Simultaneous determination of Cu(II), Ni(II) and Zn(II) by peroxyoxalate chemiluminescence using Partial Least Squares calibration.

It was found that the ions Cu(II), Ni(II) and Zn(II) can attenuate the peroxyoxalate chemiluminescence emission, which was used to develop an analytical procedure for the simultaneous determination of these ions in a stopped-flow system using Partial Least Square (PLS) calibration. Acetonitrile was used to dissolve TCPO and to prepare a mixture of fluorescein, H(2)O(2) and imidazole. These solutions were carried using two peristaltic pumps, while a third pump was employed to propel the aqueous solutions of the metallic ions. All solutions were mixed in the quartz cell of a Campsec CL detector connected to a personal computer to register the CL development using the Clarity software. Under the optimum operative conditions each ion produced a specific CL development with maximum intensities at 0.280 min for Zn(II), 0.307 min for Ni(II) and 0.327 min for Cu(II). The latter exhibited the highest inhibition effect. The experimental calibration set was composed of 16 sample solutions using a central design for three component mixtures with scaled values. The proposed method offers the advantages of simplicity, good precision and accuracy for the simultaneous determination of Ni(2+), Cu(2+) and Zn(2+) in water samples.

Distribution of mercury in the aquatic environment at Almadén, Spain.

The world's largest mercury mine is placed at Almadén, Spain. However, there is a lack of information about the environmental impact of these mining activities in the ecosystem that surrounds this area. The aim of this article is to document the concentration of mercury in waters, sediments and bivalves of the aquatic system impacted by historic mine wastes. Simultaneously, a comprehensive study has been undertaken to characterise this hydrosystem and to determine the influence of some major physico-chemical parameters on the fate of mercury. Samplings were carried out for the last few years. Concentration of mercury in waters ranged from not detectable to 20 microg/l. For the sediments study, samples have been taken both from contaminated and non-contaminated sites within the basin. The regional background mercury concentration is higher than values typically cited for natural backgrounds. At exposed sites the mercury concentrations between 5 and 1000 microg/g were measured. These values are one to four order of magnitude greater than regional background levels. In the comparison between the results obtained at the present moment and those available for the 1974-1977 period, a general diminution of mercury levels is observed. Mercury concentrations in fresh water bivalves ranged between 1 and 4 microg/g (d.w.), with around 30% as monomethylmercury. In the discussion of the implications for risk assessment data available for other areas affected both for mine activities and mercuriferous belt are included.

Chemical availability of mercury in stream sediments from the Almadén area, Spain.

The chemical speciation, fractionation and availability of mercury in sediments from a cinnabar mining area (Almadén, Spain) was studied with different extraction and analytical procedures, in order to determine the degree to which the ecosystem is harmed by this pollutant. Three total extraction procedures, a sequential extraction and the speciation of organo-mercury compounds were performed in nine sediment samples. In the study area, although concentrations of mercury can be extremely high (up to 1,000 mg kg(-1)), no organomercury compounds were detected (< 2 microg kg(-1) and the availability of this element seems restricted. One of the methods for total extraction presented considerably lower recovery in Almadén's sediments, yet the results were controlled with certified reference materials. This disagreement was attributed to the fact that the mercury is in a refractory form. Sequential extraction was able to show that most of the mercury is associated with sulfides (probably as metacinnabar) or in the residual refractory phase (probably as red cinnabar).

Fluorimetric determination of salsalate in urine, serum and pharmaceutical preparations.

A method for the determination of salsalate at concentrations between 0.10 and 1.00 mug ml(-1) by means of fluorescence spectrometry technique is proposed. Salsalate, lightly soluble in water, is totally extracted into chloroform. In this organic phase, the drug shows low fluorescence but when an alkaline medium is provided, salsalate undergoes a substantial increase of the fluorescent intensity. Thus, the determination is performed in a chloroformic medium, where pyrrolidine chloroformic solution is added to give the basic character. The fluorescence measurements to quantify salsalate are carried out in its fluorescent band centered at lambda(ex)=299 nm and lambda(em)=410 nm. The method was successfully applied to the determination of salsalate in authentic pharmaceutical preparations, urine and serum. Samples of these latter two matrices, urine and serum, are extracted into chloroform, using in the aqueous phase a pH 4.8, provided by adding acetic acid/sodium acetate buffer solution. Owing to matrix interference, the method of standard additions was used to determine salsalate in the serum. The sensitivity and repeatability achieved with the proposed method are adequate for the determination of salsalate in these matrices.

Simultaneous determination of salicylamide and salsalate in serum and urine by first derivative variable-angle synchronous fluorescence spectrometry.

The determination of salicylamide and salsalate in human serum and urine is performed using a simple, rapid, sensitive, and selective method. The broad-band overlapping conventional spectra of both compounds are resolved by means of first derivative variable-angle synchronous fluorescence spectrometry. The method is based on the intrinsic fluorescence of both drugs in chloroformic solution. The measurements are performed in an alkaline medium, which is adjusted by adding 0.40 M pyrrolidine chloroformic solution to the organic phase. The method was applied for the simultaneous determination of salicylamide and salsalate, at concentrations between 0.100 and 1. 000 microg mL-1 for both components, by means of absolute values of a first derivative variable-angle synchronous scan at the emission/excitation wavelengths of 410/299 nm for salicylamide and 440/307 nm for salsalate. Serum and urine are extracted with chloroform, by adding acetate buffer solution to provide pH 4.8 in the aqueous phase. Finally, pyrrolidine chloroformic solution is added to organic phase, where both components are determined, without the need for a reextraction step to an aqueous phase.