Giancarlo Torsi

Determination of Se, As, Cu, Pb, Cd, Zn and Mn by anodic and cathodic stripping voltammetry in marine environmental matrices in the presence of reciprocal interference. Proposal of a new analytical procedure

Arsenic(III), selenium(IV), copper(II), lead(II), cadmium(II), zinc(II) and manganese(II) have been determined in environmental matrices by differential pulse cathodic (DPCSV) and anodic (DPASV) stripping voltammetry. The voltammetric measurements were carried out using a conventional three-electrode cell and the ammonia–ammonium chloride buffer (pH 9.4) as the supporting electrolyte. The analytical procedure was verified by the analysis of the standard reference materials: Sea Water BCR-CRM 403; Lagarosiphon Major BCR-CRM 060; and Cod Muscle BCR-CRM 422. The precision, expressed as relative standard deviation, and the accuracy, expressed as relative error, were, in all cases, lower than 5%; the detection limits, for each element in the experimental conditions employed, was approximately 10−9 M. The standard addition technique significantly improved the resolution of the voltammetric method, even in the case of very high metal concentration ratios.

Determination of particle size distribution by gravitational field-flow fractionation: Dimensional characterization of silica particles

SummaryGravitational field-flow fractionation (GFFF) is the simplest and cheapest of field-flow fractionation (FFF) techniques, although it is still at an early development stage. The application of GFFF to the determination of particle size distribution (PSD) of silica particles used as chromatographic supports is described. The accuracy of the method is evaluated by comparing PSDs obtained by GFFF with those obtained by laser diffraction, a non-separative technique widely applied to particle characterization. It is ultimately demonstrated that a low-cost GFFF channel can simply replace the column of a standard HPLC system, allowing laboratories that are not specialized in size analysis to perform accurate PSD studies with standard HPLC expertise.

Analytical procedures for the simultaneous voltammetric determination of heavy metals in meals

Abstract An analytical procedure regarding the determination of copper(II), lead(II), cadmium(II), zinc(II) and antimony(III) in matrices involved in foods and food chain as wholemeal, wheat and maize meal is proposed. The digestion of each matrix was carried out using concentrated HCl suprapure at 130 °C for 3 h. Differential pulse anodic stripping voltammetry (DPASV) was employed for simultaneously determining all the elements, using a conventional three-electrode cell and 0.5 M HCl as supporting electrolyte. The analytical procedure has been verified on the reference standard materials Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a. For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation (s r ), and the accuracy, expressed as relative error (e), were of the order of 3 to 6%. The limits of detection were in the range 0.009–0.096 μg/g.

Standardless method for quantitative particle-size distribution studies by gravitational field-flow fractionation. Application to silica particles

SummaryGravitational field-flow fractionation is a separative analytical technique which has already proved suitable for quantitative particle-size distribution analysis. One of the most attractive aspects of the technique is that it can allow for direct conversion of fractograms into size distributions of the samples, although retention exhibits substantial dependence on flow rate, compared to other field-flow fractionation methods.It is shown here that conversion of fractograms into quantitative, size-distribution profiles of micron-sized silica particles is possible through gravitational field-flow fractionation in standardless mode. Standardless means that the conversion of fractograms is performed by single-run analysis because all the parameters necessary for the calculations can be obtained, from sample specifications and previous instrumental calibration, by means of semiempirical models.

Experimental study on the retention of silica particles in gravitational field-flow fractionation effects of the mobile phase composition☆

Effects of mobile phase composition can play an effective role in modulating the retention of particles in gravitational field-flow fractionation (GFFF), the simplest and cheapest among field-flow fractionation (FFF) techniques. In the framework of an optimized procedure for the GFFF characterization of particulate systems, an experimental approach to the effects of the mobile phase composition on the retention of silica particles retention is presented. The role of the ionic strength and the presence of surfactant are emphasized, with special regards to the shape of the particles. Moreover, the first experimental evidence of potential-barrier GFFF is reported.

Determination of the absolute number of moles of an analyte in a flow-through system from peak-area measurements

Abstract A simple model is proposed for the determination of the absolute amount of an analyte when non-destructive detection systems are used in high-performance liquid chromatography and flow-injection analysis. The method requires only a knowledge of the cell thickness, molar absorptivity of the analyte and flow-rate if absorption is measured. The data obtained with a commercial apparatus are consistent with the model both for a compound with well known spectroscopic characteristics (K2CrO4) and for common organic substances such as toluene and p-nitroaniline. A systematic error of ca. 18% is present with the detector used for all analytes. The possible origin of this error is discussed.

A new voltammetric method for the simultaneous monitoring of heavy metals in sea water, sediments, algae and clams: application to the Goro Bay ecosystem.

Arsenic(III), selenium(IV), copper(II), lead(II), cadmium(II),zinc(II) have been determined in sea water, sediments, algae andclams by differential pulse cathodic (DPCSV) and anodic (DPASV)stripping voltammetry. The voltammetric measurements are carriedout using a conventional three-electrode cell and the ammonia-ammonium chloride buffer pH 9.2 as supporting electrolyte.The analytical procedure has been verified by the analysisof the standard reference materials (Estuarine SedimentBCR-CRM 277, Ulva Lactuca BCR-CRM 279 and Mussel Tissue BCR-CRM278). The precision and the accuracy are less than 5%. Thisprocedure is utilized for the monitoring of heavy metals inthe Po river mouth area (Italy).

FMOC-Cl as derivatizing agent for the analysis of amino acids and dipeptides by the absolute analysis method

SummaryOne classical method for quantitation of amino acids in proteins is hydrolysis of the proteins and determination of the free amino acids. Although the drastic experimental conditions necessary for complete hydrolysis always cause degradation of some of the amino acids, if mild hydrolysis conditions are used, a mixture of amino acids and oligopeptides is obtained. If these conditions are adequately tuned, the oligopeptides are almost exclusively dipeptides. For this reason we have initiated a study to find a derivatizing agent suitable for the analysis of amino acids and dipeptides by an absolute method of quantitation already tested for amino acids. FMOC-Cl was found to be a suitable derivatizing agent for this purpose.

Particle collection mechanism and efficiency in electrostatic accumulation furnace for electrothermal atomic spectrometry

Abstract A deeper insight into the collection mechanism of an electrostatic accumulation furnace for electrothermal atomic spectrometry has been obtained. It has been found that the electrostatic filter operates in the “Trichel pulses” region and that most of the captured species are accumulated in a region 3–4 mm wide centered around the tip of the active electrode. The capture efficiency, evaluated by direct particles counting, can be easily raised to over 99% and is mainly related to the quantity of charge acquired by a particle within the “active volume” of the electrostatic precipitator.

Cathodic and anodic stripping voltammetry: simultaneous determination of As–Se and Cu–Pb–Cd–Zn in the case of very high concentration ratios☆

Arsenic(III), selenium(IV), copper(II), lead(II), cadmium(II) and zinc(II) are determined in environmental matrices. The voltammetric measurements were carried out using a conventional three-electrode cell and the ammonia-ammonium chloride buffer pH 9.3 as supporting electrolyte. The analytical procedure was verified by the analysis of the standard reference materials Estuarine Sediment BCR-CRM 277 and River Sediment BCR-CRM 320. The precision, expressed as relative standard deviation (s(r)), and the accuracy, expressed as relative error, were, in all cases, less than 5%; the detection limits, for each element and in the experimental conditions employed, were around 10(-9) M. The standard addition technique significantly improved the resolution of the voltammetric method, even in the case of very high metal concentration ratios.