Trends in sample preparation and separation methods for the analysis of very polar and ionic compounds in environmental water and biota samples

• Published in: Analytical and bioanalytical chemistry 2020-09, Vol.412 (24), p.6149-6165
• Main Authors: Knoll, Sarah, Rösch, Tobias, Huhn, Carolin
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Automation; Biochemistry; Biota; Capillary electrophoresis; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Chromatography; Chromatography, Liquid - methods; Desalination; Electrophoresis; Electrophoresis, Capillary - methods; Female Role Models in Analytical Chemistry; Food additives; Food Science; Gas chromatography; Household chemicals; Hydrophobic and Hydrophilic Interactions; Instrumentation; Ionization; Ions; Laboratory Medicine; Limit of Detection; Liquid chromatography; Liquid Phase Microextraction - methods; Liquid phases; Mass spectrometry; Mass Spectrometry - methods; Mass spectroscopy; Micropollutants; Miniaturization; Monitoring; Monitoring/Environmental Analysis; Neomycin; Pesticides; Polarity; Review; Sample preparation; Scientific imaging; Selectivity; Separation; Solid Phase Extraction - methods; Spectroscopy; Supercritical fluids; Surface water; Trends; Water; Water - chemistry; Water analysis; Water Pollutants, Chemical - analysis; Water sampling
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-020-02811-5

Recent years showed a boost in knowledge about the presence and fate of micropollutants in the environment. Instrumental and methodological developments mainly in liquid chromatography coupled to mass spectrometry hold a large share in this success story. These techniques soon complemented gas chromatography and enabled the analysis of more polar compounds including pesticides but also household chemicals, food additives, and pharmaceuticals often present as traces in surface waters. In parallel, sample preparation techniques evolved to extract and enrich these compounds from biota and water samples. This review article looks at very polar and ionic compounds using the criterion log P  ≤ 1. Considering about 240 compounds, we show that (simulated) log D values are often even lower than the corresponding log P values due to ionization of the compounds at our reference pH of 7.4. High polarity and charge are still challenging characteristics in the analysis of micropollutants and these compounds are hardly covered in current monitoring strategies of water samples. The situation is even more challenging in biota analysis given the large number of matrix constituents with similar properties. Currently, a large number of sample preparation and separation approaches are developed to meet the challenges of the analysis of very polar and ionic compounds. In addition to reviewing them, we discuss some trends: for sample preparation, preconcentration and purification efforts by SPE will continue, possibly using upcoming mixed-mode stationary phases and mixed beds in order to increase comprehensiveness in monitoring applications. For biota analysis, miniaturization and parallelization are aspects of future research. For ionic or ionizable compounds, we see electromembrane extraction as a method of choice with a high potential to increase throughput by automation. For separation, predominantly coupled to mass spectrometry, hydrophilic interaction liquid chromatography applications will increase as the polarity range ideally complements reversed phase liquid chromatography, and instrumentation and expertise are available in most laboratories. Two-dimensional applications have not yet reached maturity in liquid-phase separations to be applied in higher throughput. Possibly, the development and commercial availability of mixed-mode stationary phases make 2D applications obsolete in semi-targeted applications. An interesting alternative will enter routine analysis soon: s