The Indicator Impregnated Fibrous Chemisorbents of Sulfur Dioxide Based on Sodium, Monoetanolammonium and Polyethylenepolyammonium Citrates

A spectrophotometric method for determining ceftriaxone based on the formation of a red-colored azo compound from the diazotized antibiotic and the phenolic reagent o-cresol has been developed. The optimal conditions for ceftriaxone diazotization were determined to be a 12.0 M hydrochloric acid medium with sodium nitrite in 10-fold excess relative to ceftriaxone. Conditions for the azo coupling reaction between ceftriaxone diazonium salt and o-cresol were optimized, with maximum yield achieved in an alkaline medium (final NaOH concentration of 0.16 M) and a 10-fold reagent excess relative to ceftriaxone. The azo compound formed remains stable for 1 hour. Effective molar absorptivity at the absorption maximum (516 nm) for the ceftriaxone–o-cresol azo compound was found to be (6.90 ± 0.16)·10³ L∙mol-¹∙cm-¹. The developed spectrophotometric method is sensitive and rapid, allowing ceftriaxone determination within the concentration range of 0.79–51.30 μg∙mL-¹, with a detection limit of 4.3·10-⁷ M. The method was successfully validated for ceftriaxone analysis in pharmaceutical preparations, including mono-component drugs and injection powders.