Griess method

Spectrophotometry, Griess method (reduction to nitrite and diazotation) Spectrophotometry [displacement of SCN in Hg(SCN)T, determination of colored Fe(SCN) complex]... 

The components of the desired compounds are redu " equimolecular proportions under conditions which make p the union of the two radicals during the azo-phase. By of this method azo-compounds in which the substitute in any desirable position to the azo-bond, and which i r< obtainable by the Griess method, can be prepared. 

The classical Griess method for nitrite determination is very well known. However, some of the more recent methods which are also based upon the formation of azo dyes may be better. A critical review of the nitrite determination methods has been published [58]. 

In the Griess method (1879), nitrite, sulphanilic acid, and 1-naphthylamine are reacted as follows ... 

The Griess method is highly sensitive. The molar absorptivity at A,max = 520 nm is 4.0-10", specific absorptivity 2.8). The method is specific, but only of moderate precision. 

The Griess method has been applied widely for determining nitrite in foods and waters. The method has also been used for automatic determination of nitrite (and NOs" after reduction to NO2 ) in waters and in soil extracts [81], in living cell fluids [82], and in blood [83]. 

Experiments were carried out in a 500-mL photochemical reactor with a quartz immersion well. A 10 x 20 cm2 piece of film was wrapped around the immersion well and tied in place with Teflon tape. Then 350 mL of H20 was placed in the reactor and NaOH was added to adjust the pH to 12. The system was purged continuously with air or N2 and irradiated with a 400-W medium-pressure Hg lamp. After a period of time the solution was tested for NH3 by the indophenol method, and for NOJ/NOJ (combined total nitrite and nitrate) by Cd reduction, followed by colorimetric analysis by the azo-dye method [84]. The azo-dye method, sometimes known as the Griess method or the sulfanilic acid method, has been described elsewhere [87]. 

Therefore, reduction of nitrate to nitrite [562] is required in order to apply the classical Griess method [563]. According to the Griess method, nitrite is diazo-tized with sulfanilamide and then reacted with A/-l-naphthylethylenediamine to form a colored product However, this method is not very reliable when applied to complex matrices such as serum, as the reduction of nitrate to nitrite is chemically difficult and enzymatically very expensive. Stains and clouding in the sample also cause interferences, and the presence of copper in the sample... 

Table 33 Measurements of NO3 in Beetroot Supplements Using Present Biosensor and Griess Method...

S. No. Nitrate Cone, by Griess Method (gM) Nitrate Cone, by Biosensor (gM)... 

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