Direct determination of phosphorus in biodiesel samples by graphite furnace atomic absorption spectrometry using a solid sampling accessory

A procedure for the direct determination of P in biodiesel samples by graphite furnace atomic absorption spectrometry (GF AAS) using an automatic solid sampling accessory without any sample pre-treatment or dilution is proposed. Studies showed that it is necessary to use a chemical modifier and a Pd in Triton X-100 solution showed the best results. The pyrolysis and atomization temperatures (1300 degrees C and 2700 degrees C, respectively), as well as the Pd mass (30 mu g) were determined by multivariate optimization. The other parameters of the temperature programs were defined by univariate optimization. The limit of detection at the optimized conditions was 7.2 ng (1.2 mu g g(-1)) using 20 mu L of chemical modifier solution as blank for typical sample masses between of 2.00 and 6.00 mg. Aqueous calibration solutions were used and the calibration curves showed correlation coefficients better than R-2 = 0.99. The characteristic mass was 9.1 ng. The method's accuracy was confirmed both by the analysis of reference materials and by comparison with an independent procedure (EN 14107). No statistically significant difference was observed between obtained and expected values.