Highly selective antibody-mediated extraction of isoproturon from complex matrices

Solid Phase Extraction for Monitoring of Occupational Exposure to Cr (III)

Chromium is an important constituent widely used in different industrial processes for production of various synthetic materials. For evaluation of workers' exposure to trace toxic metal of Cr (III), environmental and biological monitoring are essential processes, in which, preparation of samples is one of the most time-consuming and error-prone aspects prior to analysis. The use of solid-phase extraction (SPE) has grown and is a fertile technique of sample preparation as it provides better results than those produced by liquid-liquid extraction (LLE). SPE using mini columns filled with XAD-4 resin was optimized regarding to sample pH, ligand concentration, loading flow rate, elution solvent, sample volume, elution volume, amount of resins, and sample matrix interferences. Chromium was retained on solid sorbent and was eluted with 2 M HNO3 followed by simple determination of analytes by using flame atomic absorption spectrometery. Obtained recoveries of metal ion were more than 92%. The optimized procedure was also validated with three different pools of spiked urine samples and showed a good reproducibility over six consecutive days as well as six within-day experiments. Through this study, suitable results were obtained for relative standard deviation, therefore, it is concluded that, this optimized method can be considered to be successful in simplifying sample preparation for trace residue analysis of Cr in different matrices for evaluation of occupational and environmental exposures. To evaluate occupational exposure to chromium, 16 urine samples were taken, prepared, and analyzed based on optimized procedure.

Miniaturization in sample treatment for environmental analysis

The increasing demand for faster, more cost-effective and environmentally friendly analytical methods is a major incentive to improve the classical procedures used for sample treatment in environmental analysis. In most classical procedures, the use of rapid and powerful instrumental techniques for the final separation and detection of the analytes contrasts with the time-consuming and usually manual methods used for sample preparation, which slows down the total analytical process. The efforts made in this field in the past ten years have led to the adaptation of existing methods and the development of new techniques to save time and chemicals, and improve overall performance. One route has been to develop at-line or on-line and, frequently, automated systems. In these approaches, miniaturization has been a key factor in designing integrated analytical systems to provide higher sample throughput and/or unattended operation. Selected examples of novel developments in the field of miniaturized sample preparation for environmental analysis are used to evaluate the merits of the various techniques on the basis of published data on real-life analyses of trace-level organic pollutants. Perspectives and trends are briefly discussed.

Immunoaffinity solid-phase extraction for pharmaceutical and biomedical trace-analysis—coupling with HPLC and CE—perspectives

Immunoaffinity solid-phase extraction (SPE) technique is based upon a molecular recognition mechanism. The high affinity and the high selectivity of the antigen-antibody interactions allow the specific extraction and the concentration of the analytes of interest in one step. In pharmaceutical and biological fields, where most often matrices are complex and analytes at trace-levels, this approach constitutes a unique tool for fast and solvent-free sample preparation. This review presents a general description of this extraction technique and gives numerous examples of its applications in pharmaceutical and biomedical fields. It emphasizes the on-line coupling with chromatographic and electrophoretic separation techniques and introduces new developments. The future directions, especially with regards to the current development of analytical microsystems, are discussed.

Experimental comparison of three monoclonal antibodies for the class-selective immunoextraction of triazines. Correlation with molecular modeling and principal component analysis studies

The specificity of three immunosorbents (ISs) based on different monoclonal anti-triazine antibodies has been characterized by extraction recoveries studies and with step elution experiments. Both indicated that the anti-dichloroatrazine IS is specific of terbutylazine and cyanazine. The anti-atrazine IS is specific of the chlorotriazines, whereas the anti-ametryn IS can trap all the triazines. This confirms the great influence of the hapten design on the specificity of the resulting antibodies, even if the target molecules are small. Moreover, the anti-ametryn IS is suitable for class-selective extraction of triazines contained in complex matrices. An approach designed to learn more about the specificity for a group of structurally related compounds of antibodies produced with a given compound is proposed and evaluated. Molecular modeling followed by principal component analysis has been used to obtain distribution maps with the relative position of each immunoconjugate and all the triazines. In all three cases, conclusions on specificity made with the analysis of the maps fit well with the experimental results. Consequently, molecular modeling coupled with principal component analysis seems to be a unique, inexpensive, and rapid tool to select the appropriate hapten providing highly specific or class-specific antibodies according to the given problem.

