Determination of Nitrate in Food by Thymol

[Objective] To establish the method for the determination of nitrate concentration in food by using thymol. [Methods]After extracting the samples, the reaction between thymol and nitrate produced nitrothymol in the presence of sulphuric acid; then nitrothymol was made to react with sodium hydroxide; determination was made on the concentration of nitrate by spectrophotometry at 412 nm.[Results]The linear calibration showed a direct ratio between the concentration of nitrate and the absorbance measurement within the range of 0.1~2.0μg/ml (r=0. 9993); the detection limit was 0.04 μg/ml; the relative standard deviations were 2.30~3.52%; the recovery rate was 91.5%~95.2%. [Conclusion]This method is proved to be simple to operate with good accuracy and linear range; it can be applied in the determination of nitrite in food.