The researchers developed a new method to test for nitrate and nitrite in milk using ion chromatography. They found that nitrate was present in all milk samples, but nitrite was not detected. The average nitrate level in milk was 34 mg/L, which is below the recommended limit by the World Health Organization. The maximum safe level of nitrate in milk was determined to be 82.8 mg/L. This method is fast, accurate, and can be used in food control labs to check for nitrate and nitrite levels in milk.