Nitrate (as Nitrogen) Standard, 1000 ppm, available in 500mL (No. 146514) and 125mL (No. 154380) poly bottles.Traceable to NIST.Potassium Nitrate-water (1ml = 1mg N, 1 ml = 4.43 mg NO3).APHA 4500-NO3- E.Shipping: No restrictions apply.