Hi,
This will be an excellent project.
Did you mean spectrophotomer? This is an instrument used to measure concentrations of analytes quantitatively. Here is a brief description. You might have access to a spectrophotometer at your school; this would provide an accurate and sensitive method for nitrate analysis. However, if you don’t have access to this instrument, you will need to pick one of the other methods.
http://en.wikipedia.org/wiki/Spectrophotometry
There are several methods of nitrate analysis available. Which nitrate test kit were you thinking about purchasing?
Here is an undated website which reviews the advantages and disadvantages of various method of nitrate analysis. All of the methods are useful, but there are definite differences between sensitivity, speed, accuracy, and price with all of the methods.
http://www.usu.edu/cpl/Nitrate%20analys ... ometti.pdf
Here is a website with a review of a new automated method for nitrate analysis. There is some helpful background information included. It might not be feasible for you to do this assay, but there is a name and phone number of an expert in nitrate analysis that you could try calling to ask for additional information/ referral/samples, etc. Companies vary in their response to requests for assistance on science fair projects, and I am not familiar with this company, but it won't hurt to try.
http://www.labmanager.com/articles.asp?id=149
Here is a website that describes how to do nitrate analysis samples for vegetables, and it includes typical values, which should be useful for your project.
http://www.extension.umn.edu/distributi ... _35-36.pdf
You will need to run some control samples for whatever method you choose.
Please let me know if you have any other questions.
Donna Hardy