The Nitrate test strip is used to detect Nitrate in solution at 10, 25, 50, 100, 250, & 500ppm. Nitrate test strips are often used to test fertilizer run-off in agricultural areas. This strip is very sensitive to light and moisture, so be sure to keep the vial tightly sealed. For a dual Nitrate-Nitrite test, check out or combo test strip with both tests in one.