Filippo Pucciarelli

Ion interaction chromatography of neutral molecules

SummaryThe chromatographic behavior of neutral molecules in ion-interaction chromatography (IIC) is investigated theoretically. The physical and chemical modification of the stationary phase in the presence of ion interaction Reagent (IIR) in the eluent, and adsorption competition between test analytes and IIR for inner layer sites are shown theoretically to change the partition coefficient of neutral molecules.The most reliable, literature experimental results, concerming retention behaviour of neutral molecules in IIC, were used to test the new theory. The wide variability among them was elucidated on the basis of the exhaustive retention model developed. Retention equations were compared to those which can be obtained, if the change of the analyte is zero, from the most important retention model in IIC.

Meat fatty acid composition of llama (Lama glama) reared in the Andean highlands

This study reports the results of the chemical analysis of the Longissimus thoracis and lumborum taken from 20 llama males, reared in the Andean highlands. The animals were slaughtered at 25 months and had a mean final body weight of 63kg. Llama meat shows a low fat (3.51%) and cholesterol content (56.29mg/100g). The fatty acid composition in llama meat contains 50.34% saturated fatty acids, 42.48% monounsaturated fatty acids and 7.18% polyunsaturated fatty acids. Llama meat appears to be a healthy alternative red meat choice.

Application of Cu(II) and Zn(II) coproporphyrins as sensitizers for thin film dye sensitized solar cells

We synthesized the Cu(II) and Zn(II) complexes of the 2,7,12,17-tetrapropionic acid of 3,8,13,18-tetramethyl-21H,23H porphyrin (coproporphyrin-I) and successfully employed them as sensitizers in dye-sensitized solar cells. Copper(II) coproporphyrin-I exhibits a power conversion efficiency of 3.8% measured under irradiation of AM 1.5G full sunlight (100 mW cm−2).

The dipole approach in ion-interaction chromatography of zwitterions

SummaryThe chromatographic behavior of zwitterions in Ion-interaction chromatography (IIC) is, investigated theoretically for the first time. The modification of the stationary phase in the presence of Ion-interaction reagent (IIR), and adsorption competition between test analytes and IIR for inner layer sites are shown theoretically to change the partition coefficient for zwitterions.Experimental results from the literature concerning retention behavior of zwitterions in IIC, were used to test the new thermodynamic theory. Very reasonable estimates of (i) ΔGo values for the IIR adsorption onto the stationary phase (II) total ligand concentration, and (iii) dipolar moments validate the present thermodynamic model for the IIC of zwitterionic analytes.Retention equations are compared to those which can be obtained, if the net charge of the analyte is zero, from the most important retention models in IIC. None of them is able to explain, even in a qualitative way, the retention behavior of zwitterions in IIC whereas, the present model is quantitatively able to do this.

Extended thermodynamic approach to ion interaction chromatography: effect of the electrical charge of the solute ion

Abstract The chromatographic behavior of multiply charged analytes in ion interaction chromatography (IIC) was theoretically investigated. Practical equations that describe the relationship between the retention factor and the concentration of the ion interaction reagent (IIR) were developed. They can be used to model analyte retention as a function of both the mobile and stationary phase concentrations of the IIR. A comparison between the retention behaviour of singly and doubly charged analytes is given.

Kinetic model for astaxanthin aggregation in water-methanol mixtures

The aggregation of astaxanthin in hydrated methanol was kinetically studied in the temperature range from 10 degrees C to 50 degrees C, at different astaxanthin concentrations and solvent composition. A kinetic model for the formation and transformation of astaxanthin aggregated has been proposed. Spectrophotometric studies showed that monomeric astaxanthin decayed to H-aggregates that after-wards formed J-aggregates when water content was 50% and the temperature lower than 20 degrees C; at higher temperatures, very stable J-aggregates were formed directly. Monomer formed very stable H-aggregates when the water content was greater than 60%; in these conditions H-aggregates decayed into J-aggregates only when the temperature was at least 50 degrees C. Through these findings it was possible to establish that the aggregation reactions took place through a two steps consecutive reaction with first order kinetic constants and that the values of these depended on the solvent composition and temperature.

