Francesco Fagioli

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.

The adaptation of the dichromate digestion method for total mercury determination by cold-vapor atomic absorption spectrometry to the analysis of soils, sediments and sludges

Previous research demonstrated the overall validity of a two-component wet digestion procedure based on the action of K2Cr2O7 + H2SO4 (50%, v/v) at boiling temperature (180°C) with vapors refluxing in an air condenser in the treatment of biological samples to be analyzed for total mercury by cold-vapor atomic absorption spectrometry (CVAAS). This study explored the ability of this procedure to cope with soils, sediments and sewage sludges. After demonstrating that cinnabar (HgS) is completely dissolved under the experimental conditions employed, a set of nine standard reference materials having a mercury content ranging from 0.0568 to 9.49 μg g−1 was analyzed. One difficulty was posed by chloride containing samples and was due to the formation of chlorine, a strong inhibitor of the spectrometric signal. Evidence is given that this effect is ascribable to the re-oxidation of elemental mercury by the chlorine present inside the reduction-aeration system. The elimination of chlorine by simply running the digestion without a condenser proved effective in some cases. However, when the samples had a high content of organic matter or carbonates the absence of the condenser caused mercury losses. A study employing mercuric nitrate and methylmercury chloride showed that the escape of mercury from the digestion tube not surmounted by the condenser is related to the rapid release of CO2 when organic matter and carbonates react with the digestion mixture at its boiling point; high temperature alone is not sufficient for mercury to be lost. Therefore, the digestion procedure was duly reconsidered and split in two parts: (a) an initial 60 min period with the condenser in place during which the destruction of all organic matter and carbonates takes place followed by (b) a 30 min span without condenser to allow chlorine and other potential interfering vapors and gases to leave the digest. The modified procedure was applied to the same reference materials as above and additionally to a biological standard of mussel tissue. The analytical results showed that total mercury could be determined in all samples with consistently good precision and accuracy (R.S.D.% range = 1.2–4.5; error %range = −3.8 to + 8.7).

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.

Cisplatin cytotoxicity in organ of corti-derived immortalized cells

Cisplatin is an anticancer drug currently used in the treatment of genital and head and neck tumors. Its use in these and other types of tumors is narrowed by onset of chemoresistance and severe undesired side effects, like as nephro‐ and ototoxicity, whose mechanisms of action are only partially understood. In the present study we investigated the effects of cisplatin (cis‐dichlorodiaminoplatin, CDDP) on a cell line (OC‐k3) developed from organs of Corti of transgenic mice. We observed at 48 h that cell death due to cisplatin was time and concentration‐dependent. The cell death displayed some morphological hallmarks of apoptosis, including nuclear fragmentation into several large nuclear fragments, surrounded by a rearranged and thickened actin cytoskeleton. No DNA laddering was detected, suggesting absence of endonuclease activity, nor annexin V positivity, suggesting absence of phosphatidylserine externalization. Several molecules protected the cells against CDDP induced cytotoxicity, including methionine, suramin and PD98059. Methionine reduced CDDP‐uptake, while suramin, a polycathionic compound a specifically binding external proteins, did not. This finding suggested that suramin could exert its protective effect by acting on an intracellular transduction pathway. We tested this hypothesis by studying the effect of suramin and PD98059, a MEK inhibitor, on the mitogen activated protein kinase (MAPK) cascade. After CDDP treatment, we found an increase of phosphorylation of extracellular regulated kinases (ERK)1/2, that could be inhibited by PD98059 and suramin. These data suggest that ERK pathways can play a role in mediating the cell death induction in presence of a CDDP challenge. J. Cell. Biochem. 101:1185–1197, 2007.

Digestion method for the determination of mercury in vegetable matrices by cold vapour atomic absorption spectrometry

A simple and rapid wet-digestion procedure is described for the determination of total mercury in botanical samples by cold vapour atomic absorption spectrometry. The method is based on the oxidising properties of potassium dichromate in dilute sulphuric acid and was tested on two National Institute of Standards and Technology Standard Reference Materials. The mass of the samples taken for analysis was about 0.5 g in all instances, corresponding to an amount of mercury of the order of 0.075-0.040 micrograms depending on the material. The results were compared with those obtained using the Association of Official Analytical Chemists official digestion technique, which involves the use of nitric and sulphuric acids, and a second technique based on the action of nitric and perchloric acids. The proposed method provided better accuracy and showed good precision. Its ability to achieve the decomposition of two organomercurials for full mercury recovery was verified.

