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

This study developed a dispersive liquid-liquid microextraction technique followed by spectrophotometric analysis for preconcentrating/determining penicillin G benzathine and penicillin G potassium.

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.

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.

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%.