nitrates nitrities in cow's milk by ion chromatographyContinuing our blog series on the analysis of milk and dairy products. The first blog post covered accelerated solvent extraction (ASE) of the total fat in dairy products and the second one focused on the Ion Chromatography (IC) analysis of iodide in milk products.

Here, we present the analysis of nitrates and nitrates in cow’s milk, which is of particular dietary value to infants, small children, and expectant mothers, and must be free of nitrate and nitrite contamination. The most likely source of nitrate is from drinking water contaminated from excessive application of nitrate-based fertilizers or rodenticides.

Excessive consumption of nitrate can lead to low oxygenation of the blood and concomitant low oxygenation of the tissues, which can lead to health problems and even death. Infants and small children are more severely impacted than adults because of their much smaller total blood volume. Infants can ingest nitrates from formula or baby food prepared with contaminated water, milk of the nursing mother who consumed contaminated water, or the milk of dairy cows that consumed contaminated water. Nitrite is also a concern because it is easily oxidized to nitrate.

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Both water and milk, therefore, need to be tested for nitrate and nitrite. Application Note 279, Time Savings and Improved Reproducibility of Nitrate and Nitrite Ion Chromatography Determination in Milk Samples, (downloadable PDF), discusses a complete solution from sample preparation to IC analysis that saves time and improves reproducibility. In this study, after minimal off-line sample preparation, the rest of the sample preparation is completed in-line thus saving time and reducing the possibility of sample contamination. Nitrite and nitrate are then separated on an anion-exchange column (Thermo Scientific Dionex IonPac AS20 column) and detected by suppressed conductivity detection using a Reagent-Free IC (RFIC) system (Thermo FisherDionex ICS-3000 system). The RFIC system prepares the hydroxide eluent with high fidelity, which augments method reproducibility.

Let us know of your testing challenges in milk and dairy products in the comment box below. We look forward to hearing from you!