Determination of currently used pesticides in biota

Although pesticides enable control of the quantity and quality of farm products and food, and help to limit diseases in humans transmitted by insects and rodents, they are regarded as among the most dangerous environmental contaminants because of their tendency to bioaccumulate, and their mobility and long-term effects on living organisms. In the past decade, more analytical methods for accurate identification and quantitative determination of traces of pesticides in biota have been developed to improve our understanding of their risk to ecosystems and humans. Because sample preparation is often the rate-determining step in analysis of pesticides in biological samples, this review first discusses extraction and clean-up procedures, after a brief introduction to the classes, and the methods used in the analysis of pesticides in biota. The analytical methods, especially chromatographic techniques and immunoassay-based methods, are reviewed in detail, and their corresponding advantages, limitations, applications, and prospects are also discussed. This review mainly covers reports published since 2008 on methods for analysis of currently used pesticides in biota.     

Evaluation of enantioselective binding of fluoxetine to human serum albumin by ultrafiltration and CE--experimental design and quality considerations

Several pharmacokinetic processes are affected by enantioselectivity (ES). At the level of distribution, protein binding (PB) is one of the most important. The enantioselective binding of fluoxetine (FLX) to HSA has been evaluated in this work by ultrafiltration of FLX–HSA mixtures and chiral analysis of unbound fractions by EKC-CD. PB, affinity constants (K) and ES were obtained for both enantiomers of FLX. In order to improve the consistency of the estimations, the evaluation of affinity constants of each enantiomer was performed using two designs, one keeping constant the total concentration of protein and varying the total concentration of the enantiomers, and the other in the opposite way, in both cases via an unusual short-concentration interval strategy to assure model validity. Different mathematical approaches were compared and characterised and some of them, judged as the most consistent under the experimental conditions used, were selected to provide final estimates. Quality considerations include criteria for three critical aspects: (i) detecting/eliminating outliers, (ii) checking the number of binding sites in the protein and (iii) evaluating the robustness of each approach. The differences on estimates from the selected approaches were used as an uncertainty source to delimit the reported values. The ES of HSA for FLX enantiomers was approximate. Estimates include the assumptions of independent and competitive models. In the last case, a SIMPLEX function was designed capable of simultaneously optimizing the non-linear binding models for both enantiomers, thus improving the consistence of results.     

Variability of polyphenol compounds in Myrtus communis L. (Myrtaceae) berries from Corsica

Polyphenol compounds were extracted from Myrtus communis L. berries (Myrtaceae) by maceration in 70% ethanol and analysed by HPLC-DAD and electrospray mass spectrometry. The Myrtus berries were collected at maturity from seven localities on the island of Corsica (France) and the sampling was carried out during three years. The polyphenol composition of Corsican Myrtus berries was characterized by two phenolic acids, four flavanols, three flavonols and five flavonol glycosides. The major compounds were myricetin-3-O-arabinoside and myricetin-3-O-galactoside. Principal components analysis (PCA) is applied to study the chemical composition and variability of myrtle berries alcoholic extracts from the seven localities. Canonical analysis and PCA data distinguishes two groups of myrtle berries characterized by different concentrations of polyphenols according to soil and years of harvest. The variations in the polyphenol concentration were due to biotic and abiotic factors.     

Syntheses and structural studies of hexa- and pentacoordinated Zn complexes derived from 2-(aminomethyl)benzimidazole and water

The complexes trans-bis[2-(aminomethyl)-1H-benzimidazole-κ ² N′,N″]diaquazinc(II) dichloride dihydrate 1 and trans-bis[2-(aminomethyl)-1H-benzimidazole-κ ² N′,N″]aquazinc(II) dichloride dihydrate 2 were synthesized selectively by the promotion of O–H···Cl hydrogen bond interactions. The hexacoordinated complex 1 was synthesized at pH 4.5. The dilution of 1 in deionized water produced the pentacoordinated complex 2. NMR and vibrational spectroscopies corroborated the presence of these compounds. Moreover, mass spectrometry and thermogravimetric (TGA) studies demonstrated that chloride ions and crystallization water molecules are essential for the stabilization of 1 but not for complex 2. X-ray diffraction crystallography studies indicated that the presence of two water molecules bonded to the Zn atom elongated all of the coordination bonds. The incidence of a network of hydrogen bond interactions compensates for the unstable hexacoordination. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) studies of the crystal structures of 1 and 2 were used to explain the nature of the coordination bonds and the complexes’ stability .     

