Dimethylglyoxime spectrophotometry is a chemical analysis method commonly used for the determination of metallic nickel. It detects the content of metallic nickel by butanedione, oxime-based reagent and molecular absorption principle. In general, butanedione is added to the sample (solution or suspension) to be tested, and the pH value is adjusted to 2, so that the metal nickel in the sample reacts with oxime-based reagent to generate a nickel phosphonate complex.

The complex has a maximum absorption peak at a specific wavelength of about 400nm, and the absorption intensity and concentration of the maximum absorption peak affect the maximum absorption peak, so that the content of metallic nickel in the sample can be accurately measured.

Knowledge expansion:

Dimethylglyoxime is a chemical substance with the molecular formula of C4H8N2O2. White triclinic crystal or crystalline powder, soluble in ethanol, ether, acetone and pyridine, almost insoluble in water. Used for verification and determination of nickel. Nickel is separated from cobalt and other metals, and palladium is separated from tin, gold, rhenium and iridium. Photometric determination of cyanide, nickel and palladium.

In 1905, L. A. Chugaev discovered the method of detecting nickel with dimethylglyoxime as reagent. When used as an analytical reagent, dmgH2 is usually used in ethanol solution. It is the * * * yoke base of dimethylglyoxime that forms the complex, not dmgH2 itself; However, two dmgH ligands form macrocyclic ligands by hydrogen bonding.

The most famous complex is bright red Ni(dmgH)2 formed by bivalent nickel and dmgH2. This planar complex is extremely insoluble in water, so it is often used for gravimetric analysis of nickel (such as in ores).

DmgH2 is sp2, which hybridizes with the nitrogen atom in its complex. Because the macrocycle of [dmgH]22- is planar, its structure is similar to some biologically important macrocyclic ligands, such as vitamin B 12 and myoglobin. A famous model compound of this type is a cobalt oxime complex with the molecular formula of CoR(dmgH)2L, where R is alkyl and L is usually pyridine. In this complex, L and R are located in the axial position of cobalt and perpendicular to the plane of (dmgH)2.