Sample pretreatment and SERS-based detection of ceftriaxone in urine

The aim of the work is the development of the procedure for ceftriaxone (antibiotic drug of cephalosporin class) detection in urine using surface-enhanced Raman spectroscopy (SERS). Hydroxylamine stabilized silver nanoparticles were used as SERS-active material. Additional urine pretreatment steps were developed in order to eliminate the influence of creatinine on the ceftriaxone SERS signal. These steps include adjusting of the sample pH to alkaline value (pH 13) and purification of the sample using silica gel column chromatography. Alkali pH increases SERS signal of ceftriaxone, while silica gel separates the analyte from creatinine-the main admixture in urine which provides inappropriate SERS signal background. Additionally, it was found that total protein content up to 0.2 mg/mL (upper level for urine of healthy person) and pH deviation of initial urine do not influence on SERS signal of ceftriaxone. The proposed detection procedure enables fast (similar to 10 min) determination of ceftriaxone in artificially spiked urine samples within 5 to 500 mu g/mL range of concentrations which matches the range of the drug concentrations in urine after injection of therapeutically required dosages. Limits of detection (3 sigma) and quantification (10 sigma) were found to be 0.4 and 2.0 mu g/mL, correspondingly.