Enzymatic spectrophotometric determination of nitrites in beer

Enzymatic spectrophotometric determination of nitrites in beer, Girotti, S., Ferri E. N., Fini F., Ruffini F., Budini R., Moura I., Almeida G., Costa C., Moura J. J. G., and Carrea G. , Analytical Letters, 1999, Volume 32, Number 11, p.2217-2227, (1999)


A colorimetric assay for nitrite determination in beer based on c-type multiheme enzyme Nitrite reductase (NiR) isolated from Desulfovibrio desulfuricans ATCC 27774, was developed. Using the enzyme in solution, nitrite assay was linear in the 10(-8) - 10(-2) M range with a detection limit of 10(-8) M. and a recovery ranging from 90 to 107%. The imprecision ranged from 4 to 10% on the entire calibration curve. With NIR immobilised onto a nylon coil, a flow reactor was developed which showed a narrower linear range (10(-5) - 10(-2) M) and a higher detection limit (10(-5) M) than with the enzyme in solution, but made it possible to reuse the enzyme up to 100 times (50% residual activity). Sample preparation was simple and fast: only degassing and beer dilution by buffer was needed. This enzymatic assay was in good agreement with the results obtained using commercial nitrite determination kits.


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