Application of Supercritical fluid Extraction For Analysis of Organophosphates in Cereals

Abstract

Application of supercritical fluid extraction (SFE) utilizing pure carbon dioxide for selective isolation of organophosphates from contaminated cereals has been tested.

At the beginning of the experiments the extractability of added standards from an empty extraction vessel (thimble) and from various materials such as filter paper, sand, Celite and anhydrous sodium sulfate was tested to estimate the behavior of organophosphates. Further method development was carried out using a spiked sample of flour, which was analyzed within the proficiency testing for organophosphorus pesticides analysis (round 7) organized by Food Analysis Performance Assessment Scheme (FAPAS, MAFF-UK).

Comparison of the SFE method with a classical method currently employed for sample preparation (i.e. extraction with acetone/methanol mixture followed by gel permeation chromatographic clean up) showed advantages of the SFE technique such as simplification of the sample preparation step and thereby significant speeding up of the determination of organophosphates in cereals.     

Analysis of PCBs in Biotic Matrices by Two-Dimensional GC-ECD

Abstract

The suitability of three GC-ECD systems for the separation of a model mixture containing various congeners of PCBs together with persistent chlorinated aromatics (pesticides and their metabolites, industrial chemicals) was tested. Analyses were performed on two parallel capillaries, the stationary phase of one of them was always in routine practice very common 5% phenyl-methylpolysiloxane, the second one was either 50% phenylmethylpolysiloxane or 7% phenyl-7% cyanopropyl-methylpolysiloxane. The number of unresolved (coeluted) analytes was significantly reduced in these systems and thus unbiased quantitation of PCBs and other components used for regulation was possible. The utilization of this type of multidimensional chromatography for rapid and reliable analysis of real samples (fish oil, human fat) was documented.     

Highly Chemoselective Synthesis of Indolizidine Lactams by SmI2‐Induced Umpolung of the Amide Bond via Aminoketyl Radicals: Efficient Entry to Alkaloid Scaffolds

Samarium(II) iodide enables a wide range of highly chemoselective umpolung radical transformations proceeding by electron transfer to carbonyl groups; however, cyclizations of important nitrogen‐containing precursors have proven limited due to their prohibitive redox potential. Herein, we report the first reductive cyclizations of unactivated cyclic imides onto N‐tethered olefins using SmI₂/H₂O. This new umpolung protocol leads to the rapid synthesis of nitrogen‐containing heterocycles that are of particular significance as precursors to pharmaceutical pharmacophores and numerous classes of alkaloids. The reaction conditions tolerate a wide range of functional groups. Excellent chemoselectivity is observed in the cyclization over amide and ester functional groups. Such unconventional reactivity has important implications for the design and optimization of new bond‐forming reactions by umpolung radical processes. The reaction advances the SmI₂ cyclization platform to the challenging unactivated N‐tethered acyl‐type radical precursors to access nitrogen‐containing architectures.     

A new platinum–bromine cyclohexanediamine complex from the family of cancer cytostatics

Another new substance from the family of Pt‐based coordination complexes with potential use in cancer chemotherapy has been synthesized, crystallized and structurally characterized. In this compound {systematic name cis‐dibromido[(1R,2R)‐cyclohexane‐1,2‐diamine‐κ²N,N′]platinum(II)}, cis‐[PtBr₂(C₆H₁₄N₂)], there are two molecules with very similar conformations in the asymmetric unit. The component species interact by way of N—H...Br and C—H...Br hydrogen bonds to give two‐dimensional networks which lie parallel to the (100) plane.     

Functionalised, photostable, fluorescent polystyrene nanoparticles of narrow size-distribution

Fluorescent nanoparticles continue to be of wide interest, as they have many advantages over single fluorescent molecules for biological imaging and sensing applications, such as increased fluorescence intensity and reduced photobleaching. In the following work, styrene was copolymerised with a newly synthesised, fluorescein-based, vinylic crosslinking monomer, by emulsion polymerisation, to create a series of different sized fluorescent nanoparticles (35-100 nm), each of narrow size-distribution. The particles were found to be highly fluorescent and with lower photobleaching compared to fluorescein isothiocyanate (FITC), offering an attractive alternative. The fluorescence excitation and emission spectra were recorded, being similar to fluorescein, but with interesting variation in the excitation spectra. The particles also have a wide range of potential uses, such as examining particle uptake activity of a macrophage cell line, also demonstrated. The nanoparticles were coated with albumin to provide functionality for potential conjugation to biological targeting agents.     

Mass separator for radioactive isotopes

A new isotope separator has been designed, constructed, and put into routine operation for separation of ¹³³Xe providing a major advancement and significant cost reduction in preparation of this radioactive isotope. The design features and advantages are discussed that expedite high purity separation of relatively small quantities of this isotope. These advantages could be easily used to expedite separation of other shorter-lived radioactive isotopes.     

Discontinuous alkylation of diphenylamine with nonene for maximum catalyst utilization

This study examines the alkylation of diphenylamine (DPA) with nonene (NON) in a liquid phase catalyzed by acid-treated clay-based catalysts from commercial suppliers (Fulcat 22B, Nobelin MM, and Jeltar 300). Alkylations were conducted to achieve the highest possible selectivity of diisononyldiphenylamine (DNDPA), low selectivity of monoisononyldiphenylamine, and a maximum triisononyldiphenylamine yield of 4%. This study also examines the reaction conditions to selectively form dialkylated diphenylamine from DPA and NON in a batch reactor. Repeated use of the catalyst during the alkylation of DPA with NON was also investigated. Catalyst deactivation takes place during the alkylation of each batch and intensifies with repeated catalyst use, resulting in low DNDPA selectivity. The regenerated catalyst was sufficiently active only until the regeneration of the first and second batches. After the third batch, the catalyst’s selectivity for DNDPA was very low, and its reuse in the alkylation of DPA with NON was not efficient. Therefore, to achieve the maximum length of catalyst activity, the fresh catalyst was gradually added to the used catalyst from a previous batch, thus maintaining a high activity of eight batches. The reduction in catalyst activity was probably caused by the irreversible adsorption of substances on the surface, a loss of microporous structure, and a loss of surface acidity. DPA or alkylated products are adsorbed on the surface oxygen of the catalyst through nitrogen and form nitro formations. The fresh and regenerated catalysts were characterized by their surface area, surface acidity, pore size distribution, and pore volume.