Rapid food decomposition by H2O2-H2SO4 for determination of total mercury by flow injection cold vapor atomic absorption spectrometry.
A mixture of 50% H2O2-H2SO4 (3 + 1, v/v) was used for decomposition of food in open vessels at 80 degrees C. The treatment allowed rapid total mercury determination by flow injection cold vapor atomic absorption spectrometry. Cabbage, potatoes, peanuts paste, hazelnuts paste, oats, tomatoes and their derivatives, oysters, shrimps, prawns, shellfish, marine algae, and many kinds of fish were analyzed by the proposed methodology with a limit of quantitation of 0.86 +/- 0.08 microg/L mercury in the final solution. Reference materials tested also gave excellent recovery.
Elemental Trace Analysis in Studies of Food Products
Mineral elements play a key role in the human body and especially in the regulation of cell metabolism. They are either incorporated into the tissues or else are present in body liquids in ionic form. They also participate in metabolic processes such as electrolyte and hormone economy, haematopoiesis, and development of the nervous and skeletal systems [1, 2].
Enantioselective Synthesis of Dihydropyrans. Catalysis of Hetero Diels−Alder Reactions by Bis(oxazoline) Copper(II) Complexes
C2-symmetric bis(oxazoline)−Cu(II) complexes 1 and 2 catalyze the inverse electron demand hetero Diels−Alder reaction of α,β-unsaturated carbonyl compounds (heterodiene) with electron-rich olefins (heterodienophile) in high diastereo- and enantioselectivity. α,β-Unsaturated acyl phosphonates and β,γ-unsaturated α-keto esters and amides are effective heterodienes, while enol ethers and sulfides function as heterodienophiles. A range of substitution patterns is possible on the heterodiene:  terminal alkyl, aryl, alkoxy, and thioether substituents are all tolerated. The enantioselective synthesis of dihydropyrans by this method has been shown to be straightforward:  cycloadditions may be conducted with as little as 0.2 mol % of the chiral catalyst and are readily run on multigram scale. The reactions exhibit a favorable temperature−enantioselectivity profile, with selectivities exceeding 90% even at room temperature. A simple reaction protocol that employs a solid air-stable catalyst, convenient reaction tem...