Spectrophotometric determination of nitrate nitrogen using thymol

Abstract

The use of thymol solution in place of 2, 4-xylenol in the determination of nitrate nitrogen increases threefold in sensitivity and simplifies the analytical procedure because heating procedure is not necessary. Interference from nitrite nitrogen is removed with sulfanilic acid. The proposed analytical procedure for nitrate nitrogen using thymol is as follows.Take a sample solution of 5 ml {containing (110) μg NO3-N} and 0.5 ml of 1% sulfanilic acid solution in a 100 ml separatory funnel and mix well. Add 15 ml of 85% sulfuric acid and 0.5 ml of thymol solution. After standing for 5 minutes at room temperature, dilute to about 70 ml with water. Mix well and stand for 20 ml. Extract nitrate nitrogen after shaking for 2 min with 10 ml of n-butyl acetate and (23) drops of 0.1% pentamethoxyred solution. After discarding the aquous layer, add 10 ml of 1 M NaOH solution in n-butyl acetate, and shake for 2 min. Filter the NaOH solution through a dry filter paper and measure the absorbance at 395 nm against reagent blank obtained by the same procedure. The molar extinction coefficient is 6.2×103.