Development and comparison of two analytical methods to quantify the mercury content in honey

The traditional method routinely used in laboratories to analyze mercury (Hg) in honey includes decomposition of samples, cold vapor generation and atomic absorption detection. Methods that avoid sample digestion could be applied in these laboratories and would represent an innovation relevant to the control of Hg in honey. In this paper, two methods were developed to determine Hg concentration in honey samples: one utilized cold vapor atomic absorption spectrometry (CVAAS), and the other used a direct mercury analyzer (DMA). The CVAAS method consisted of preparing solutions containing 5.0% (w/v) honey, 4.0% (v/v) H2O2 and 6.0% (v/v) HNO3. Hg determination was accomplished by treatment with 0.6% (w/v) NaBH4 in 0.5% (w/v) NaOH and 6.0 mol/L HCl. In the DMA method, measurements were made using up to 100 mg of honey sample without any prior treatment. The drying and decomposition times along with drying temperature were each optimized. After validation, the methods were used to quantify Hg in 35 honey samples collected from several cities in Minas Gerais, Brazil. All honey samples showed Hg concentrations below 2.5 ng/g. The proposed methods were rapid, simple and did not require sample decomposition using concentrated acids at high temperatures, which is advantageous considering the high volatility of Hg.