Microdetermination of 1-Naphthaleneacetic Acid

Abstract

1-Naphthaleneacetic acid (NAA) in fruits was extracted with acidic acetone and the extract was evaporated under a reduced pressure, diluted with water and then washed with n-hexane. NAA was extracted with ether from the aqueous solution and reextracted with aqueous sodium carbonate solution from ether. The solution was extracted with ether after being adjusted to pH 2.0. The ether solution was dryed with anhydrous sodium sulfate and the solvent was evaporated under vacuum. The residue was dissolved in 1 ml of methanol and 50μl of the solution was injected to a high speed liquid chromatograph fitted with a glass column (3 mm × 50 cm) packed with Hitachi-gel ♯3010. The column was eluted with methanol and water (19: 1) at a flow rate of 1.5 ml/min and the effluent was mixed with 0.1% potassium hydroxide in 90% methanol at a rate of 0.6ml/min just before flowing into a detector. A fluorophotometer with a flow cell (2×20mm) was used as the detector. Wave length for exitation was 230nm or 290 nm and that for emission was 330 nm. The amount of NAA was calculated with peak area on the chromatogram by using calibration curve prepared by injecting 10 to 50μl of 5 ppm methanol solution of NAA into the chromatograph. Any interfering and quenching of fluorescence were not observed in analyses of melon, pineapple and apple. The limit of the detection using 50 g of sample was 0.004 ppm and the recovery was about 80%. © 1976, Pesticide Science Society of Japan. All rights reserved.