Try the method by Swann and Adams (http://pubs.acs.org/doi/abs/10.1021/ac60118a038).

Have you consulted the Standard Methods for Examinatioon of Water and Wastewater (APHA)?

If you use the ICP (Inductive Couple Plazma) by initiating a standard curve of known concentration you can get direct measurements for your sampl (Aqueous state). Also the HLPC can do the test directly

within this range you have to dissolute the water by a factor of 50 to 500 to use any analytics at all. if you don't need exact values, there are quick tests available from Merck

@GIORGOS : Will try this.

@Antoiine : Upto what concentration i can use Ion chromotography ?

@Ariovaldo : Ya.i referred to all methods AND SELECTED CADMIUM Method.

@Ziyad : Will read about it.If possible provide me related link.

Thanks to all !!

Why you do not try ion selective elctrode

You could try a nitrate ion-selective electrode.

First the nitrate in water is to be reduced to nitrite by passing through cadmium reduction column. . Then sulphanilamide test can be used for the determination of nitrite. Take 10 ml sample in a test tube.Add 2 ml sulpanilamide and 2ml NEDA . Keep it for 10 minutes. measure the absorbance in 543nm in spectrophotometer. Standards shall also be prepared. Please read APHA method.

Concentration of nitrite-nitrogen = concentration of standard * Absorbance of sample/Absorbance of standard

you may consult book on ENVIRONMENTAL CHEMISTRY by A.K .DE. ISBN 81-224-1247-5

There are colormetric test kits such as by Hach, that will work in that range at low cost.

You can try HACH method

http://www.hach.com/quick.search-quick.search.jsa?keywords=nitrate

we use a DR2800 spectrophotometer with method:

http://www.hach.com/nitraver-5-nitrate-reagent-powder-pillows-10-ml-pk-100/product?id=7640208933&callback=qs

You could use the ion chromatography

I was working on a microalgae culturing system as my MS project. We used to use the spectrophotometer as an instrument for measuring the nitrate concentration

For filling cadmium in cadmium reduction column, take 100 g of coarse cadmium granules in a 250 ml beaker. Wash with 100 ml 2N HCl and then with plenty of distilled water to remove acid. Add 100 ml 1% mercuric chloride solution. Stir for 5 minutes. Drain out mercuric chloride and wash will distilled water till all mercuric chloride is removed. Keep the washed amalgamated cadmium granules in distilled water.

Packing Place a bit glass wool plug at the bottom of the column. Pour distilled water to remove the column slowly add cadmium so that no air bubble gets trapped. After filling, place another bit of glass wool at the top. Filled cadmium should never get dry.

For me it worked very well the method of Cawse with sulfamic acid and perchloric acid and reading A210 minus A250 (Analyst vol 92, 311-315). It is so fast and easy...

When the sample includes some substances that may interfere with ultraviolet determination, a rather sensitive method is that of E. coli cells that reduce nitrate to nitrite (I don't have here the reference, sorry, but you can have a look in the literature and easily find it). You must grow first E. coli anaerobically in the presence of nitrate and then harvest, allicuote and freeze the biomass; this will las for hundreds of accurate determinations.

Good luck!

The possible analytical options are:

(1) cadmium reduction method (EPA 353.2 or 353.3) – ranges 0.01 mg/L to 1.0 mg/L. Good low level sensitivity. The interferences: TSS; iron, copper, and other metals greater than several mg/L; O&G; residual chlorine. Most interferences should be overcome via proper sample preparation. The hold time: 2d. Please note preservation may cause artificially high nitrate concentrations, if nitrite is present.

(2) ion chromatography (SM4140) – ranges from 0.1 mg/L to 10 mg/L The interferences: high TDS matrix.

For both methods, stronger samples can be diluted. I’d suggest, since you have a better understanding of your water matrix, that you contact your laboratory and discuss the pros/cons of each method.

I think the hydrazine reduction method will do

Tip: Hach methods 8039 and 8171. Range: 0.1 to 10.0 or 0.3 to 30.0 mg/L as nitrate-N. Sample Size: 10 mL.

The mean concentration of nitrate ranged from ---- to --------------? in your sampling site?

I think if you use the spectrophotometer method you will obtain confident results!!!

By using electrode analyzer (instrument) we can easily estimate the nitrate ion concentration. But for these need a nitrate ion selective electode. this is very easiest method

You can use spectrophotometric method at U.V -range 220nm. Check out the method in "Standard Method for the examination of water and waste water"(APHA, 2005). Other methods for determination of Nitrate are also given in this book..including preparation of calibration curve.

the oldest method was their for the determination of nitrate by nephlometry determination making into suspension.... and also spectrophotometric methods also available using Chromo tropic Acid method.

