Wojciech Chrzanowski

This article presents an analysis of available literature data on metrological parameters of the amperometric gas sensors containing ionic liquids as an electrolyte. Four mechanism types of signal generation in amperometric sensors with ionic liquid are described. Moreover, this article describes the influence of selected physico-chemical properties of the ionic liquids on the metrological parameters of these sensors. Some metrological parameters are also compared for amperometric sensors with GDE and SPE electrodes and with ionic liquids for selected analytes.

Preparation of samples for analysis, first of all isolation and/or enrichment of analytes, is becoming a key stage of each analytical procedure including determination of trace components. Effectiveness of this stage, i.e., analyte enrichment, removal of interferents and change of the original sample matrix, depends both on the chosen extraction technique and utilized materials and reagents. Though liquid-liquid extraction is still widely used in analytical practice, it seems that solid phase extraction (SPE) techniques are gaining the dominating position. In these techniques, solid sorbents and pseudo-liquid materials are used as the analytes retaining media. Although a variety of sorbents and stationary phases usable in analytical procedures is known, due to an even larger assortment of analytes present in samples differing in matrix composition, the need for search for new types of sorbents exists. In this field, the sol-gel technique offers good opportunities of producing new sorption materials. Using this technique, one can obtain fit-for-purpose materials. Although sol-gel technique had been known for many years, its first applications in analytical chemistry were described in early 1990s. Since then, an increasing number of papers discussing the preparation of new sorbents using this technique and their applications is a proof positive of great opportunities offered by the technique.

The majority of techniques currently applied for isolation/enrichment of organic analytes from gaseous and liquid samples are based on extraction and utilize solid absorbents or organic solvents. While techniques fulfill their tasks, they reveal some important inconveniences. In the case of liquid-liquid extraction, the problem lies in consumption of considerable quantities of organic solvents, which is both environmentally unfavorable and increases the costs of the analytical procedure (storage and utilization costs of these solvents). In the case of techniques in which adsorbents are used, problems may arise when polar or high molecular mass compounds have to be analyzed, or when phenomena of incomplete desorption or artifacts formation (like decomposition of some sample components) may occur. Thus, a number of techniques with reduced solvent consumption (Liquid Phase Microextraction) or practically solventless techniques (e.g., absorption in liquid-like polymers) have been introduced over the past two decades. These techniques show many favorable characteristics; nevertheless, they also have their own limitations. In this paper, a review of the wide spectrum of sample preparation techniques with special attention paid to environment-friendly techniques is presented. The techniques are described from the point of view of analyte isolation mechanisms, and both theoretical and technical aspects are discussed.