Spectrophotometric determination of ceftazidime in urine by the reaction of the azo coupling with resorcin

Treatment with antibiotics requires control over the drug dosage strength since not reaching the therapeutic concentration can lead to ineffective treatment, and drug overdose can cause toxic effects and adverse reactions on the human organism. Such control can be carried out by monitoring the content of antibiotics or their metabolites in biological fluids. For the study, we chose one of the most common in medical practice, the b-lactam antibiotic of the cefalosporine group, ceftazidime (CEFT). A feature of cefalosporine antibiotics is that they are practically not metabolized in the body, which makes it possible to determine them in biological fluids, such as blood, urine, and saliva. According to the literature data, the biological half-life of CEFT is 2 hours, and about 80–90 % of the dose is eliminated after 24 hours, mainly through the kidneys, excreted in the urine unchanged. Chromatographic methods are usually used to quantify the AM amount in biological fluids. Still, enzyme immunoassay method and spectrophotometric determination methods are also used according to the literature data, which are more rapid, simpler, and accessible. However, the complex matrix of these objects requires preliminary sample preparation for CEFT extraction. For the ceftazidime determination in the urine, the spectrophotometric method developed by us previously using the reaction of azo coupling with resorcinol (Res) was chosen. The technique is based on the CEFT diazotization by the action of sodium nitrite in a medium of 12.0 M hydrochloric acid and subsequent azo coupling with Res in an alkaline medium with a final NaOH concentration of 0.16 M under the 10-fold excess of the reagent toward CEFTR, with the formation of a red-colored azo compound, which is characterized by a new absorbance maximum at l = 519 nm ((LOD = 0.84 μg/ml). The results of the study showed that the CEFT azo compound absorbance in the presence of urine is significantly lower, which is due to the ability of diazotated CEFT to react with some urine components (interaction products in the study area do not absorb), resulting in a significant decrease in the yield of CEFT azo compound from resorcinol. In the case of ceftazidime determination, the standard addition method gave worse results than the method of a calibration curve. Keywords : ceftazidime, resorcinol, urine, azo coupling, spectrophotometry.