Gabriella Blo

Characterisation of River Po particles by sedimentation field-flow fractionation coupled to GFAAS and ICP-MS

Abstract A procedure for elemental composition determination of water-borne river particles (Po River) on both size-fractionated and unfractionated submicron particles (0.1–1 μm) by graphite furnace atomic absorption spectroscopy (GFAAS) and inductively coupled plasma-mass spectrometry (ICP-MS) is reported. Sample fractionation was performed using sedimentation field-flow fractionation (SdFFF). The distribution of relative mass vs. particle size was determined using UV detection. Fractions were collected over a narrow size range for scanning electron microscopy. With this combination of techniques the mass, elemental composition, and shape distributions can be obtained across the size spectrum of the sample. The size distributions of the major elements (Al, Fe) were determined by coupling both GFAAS and ICP-MS techniques to the SdFFF. The procedure was validated using a reference clay sample. Satisfactory agreement was found between both the GFAAS and ICP-MS aluminium signal and the UV detector signal. Some discrepancies were observed in the Fe Al ratios when comparing GFAAS and ICP-MS. Thus further investigation is in order to fully assess the role of SdFFF-ICP-MS and SdFFF-GFAAS techniques for elemental characterisation of aquatic colloids. Both GFAAS and ICP-MS signals unambiguously indicate a significantly higher Fe content in the lower size range, which is consistent with previous investigations. Trace element levels in unfractionated Po River particles, determined by both GFAAS and ICP-MS, show good agreement. The high levels of Cu, Pb, Cr and Cd found associated with the colloidal particles underlines the significance of the environmental role played by the suspended matter in rivers in both highly industrialised and intensively cultivated areas.

Solvent selectivity effects in reversed-phase high-performance liquid chromatography of flavonoid compounds

Abstract The selectivity properties of methanol, acetonitrile and tetrahydrofuran as organic modifiers in the reversed-phase high-performance liquid chromatographic separation of flavonoid compounds was studied. Conditions for achieving separations between compound classes are described, in particular the possible separation of glycosides from aglycones in acetonitrile and tetrahydrofuran. Eleven retention contributions as Δlog k ′ are reported, and their dependence on mobile-phase composition is described. Solvent strength values and useful gradient elution conditions are given.

Determination of histamine in the whole blood of colon cancer patients

The aim of the present work is to investigate whether histamine assay could be useful in detecting the presence of primary cancer. The high-performance liquid chromatographic (HPLC)-based o-phthalaldialdehyde (OPA) histamine derivatization assay was investigated with respect to several variables, dramatization reagent concentration, organic solvent requirement, derivatization time and counter-ion effect on chromatographic separation. The OPA histamine assay, in the absence of added -SH groups, was found to detect histamine in whole blood samples with relative standard deviations <14% and recoveries not less than 90%. The assay showed high selectivity towards other aminic-containing compounds and a detection limit of 18 nM of histamine was evaluated. Calibration curves in the range 50-500 nM were obtained by using histamine standards in 0.1 M HCl with a regression coefficient value (r(2)) of 0.9969. In order to assess the usefulness of this assay in primary tumor monitoring, two groups of individuals, 29 controls and 29 colon cancer patients were selected, and serum levels of histamine, carcinogen embrionary antigen (CEA), carcinogen antigen 19.9 (CA19.9), and tumor staging, were determined. A significant histamine reduction (P=0.028) between controls (180.12+/-70.4 nM) and patients (134.5+/-90.3 nM) was found, and a cut-off value of 157.5 nM was extrapolated as intercept point of sensitivity and specificity curves. Fifty percent of patients showed a histamine value below the cut-off, while 45.8 and 8.3% of patients were positive for CEA and CA19.9, respectively. No correlation was found between Tumor Node Metastasis staging and histamine amount, indicating that this marker is not related to the tumor mass. Our data suggest that histamine level, together with other classical tumor markers, could be a potentially interesting tumor marker in colon cancer monitoring.

SPLITT cell separation of polydisperse suspended particles of environmental interest

SummarySplit-flow thin (SPLITT) cell, continuous two-way separation has been investigated for the separation of particulate matter of environmental interest. The basic SPLITT cell operation equation is reconsidered and the effects of the particle porosity, dimension, shape and density are discussed. Suspensions of porous silica, kaolin and montmorillonite in the submicron to micron diameter range were separated by means of the SPLITT cell with appropriate carrier composition. The results of the separations were checked by use of optical and scanning-electron microscopy and are discussed with reference to the basic equations for SPLITT cell working conditions. Optimum results were in agreement with the theoretical expressions as long as the pertinent SPLITT separation expression was employed. Quantitative results from SPLITT cell separations were compared with those obtained by the classical static sedimentation procedure; the agreement and discrepancies found are discussed.

