Massimo Sinibaldi

High-performance liquid chromatography study of the enantiomer separation of chrysanthemic acid and its analogous compounds on a terguride-based stationary phase

The direct enantioseparation of chrysanthemic acid [2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylic acid] and its halogen-substituted analogues was systematically studied by HPLC using a terguride-based chiral stationary phase in combination with a UV diode array and chiroptical detectors. Isomers with (1R) configuration always eluted before those with (IS) configuration. The elution sequence of cis- and trans-isomers was strongly affected by mobile phase pH, whereas the enantioselectivity remained the same. Conditions for the separation of all the enantiomers were also examined. This method was used for monitor the hydrolytic degradation products of Cyfluthrin (Baythroid) in soil under laboratory conditions.

Direct resolution of optically active isomers on chiral packings containing ergoline skeletons: II. Enantioseparation of carboxylic acids

Structurally different carboxylic acids and dansyl derivatives of amino acids were examined on a chiral stationary phase for high-performance liquid chromatography. The packing was prepared by bonding to silica gel an aminopropyl derivative of the ergot alkaloid (+)-terguride. Optimization of the enantioseparations was attained through the study of the influence of the organic modifier content and the pH and ionic strength of the buffer in the eluent. Electrostatic and hydrophobic interactions between the ergot alkaloid and the analyte contribute to a large extent to the retention and chiral discrimination. The selector was shown to be effective for the resolution of dicarboxylic acids, 2-arylcarboxylic acids and amino acid derivatives.

Enantiomeric separations of halogen-substituted 2-aryloxypropionic acids by high-performance liquid chromatography on a terguride-based chiral stationary phase

Abstract A number of racemic halogen-substituted 2-aryloxypropionic acids, most of which have not yet been resolved, were examined by HPLC on an ergot alkaloid-based chiral stationary phase (CSP). baseline enantiomeric separations were obtained with a selectivity factor (α) within the range 1.06–1.7, thus showing the suitability of this CSP for resolving these compounds in optical purity control of formulations, in stereochemical studies as well as in transformation processes in soil and vegetable tissues. Furthermore, a semipreparative-scale separation of 2-(2,4,5-trichlorophenoxy)propionic acid (Fenoprop) enantiomers was carried out on a 250×7.8 mm I.D. column, yielding approximately 1.0 mg of each enantiomer in a single chromatographic run, with a recovery of 88% and optical purity greater than 99%.

Direct resolution of optically active isomers on chiral packings containing ergoline skeleton. 6. Enantioseparation of profens.

The enantioselective behaviour of some underivatized 2-arylpropionic acids (profens) and flobufen by HPLC using a terguride-based chiral stationary phase was tested. X-ray analysis of crystals of the chiral selector and its complexes with naproxen allowed a deeper insight into the enantiodiscriminative process. The column stability and reproducibility, and the potential of the packing for semipreparative scale separations were also determined. A method for determining flobufen enantiomers and metabolites in plasma samples is described.

Enantiomer separation of 2-arylpropionic acids on an ergot alkaloid-based stationary phase microbore column application

Abstract The separation of enantiomers of underivatized ketoprofen, as well as a number of other non-steroidal anti-inflammatory drugs, was studied by high performance liquid chromatography using a recently developed chiral stationary phase packed in a microbore column. Electrostatic and π-π interactions are assumed to control the retention of the analytes. The enantioselectivity remains constant in a wide range of organic modifier concentration, and is restricted to a pH window ranging from 2.5 to 5.0.

High-performance liquid chromatographic resolution of enantiomers on chiral amine-bonded silica gel

SummaryA chiral stationary phase with an immobilized, optically active diamine was prepared for the separation of enantiomers. The synthesis of the phase was carried out by bonding (−)trans-1,2-cyclohexanediamine to microparticulate silica gel through the coupling agent 3-glycidoxypropylsilane. The resolution of the racemic compounds catechin, 2,2′-dihydroxy-1,1′binaphthyl and trans-1,2-cyclohexandiol, is reported.

High-performance ligand exchange chromatography on chiral diamine-bonded silica gel

SummaryThe resolution of racemates on chiral chemically bonded silica gel by high-performance ligand-exchange chromatography is described. The stationary phase was prepared by bonding (−) trans 1,2 cyclohexanediamine to silica gel through the coupling agent 3-glycidoxypropyl silane. The resolution of several α-amino acids and of compounds of pharmaceutical interest is reported.

Identification of proteinaceous adhesives in the wooden backing of Piero della Francescaˈs painting Pala of Saint Bernardino: a gas chromatographic study

Abstract Samples from the wooden backing of Piero della Francescaˈs 15th century painting Pala of Saint Bernardino were analyzed in order to determine the type of adhesive used for the preparation of the panel. Wood, tow and drop-shaped glue fragments were collected from different sections of the reinforcements and the material connecting the planks. Samples were hydrolyzed and the resulting free amino acids were derivatized and analyzed by gas chromatography. On the basis of amino acid composition and D/L ratios of aspartic acid, two types of proteinaceous adhesives were identified: collagen from animal-skin glue (used in restoration works) and casein (the original adhesive, prepared from cheese and lime). Only a few samples were found to consist of pure casein or collagen, the others being a mixture of the two adhesives. The results are consistent with historical evidence indicating the use of caseinate as an adhesive at the time of the painterˈs activity.

Separation of dansylamino acid enantiomers by thin-layer chromatography

A simple thin-layer chromatographic method for the separation of D- and L-dansylamino acids using a new resolving agent is described. The enantiomeric resolution of racemates was accomplished on reversed-phase plates pre-treated with a poly-L-phenylalaninamide-copper(II) complex using water-acetonitrile mixtures as eluent under isocratic conditions. The polymeric ligand was easily prepared by reaction of the optically active amide with ethylene glycol diglycidyl ether at room temperature. The method is rapid and sensitive, and was successfully employed to resolve various dansylamino acids.

Chitosan-coated silica gel as a new support in high-performance liquid chromatography

SummaryA new stationary phase was prepared by immobilizing the chitosan, a natural hydrophilic polymer, on microparticolate silica gel. The effect of the polarity, pH and ionic strength of the mobile phase has been studied in order to find optimal conditions for the separation of nucleotides and aminoacids. The influence of the properties of the mobile phase on the retention was examined, allowing to employ the chitosan-coated silica gel both to anion exchange and adsorption, depending on the pH and the polarity of the eluent used.