Determination of aluminium by inductively coupled plasma mass spectrometry in serum of patients treated by haemodialysis, dialysis solutions and tap water, and a comparison with atomic absorption spectrometry

Inductively coupled plasma mass spectrometry has been applied for the determination of aluminium in serum (diluted 1 + 4) of patients treated by haemodialysis, concentrated solutions for haemodialysis diluted 1 + 35, haemofiltration solutions and peritoneal dialysis solutions. Matrix effects were studied from the ratio of the slope of the analytical calibration function obtained in the matrices to that in aqueous standard solutions. Comparison was made with electrothermal atomic absorption spectrometry and there is no evidence for systematic differences between the results obtained by the two methods.

Absolute analysis in electrothermal atomization atomic absorption spectroscopy—an atomization system for confining all the atoms injected in the opti

Abstract The apparatus presented in this paper is able to simultaneously confine all the atoms injected into the atomizer within the optical beam. As a consequence, during the time interval fulfilling this condition, the absorbance is constant. Experimental absorbance vs time curves, with Cd as analyte, show a constant value for more than 0.2 s. The curve shapes are in agreement with those theoretically derived for pure diffusion. This finding should lead to a method for absolute analysis that is more accurate than the methods used in ETA-AAS up to now. In fact, with this approach, one has to measure a constant signal while in the case of area measurements one has to integrate a signal that exponentially decays toward the baseline value. Data presented in this paper refer to the most volatile elements (Cd, Hg and Pb) in simple matrices. The possibility of extending the presented method to complex matrices and less volatile elements is dependent on the availability of both a more powerful power supply system and well-suited atomizer design.

Evaluation of a New Method for the Determination of Elements in Vegetable Foods and Feeds by Atomic Absorption Spectroscopy with Sampling of Carbonaceous Slurry

Abstract The new method, proposed in a preceeding paper for the determination of elements in plant material by flame atomic absorption spectroscopy (FAAS) with liquid sampling of carbonaceous slurry, was tested on other kinds of organic material such as vegetable foods and feeds. Results are reported for the determination of calcium, magnesium, potassium, iron, manganese, zinc and copper in these materials. Also, the analytical results relative to the determination of cadmium by graphite-tube furnace atomic absorption spectroscopy (GTFAAS) for two matrices are given. In all cases accuracy and precision of the analytical procedure were ascertained.

Experimental measurement of absolute number of atoms vaporized in a graphite cuvette.

A new method based on electrothermal atomic-absorption spectrometry is proposed for the experimental calculation of the product KN(0) where K is a constant which relates the instantaneous absorbance to the instantaneous number of atoms electrothermally atomized in a graphite cuvette, and N(0) is the number of atoms initially deposited in the graphite cuvette. The method is based on measurement of the integrated absorbance A(i) and the average residence time tau(R) of the atoms in the optical path, from an absorbance vs. time curve. The data so obtained can be used to compare the K values with those in the literature or, if K is known, to calculate N(0) under widely different experimental conditions. The ratio A(i)/tau(R) remains constant even if both A(i) and tau(R) change with different heating rates and the final constant temperature of the euvette surface, T(f).

Second harmonic a.c. anodic stripping voltammetry of metals at trace level: simultaneous determination of lead and thallium, and bismuth and antimony

Pairs of elements with very small differences in their half-wave potentials were determined at trace levels by second harmonic a.c. anodic stripping voltammetry. The simultaneous determination of lead and thallium as well as that of bismuth and antimony in 1M hydrochloric acid as supporting electrolyte was found to be possible in the range of concentration ratios: 7:1 > or = C(Pb):C(Tl) > or = 1:36 and 45:1 > or = C(Sb):C(Bi) > or = 1:35, with <5 % relative error due to mutual interference. The limit of detection was approximately 10(-8)M for all four elements, and the precision and error were 2-3%. The simultaneous determination of these metals in mixtures with concentration ratios outside the quoted ranges is still feasible by the standard-addition technique.