Continuous split flow-thin cell fractionation of starch particles

The fractionation of starch granules was investigated using a SPLITT (split flow-thin) cell, a relatively new system for fast, continuous binary separations. The effect of such basic separation parameters as carrier composition, relative flow-rates and sample concentration on the SPLITT cell performance were exploited. The obtained starch fractions were checked by both optical microscopy and sedimentation/steric field flow fractionation (Sd/StFFF). The sedimentation field flow fractionation technique was employed for the starch sample using the density compensation procedure.

High-performance liquid chromatographic determination of naphthols as 4-aminoantipyrine derivatives : Application to carbaryl

Abstract The high-performance liquid chromatographic determination of 1- and 2-naphthol after derivatization with 4-aminoantipyrine is described. The chromatographic analysis of the reaction mixtures showed two main coloured products for each naphthol. In order to investigate the nature of the reaction products a spectroscopic study ( UV — VIS , IR , NMR ) of the products separated by chromatography was performed. On the more stable 1-naphthol reaction product the quantitative determination of 1-naphthol was performed in the 0.05–10 ppm concentration range. Instability of the 2-naphthol products made their quantitative determination difficult; detection at two different wavelengths (460 and 412 nm) gave a very reliable criterion of qualitative identification. As 1-naphthol is the major degradation product of the insecticide carbaryl, this determination reaction of 1-naphthol was applied to carbaryl. The applicability and performance of the method was checked by determining the carbaryl content in commercial powder formulations and residues in apples.

Determination of phenols in water samples as 4-aminoantipyrine derivatives by high-performance liquid chromatography

Abstract The determination of 22 monohydric phenols by high-performance liquid chromatography after derivatization with 4-aminoantipyrine is described. The reaction variables were evaluated in order to examine the performance of the method at low ppb★ concentrations. The chromatographic behaviour of the derivatives was investigated by carrying out separations on different bonded-phase columns, which provided a satisfactory selectivity under isocratic elution conditions. Separations of complex mixture obtained on normal and reversed bonded phases, in addition to bathochromic and hypsochromic effects shown by derivatives, provided effective information for identifying individual phenols. The technique was applied to the determination of phenols at ppm and ppb concentrations in water and wastewater samples.

Experimental approaches for size-based metal speciation in riversElectronic supplementary information (ESI) available: Experimental details, tables A?D showing parameters for GF and AAS, detection limits for ETAAS, SdFFF operative parameters and metal concentrations determined in the void time at the two different pH values, and SEM images of the void time fractions. See http://www.rsc.org/suppdata/em/b3/b308877d/

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. The fact that there is no homogeneity in methods and data collection in this field is underlined. Among the different fractionation techniques, Field Flow Fractionation (FFF) methodologies have proved to be a good approach to study the role of SPM in metal load and transport. The possibility of studying size-based metal speciation using the SdFFF technique is presented and the importance of metal speciation in rivers is underlined.

Analysis of kaolin by sedimentation field-flow fractionation and electrothermal atomic absorption spectrometry detection

SummaryElectrothermal (graphite furnace) atomic absorption spectrometry (ETAAS), as off-line detector for sedimentation field-flow fractionation (SedFFF) is exploited in clay analysis.Quantitation limits of coupled SedFFF-ETAAS for the determination of a submicron kaolin sample, considered a representative model of natural water suspended particulate, are theoretically established and experimentally validated with reference to Al and Si determination by ETAAS.Complete sample recovery for a 4 µg injected kaolin sample was obtained by keeping adsorption in the SedFFF apparatus to a minimum under control. The best experimental conditions, ensuring sample integrity, were low ionic strength (Na2CO3, 10−5 M), pH 8 and a Teflon covered accumulation wall. Several different runs, revealing the various experimental parameters affecting quantitative recovery, are reported and the different physico-chemical processes affecting such recovery are discussed. The advantages and drawbacks of SedFFF-ETAAS coupling compared with inductively coupled plasma-mass spectrometry (ICP-MS) technique are also discussed.

Influence of thermal pre-treatment on adsorption properties of porous polymer air samplers

Abstract A study of the influence of thermal pre-treatment on the adsorption properties of various polymers (Porapak Q, Chromosorb 101, 102 and Tenax GC) is reported. The linear extrapolation of ln Vg against 1/T is examined in the context of the preheating temperatures. At higher temperatures, chromosorb 101 and 102 show a polarity increase, while Porapak Q shows a decrease. For styrene copolymers, the function ln Vgversus 1/T is fully linear only when the pre-heating temperature coincides with the temperature limit suggested by the manufacturers. Pre-heating temperatures between 200 and 300°C do not influence the adsorption characteristics of Tenax GC, for which the function ln Vg, versus 1/T is always linear.