The iodine is introduced in proportion to your oxygen during the sample, thus the oxygen focus is set with a redox titration of iodine with thiosulfate using a starch indicator.[forty nine]17. Qureshi SZ, Qayoom T, Helalet MI. Simultaneous spectrophotometric and volumetric determinations of amoxycillin, ampicillin and cloxacillin in drug formulatio