Determination of N-Ethylglycine in Urine of Cancer Patients with Metastatic Bone Disease by HPLC Using 4-(5,6-Dimethoxy-2-phthalimidinyl)-2-methoxyphenylsulfonyl Chloride as a Fluorescent Labeling Reagent

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A simple and highly sensitive HPLC for the determination of N-ethylglycine in urine was developed. The labeling reaction of N-ethylglycine with 4-(5,6-dimethoxy-2-phthalimidinyl)-2-methoxyphenylsulfonyl chloride was carried out at 70°C for 15 min at pH 9.0. The fluorescent derivative was separated on a reversed-phase column and detected at excitation and emission wavelengths of 320 and 400 nm, respectively. The detection limit of N-ethylglycine was 15 fmol (S/N = 3). The recovery of N-ethylglycine added to urine was 101.9%. The concentration of N-ethylglycine in urine of cancer patients with metastatic bone disease was 11.3 ± 22.0 nmol/mg creatinine, and that of normal subject was 0.4 ± 0.4 nmol/mg creatinine.