Researchers developed a method to quickly and accurately measure nitrite and nitrate levels in seawater. They used a technique called Flow Injection Analysis with copper cadmium to automate the process. Nitrite and nitrate were detected by forming a red dye that absorbs light at 530 nm. Nitrate was converted to nitrite for measurement. The method had a wide detection range and low limits of detection. It could analyze samples rapidly and with good precision. When tested on seawater samples, the method gave accurate results with a recovery rate of 93.5% to 111.0%. This method is simple, fast, and reliable for practical use in detecting nitrite and nitrate in seawater.