Development of a Dispersive Liquid-Liquid Microextraction for the Spectrophotometric Determination of Penicillin G in Milk and Biological Samples

Background: This study developed a dispersive liquid-liquid microextraction technique followed by spectrophotometric analysis for preconcentrating/determining penicillin G benzathine and penicillin G potassium. Methods: The procedure was based on forming a color complex of penicillin G with bromothymol blue and its extraction by DLLME. The univariate method was employed for optimizing the parameters. Results: Optimized conditions for extracting benzathine and potassium penicillin G were 1.5 mL methanol and acetone as dispersive solvents; 300 μL CHCl3 and 250 μL CCl4 as extracting solvents; pH 4 and 3; 0.8 mL and 0.9 mL bromothymol blue (10-3 M), and NaCl 0.8 M for both analytes. The calibration curves were linear over the ranges 50-750 and 800-950 IU mL-1 for analyzing benzathine, and 800-1600 and 1750-6500 IU mL-1 for potassium penicillin G. The relative standard deviations and detection limits were obtained to be 6.53% and 0.101 IU mL-1 and 4.65% and 0.149 IU mL-1 for determining benzathine and potassium penicillin G, respectively. Conclusion: The proposed method was employed for extracting and determining penicillin in human plasma, urine, orange juice, and milk, with acceptable recovery values of 94.3-102%.