Clean-up methodology

Castro M, Silva-Ferreira AC, Manaia CM, Nunes O. (2005). A case study of mohnate application in a Portuguese rice field Herbicide dissipation and proposal of a clean-up methodology. Chemosphere 59 1059-1065. 

AC Good, R Lewis. New methodology for profiling combinatorial libraries and screening sets Cleaning up the design process with HARPick. I Med Chem 40 3926-3936, 1997. 

The on-line principle has also been extended into the field of detection (Fig. 8). Thus, it is now possible to record FTIR [27-31] and Raman spectra in situ [32, 33], and there have been considerable advances in the on-line coupling of thin-layer chromatography with mass spectrometry. Here it has been, above all, the research groups of Wilson [34-36] and Busch [37-40] that have made the necessary instrumental and methodological advances, so that TLC must no longer be viewed as merely a clean-up method. Rather it forms the essential central point for all these on-line coupling techniques. 

These procedures outlined are not all-encompassing and should serve only as guidelines. Additionally, the end use of the extract (i.e., biochemical studies, analytical methodology, toxicological studies) will have a large effect on the required purity of the final product. Some uses need only water extraction while others need a more rigorous clean-up procedure with methods outlined in Chapter 3. 

Using nano LC-MS at submicroliter per minute flow rates requires special attention to plumbing, system dead volume, valve switching, large volume sample injection, precolumn methodology, automation, online sample clean-up, and multichannel parallel operation of a single MS. The techniques discussed below are particularly useful for nano LC-MS-MS applications. 

It is quite clear that in the near future extraction of non-ionic surfactants from solid matrices will be based on SFE, PLE and sonication methods. The initial costs for SFE/PLE equipment will be earned back quickly by the reduction of man-hours and solvent consumption per sample. For sonication methods, not even this financial barrier is present. More emphasis must be laid on quality assurance of the extraction, clean-up and detection methodologies. The recently available 13C-labeled standards will help to account for matrix... 

Recent trends in pesticide analysis in food aims for reduced sample pretreatments or simplified methodologies (as QuEChERS approaches), the use of online purification processes, the use of new adsorbents (such as molecular imprinted polymers (MIPs) and nanomaterials) for the extraction and clean-up processes, and focused on the development of large multiresidue methods, most of them based on LC-MS/ MS. In spite of the relevant role of LC-MS/MS, GC-MS-based methods still play an important role in pesticide analysis in food. Despite the development achieved in the immunochemical approaches, the need for multi-residue methods has supported the development and use of instrumental techniques. 

Extraction methodologies obviously need to be further compared and optimised. Clean-up of extracts has been applied but this may generate losses as observed for TBT in biological materials (Astruc et al., 1989). Supercritical extractions offer good possibilities for extracting the species without alteration as demonstrated for butyltins (Bayona, 1996) and MeHg (Quevauviller et al., 1998a). Much work... 

A methodological approach for an effective and reliable quality control of Chinese star anise [I. verum Hook. F.) was developed and validated by Lederer et al. (2006). A combined method of TLC and HPLC-MS/MS was used for differentiation ofvarious Ulicium species, especially Chinese and Japanese star anise. Species can be distinguished by their TLC flavonoid pattern. A sensitive and selective HPLC/ESI-MS/MS method was developed for the detection and quantification of lower admixtures of I. anisatum and of further toxic Ulicium species at a low concentration range using the sesquiterpene, lactone anisatin, as a marker. This assay includes a solid-phase extraction clean-up procedure with a high recovery (> 90%). 

Good, A.C. and Lewis, R.A. New Methodology for Profiling Combinatorial Libraries and Screening Sets Cleaning Up the Design Process with HARPick. J. Med. Chem., 1997, 40,3926-3936. 

Paper Chromatography. The first important step for any pesticide residue methodology is to extract the residue from the substrate and isolate it in a pure enough state so that it can be identified and measured. This purification step is called clean-up, and there is a great quantity of literature concerning the different approaches 2, 3, 4, 5, 6). 

Love Canal also contributed strongly to the development of risk assessment methodologies since the Superfund Act required that determinations of clean-up levels be made based on a scientific assessment of data on the toxicity of contaminants found at the hazardous waste sites and the potential for exposure to those contaminants. In light of the limitations in available knowledge, new approaches had to be devised to answer the question of how clean is clean The methodology that was adopted married scientific data to value judgments about acceptable risk and margins of safety. This approach remains in use. 

Adsorption of aniline on minerals, such as kaolinite, montmorillonite and vermiculite as well as on a-alumina and iron powders, has been studied in order to better understand the interaction of the adsorbate with natural adsorbents154-157. However, the results, similarly to those obtained on a smooth polycrystalline platinum electrode158, are not useful for the removal of aniline from waste water. The commonly used activated charcoal is also deficient owing to slow kinetics of the removal of dissolved pollutants. In this situation, activated carbon fibers, woven as a C-cloth, seem to be the ideal adsorbents for removal of aniline from waste streams. The reports of Niu and Conway159,160 explained the adsorptive and electrosorptive behavior of aniline on C-cloth electrodes and suggested a methodology for clean-up of industrial waste waters. 

The LC/MS separation and detection shown in this method illustrate the multiresidue capabilities of LC/MS. The combination of the LC separation for six sulfonylurea herbicides within 25 minutes and the selectivity and structure confirmation of the mass selective detector offer the basis for efficient residue analysis. LC/MS residue methodology can be a cost effective alternative to conventional residue methodology. The mass selectivity will simplify the extraction procedure and minimize sample clean up. A simplified sample preparation saves time and reduces analyte loss during sample preparation which will maximizes recovery. 

LC/MS has emeiged as a sensitive and selective residue methodology for the trace organic analysis of crop protection chemicals. This technology is especially applicable to low application rate herbicides such as sulfonylureas because it requires minimal sample processing and clean-up prior to chromatographic and spectroscopic quantitation. 

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