Lichen (Xanthoria parietina) biomonitoring of trace element contamination and air quality assessment in Pisa Province (Tuscany, Italy).

In the northern part of Pisa Province (Tuscany, Italy), the use of lichens as both airborne trace element biomonitors and air quality bioindicators is described. The following elements were analysed in Xanthoria parietina: As, Cd, Cr, Ni, Pb, V, Zn and Hg, and the results are compared with those we previously obtained in Livorno Province (Tuscany) using the same lichen species. The results identify spots of different environmental metal contamination and air quality. Median values of Pb, V and Ni concentrations were much lower than those of Livorno Province, with maximum values even nine times lower. Arsenic contamination was also lower, while Cd, Hg and Zn levels were similar in the two areas. In Pisa Province, the highest levels of contamination were recorded for Zn, Pb, Cr and Ni, and a degree of agreement was found between air quality and metal concentrations in lichens. The air quality in Pisa Province is better than in Livorno Province, even if the different climatic and orographic features of the two areas may influence the presence of lichen species and thus an assessment of air quality.

New method for separation and determination of denatured caseins by hydrophobic interaction chromatography.

A new method for the separation of denatured alpha-, beta- and kappa- caseins by hydrophobic interaction chromatography (HIC) is proposed. The method is based on an easy solubilization of commercial and real samples by 4.0 M guanidine thiocyanate (GdmSCN) and elution on a TSK-Gel(R) Phenyl-5PW column (TosoHaas) in the presence of 8.0 M urea in the mobile phase. The procedure, applied to commercial caseins and to real, raw samples (whole milk powder and fat-free yoghurt) is not expensive, it requires common high performance liquid chromatography (HPLC) instrumentation and allows the separation of caseins also in the presence of whey proteins. Quantitative results on the analysis of alpha-, beta- and kappa-caseins in real samples are also reported.

Application of mercury cold vapor atomic fluorescence spectrometry to the characterization of mercury-accessible -SH groups in native proteins.

A new analytical approach has been applied to the determination and characterization of mercury-accessible -SH groups in pure native protein samples (ovalbumin, hemoglobin, glyceraldehyde-3-phosphate dehydrogenase, aldolase, pyruvate kinase, hexokinase, lactate dehydrogenase, alcohol dehydrogenase, creatine phosphokinase, lysozyme, and cytochrome c). The method is based on the selective reduction of Hg(II) in the presence of Hg(II)-thiol complexes with alkaline sodium tetrahydroborate, to give Hg(0) in a continuous flow reaction system coupled with atomic fluorescence spectrometric (AFS) detection. The method is fast and specific and allows one to work with nanomole amounts of a single protein without any preliminary incubation and without any separation of Hg(II) from thiol-complexed mercury. The meaning of the results obtained in the determination of the accessible -SH groups in native proteins by using chemical probes is discussed.

An approximate CUSUM procedure for surveillance of health events.

The CUSUM method is frequently used by epidemiologists for detecting a shift in the incidence of rare health events. An exact solution for a Poisson process has been proposed by other works, but potential applications have been limited by the fact that the size, the structure of the at-risk population and the baseline rate may not be constant during the period of surveillance. Furthermore, for practical use tables of critical values are available only for some expected values and in any case less then 9. This paper proposes an approximate CUSUM procedure, based on the normal approximation to a Poisson process, which may be an efficient solution of the problems previously pointed out. Analyses of simulated and actual data sets illustrate the usefulness of the proposed procedure. An application to mortality data for respiratory diseases in a north Tuscany area, characterized by the presence of chemical plants, is showed. No shift in the mortality rate during the 1980-1989 period was detected compared with the 1970-1979 period, in contrast with the result obtained with the standard CUSUM method for a Poisson variate.

Elimination of hydrofluoric acid interference in the determination of antimony by the hydride generation technique.

For the determination of antimony by hydride generation techniques a pretreatment procedure has been developed for the reduction of Sb(V) to Sb(III) in order to remove the effect of hydrofluoric acid which strongly interferes with the reduction of pentavalent antimony to the trivalent state. It is based on the combined action of l-cysteine and boric acid at 80 degrees C. The pretreatment is effective in both nitric and hydrochloric acid media. Quantitative recoveries are obtained in less than 60 min. Under these conditions antimony is reduced to the trivalent state in acid media containing both nitric and hydrochloric acid. The method has been applied to the determination of total antimony in certified reference materials of sediments after pressurized microwave digestion with HNO(3)-HCl-HF. Good agreement is obtained by using both analytical techniques: continuous flow hydride generation atomic fluorescence spectrometry and flow injection electrothermal atomic absorption spectrometry with in-situ trapping of stibine in a graphite atomizer.

Electron Transfer in Donor-Acceptor Molecules of Substituted Naphtoquinones: Spectral and Redox Properties of Internal Charge Transfer Complexes

The investigated compounds were substituted naphtoquinones containing aniline moiety separated from the quinoid system by a methylene bridge. The nature of substituents on both donor and acceptor parts influenced the degree of formation of an internal charge transfer complex. Properties of the internal charge transfer interactions were investigated by voltammetry, spectroscopy, and in situ spectroelectrochemistry. Quantum chemical interpretation of experiments is given.

Rapid colorimetry of zinc in seminal fluid.

This colorimetric method for determination of zinc in seminal liquid is based on the reaction between zinc and 4-(2-pyridylazo)resorcinol in a buffered solution at pH 9.5. It is very simple, fast (approximately equal to 10 min), and economical. It can be used to determine zinc in "whole" semen, seminal plasma, or isolated spermatozoa. We verified its accuracy for sample concentrations up to 0.4 g/L by comparison with a reference method based on atomic absorption spectroscopy of acidic wet-ashed samples. Calcium and magnesium do not interfere, even in concentrations exceeding the physiological values. Between-run precision at a normal concentration of 0.14 g/L is about +/- 7 mg/L; within-run precision at the same concentration is about +/- 2 mg/L.

Binary data acquisition from instrumentation with BCD-coded output: a hardware converter and an example of the relative software control.

Simple hardware for conversion from BCD into binary code is described. The device is of low cost, performs a 16-bit conversion in a maximum time of 400 nsec, and is able to output the converted number to either an 8-bit or a 16-bit data bus. An example of the software necessary to perform data acquisition from a digital voltmeter by using this converter is also presented.