A method for the trace analysis of naptalam (N-1-naphthylphthalamic acid) in water

A method for the trace analysis of naptalam, N-1-naphthylphthalamic acid, in water is presented. Naptalam, a pre-emergent, broad-leaf, and grassy herbicide, is used with soybean, peanut, and vine crops. Tap and well water samples are extracted on a cyclohexyl solid phase extraction cartridge, eluted from the cartridge with methanol, and evaporated to dryness. The sample is esterified with diazoethane, evaporated to dryness, reconstituted with methanol, and converted to the stable N-1-naphthyl phthalimide in the gas chromatograph (GC) injector port for detection and quantitation using a nitrogen-phosphorus detector. Sample injection technique and injector port temperature are critical to high derivatization yields. Confirmation of conversion to N-1-naphthyl phthalimide was made by gas chromatograph/mass spectrometer (GC/MS). Spiking tests at levels of 3 to 100 micrograms/L showed good recovery.