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.

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 degrees 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.