Cefoperazone sodium Imp A (EP):(5aR,6R)-6-[[(2R)-2-[[(4-ethyl-2,3-dioxopiperazin-1-yl)carbonyl]amino]-2-(4-hydroxyphenyl)acetyl]amino]-5a,6-dihydro-3H,7H-azeto[2,1-b]furo[3,4-d][1,3]thiazine-1,7(4H)-dione.