Quantitation of amoxicillin in urine by nuclear magnetic resonance. Application to five cases

Aim: In this paper, we propose a procedure for the analysis and quantification of amoxicillin in urine with minimum pre-treatment of the samples using Nuclear Magnetic Resonance spectroscopy (NMR). Five clinical samples were analyzed and amoxicillin was detected and quantified in each case. Material and Method: Samples of urine from amoxicillin users were collected in accor-dance with an IRB-approved protocol. Donors were asked to record the day of urine collection, the length of treatment and the amount of drug prescribed. Samples were collected and immediately frozen at -20°C until required for experiments. The water suppression technique “Watersculpt” was used in all samples. A rapid acidic pre-treatment eliminated the urea signal from the NMR spectra of urine samples. A calibration curve was obtained using spiked samples and by integration of selected signals from amoxicillin. The method gave a linear response (correlation coefficient of 0.995) over the range 0.01-1 mg/mL. Results: Subsequent quantitation of the amount of amoxicillin present in samples from clinical cases was performed. The concentration of the drug in urine varied from 0.517 mg/mL to 0.326 mg/mL. Discussion: The benefit and reliability of NMR investigations of human urine for the detection of amoxicillin are discussed.