A colorimetric micro method for the determination of formyl groups

Usha Lakshmi, S. ; Ramachandran, L. K. (1969) A colorimetric micro method for the determination of formyl groups Biochemical Journal, 111 . pp. 401-406. ISSN 0264-6021

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Official URL: http://www.biochemj.org/bj/111/bj1110401.htm


The characteristic purple colour formed by N-formyl-N-2,4-dinitrophenyl-hydrazine in the presence of piperidine and acetone was made the basis of a new quantitative method for the determination of formyl groups. Samples containing N-formyl groups (up to 0.4mmole) are hydrazinolysed at 97-98° for 1hr. and are dinitrophenylated after the removal of excess of hydrazine. Interference from 2,4-dinitrophenylhydrazine is eliminated by subjecting the dinitrophenylated samples to chromatography on an alumina column. Interference arising from the formation of N-acetyl-N-2,4-dinitrophenylhydrazine, when determining formyl groups in samples containing acetyl, can be avoided by a paper-chromatographic separation before analysis. A standard procedure is described. The method gives satisfactory results when applied to N-formyl-amino acids. Gramicidin, when analysed by this method, was found to contain 0.89 mole of formyl group/mole for a molecular weight of 1880. The method indicated the absence of formyl groups from lysozyme, a protein known not to contain such groups. Generally, the analytical values obtained by the method are within 100±4% of theory.

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