The analytical performance of a dual nebulization system is evaluated for sample nebulization at lower solution uptake rates in inductively coupled plasma optical emission spectrometry (ICP-OES). The system is essentially a modified cyclonic spray chamber that allows the simultaneous operation of two micronebulizers. This work is focused on the optimization and evaluation of the main analytical figures of merit of this sample introduction system. The usefulness of this dual micro-nebulizer in practical ICP-OES studies is demonstrated by using a tandem calibration technique and by operating this system for hydride generation studies. Results showed that this system presents similar figures of merit to a conventional spray chamber but that the non-spectroscopic interferences, usually present at lower solution uptakes rates, can be compensated for by using the tandem calibration technique with this system. Additionally, the two micronebulizers coupled to the modified cyclonic spray chamber can be used for efficient volatile hydride generation from sub-mL amounts of samples. Interference effects by transition metals have been shown to be corrected by the addition of thiourea. The analytical applicability of the dual system was checked by analyzing two standard reference materials: NIST 1577b, Bovine Liver and NIST 1566a Oyster Tissue. The accuracy achieved when using different calibration techniques and hydride generation are within the certified values when applying the significance t-test at the 95% confidence level.

The determination of copper, iron and nickel in edible oils was carried out using emulsion sample preparation followed by analysis by ICP-AES. Response surface methodology was applied in order to find the optimum emulsion and surfactant concentrations. The optimum amount of oil in the emulsion was in the range ca. 2-35% in most of the surfactants studied, except for Triton X-100, which showed a maximum response above 35% oil. The surfactant concentration in the emulsion varied between 0.5 and 9%. Good agreement was found between calibration curves for emulsified aqueous standards solutions and oil-in-water emulsions for most elements studied with Tween 80, ethoxynonylphenol and Triton X-100. The best agreement for all elements was shown when Tween 80 was used. Hence emulsified aqueous standard solutions could be used for the determination of these elements in emulsified edible oil samples using ICP-AES. Recoveries ranged from 90 to 110% for most of the elements studied, with relative standard deviations lower than 8%. the use of surfactants to enhance the sample transport process.

A new nebulizer system is described that extends the analytical capability of the inductively coupled plasma technique to include the simultaneous determination of two elements Sb and Sn (hydride-forming), with two conventional elements, V and Zn. The main advantage of this system is its simultaneous determination of elements that form volatile hydrides and elements that do not, without any instrumental changes. Optimization of reaction and instrumental conditions was performed to characterize the new system. The performance of the new nebulizer system was evaluated by studying the effect of some transition metals (Ni, Cu, Co, and Fe, 1-1000 mg L(-1)) on the Sb, Sn, V, and Zn emission signals (1 mg L(-1)). Interferences from transition metal ions were found to be insignificant for determination of the four elements in presence of L: -cysteine. Long-term and short-term stability was also evaluated. The precision, expressed as RSD for 15 replicate measurements was 0.7% for Sb, 1.7% for Sn, 2.5% for V, and 2.3% for Zn at 200 microg L(-1) of each analyte. The detection limits obtained were 0.52, 1.3, 3.2, and 4.7 microg L(-1) for Sb, Sn, V, and Zn, respectively. Spike and recovery experiments were performed on the NIST 1643c trace metals in water standard reference material and results were in agreement with the certified values.

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The mechanochemical transformation of Ca(OH)(2)-(NH(4))(2)HPO(4) with different Ca/P ratios 1; 1.5; 1.67 and 1.75 was carried out for different periods of time from 10 min to 24 h in a horizontal vibration mill using steel and agate vials and balls. The phase transformations obtained at each milling stage were characterized by X-ray diffraction, infrared spectroscopy and transmission electron microscopy. Complete transformation to hydroxyapatite took place during the first 5 h of milling, for Ca/P ratios 1.5 to 1.7, when milling was carried out with steel vials and balls. The contamination was not significant for the periods of milling studied for both milling media.