spectrometry and processed digital images obtained with a smartphone have been used as measurements and several transformations for quantitation are proposed; a linear concentration range of hydrogen sulfide from 150 to 1000 ppbv and a detection limit (LOD) of 45 ppbv were achieved, measuring after 10 min of the sensor exposition to the hydrogen sulfide atmosphere (2 L) for humidity percentages between 50 and 96% and room temperature. Satisfactory results in terms of precision (<10%) and selectivity were obtained. The new sensor reported was stable, sensitive, inexpensive, disposable, safe, and user-friendly. Furthermore, it has successfully been applied to determine VSCs expressed as hydrogen sulfide in breath samples (2 L and 250 mL) as a proof of concept. The limit of detection can be improved by increasing the exposition time, if necessary.

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In this study, polydimethylsiloxane (PDMS)-coated capillary columns (TRB-5 and TRB-35), both unmodified and functionalized with single-wall carbon nanotubes (SWCNTs) or multiwall carbon nanotubes (MWCNTs), have been tested and compared for the extraction of amphetamine (AMP), methamphetamine (MET) and ephedrine (EPE) by in-tube solid-phase microextraction (IT-SPME). Prior to their extraction, the analytes were derivatized with the fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC). For separation and detection capillary chromatography with fluorimetric detection has been used. The presence of carbon nanotubes in the extractive coatings enhanced the extraction efficiencies and also significantly improved the chromatographic profiles, thus resulting in a reliable option for the analysis of these drugs. As an example of application, a new method is proposed for the analysis of the tested amphetamines in oral fluid using a TRB-35 capillary column functionalized with MWCNTs. The proposed conditions provided suitable selectivity and reproducibility (CV ď 6%, n = 3) at low µg/mL levels, and limits of detection of 0.5-0.8 µg/mL.