Michał Pilarczyk

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.

Mobilities of complex forming cations in non-aqueous donor solvents

Conductance measurements are reported for Al(ClO4)3 in acetonitrile Co(ClO4)2, Zn(ClO4)2, and Al(ClO4)3 in dimethylformamide, and Al(ClO4)3, Fe(ClO4)3, and FeCl3 in dimethylsulfoxide (DMSO), at 25°C. From uv spectral effects the FeCl (DMSO)52+ complex cation is shown, to predominate in DMSO, while hexasolvated cations occur in the metal perchlorate solutions. The limiting conductances of the cations, including earlier data, indicate non-Stokesian dependences of mobility on the ionic charge, a unique property of the structurally related complex ions ML6z+ and MXL5(z−1)+. The observed regularities are discussed in terms of both their possible applications and the migration mechanism.

Using different types of capillary chromatographic columns as denudation traps: a comparison of sorption properties.

The research presented concerns segments of capillary chromatographic columns of different types (WCOT, SCOT, PLOT) used as traps for collection of samples of volatile organic analytes from a stream of air utilizing the equilibrium denudation technique. During the model experiments (utilizing standard mixtures), values of the partition coefficients (Kfs) were determined for volatile organic compounds frequently occurring as pollutants of atmospheric air (benzene, toluene, ethylbenzene, o-xylene, chlorobenzene). The conducted research demonstrated that the stationary phase film thickness did not affect the partition coefficient value. It was also proved that there is no dependence between the manner of applying the stationary phase in the column and the partition coefficient value.

The application of an open tubular trap in analysis of organic air pollutants

The paper presents the studies on equilibrium trapping of organic air pollutants. A piece of a commercial capillary chromatographic column coated with polydimethylsiloxane was used for trapping. This kind of the trap was applied for sampling and enrichment of selected volatile nonpolar organic compounds from workplace atmosphere (woodworking shop). In the method developed, which is based on equilibrium trapping the concentration of analytes in a studied medium can be calculated from the partition coefficients determined in a calibration step and the amount of particular analytes trapped. Simultaneously with equilibrium trapping, analytes were sampled into sorbent packed tubes. The concentrations of analytes in woodworking shop atmosphere obtained with both sampling methods (equilibrium and dynamic) were in good agreement.

A review of denudation — technique for sampling and measurement of atmospheric trace constituents

Theoretical aspects and practical applications of denuder based sampling techniques of gaseous species (organic and inorganic) from the atmospheric air are presented on the basis of literature data. These techniques permit separation of analytes present in different physical phases (gaseous and particulate).