Identification Positive PH (1%, W/V) 4.5-7.5 Specific rotation -203°- -216° UV absorption at 353nm(1%,1cm) 290-310 UV absorption of impurity at 430nm 490nm ≤0.25 ≤0.20 Related substances 4-epoxytetracycline : 0.5%Tetracycline hydrochloride: 2.0% ain peak tailing: 2.0% Heavy metal 50ppm Water 4.0-8.0% Ash ≤0.5% Assay (HPLC) 95.0-100.5%