HJ479-2009
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The standard curve for the determination of nitrogen oxides in ambient air, according to standard HJ479-2009, is as follows: Tube number: 0, 1, 2, 3, 4, 5; Standard working solution concentration/mL: 0.00, 0.40, 0.8, 1.20, 1.60, 2.00; Water concentration/mL: 2.00, 1.60, 1.20, 0.80, 0.40, 0.00; Color-developing solution concentration/mL: 8.00, 8.00, 8.00, 8.00, 8.00, 8.00; Mass concentration of NO2-/ug/ml: 0.00, 0.10, 0.20, 0.30, 0.40, 0.50; Absorbance: 0.028, 0.128, 0.227, 0.323, 0.421, 0.515. Both the slope and intercept of the curve are within the specified limits; however, the absorbance of the solution does not meet the requirement (it should be less than or equal to 0.005). Questions: 1. Is it due to the water or reagents? 2. The color-developing solution is colored; could that have an impact? 3. The color development solution was prepared twice, and color appeared in both cases. Is there anything special to pay attention to? (Aminobenzenesulfonic acid is poorly soluble in water at 40-50 degrees Celsius)
Solution: Do not use ultrasound when preparing the color-developing solution; store it in a dark bag and stir it using magnetic stirring. (Unverified)