Griess’ reagent detects nitrites in solutions, which can be toxic in high concentrations. The reagent consists of sulfanilamide and naphthylenediamine dihydrochloride, and the color produced by the reagent indicates the level of nitrites. The Griess test is used in forensics, food testing, and medical diagnosis. Nitrites in the body can be dangerous and can cause death, so their levels must be determined for diagnosis and autopsy.
Griess’ reagent was first developed in 1879 by Peter Griess. It is used to determine the level of nitrites, chemicals that contain two oxygen molecules bonded to one nitrogen molecule (ONO), in solutions. In the presence of nitrites, the reagent causes the solution to change color until it becomes deep pink. Nitrites are present in food and water and high concentrations can be toxic to humans.
Peter Griess was a pioneer in the field of organic chemistry. He was the first to describe the Griess diazotization reaction, the basis of the Griess test, which detects nitrite molecules. This diazotization reaction describes the change of nitrite into a diazo compound, a compound that contains two nitrogen atoms bonded together at the end of a molecule.
Griess’ reagent consists of one part of a 1% solution of sulfanilamide in 5% phosphoric acid and 0.1% naphthylenediamine dihydrochloride in distilled water. Sulfanilamide is also known as sulphanilic acid and is normally a solid that dissolves in acidic liquid solutions. In contact with nitrites, it forms a diazo compound. Nathylenethylenediamine then turns diazo compounds a pinkish color.
The greater the number of nitrites in a solution, the greater the color produced by the addition of Griess’s reagent. This entire chemical process forms the chemical basis for the Griess test. The color produced by adding Griess’s reagent is read by a spectrophotometer, a machine that measures the transmittance or absorbance of light. The darker the color, the more nitrites are present.
There are many different contexts where nitrite measurement is important. In forensics, the Griess test is used to test for nitroglycerin, an explosive compound. Griess reagent is used to test the levels of nitrites in food products, especially meats. Nitrites are also found in human blood, where high concentrations can be dangerous.
In the blood, nitrites react with hemoglobin and convert it into methemoglobin. Hemoglobin is a protein found in blood that carries oxygen from the lungs to cells throughout the body. Methglobin cannot carry oxygen to cells; as hemoglobin is converted into methglobin, it results in less oxygen being carried through the body. Griess’s reagent is used to determine the levels of nitrites in blood plasma, the liquid that contains red blood cells. In high concentrations, nitrites are toxic and can cause death, so the determination of nitrite levels in the body is necessary for the diagnosis of some diseases and may be requested during an autopsy.
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