I think that this is unlikely. Recall the teaching adage: all nitrates are soluble .... Can you not use a colorimetric ?

Khaled Elnagar

Wet gravimetric analysis for determining nitrates in water can be susceptible to interferences caused by the presence of other nitrogen-containing compounds, such as ammonia or amines. These compounds can react with reagents, leading to false results or an overestimation of nitrate concentrations. To detect these interferences, selective reagents are used that can differentiate nitrates from other nitrogen compounds, or additional analytical techniques, such as spectrophotometry or ion chromatography, are applied to confirm the results. To eliminate interferences, it is recommended to use reagents that selectively react with nitrates, while other nitrogen compounds are removed through pre-treatment of the sample, such as distillation or filtration. Additionally, the use of internal standardization can help compensate for interferences, and combining wet gravimetric analysis with other methods can provide extra assurance of result accuracy.

I concur that all nitrates are soluble in water, that many of them interfere with other nitrogenous compounds, and that IC can detect them with ease and high precision. However, I find it difficult to try it using wet chemistry because most labs and my students lack such sophisticated equipment.

So I need simple methods give me comparable results with IC having the lowest interferences

Khaled Elnagar

If nitrate detection needs to be conducted without the use of ion chromatography (IC), which requires sophisticated laboratory equipment, it is recommended to apply a spectrophotometric method based on the reduction of nitrates to nitrites, followed by a reaction with reagents such as sulfanilamide and NED (N-(1-naphthyl)ethylenediamine dihydrochloride), resulting in the formation of an azo dye measured at a wavelength of 540 nm. This method, known as the Griess Reaction, represents a simple, accessible, and sufficiently sensitive procedure for determining nitrate concentrations in aqueous solutions, with relatively low levels of interference. When proper sample preparation and quality control are applied, this approach can yield results comparable to the IC method, making it particularly suitable for use in educational and less-equipped laboratory environments.

The simplest gravimetric technique to analyze nitrates while minimizing interference from ammonia and other nitrogen-containing compounds is the precipitation of nitrate as a sparingly soluble salt, typically nitrate of strontium or barium, after appropriate sample preparation. Among these, strontium nitrate precipitation is favored due to its relatively low solubility and specificity. To avoid interference from ammonia and organic nitrogen compounds, the sample is first treated with reagents such as Devarda’s alloy to reduce nitrate selectively or with sulfuric acid and heat to drive off ammonia as gas. Alternatively, ammonia can be removed through prior distillation or by raising the pH to volatilize it as NH₃. After interference removal, nitrates are precipitated and weighed as a stable compound. While less common today due to the precision of spectrophotometric and chromatographic methods, this gravimetric approach remains a straightforward, low-tech option where resources are limited.

The simplest gravimetric technique to analyze nitrates while avoiding interference from ammonia and other nitrogen compounds is precipitation as sparingly soluble nitrates viz., using brucine or nitron reagents to form insoluble nitrate complexes. These selectively precipitate nitrates without reacting with ammonia or organic nitrogen compounds.