Determination of copper and mercury in phosphate fertilizers employing direct solid sampling analysis and high resolution continuum source graphite furnace atomic absorption spectrometry

•Three methods for determination of the Cu and Hg in fertilizers by SS–HR-CS GF AAS were proposed.•The optimized methods were satisfactorily applied to the quantitative analysis of fertilizers.•Analytical methods using small amounts of reagents were compared with others methods in the literature.•The analytical methods were simple, fast, accurate, precise and free of spectral interferences.

The present study proposes the determination of copper and mercury in phosphate fertilizers by direct solid sampling analysis (SS) employing high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). For Cu determination, two analytical lines were used: 327.3960 nm and 249.2146 nm. Hg determination was carried out on the line 253.6521 nm and 100 μg KMnO4 was used as chemical modifier. The optimal pyrolysis temperature for Cu determination was 1300 °C. Atomization temperatures for Cu and Hg were 2400 and 1100 °C, respectively. External calibration with aqueous standard solutions was adopted for both elements. The limits of quantification (LoQs) and characteristic mass (m0) obtained for Cu determination were 0.4 μg g− 1 and 1.12 ng, respectively, on line 249.2146 nm, and 64 μg g− 1 and 25 pg on 327.3960 nm. For mercury, LoQ and m0 were 4.8 ng g− 1 and 39 pg, respectively. The accuracy of the proposed methods was confirmed by the analysis of standard reference material (SRM) of Trace Elements in Multi-Nutrient Fertilizer (SRM NIST 695). The precision expressed as relative standard deviation (RSD), was better than 8.2% for Hg and 7.7% for the Cu (n = 5), considered satisfactory for microanalysis in solid sample. Four fertilizer samples acquired in commercial establishments in the city of Salvador, Bahia, Brazil, were analyzed. The optimized analytical methods were simple, fast, accurate, precise and free of spectral interferences for the determination of Cu and Hg in phosphate fertilizer samples by SS–HR-CS GF AAS, avoiding the dissolution of the sample, the use of harmful reagents and the generation of residues.