“Under the HCl solution … heating condition, penicillin antibiotics such as amoxicillin (AMO), ampicillin (AMP), sodium cloxacillin (CLO), … carbenicillin (CAR) and sodium benzylpenicillin (BEN) could react with Fe(III) to produce Fe(II) which further reacted with Fe(CN)(6)(…-) to form a Fe(3)[Fe(CN)(6)](2) complex.”