Ninhydrin-sodium molybdate chromogenic analytical probe for the assay of amino acids and proteins

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 173; pp. 897 - 903
• Main Authors: Anantharaman, Shivakumar, Padmarajaiah, Nagaraja, Al-Tayar, Naef Ghllab Saeed, Shrestha, Ashwinee Kumar
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 15-02-2017
• Subjects: Amino acid; Amino Acids - analysis; Animals; Cattle; Hydrindantin; Hydrogen-Ion Concentration; Kjeldahl nitrogen; Leucine equivalents; Molybdenum - chemistry; Ninhydrin; Ninhydrin - chemistry; Ruhemann's purple; Serum Albumin, Bovine - analysis; Sodium molybdate; Amino acid; Ninhydrin; Sodium molybdate; Ruhemann's purple; Kjeldahl nitrogen; Hydrindantin; Leucine equivalents
• ISSN: 1386-1425; 1873-3557
• DOI: 10.1016/j.saa.2016.10.040

A sensitive method has been proposed for the quantification of amino acids and proteins using ninhydrin and sodium molybdate as chromogenic substrates in citrate buffer of pH5.6. A weak molybdate-hydrindantin complex plays the role in the formation of Ruhemann's purple. The linear response for the amino acid, amino acid mixture and Bovine serum albumin is between 0.999 and 66.80μM, 1.52 and 38μM and 5 and 100μg/L, respectively. The molar absorptivity of the individual amino acid by the proposed reaction extends from 0.58×104 to 2.86×104M−1cm−1. The linearity equations for the proposed ninhydrin-molybdate for amino acid mixture is Abs=0.021×Conc (μM)−0.002. The applicability of the proposed method has been justified in food and biological samples in conjunction with Kjeldahl method.
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•Sodium molybdate as an alternative to cadmium chloride/stannous chloride increase the sensitivity.•The formation of weak π-complex of molybdate ion with hydrindantin enhances the homogeneity of the reaction.•The sodium molybdate-ninhydrin analytical probe has a minimum interference by glucose.