Determination of streptomycin sulphate with the method of ponceau S spectrophotometric

In the condition of pH 4.0～5.0,ponceau S reacted with streptomycin sulphate to form ion-association 1∶1 complex,which faded the color of ponceau S and generated a new absorption.The maximum fading wavelength was at 537 nm and the absorption wavelength was at 575 nm.The content of streptomycin sulphate was determinated with the difference between the best faded peak valve and the new absorption peak value.The apparent molar absorptivity(e) was 1.25×104 L·mol-1·cm-1 and Beer's law is obeyed under the concentration range 1.46～58.30 mg·L-1,a detection limit was 0.91 mg·L-1.The relative standard deviation was 1.20%～1.82% for six parallel determinations.The recovery range was 95.6%～102%.The method has been applied for determination of the real sample with a satisfactory result.