Nitrate concentration can best be measured either by the classical method of cadmium reduction-reduction to nitrite and, developing color and measuring by photometer or simply measure by Ion chromatography (see ph adjustment)- IC measurement will separately give u NO3 and NO2

You could use the IC (ion chromatography) method. I have good experiences with Dionex IonPac AS11-HC 250 mm x 2 mm analytical column, KOH eluent generator and suppressed conductivity detection

You can found it at "vogel - qualitative inorganic analysis" 5th ed1979 page 334

The Ion Chromatography with conductivity detection (all anions and cations) and UV (in case of nitrate, nitrite or carbonate ions) is the best resolution. If you do not expensive Ion Chromatograph nitrate ions, only, you can measure spectrophotometric in UV range (240 nm). irreversible HPLC using RP 18 column in UV range is also possible to use. You should add approximately 5 mM benzoic or phtalic acid to the eluent. Buy in this case the "system peaks" appears.

Most promising answers have already been given. To surmise, spectrophotometric absorption in the UV regions near 220 nm will be easiest and mostly followed method in any laboratory.. However, it has it has its own drawbacks. This method can not be as sensitive as nitrate ion selective electrode. As Dr. Pizarro suggested, HPLC-C18 column can also be used.

There is also one more method called Total Nitrogen analyzer. Once total nitrogen is arrived at , there seems to a formula by which nitrate and nitrite concentrations could be determined for which a separate standard curve for NO3 and NO2 will be more helpful

Elemental analyzer

ion selective electrode method is very good method because it is to some extent accurate and there are some electrodes with high sensitivety. the calibration is very simple just follow the manufacturer instructions. the good thing is that the electorde system is non distructive for the sample you can just insert the electrode and get the reading (the best one i have tried is from Thermo) but Hach also has ISE for nitrates.

One additional method is to use UV analytical method this can be applied if your sample is free from organic matter, and if you have quartez spectrophotometric cell. even if you have small concentration of organic matter and this concentration is constent over all you measurments the UV method can work with some simple modifications.

best wishes

Ilosvay-Ilosva modification may help (Griess variation)

The UV Absorption (nm) Spectroscopy method is probably the simplest, so long as your sample does not contain apprecialble concentrations of organic matter and [NO3-] > 10 mg/L.

Protocol:

1. To 5 mL of sample (membrane-filtered, treated wastewater) in a Bijoux bottle, add 0.1 mL HCl (1.0 molar) and mix thoroughly by capping sample bottle and inverting 5 times. (Acidification prevents interferences from hydroxide ions or carbonate up to 1000 mg CaCO3/L.)

2. Transfer 1.0 mL to a quartz micro-cuvette (or 3.0 mL to a normal quartz cuvette).

3. Zero spectrophotometer at 220 nm, using organic-free, deionised water in a quartz cuvette matched to the one used above.

4. Measure sample absorbance at 220 nm (NO3- + organic matter).

5. Zero spectrophotometer at 275 nm.

6. Measure sample absorbance at 275 nm (organic matter).

7. If Abs275 nm x 2 > 10% Abs220 nm, the sample contains too much organic matter and an alternative method should be used. If not, subtract Abs275 nm x 2 from Abs220 nm, to obtain value for NO3- corrected for organic matter content.

8. Convert Abs220 nm to concentration, using calibration curve.

Has anybody ever use Cadmium reduction column to reduce nitrate to nitrite? Nitrate is hard to detect anyway, however, nitrite is much easier. Thanks.

I have used cadmium column and it works fine to standard solutions of nitrate (MILLIPORE WATER). i found it difficult when nitrate is prepared using a supporting electrolyte, 0.5M HCLO4.

To have an acceptable results you have to follow standard method, you can find the details in Standard Methods for the Examination of Water and Wastewaterm American Public Health Association, Washington, DC. If you faced problem in finding the reference please contact me to provide you with this part.

Do you consulted Standard Methods (APHA)?

Spectro photometeric method with fresh standard and proper calibration. This is quick, cast effective and accurate.

Nitrate analysis by UV- spectrophotometry

Nitrate afer reduction is converted in to to nitrite. The nitrite can be determined by Diazotization using sulphanilic acid and aniline solution to produce a complex yellow color dye. The intensity of the resultant dye can be detected by using Schimadzu UV Spectrophotometer 160-A.

Most important is analysis should be processed within 24 hours after collecting water sample. Sample must be taken in plastic bottle air tight. Apply UV spectro photometeric method with fresh standards. Calibrate accurately.

 Thanks a lot #Michael John Dempsey for the protocol. Hope this will help me.

Since I am working on microalgal system, can you tell me if the UV absorption protocol  for measurement of nitrate  that you have mentioned above can be used to determine the nitrate level in the liquid  algae culture medium.

It all depends on the organic matter content of the medium, which is what the measurements at 575 and 220 nm are to determine.

Can you please share the absorbance of Synthetic samples of Nitrates at 220 and 275 nm?

Like for 1,2,4,6,8,10 mg/L of Nitrates