New derivatizing reagent for analysis of diethylene glycol by HPLC with fluorescence detection

N-(2-Phenyl-indolyl)-acetic acid (PIAA), a new fluorescent derivatizing reagent, was used for the determination of diethylene glycol (DEG) by high-performance liquid chromatography with fluorescence detection. DEG was derivatized to ester by using PIAA in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodimide hydrochloride (as dehydrating agent) and 4-(dimethylamino)pyridine (as base catalyst) in acetonitrile at 60°C for 75 min. The influence of solvent, temperature, catalyst base, concentration of labeling reagent, and couple reagent on the derivatization was investigated. The fluorescence detection was performed with excitation at 340 nm and emission at 377 nm. Baseline separation was obtained on an Ultimate XB-C18 analytical column with water/acetonitrile gradient elution, good linearity was obtained within 0.5-50 μg/mL with a correlation coefficient of 0.9997. The limit of detection was 0.01 μg/mL (signal-to-noise ratio = 3). The method has been successfully applied to determine DEG in toothpaste samples with satisfactory recoveries ranging from 89.0 to 94.9%. The proposed method was shown to be a promising technique for the determination of DEG with high sensitivity.