You can measure at 220 nm. The problem is that the organic material also absorbs at that length.

You're outside my area of expertise. Sorry, I'll see if I can find a solution for you later today. Don't wait for me. Keep looking.

The formed compound is red... not measurable at 220 nm ! It might be something around 500 nm.

I am not familiar with the kit, but it sounds as if you are trying to do a 4500 series test and then measure results with UV-VIS. You'll need to get a copy of Standard methods and look up NO3- NO2 testing, but I think it is measured at 425 nm. I could be wrong, but the book test can give you an exact procedure.

I hope this helps.

Jeff

I haven' t use this kit but the Merck technical support is pretty good. Ask them for the right condition for this kit.

Hi Pierre,

This is slightly out of my field but here is what I found:

Nitrate: Merck Nitrate Test 0.2-25,0 mg/L NO3--N Spectroquant®#114773. Quantified by adsorption at 517,1 nm as measured with a Specord S100 from Carl Zeiss Technology.

The source is Andersen et al 2004:

http://www2.mst.dk/udgiv/Publications/2004/87-7614-168-3/pdf/87-7614-169-1.pdf

Hope it helps

Try to measure at variuos nm near red region (increase 50 nm inbetween) to get the maximumasborption curve of ur own

I suggest you to put your sample in the spectrophotometer and run the scan, during the process wavelength vs. absorbance graph will be plotted from where you can find out the wavelength with maximum absorbance or else some instruments not having graphing facility will directly gives the wavelength with maximum absorbance during scan.

i agree with Dr M. Shahid about scanning, and with . Drake about 400-500nm if scanning isn't available

I use this method and I have no problems (attachment). Here I command simplified.

NO3 - were obtained through the ultraviolet method, based on the absorption of ultraviolet radiation by the nitrate ion. So the calibration line was built from known concentrations of this anion. Then analysed each of the diluted extracts, to which was added a proportional amount of 1N hydrochloric acid according to the aliquot of sample used. The dilutions were measured at two different wavelengths: 220 nm for the corresponding nitrates, and 275 nm reading for interference due to dissolved organic matter.

Hi, I use sodium salicylate method (yellow complex) and I read at 420.

i suggest you , your sample run on UV-VIS 4500 Spectrophotometer.At 520 nm for No2 & 410 nm For No3 .for more information refer the APHA 4500 No2 &APHA 4500 No3.

Thank you all !

Here is the answer (i got it from Merck chemicals) : 525 nm.

It is nice to see so much people trying to help. I hope i will be able to give you help back in the future.

Have a nice day,

Pierre

I don't know if some people might still be interested as this post is already a bit older. But you may try to look up on google for "Merck" and "Programming data for spectrophotometer and Spectroquant test kits". Then you will find a pdf with all wavelengths of all available test sets, along with measurement ranges, cell sizes and other details.

Hope this helps!

Klaus