Direct chiral resolution of underivatized amino acids on a stationary phase dynamically modified with the ion-exchanger N(τ) -decyl-L-spinacine.

Increasing attention has been devoted in the last decades to chiral chromatography, principally to high-performance liquid chromatography techniques using a chiral stationary phase. Many chiral high-performance liquid chromatography columns are commercially available, but, unfortunately, they are most often rather expensive. A cheap alternative to the commercial chiral columns is the dynamic-coating procedure of a standard achiral stationary phase with a chiral selector containing both a chiral domain and a chain or a group able to tightly (but noncovalently) bind the achiral support.

Chiral ligand-exchange resolution of underivatized amino acids on a dynamically modified stationary phase for RP-HPTLC.

The synthesis of Spi(τ-dec), derived from the selective alkylation of L-spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) at the τ-nitrogen of its heteroaromatic ring, with a linear hydrocarbon chain of 10 carbon atoms, is described here for the first time. Spi(τ-dec) was successfully employed in the past to prepare home-made chiral columns for chiral ligand-exchange high-performance liquid chromatography. In the present article a new method is described, using Spi(τ-dec) as a chiral selector in high-performance thin-layer chromatography (HPTLC): commercial hydrophobic plates were first coated with Spi(τ-dec) and then treated with copper sulfate.

The unusual stabilization of the Ni2+ and Cu2+ complexes with NSFRY.

The binding mode provided by an unprotected peptide with non-coordinating side-chains is simple and well understood. However, when particular residues are inserted into the peptide sequence, they can have a significant impact on the stability of the formed complexes. The presence of non-bonding side chains of amino acids close to the metal binding centre in the peptide/protein can provide special interactions which result in increasing the stabilization of the formed species.

Quantitative SPLITT fractionation of lagoon sediments.

In this work, SPLITT Fractionation (split flow thin cell) is used to sort hydrodynamically sedimented particles coming from the Sacca di Goro, a lagoon-like system close to the Po River delta (Italy). First the possibility of performing quantitative mass separations with a SPLITT cell apparatus was checked on a standard silica sample of known particle size distribution (PSD). Environmental sediment samples and relative SPLITT sub-fractions were subject to Inductive Coupled Plasma--Atomic Emission Spectroscopy (ICP-AES) characterization for the following elements: Al, Fe, Cd, Cr, Cu, Ni, Mn, Pb and Zn.

Metal content in river suspended particulate matter: data on Po River.

The present study summarizes the last ten years of literature on heavy metal distribution in Suspended Particulate Matter (SPM) and dissolved phase in the Po River (Italy). The work compares different methodologies employed to collect, concentrate and fractionate the samples. The importance of metal speciation as a function of particle size is underlined and two approaches to metal speciation in the colloidal fraction of Po River SPM are presented: Sedimentation Field-Flow Fractionation (SdFFF) and pH-dependent extractions.

Experimental approaches for size-based metal speciation in rivers.

A review of the different methodologies employed to fractionate and characterize riverine suspended particulate matter is presented. The importance of size-based metal speciation is underlined and the possibility of studying it by the Sedimentation Field Flow Fractionation (SdFFF) technique is illustrated. The studies on the metal load in river Suspended Particulate Matter (SPM) performed over the last ten years are critically reviewed focusing on the different methods employed to collect, concentrate and size-fractionate samples.

Formation equilibria of nickel complexes with glycyl-histidyl-lysine and two synthetic analogues.

Complex-formation equilibria between the Ni(II) ion and the natural tripeptide glycyl-L-histidyl-L-lysine have been investigated. Two synthetic analogues, where the histidine residue has been substituted with L-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid (L-Spinacine) and L-1,2,3,4-tetrahydro-isoquinolin-3-carboxylic acid (Tic), respectively, have been considered, as well. Different experimental techniques have been employed: potentiometry, calorimetry, visible spectrophotometry and CD spectroscopy.