Abstract
A colorimetric determination of INAH was devised by application of 2-bromo-1′-acetonaphthone to INAH to form 1-(1-naphthylcarbonylmethyl)-4-hydrazinocarbo-nylpyridinium bromide and its coloration by basification. This procedure is as follows: A mixture of 1cc. of ethanol containing 1-40γ of INAH and 0.5cc. of 0.25% solution of 2-bromo-1′-acetonaphthone is refluxed in a boiling water bath for 25 minutes, 0.1% ethanolic solution of sodium ethoxide is added, and the whole volume is brought accurately to 5cc. with ethanol. After standing this solution for 3 minutes, its absorbance is measured at 470mμ and the concentration is calculated from the calibration curve.
In the presence of isonicotinic acid, nicotinic acid is measured at 500mμ by which INAH in the range of 4-70γ can be determined selectively in the presence of 15γ of isonicotinic acid, 30γ of nicotinic acid and nicotinamide, and 200γ of 3-pycoline and 4-pycoline. Determination error is within 2.5%. 2-Pycoline and picolinic acid do not undergo coloration under these conditions.
