Studies aimed at the development of analytical methods based on electrothermal atomic absorption spectrometry for the determination of antimony, selenium and arsenic in gasoline and kerosene were performed. The goal was to develop sensitive methods that allow a simple calibration procedure to be used through direct correlation between analyte signals measured in the sample and signals from aqueous standards. This was possible by optimization of both the sample preparation procedure and furnace conditions. The platform atomization technique was used together with chemical modification (ruthenium permanent modifier or Pd/Mg nitrate chemical modifier). Better results were obtained when samples were introduced as microemulsions prepared with a surfactant (Triton X-100) rather than sample introduction as detergentless microemulsions (three component solution). Good sensitivity was achieved, which allowed the determination of analytes in gasoline and kerosene samples in the µg L⁻¹ range. Linear ranges up to three decades were observed for the analytical curves. Laboratory-prepared samples were analyzed with good precision and recovery.

The quantification of trace elements in used lubricating oil is useful for evaluating the wearing of specific components of engines. In the present work, inductively coupled plasma optical emission spectrometry (ICPOES) was used for determining five refractory elements (Ni, Mo, Cr, V and Ti) in lubricating-oil samples. The methodology was developed while aiming at the introduction of such organic samples into the ICP as emulsions. Several nebulization systems were tested with clear advantage for Meinhard K3 coupled with a cyclonic spray chamber. The carbon deposition on the injector tip as well as the plasma background was minimized through careful optimization of the Ar and O2 gas mixture flows into the plasma. The optimization of instrumental and experimental parameters allowed quantification using calibration curves prepared with analyte inorganic standards. An internal standard (Sc) was used to correct the matrix effects and signal fluctuations. The limits of detection (3Sb/m), in the ng g-1 range were obtained for all five elements. The methodology was validated through an analysis of standard reference materials (SRM 1084a, 1085a and 1085b). Good analyte recoveries (from 92.6 to 104.7%) were achieved. Comparison studies against established ICPOES methodologies (sample acid decomposition or sample direct dilution in an organic solvent) have shown that the proposed methodology present clear advantages in terms of simplicity of sample preparation, overall analysis time, and the use of inorganic standards for calibration instead of expensive metallorganic standards.

The determination of Cr, Mo, Ti, V, Cd, Fe, Mn, Ni and Zn in crude oil by ICP-OES using ultrasound-assisted acid extraction is proposed. The crude oil was treated with concentrated nitric acid and heated at 85 °C for 30 min. Then, the mixture was placed in an ultrasonic bath for 15 min in order to obtain total extraction of trace elements from the oil sample into the acid solution, which was directly aspirated into the ICP to be quantified using analytical curves constructed with inorganic standards. Principal component analysis (PCA) and factor analysis (FA) were used to evaluate the effect and importance of the experimental variables in this sample preparation procedure. The proposed method was tested using NIST 1634c (Trace Elements in Residual Fuel Oil) and two petroleum samples. Recoveries between 90 and 105% were achieved. Limits of quantification in the sample ranged from 0.008 to 0.62 μg g⁻¹, depending on the analyte.