Reactions of anionic porphyrin with group 11 elements: a spectrophotometric and electrospray ionization mass spectrometry study

The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) with the elements of 11 group have been studied. CPI is an anionic porphyrin that slowly reacts with copper ion to form Cu(II)CPI and with silver ions to form Ag(II)CPI, Ag(III)CPI complexes and colloidal silver. Gold ions do not form complexes with CPI, but, in the main, colloidal gold and some CPI-N-oxide. The kinetics of the reactions with copper and silver were spectrophotometerically studied and the rate constants were calculated. The identification and characterization of this water-soluble anionic porphyrin and its metal complexes have been performed by electrospray mass spectrometry (ESI-MS) that proved to be an excellent method for these determinations. The multiple charged parent ions for metal free ligand and their metal complexes were identified.

Ion-interaction chromatography of zwitterions. The fractional charge approach to model the influence of the mobile phase concentration of the ion-interaction reagent

The chromatographic behavior of zwitterions in ion-interaction chromatography (IIC) was investigated theoretically, on the basis of the following picture of the retention mechanism. The zwitterionic analyte is considered to interact with the charged stationary phase via an effective fractional charge, opposite to the surface one. Adsorption competitions between analytes and the ion interaction reagent (H) concur to explain the retention factor of zwitterions. The present model is quantitatively able to explain the retention behavior of zwitterions in IIC and also to account for the influence of the zwitterion ionization degree, according to the mobile phase pH, on the course of retention as a function of the H concentration. The approach we used is simple and epistemologically interesting because the retention equation for zwitterions may also be obtained from the general retention equation of our extended thermodynamic approach to IIC. Estimated magnitudes of the effective charges are very reasonable and show the same trend as that of the molecular dipole moments, as expected; the total ligand concentration compares well with the bonded phase coverage of the two columns used. For the homologous series from 4-aminobutyric-, to 8-aminocaprylic acid, the estimated effective charge always increases with increasing chain length and this results in parallel growth of the analyte retention increase upon H addition, so that the retention increase for the highest member of the series compares with that of a positively charged analyte. The estimated dipole for this analyte compares excellently to the estimate obtained via a quantum mechanics calculation. The influence of the mobile phase pH on retention was taken into account for the very first time. The good predictive abilities of the retention equations, and the reliability of the estimated constants that make sense physically confirm that retention modeling is able, at the thermodynamic level, to disclose the complexity of the IIC system.

Determination of Captropril using adsorptive cathodic differential pulse stripping voltammetry with the HMDE

Abstract A voltammetric method for the determination of 3-mercapto-D-2-methylpropanoyl-L-proline, a hypotensive drug whose pharmaceutical name is Captopril (CPT), in the concentration range from 9.0×10 −10 M to 3×10 −6 M , is described. In this range the peak current increases linearly with drug concentration even when different collection periods are used. A self-cleaning Hanging Mercury Drop Electrode (HMDE) was used and a negative Differential Pulse potential (DP) was applied to the indicator electrode. The stripping peak of CPT splits into two peaks as soon as the concentration is increased over about 10 −5 M ; in the oxidation DP scan, instead, this splitting is observed at a concentration of 2.0×10 −4 M . Some attempts were made to verify the suitability of other techniques such as Alternating Current polarography (AC) and the use of a different electrode, the Wax-Impregnated Graphite Electrode (WIGE).

Extended thermodynamic approach to ion-interaction chromatography for high surface potential: use of potential approximation for simplified retention equations

SummaryThe chromatographic behaviour of charged analytes in ion interaction chromatography (IIC) has been investigated theoretically. A potential approximation for high surface potential was used to obtain simplified retention equations that are able to model analyte retention as a function of both the mobile and stationary phase concentrations of the ion-interaction reagent (IIR). The main advantage of using this potential approximation is that it allows calculation of the surface potential, without needing detailed information on physical and chemical properties of the mobile phase.Retention equations of previous thermodynamic retention models can be viewed as limiting cases of the present theory. One of the most reliable data sets conceming the retention behaviour of charged substances in IIC, obtained at high surface potential, was used to test the new retention equations.