The use of a so-called T-shaped cross-flow nebulizer (T-CFN), which is a modified cross-flow nebulizer with an additional solution introduction channel, has been described for elemental determinations in organic solutions by inductively coupled plasma-optical emission spectrometry using aqueous solutions for calibration. With this nebulizer, the simultaneous generation of an aerosol from a kerosene and from an aqueous solution was possible, a mixed aqueous/organic solution aerosol can be directly formed in the spray chamber and carried to the plasma without the use of a surfactant. The additive properties of the analyte signals were demonstrated, as well as the constancy of the intensity ratios for analyte and reference element lines. These ratios, however, were found to be not significantly different when the analytes were introduced in the plasma via the aqueous or via the organic solution. Therefore, a calibration by standard addition could be carried out in an on-line way after determining the relative efficiency of the nebulization of both solutions. So as to minimize the effect of drifts and fluctuations in the set-up, the instantaneous value of the efficiency of the nebulization was monitored by calculating the line intensity ratio of the so-called reference and auxiliary elements. For analysis, 200 mg of oil standard sample containing 5 mg g⁻¹ of Ba, Ca, Mg, P and Zn were diluted with kerosene up to a volume of 50 mL and the calibration was done with aqueous standard solutions using the T-CFN. The limits of detection in solution of Ba, Ca, Mg, P and Zn obtained for the simultaneous nebulization of kerosene and aqueous solutions were, respectively, 7, 13, 4, 51 and 7 μg L⁻¹ and were found to be not higher, by a factor of 10, for the investigated lines when separately analyzing kerosene and aqueous solutions with a conventional cross-flow nebulizer. Ca, P and Zn were determined in the same way in two further oil samples at the mg g⁻¹ level. The results of the analysis for the oil samples mentioned before were found to be in good agreement, respectively, with the certified values and with those obtained in an inter-laboratory test.