Fast assessment of bioaccessible metallic contamination in marine sediments.

A fast (16min) procedure to assess the bioaccessible metallic fraction of Cd, Cr, Cu, Ni, Pb and Zn simultaneously extracted (SEM) from marine sediments plus an indirect approach to determine acid volatile sulfides (AVS) are presented. For the extraction process magnetic agitation was compared with ultrasonic stirring (using a bath and a probe), and several stirring times were assayed. The proposed SEM procedure uses an ultrasonic probe and 1mL of HCl. It dramatically minimizes the turnaround time and the residues. AVS were evaluated as the difference between the amounts of sulphur in the solid residue after the extraction and total sulphur in the original sample. These procedures are fast, easy to implement and cost-effective to assess the potential risk posed by metals in marine sediments. They were tested using several CRMs and applied to sediments from two Galician Rias (NW Spain); their SEM-AVS differences indicated no biological risk.

Interpolation in the standard additions method.

The standard additions method (SAM) has traditionally been performed by using extrapolation. This practice is suboptimal because predictions are affected by even slight departures of calibration points from a straight line. Despite this, most textbooks and papers in analytical chemistry still refer exclusively to extrapolation. In contrast, the use of interpolation is recommended in this paper as a way to get predictions on the central part of the regression line and thus minimize the bias in the prediction and the variance associated with the analytical result. Several scenarios were studied, with concentration errors simulated in different calibration solutions. It was found that translational effects due to variations at the central part of the calibration caused the lowest disturbances on the predicted concentrations. The differences between the interpolated and extrapolated predictions can be as large as ±30%. The confidence interval associated with the extrapolation result is wider than that due to interpolation by as much as 100%. It is shown that commonly used equations underestimate the correct confidence intervals. Both, absence of bias and improved precision, are of relevance in quality assurance, method validation and error propagation.

Carcinogenicity of policosanol in mice: an 18-month study.

Policosanol (trade name Ateromixol) is a new cholesterol-lowering drug that has been isolated and purified from sugar cane wax. The effects of policosanol (50-500 mg/kg) administered orally for 18 months to male and female Swiss mice were investigated. No differences in daily clinical observations, weight gain, food consumption and mortality (survival analysis) between groups were found. Histopathological study showed that the frequency of neoplastic (benign and malignant) lesions was similar in the control and policosanol-treated groups. The lesions observed were similar to the spontaneous lesions in Swiss mice reported in previous studies. As no drug-related increase in the occurrence of malignant or benign neoplasm was found, nor acceleration in tumour growth in any specific group observed, this study shows no evidence of policosanol-induced carcinogenicity in Swiss mice.