Surfactant-mediated microextraction approach using switchable hydrophilicity solvent: HPLC-UV determination of Sudan dyes in solid food samples

Abstract An easy performed surfactant-mediated microextraction approach using switchable hydrophilicity solvent was proposed for the sample pretreatment of solid food samples. The procedure included mixing of solid food sample and aqueous solution of sodium hexanoate provided a micellar solution formation. By this sample pretreatment step, the hydrophobic analytes were extracted into the micellar solution. The injection of sulfuric acid solution into the sample suspension decreased the pH value of the aqueous phase and as a result promoted the hexanoic acid phase formation and final phase separation from the sample suspension. The performance of the suggested approach was demonstrated by the HPLC-UV determination of Sudan dyes (Sudan I, Sudan II and Sudan III) in spiked salted salmon and spices powder samples. This analytical task was used as a proof-of-concept example. The LOD values, calculated from the blank tests based on 3σ, were 0.15 μmol L −1 (0.19 mg kg −1 ), 0.02 μmol L −1 (0.028 mg kg −1 ) and 0.10 μmol L −1 (0.18 mg kg −1 ) for Sudan I, Sudan II and Sudan III, respectively. The sample pretreatment time was 25 min. The proposed method has advantages in comparison with previous developed methods for Sudan dyes determination due to the low consumption of extraction solvent and simplicity of sample pretreatment steps. The developed method can be applied for hydrophobic analytes microextraction from various solid samples (pharmaceutical, food, soil samples, etc.).