Determination of ortho-phthalaldehyde in water by high performance liquid chromatography and gas chromatography–mass spectrometry after hydrazine derivatization

A simple high performance liquid chromatographic (HPLC) method and a highly sensitive gas chromatography mass spectrometric (GC–MS) method have been established for the determination of ortho-phthalaldehyde (OPA) in water. These methods are based on the derivatization of OPA with hydrazine in water. The following optimum reaction conditions were established: reagent dosage, 20 mg/mL of hydrazine; pH 2; reaction for 20 min at 70 °C. The organic derivative was detected directly by HPLC or after the extraction with methylene chloride/concentration by GC–MS. The limit of detection of OPA in water was 4.0 and 0.3 μg/L by HPLC and GC–MS, respectively. The calibration curve showed good linearity with r2 = 0.9993 and r2 = 0.9994 by HPLC and GC–MS, respectively, the accuracy was in a range of 95–105%, and the precision of the assay was less than 13% in water. The HPLC method was simple and reproducible enough to permit the OPA content analysis in the disinfectant products, and the GC–MS method is sensitive enough to permit reliable analysis of OPA to the μg/L level in environmental water.