| Abstract: | Abstract A sequential injection system for the determination of nitrate (NO3 ?) in vegetables was developed to automate this determination, allowing for substantially reduced reagent consumption and generated waste using low‐cost equipment. After extraction with water and filtration, the extracted nitrate is reduced inline to nitrite in a copperized cadmium (Cd) column and determined as nitrite. According to the Griess–Ilosvay reaction, nitrate is diazotized with sulfanilamide and coupled with N‐(1‐naphtyl)‐ethylenediamine dihydrochloride to form a purple‐red azo dye monitored at 538 nm. Nitrate can be determined within a range of 1.35–50.0 mg L?1 of NO3 ? (corresponding to 0.270–10.0 g of NO3 ? per kg of vegetable), with a conversion rate of nitrate to nitrite of 99.1±0.8%. The results obtained for 15 vegetable extracts compare well with those provided by the classical procedure, with a sampling throughput of 24 determinations per hour and relative standard deviations better than 1.2%. |
