Adam Kloskowski

Understanding solid-phase microextraction: key factors influencing the extraction process and trends in improving the technique.

Analytical chemists are faced with the daunting challenges of accurately monitoring the state of the environment and the processes taking place in it and of determining an enormous range of analytes often present in trace and ultratrace amounts in sample matrixes with complex or variable compositions. Further challenges are presented by the need to introduce new methodologies into current analytical practice and equipment to comply with the principles of sustainable development and green chemistry. Highest among these principles is the elimination or at least the substantial reduction of the quantities of reagents consumed (especially organic solvents and toxic compounds), solid and liquid wastes produced, and vapors and gases emitted. In analytical chemistry these principles are implemented above all by the utilization of ever more sensitive and automated instruments and of monitoring equipment which allows many analytes to be determined in a single analytical run, by the wide application of direct analytical techniques, operating in situ, and by the introduction of additional isolation and/or preconcentration steps prior to the final determination.

Perspectives on the replacement of harmful organic solvents in analytical methodologies: a framework toward the implementation of a generation of eco-friendly alternatives

Volatile organic solvents derived from non-renewable fossil feedstocks are commonplace in analytical laboratories. In spite of their convenient performance in countless unit operations, their environmental, health and safety issues represent a major area of concern. The progressive replacement of organic solvents obtained from fossil resources by eco-friendly alternatives would involve remarkable advances within the framework of green analytical chemistry, while avoiding future uncertainties regarding forthcoming regulations. This perspective tackles the problem of organic solvent use in analytical methodologies, providing relevant information for solvent selection and identifying a range of solvents derived from natural and/or renewable resources, namely bio-based molecular solvents, ionic liquids composed wholly of biomaterials and natural deep eutectic mixtures that could potentially be exploited toward advanced, more benign, analytical methodologies. In addition, physicochemical properties are provided, and a number of challenging aspects to be considered in the implementation of eco-friendly alternatives are evaluated.

Progress in Development of Molecularly Imprinted Polymers as Sorbents for Sample Preparation

Sample preparation has been one of the most often investigated steps in analytical procedures. These investigations are focused on problems such as isolation of analytes from the sample matrix, matrix simplification, analyte enrichment to the level above the detection limit of the instrumentation used, and the removal of interfering species to improve the final determination. Techniques based on solid (adsorption) and pseudo liquid (absorption) media play an important role in sample preparation because of their universal applicability, possibility of automation and low cost of implementation. The use of these techniques reduces or even completely eliminates organic solvents from analytical procedures. Solid phase extraction (SPE) and its special mode, solid phase micro-extraction (SPME), are among most commonly used sample preparation techniques. The search for novel sorbents characterized by their unique sorption properties aims at expanding the applicability of SPE and SPME. One of such novel groups of sorbents are molecularly imprinted polymers—MIPs. The purpose of this paper is to review recent publications on synthesis and applications of MIPs as well the procedures used to study MIPs.

Membrane solid-phase microextraction--a new concept of sorbent preparation.

A new sorption system for isolation/enrichment of polar organic analytes from aqueous samples was obtained by substantial modification of the solid-phase microextraction (SPME) probe. In this system, polar sorbents are separated from the sample by a hydrophobic membrane. The new membrane SPME (M-SPME) probe was made utilizing polyethylene glycol (PEG) (molecular weight = 20 kDa) and polydimethylsiloxane (PDMS) as the membrane material. In this probe, PEG behaves as a pseudo-liquid at the extraction stage, whereas, up to now, it has mainly been used as a cross-linked solid adsorbent. It has been found that such M-SPME fiber may be successfully used at the sample pretreatment stage. It is sufficiently robust and thermally stable; the latter feature permits the usage of thermal desorption for the liberation of analytes. Comparison of our probe with the commercially available polyacrylic (PA) SPME fiber, using a mixture of phenols and gas chromatography as the final determination technique, demonstrated the highly effective nature of the new sorptive system; ca. 10 times higher than in the case of the PA fiber.

Denudation — A Convenient Method of Isolation and Enrichment of Analytes

A wide variety of analytical techniques can be applied for the determination of trace components of air. Usually, a direct determination of analytes in an air sample is impossible, and a need arises to employ suitable techniques of their isolation and preconcentration, prior to the final determination stage. Any of these techniques may be included into one of the following, basic groups: • dynamic techniques • passive techniques • denudation techniques. For several years, a rapid growth of interest in the denudation techniques has been observed, although their theoretical principles had been known long before, because they facilitate the studies in the physical speciation analytics. The objective of this paper is • presentation of the theoretical principles of denudation techniques, • discussion of the major practical constructions of denuders, • reviewing current range of applications of these techniques.

Polyethylene glycol-coated solid-phase microextraction fibres for the extraction of polar analytes—A review

The article discusses the merits and limitations of commercially available solid-phase microextraction (SPME) fibres and compares them with the new type of extraction coatings, in particular those containing polyethylene glycol as sorbent, as well as the methods of the preparation of the latter. It also analyses their possible application for the extraction of a broad spectrum of analytes, with particular emphasis on the sampling of polar organic compounds from different media.

Modern Techniques of Sample Preparation for Determination of Organic Analytes by Gas Chromatography

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.

Sol-Gel Technique—A Versatile Tool for Adsorbent Preparation

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.

Silica-Based Ionogels: Nanoconfined Ionic Liquid-Rich Fibers for Headspace Solid-Phase Microextraction Coupled with Gas Chromatography–Barrier Discharge Ionization Detection

In this work, hybrid silica-based materials with immobilized ionic liquids (ILs) were prepared by sol-gel technology and evaluated as solid-phase microextraction (SPME) fiber coatings. High loadings of the IL 1-methyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide ([C4MIM][TFSI]) were confined within the hybrid network. Coatings composition and morphology were evaluated using scanning electron microscopy and energy dispersive X-ray spectrometry. The obtained ionogel SPME fibers exhibited high extractability for aromatic volatile compounds, yielding good sensitivity and precision when combined with a gas chromatograph with barrier ionization discharge (GC-BID) detection. A central composite design was used for assessing the effect of experimental parameters on the extraction process. Under optimized conditions, the proposed ionogel SPME fiber coatings enabled the achievement of excellent enrichment factors (up to 7400). The limits of detection (LODs) were found in the range 0.03-1.27 μg L(-1), whereas the repeatability and fiber-to-fiber reproducibility were 5.6% and 12.0% on average, respectively. Water samples were analyzed by the proposed methodology, showing recovery values in the range of 88.7-113.9%. The results obtained in this work suggest that ionogels can be promising coating materials for future applications of SPME and related sample preparation techniques.

Application of Ionic Liquids in Amperometric Gas Sensors

ABSTRACT 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.