o-Tolualdehyde-2,4-DNPH is the 2,4-dinitrophenylhydrazone derivative of o-tolualdehyde (2-methylbenzaldehyde). It serves as an analytical standard for the detection and quantification of carbonyl compounds, especially o-tolualdehyde, in environmental and industrial samples. This stable derivative facilitates precise analysis using techniques such as HPLC or UV-Vis spectroscopy. It is commonly used in air quality monitoring to measure airborne aldehyde pollutants and as a reference material in quality control for the chemical and pharmaceutical industries to verify product purity and composition.