Electrical field-stimulated liquid-phase microextraction for trace analysis of pyridine and its derivatives in cigarette extract

Electromembrane extraction of polar substances - Status and perspectives

In this article, the scientific literature on electromembrane extraction (EME) of polar substances (log P < 2) is reviewed. EME is an extraction technique based on electrokinetic migration of analyte ions from an aqueous sample, across an organic supported liquid membrane (SLM), and into an aqueous acceptor solution. Because extraction is based on voltage-assisted partitioning, EME is fundamentally suitable for extraction of polar and ionizable substances that are challenging in many other extraction techniques. The article provides an exhaustive overview of papers on EME of polar substances. From this, different strategies to improve the mass transfer of polar substances are reviewed and critically discussed. These strategies include different SLM chemistries, modification of supporting membranes, sorbent additives, aqueous solution chemistry, and voltage/current related strategies. Finally, the future applicability of EME for polar substances is discussed. We expect EME in the coming years to be developed towards both very selective targeted analysis, as well as untargeted analysis of polar substances in biomedical applications such as metabolomics and peptidomics.

Pyridine Detection Using Supramolecular Organic Frameworks Incorporating Cucurbit[10]uril

A physical impregnation method is presented in this study, providing a facile approach to encapsulating functional guest molecules (GMs) into robust crystalline supramolecular organic frameworks incorporating cucurbit[10]uril (Q[10]-SOF). As Q[10]-SOF has high evaporated pyridine affinity under normal atmospheric pressure, pyridine molecules in this method were successfully encapsulated into the nanospace formed by GMs and Q[10]-SOF while retaining their crystal framework, morphology, and high stability. GMs@Q[10]-SOF solid materials were found to respond to pyridine, being suitable to be used as solid sensors. Notably, Q[10]-SOF loading with pyrene exhibited a unique response to pyridine along with dramatic fluorescence quenching; loading with dansyl chloride exhibited a unique response to pyridine along with significant fluorescence enhancement, having a quick response within 60 s. Our findings represent a critical advancement in the design of pyridine detection and adsorption for commercial gas identification and sensing.

Development of an LC-MS method for determination of nitrogen-containing heterocycles using mixed-mode liquid chromatography

N-containing heterocycles (NCHs) are largely used as precursors for pharmaceuticals and can enter the environment. Some NCHs have been shown to be toxic, persistent, and very mobile in the environment. Thus, they have received increasing attention in the past years. However, the analysis of these polar compounds in environmental samples is still a challenge for liquid chromatography. This paper investigates the use of mixed-mode liquid chromatography (MMLC), which has reversed-phase and ion exchange characteristics for measurements of NCHs in water. NCHs with low pK_a (i.e., < 2.5) display mainly reversed-phase interactions (neutral species) with the stationary phase and those with higher pK_a (i.e., > 5) interact by a mixture of reversed-phase/ion exchange/HILIC mechanism. It was also shown that the presented method performs well in the quantification of the majority of the selected NCHs in surface water with MDLs between 3 and 6 μg/L, a low matrix effect and recoveries in the range of 77–96% except for pyridazine exhibiting 32% were achieved. The method was successfully employed to follow the degradation of NCHs in ozonation.