[bluemonster]

Can u help me ?
What are methods used to quantify nitrate ion in lab !? I need the simple methods, and used to do in lab !

thanks for your support !

[Borek]

Remember: library first, wiki/google second, ask on forums third!

[Mr Peanut]

There are many of coarse. The best depends upon levels expected, matrix, etc. I am most familiar with the methods for trace levels in water. Most inorganic nitrates are water soluble so an initial water extraction prep followed by filtration and perhaps dilution makes these water techniques usable for a generalized matrix provided the interferences are negligible.

In my opinion ion chromatogrphy is the preferred determinative step. But expensive if you do not already own the IC. Next, is the cadmium reduction technique. In this method we reduce NO3 to NO2 then measure NO2 by a spectrophotometric technique.

Let me know if you need more direction.
.

[bluemonster]

Hi Mr Peanut !
I know the problem is very easy if we use the chromatography or spectroscopy method ! I want to titrate nitrate ion by normal analytical chemistry method, such as complexon, oxidation-reduction, ...
can u help me ! thanks !

to Borek: thanks for your recommendation !

[Mr Peanut]

Firstly, I stress that the procedures to be discussed can be hazardous. Be certain you are appropriately equipped and professionally guided. I can't be there with you so I cannot  be responsible for injury to yourself or others.

One volumetric (titration) method is the Devarda Method. It involves the reduction of nitrate to ammonia then a subsequent determination of ammonia (which can be a titration). It is no quick, easy method and it can be quite dangerous. Its interferences include ammonia and nitrite. The detection limit isn't great.

I don't know of any other "official" methods that use volumetric or gravimetric technology. They are inherently non-selective and you will need to be quite skeptical of results if you are not certain of the absence of interferences. They also will have relatively high detection limits.

That having been said lets say you have a solution of NaNO3 in water (after a prep step or whatever). That is, you are certain there are no other oxidizing agents present. Also, pretend that you are targeting detection limits no better than a fraction of a percent. You may be able to determine nitrate by a total oxidizing agent technique (you will have to make standards and check it out at your own risk). One procedure might go like this:

In the hood with goggles etc.

1.   add NaI to an aliquot of sample (say 50 ml).
2.   add (carefully!) 2 ml H3PO4 You should see evidence of I2 (yellow, red , brown) if you are on the right track
3.   titrate with standardized thiosulfate to light straw color
4.   add 1 ml of starch indicator (blue now)
5.   titrate to clear
6.   get out the CRC and go to the electrochemical series for half reactions leading to calculation

[bluemonster]

Dear Mr Peanut !
thanks for your support !
good luck !