Internal Standardization in Dispersion Systems: an Efficient Application to Determine Mg in Crude Vegetable Oils by FS-FAAS

Abstract

This study established two sample preparation procedures based on dispersion systems for the determination of Mg in crude vegetable oil by IS-FS-FAAS. The emulsions were obtained with 0.10 g of samples [0.5% (m/v)] + 200 μL HNO₃ [1.0% (v/v)] + 200 μL Triton X-100 [1.0% (v/v)] in 16 mL of anhydrous ethanol [80% (v/v)] and 3.50 mL of aqueous phase [17.5% (v/v)], whereas the microemulsions were obtained with 0.10 g of samples [0.5% (m/v)] + 200 μL HNO₃ [1.0% (v/v)] + 200 μL Triton X-100 [1.0% (v/v)] in 18 mL of 1-butanol [90% (v/v)] and 1.50 mL of aqueous phase [7.5% (v/v)]. To overcome non-spectral interference, Cd, Co, and Cu were used as internal standards, and the slopes of calibration curves for Mg in 1.0% (v/v) HNO₃ aqueous solution, anhydrous ethanol + 1.0% (v/v) Triton X-100, and 1-butanol + 1.0% (v/v) Triton X-100 showed no significant difference at the 95% confidence level using Co and Cu. Calibration curves were obtained by plotting A^Mg/A^Co and A^Mg/A^Cu vs Mg concentration with linear correlation coefficients better than 0.9972 and 0.9986, respectively. The accuracy was evaluated using recovery tests, and recoveries of 98.4–106.6% (IS-Co) and 93.9–106.9% (IS-Cu) were obtained. The RSD (n = 5) were 0.4–3.6% (IS-Co) and 0.3–3.6% (IS-Cu), and LOD were 0.1 μg g⁻¹ (IS-Co) and 0.2 μg g⁻¹ (IS-Cu). The content of Mg in four crude vegetable oil varied in the range of 8.91 ± 0.30 to 163.88 ± 0.48 μg g⁻¹ for both dispersion systems with RSD < 4.22%.