Application of capillary electrophoresis-mass spectrometry for determining organic food contaminants and residues

Food contamination continues to be a serious problem around the world. Surveillance of chemical contaminants in foods is important not only for public health but also because of the negative economic impact of contamination. From the analytical perspective, analysis of contaminants in food is an extremely challenging area. There is a wide variety of questions, ranging from the quantification of extremely low levels of individual components to the detailed assessment and evaluation of the analytical technique possibilities. This review considers the applications of CE coupled to MS detection (CE-MS) for the analysis of organic contaminants in food. Analytical information on sample concentration techniques, as well as on the CE separation conditions and recoveries obtained from water and food are provided. Different sections include several fields of application, such as pesticides, drug residues, or toxic formed during food processing in different matrices. A number of tables report a comprehensive listing of CE-MS applications. As a result, this work presents an update overview on the principal application of CE-MS together with a discussion of their main advantages and drawbacks, and an outline of future trends on analysis of organic contaminants.     

Chiral monofluorobenzyl carbanions: synthesis of enantiopure β-fluorinated β-phenylethylamines

The preparation of a stabilized monofluorobenzyl carbanion by means of a remote homochiral sulfinyl group and its completely stereoselective reactions with N-p-tolylsulfinylimines are described. The use of these reactions followed by the simultaneous removal of both chiral auxiliaries with tBuLi, which occurs without epimerization at the benzylic position, provides the quickest entry to enantiomerically pure β-fluorinated β-phenylethylamines.     

Asymmetric Strecker synthesis of α-arylglycines

A practically simple three-component Strecker reaction for the asymmetric synthesis of enantiopure α-arylglycines has been developed. Addition of a range of aryl-aldehydes to a solution of sodium cyanide and (S)-1-(4-methoxyphenyl)ethylamine affords highly crystalline (S,S)-α-aminonitriles that are easily obtained in diastereomerically pure form. Heating the resultant (S,S)-α-aminonitriles in 6 M aqueous HCl at reflux resulted in cleavage of their chiral auxiliary fragments and concomitant hydrolysis of their nitrile groups to afford enantiopure (S)-α-arylglycines. The enantiopurities of these (S)-α-arylglycines were determined via derivatization of their corresponding methyl esters with 2-formylphenylboronic acid and (S)-BINOL, followed by (1)H NMR spectroscopic analysis of the resultant mixtures of diastereomeric iminoboronate esters.     

Synthesis of complexes with the polydentate ligand N,N′-bis(2-hydroxyphenyl)-pyridine-2,6-dicarboxamide

The pentadentate ligand N,N′-bis(2-hydroxyphenyl)-pyridine-2,6-dicarboxamide (POPYH₄) has been used to prepare a variety of new complexes [HNEt₃]₂[Zn₄Cl(POPYH)₃] (2), [HNEt₃][PdCl(POPYH₂)] (3), [HNEt₃][Ni(POPYH)] (4) and K[Ni(POPYH)] (5) which show the versatility of this multidentate ligand. The complexes have been characterised spectroscopically and their molecular and crystal structures have been determined by single crystal X-ray diffraction techniques. In these complexes the ligand exhibits different modes of coordination towards different transition metal ions. The structure of triethylammonium salt of the Zn(II) dianion 2 consists of an unusual tetra-zinc core supported by three POPYH ligands each one of which links two adjacent zinc centres through two oxygen and two nitrogen donor atoms. The salt of the square planar Pd(II) anion 3 contains one POPYH₂ ligand which coordinates in a tridentate fashion through the two deprotonated amido groups and by the central pyridine nitrogen donor. The two Ni(II) salts 4 and 5 contain the same [Ni(POPYH)]⁻ anion in which the square planar Ni(II) centre is chelated by a POPYH ligand through the two deprotonated amido nitrogen atoms, the pyridine nitrogen and a deprotonated hydroxyl group.