Development and Validation of a Method for Determination of Residual Nitrite/Nitrate in Foodstuffs and Water After Zinc Reduction

An environmentally friendly and cost-effective spectrophotometric method to analyze nitrate and/or nitrite was developed. The method is based on reduction of nitrate with zinc powder (instead of the cadmium or enzymes used in the standard methods approved by ISO/CEN). The initial nitrite concentration and total nitrite after reduction are determined by the very sensitive and widely used diazotization-coupling Griess reaction. A single-laboratory validation was applied in five different matrices (vegetable, meat product, baby food, dairy product, and surface water). The results show that the new method fulfills the international criteria for precision and recovery. The limit of detection for several matrices, calculated using fortified samples, ranged from 3 to 5 mg/kg for both nitrite and nitrate. Furthermore, the results obtained were in good agreement with those obtained using the CEN method (HPLC) and the ISO method (Cd reduction).