This test consisted of preparing microemulsions, after which their stability was monitored by simple visual inspection of the emulsion samples. In these experiments, the propan-1-ol was tested in the range of 2 to 9 mL, using 0.5 g of vegetable oil
sample and 100 μL of hydrochloric acid. Water was added under continuous agitation until a final volume of 10 mL. The results indicated that only volumes of propan-1-ol higher than 8 mL produced emulsions that remained homogeneous. Therefore, after the addition of sample Ulixertinib nmr and hydrochloric acid aliquot, the final volume of 10 mL was completed with the alcohol, avoiding phase separation when the absorbance measurements were performed. Additionally, the stability of Cu, Fe, Ni and Zn concentrations in the microemulsion were checked every 30 min, for 240 min. The signal was stable during the monitoring time, indicating stability of find more the analytes. One of the principal problems related with the determination of trace elements in organic matrix is the lack of knowledge about the form of the analyte in the sample. The standard addition techniques provide the compatibility among the calibration curves and samples in terms of possible matrix interferences, but also may provide errors since the forms of element compounds in the materials to be analysed behave differently to the spiked form (dos Santos et
al., 2007). Due to this, the feasibility Rucaparib concentration of using aqueous standards for calibration was evaluated by the comparison with the standard addition using metal-organic standards. The resulting equations and their respective correlation coefficients are shown in Table 2. As can be seen, the slopes of the calibration curves obtained using either inorganic or organic standards are very similar. This means that the Cu, Fe Ni and Zn present in vegetable oils samples can be determined through the calibration technique using either inorganic or organic standards. Table 3 presents the limits of detection (LOD) and of quantification (LOQ) in samples,
as well the precision for the determination of Cu, Fe, Ni and Zn in vegetable oils prepared as microemulsion by HR-CS FAAS. The LOD and LOQ of each analyte were calculated as the analyte concentration corresponding to three and ten times, respectively, the standard deviation for ten independent measurements of the microemulsion blank, divided by the slope of the calibration curve. The precision was evaluated as the relative standard deviation (RSD). In Table 3, the RSD range obtained for all samples are shown. The proposed method has been applied to the determination of Cu, Fe Ni and Zn in vegetable oils samples obtained from local vendors. Initially, the method was verified through spike recovery tests, by adding 2.0 and 4.