Manufacturers of ready-to-feed infant formula can use various methods to measure nitrate in their product, such as the method available for our FS 3700 Automated Chemistry Analyzer.

The most common symptom of "blue baby syndrome" is a gray-blue color that develops on a child's lips; this can eventually spread to the rest of the body, resulting in death in the most severe cases.3

One of the goals of wastewater treatment is to remove nitrogen to prevent over-enrichment of receiving waters. Processes in the nitrogen cycle – specifically nitrification and denitrification – play a vital role in accomplishing this goal.

Natural nitrate levels are relatively low – 1 mg/L or less – in some surface waters.1 At this level, nitrate is not harmful, but adverse health effects can be seen in aquatic species when nitrate concentration gets too high.
One study conducted by the Conservation Fund's Freshwater Institute investigated the effects of chronic exposure of aquaculture-raised rainbow trout to modest levels of nitrate-nitrogen (75 to 100 mg/L). Results suggested deformities and significant behavioral changes in recirculating aquaculture systems (RAS) at these levels. Check out our blog post on this topic, Nitrate Levels in Aquaculture May be More Dangerous Than You Think.

Nitrate is commonly used as a preservative for bacon, ham, salami, and some cheeses. Studies have tied the use of nitrate to the formation of nitrosamines, some of which are cancer-causing compounds. One way nitrosamines can form is when nitrites – naturally converted from nitrate in the body – are located near proteins; this condition is found in protein-rich foods such as preserved meats. When preserved meats are cooked at high temperatures, it is easier for nitrosamines to form.
While nitrate's use as a preservative receives a considerable amount of attention, humans receive very little of their dietary nitrate intake from processed meat – only about 5%. Most of the dietary nitrate (>80%) we receive is from vegetables, with leafy green vegetables often accumulating high concentrations of nitrate.
Rather than being added as a preservative, vegetables acquire nitrate from the soil in which they grow, with those grown in soil enriched with fertilizer having higher levels than organic produce.5 Nitrates in vegetables are less likely to form nitrosamines, as they aren't protein-rich foods. Veggies also contain compounds (e.g., vitamin C and polyphenols) that help minimize the chance of nitrosamine formation.
Nitrate in vegetables can be beneficial, as nitrate is tied to nitric oxide production.This gas may lower blood pressure and help fight infection, among other benefits.6 One thing to note – while it is possible to get so much nitrate from vegetables that methemoglobinemia can result, it is very unlikely to happen.

So, how are nitrate levels measured in food? Some relatively inexpensive methods we cover in the next section – specifically colorimetric and potentiometric methods – can be used for nitrate analysis as long as an aqueous solution is created. One procedure for preparing a sample for analysis is to mix oven-dried leaf samples with aluminum sulfate extracting solution.