Spectrophotometric determination of microgram amounts of penicillins by solvent extraction with azure b

Penicillins are determined by means of ion-pair formation with azure B and extraction into chloroform: the absorbance of the extract is stable for several days. The apparent molar absorptivities for sodium penicillin G and potassium penicillin V at 634 nm are 3.91 × 103 and 1.25 × 104 l mol-1 cm-1, respectively. Calibration graphs are linear over the range 60–950 μg of sodium penicillin G and 40–600 μg of potassium penicillin V in 10 ml. The method is successfully applied to pharmaceutical preparations