A green approach for the automatic quantitative analysis of additives in plastic samples using in-tube extraction dynamic headspace sampling technique coupled to GC-MS/MS.

BACKGROUND: Many of the chemicals frequently used as additives have been recognised as hazardous substances, and therefore their analysis is necessary to evaluate plastic contamination risk. Additives analysis in plastic samples is usually performed by methods involving high volumes of toxic solvents or having high detection limits. In this work, a novel, fast, solventless and reliable green method was developed for the automated analysis of plastic additives from plastic samples. The proposed method consists of in-tube extraction dynamic headspace sampling (ITEX-DHS) combined with gas chromatography (GC) and mass spectrometry (MS/MS) determination. RESULTS: Several parameters affecting the ITEX-DHS extraction of 47 additives in plastic samples (including phthalates, bisphenols, adipates, citrates, benzophenones, organophosphorus compounds, among others) were optimised. The use of matrix-matched calibration, together with labelled surrogate standards, minimises matrix effects, resulting in recoveries between 70 and 128%, with good quantitation limits (below 0.1 µg g-1 for most compounds) and precision (<20%). The method proposed can be applied to any type of polymer, but due to the existence of the matrix effect, calibrates with the adequate matrix should be performed for each polymer. SIGNIFICANCE: This method represents an effective improvement compared to previous methods because it is fast, solvent-free, fully automated, and provides reliable quantification of additives in plastic samples.

Association of cigarette smoking and metabolic syndrome in a Puerto Rican adult population.

Metabolic syndrome (MetSyn) is related to an increased risk for type 2 diabetes and cardiovascular disease. Smokers are at greater risk than nonsmokers of becoming insulin resistant and to develop cardiovascular disease. This study aimed to explore the association between cigarette smoking, MetSyn and its components among Puerto Rican adults. A representative sample of 856 persons aged 21-79 years from the San Juan Metropolitan area participated in this study. Demographic and lifestyle characteristics, including smoking habits, were gathered from a self-reported questionnaire. MetSyn was defined according to the revised NCEP-ATP III criteria and measured using biochemical measurements and anthropometric indices. Logistic regression models were used to estimate prevalence odds ratios (POR) and its 95 % confidence intervals (CI). MetSyn was significantly (P < 0.001) more prevalent in former smokers (48.4 %) as compared to current (42.7 %) and never smokers (40.0 %). However, after adjusting for possible confounders, current smokers who used more than 20 cigarettes per day were 2.24 (95 % CI = 1.00-4.99) times more likely to have MetSyn as compared to never smokers. Heavy smokers were also more likely to have high triglyceride levels (POR = 2.22, 95 % CI = 1.12-4.38) and low HDL-cholesterol levels (POR = 2.49, 95 % CI = 1.28-4.86) as compared to never smokers. This study supports previous reports of an increased risk of MetSyn among current smokers, particularly those with a heavier consumption. Tobacco control strategies, such as preventing smoking initiation and disseminating evidence-based cessation programs, are necessary to reduce the burden of MetSyn in Puerto Rico.

Neutral and cationic alkylmanganese(II) complexes containing 2,6-bisiminopyridine ligands.

Manganese alkyl complexes stabilised by 2,6-bis(N,N'-2,6-diisopropyl-phenyl)acetaldiminopyridine ((iPr)BIP) have been selectively prepared by reacting suitable alkylmanganese(II) precursors, such as homoleptic dialkyls [(MnR(2))(n)] or the corresponding THF adducts [{MnR(2)(thf)}(2)] with the mentioned ligand. For R=CH(2)CMe(2)Ph or CH(2)Ph, formally Mn(I) derivatives are produced, in which one of the two R groups migrates to the 4-position of the central pyridine ring in the (iPr)BIP ligand. In contrast, a true dialkyl complex [MnR(2)((iPr)BIP)] can be isolated for R=CH(2)SiMe(3). In solution, this compound slowly evolves to the corresponding Mn(I) monoalkyl derivative. A detailed study of this reaction provides insights on its mechanism, showing that it proceeds through successive alkyl migrations, followed by spontaneous dehydrogenation. Protonation of [Mn(CH(2)SiMe(3))(2)((iPr)BIP)] with the pyridinium salt [H(Py)(2)][BAr'(4)] (Ar'=3,5-C(6)H(3)(CF(3))(2)) leads to the cationic species [Mn(CH(2)SiMe(3))(Py)((iPr)BIP)](+). Alternatively, the same complex can be produced by reaction of the pyridine complex [{Mn(CH(2)SiMe(3))(2)(Py)}(2)] with the protonated ligand salt [H(iPr)BIP](+)[BAr'(4)](-). This last reaction allows the synthesis of analogous cationic alkylmanganese(II) derivatives, when precursors of type [MnR(2)((iPr)BIP)] are not available. Treatment of these neutral and cationic (iPr)BIP alkylmanganese derivatives with a range of typical co-catalysts (modified methylaluminoxane (MMAO), B(C(6)F(5))(3), trimethyl or triisobutylaluminum) does not lead to active ethylene polymerisation catalysts.

Studies on the atropisomerism of Fe(II) 2,6-bis(N-arylimino)pyridine complexes.

NMR spectra of free 2,6-bis(N-arylimino)pyridine (PDI) ligands displaying different substituents at the ortho and ortho' positions of the two N-aryl rings indicate that they can exist in syn (meso) and anti (chiral) configurations. These interconvert in solution at room temperature, via rotation of the aryl group. The corresponding paramagnetic FeX(2)(PDI) complexes exhibit the same kind of isomerism, a property that is thought to be important for their activity as alpha-olefin polymerization catalysts. For the first time, this has been detected by (1)H NMR and studied in solution. Although the conformational stability of the diastereoisomeric complexes varies widely (depending on the size of the substituents at the imine and the aromatic rings), a moderate degree of steric hindrance suffices to allow their chemical separation. A simple procedure is developed for the preparation of these complexes in diastereoisomerically pure form. In addition, introduction of a prochiral substituent in the pyridine ring enables positive assignment of the stereoisomers. Isomerization rate measurements of the Fe(II) complexes in solution suggest that isomerization very likely involves the dissociation of the corresponding Fe-N(imino) bond prior to the rotation of N-aryl groups. DFT calculations provide additional support to the conformational assignment as well as the dissociative isomerization mechanism.

Can ginkgo biloba combat diseases?

Herbal remedies have been widely used in many countries for centuries, and the products enjoyed a surge in popularity in the USA during the late '90s. During the past 20 years, an estimated 2 billion daily doses (120 mg) of Ginkgo biloba (GB) have been sold. French and German agencies consider it to be effective for the treatment of several diseases, and the immense amount of clinical studies concerning GB makes it worth revising the existing literature about this notable plant. Also, the National Institutes of Health (NIH) supports research on alternative therapies that include examining the effects of GB. With the rapid expansion of herbal medicine use in the United States, it is clear that our understanding of herb-herb, drug-herb and food-herb interactions should increase.