[robert.cook]

What does it mean when a nitrate standard says it is 1000 ppm nitrate (as nitrogen)?  Does this mean that the solution is 1000 ppm nitrate or 1000 ppm total nitrogen?

[Borek]

IMHO 1000 ppm total nitrogen (equivalent of 4427 ppm nitrate).

[Arkcon]

It also tells you how they figured it out, they did it by analyzing nitrogen, the element.  Its up to you to compute how much nitrate there is, like Borek: did.  With the caveat that, if there are nitrite, or complex organic nitrogenous compounds, like maybe organic ones, the result may be skewed.