Modified QuEChERS-HPLC method for determination of sodium benzoate and potassium sorbate preservatives in dairy products

Method: A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction method followed by a simple isocratic reversed-phase high-performance liquid chromatography was applied to the simultaneous analysis of Sodium Benzoate (SB) and Potassium Sorbate (PS) preservatives in some dairy products was developed. Results: At first, comparison of the obtained results using original unbuffered and modified buffered QuEChERS versions was done. Then, in order to improve the extraction recovery of SB and PS and clean-up efficiency, some effective parameters were optimized. Satisfactory extraction recoveries (94.0 and 99.8 for SB and PS, respectively) were achieved under optimum conditions. In order to obtain low matrix effect (<20%), quantitation was performed in the presence of an internal standard by referring to a matrix-free calibration curve. The regression coefficient 0.998 and 0.999, and the limit of detection 0.01 and 0.02 µg mL-1 were obtained for SB and PS, respectively. Recoveries for quality control samples prepared by blank real sample fortification were between 95-112% with relative standard deviations (RSD) less than 6%. Finally, SB and PS were determined in various dairy products such as dry milk, milk, yogurt and yogurt drink (Doogh) with relative recoveries in the range of 81-107% and RSDs less than 9%. The obtained results were confirmed using liquid chromatography-mass spectrometry. Conclusion: This methodology, which was successfully applied to dry milk, milk, yogurt and yogurt drink (Doogh) samples, enables the determination of the target analytes in the width concentration ranges.