the monitoring of food additives in Brazil, has established
concentration limits for nitrite and nitrate in meats of 150
and 300 mg kg−1, respectively (ANVISA 2009).
The method commonly reported in the literature for
the analysis of nitrate and nitrite in meat consists of the
solubilization of the analytes and determination of the
anions by considering the difference between the
amount of nitrite and the amount of nitrate plus nitrite
(AOAC 1995). In this procedure, nitrate is reduced to
nitrite by passage through a cadmium column, and nitrite
is measured using a colorimetric reaction. Another aliquot
of the same sample is used to determine nitrite, without
any treatment with reducing agent. The colorimetric
reaction involves the diazotization of nitrite with sulfanilamide
and coupling with N-(1-naphthyl)-ethylenediamine
dihydrochloride (NED) to form a highly colored
azo dye. However, this method involves laborious
procedures for sample preparation, uses a metal of high
environmental toxicity, and allows the determination of
only a single analyte at a time. Ion chromatography (IC)
and high-performance liquid chromatography (HPLC)
have been reported in the literature for the simultaneous
determination of nitrate and nitrite in various matrices
(Siu and Henshall 1998; Dennis et al. 1990; Muir and
Soroka 1992; Kodamatani et al. 2009; Tahboub 2009;
Ferreira and Silva 2008). Common to all of these
measurement methods is the sample preparation step
consisting of the solubilization of the anions. Practical
limitations of these techniques include the need for
expensive columns, long separation times, high consumption
of hazardous organic solvents, and pretreatment
steps, such as protein precipitation procedures after
extraction or use of reversed-phase cartridges to remove
sample matrix interferences.