Immuno-affinity solid-phase extraction

The measurement of trace organics such as drugs and pesticides at low concentration in biological and environmental samples is a challenging analytical task. Despite recent advances in instrumentation most analysts regard sample preparation as the rate-limiting step in the overall analytical method. In recent years there has been a lot of interest in immobilising antibodies onto solid supports such as silica to provide highly selective solid-phase extraction. This paper reviews the use of immuno-affinity for solid-phase extraction. It uses as examples extraction of chlortoluron and isoproturon from water and morphine and clenbuterol in urine and plasma respectively. An extensive list of other examples is given. Optimisation procedures are discussed in detail.

Immunoaffinity solid-phase extraction for the trace-analysis of low-molecular-mass analytes in complex sample matrices

Immunoaffinity solid-phase extraction (SPE) sorbents, so-called immunosorbents (ISs), are based upon molecular recognition using antibodies. Thanks to the high affinity and high selectivity of the antigen-antibody interaction, they allow a high degree of molecular selectivity and have shown to be a unique tool in the sample preparation area these last few years. Extraction and clean-up of complex biological and environmental aqueous samples are achieved in the same step and from large volumes when required. Their application to extracts from solid matrixes is solvent-free and more simple than any other clean-up procedure. Single analytes can be targeted, but since an antibody can also bind one or more analytes having structure similar to the one used for its preparation, ISs have been developed for targeting a single analyte and its metabolites. The cross-reactivity was also exploited for developing ISs that could selectively extract a whole class of structurally related compounds. This review describes the current technology used for the synthesis of the ISs, their properties and their field of application. The different parameters governing the antigen-antibody interactions and the solid-phase extraction process are discussed. Emphasis is given to the optimisation of the SPE sequence, especially to the desorption and regeneration steps. The importance of the capacity and its relationship with the analytes recovery and breakthrough volumes is highlighted for class-specific ISs. Multi-class-selective ISs are also presented. Validation studies are reviewed using various certified reference materials. Relevant examples, involving combination with chromatography in both off-line and on-line mode, illustrate the high selectivity provided in various complex matrixes. Miniaturisation is also described, since it allows high throughput of samples.

Solid phase extraction of clenbuterol from plasma using immunoaffinity followed by HPLC

An immuno-extraction column for clenbuterol has been prepared. Optimum conditions for the selective retention and elution of clenbuterol have been developed, based on a modification of our earlier work on morphine, chlortoluron and isoproturon. Clenbuterol could be retained on the immuno-column then eluted in one x one ml fraction using 50% methanol in phosphate buffered saline pH 2. On columns containing antisera (but not to clenbuterol) the clenbuterol was removed in the washing step. HPLC-UV determination gave clean traces. Day-to-day reproducibility was improved by precipitating the plasma proteins with acetonitrile.

Solid-phase extraction: method development, sorbents, and coupling with liquid chromatography

The objective of this review is to provide updated information about the most important features of the new solid-phase extraction (SPE) materials, their interaction mode and their potential for modern SPE. First, the recent developments are given in formats, phases, automation, high throughput purpose and set-up of new types of procedures. Emphasis is then placed on the large choice of sorbents for trapping analytes over a wide range of polarities, such as highly cross-linked copolymers, functionalized copolymers, graphitized carbons or some specific n-alkylsilicas. The method development is given which is based on prediction from liquid chromatographic retention data or solvation parameters in order to determine the main parameters of any sequence (type and amount of sorbent, sample volume which can be applied without loss of recovery, composition and volume of the clean-up solution, composition and volume of the desorption solution). Obtaining extracts free from matrix interferences in a few steps--one step when possible--is now included in the development of SPE procedure. New selective phases such as mixed-mode and restricted access matrix sorbents or emerging phases such as immunosorbents or molecularly imprinted polymers are reviewed. Selectivity obtained by combining two sorbents is described with the use of ion-exchange or ion-pair sorbents. Special attention is given to complete automation of the SPE sequence with its on-line coupling with liquid chromatography followed by various detection modes. This represents a fast, modern and reliable approach to trace analysis. Many examples illustrate the various features of modern SPE which are discussed in this review. They have been selected in both biological and environmental areas.