No abstract

A method for direct determination of manganese (Mn) in human serum by graphite furnace atomic absorption spectrometry (GFAAS) was proposed in this work. The samples were only diluted 1:4 with nitric acid 1% (v/v) and Triton(®) X-100 0.1% (v/v). The optimization of the instrumental conditions was made using multivariate approach. A factorial design (2(3)) was employed to investigate the tendency of the most intense absorbance signal. The pyrolysis and atomization temperatures and the use of modifier were available and only the parameter modifier use did not have a significant effect on the response. A Center Composed Design (CCD) presented best temperatures of 430 °C and 2568 °C for pyrolysis and atomization, respectively. The method allowed the determination of manganese with a curve varying from 0.7 to 3.3 μg/L. Recovery studies in three concentration levels (n=7 for each level) presented results from 98 ± 5 to 102 ± 7 %. The detection limit was 0.2 μg/L, the quantifying limit was 0.7 μg/L, and the characteristic mass, 1.3 ± 0.2 pg. Intra- and interassay studies showed coefficients of variation of 4.7-7.0% (n=21) and 6-8%(n=63), respectively. The method was applied for the determination of manganese in 53 samples obtaining concentrations from 3.9 to 13.7 μg/L.

In this work efficient methods to determine copper and iron in dog serum samples by graphite furnace atomic absorption spectrometry were developed. The samples were diluted at a 1 : 9 or 1 : 19 (for Cu and Fe, respectively) ratio with 1% (v/v) nitric acid containing a 0.1% Triton X-100 solution. Rhodium for copper and no modifier for iron proved to be the better permanent modifier. Optimization included fractional factorial planning using Pareto and the CCD designs. For both analytes the working linear range was 0-100 mg L À1 (r 2 > 0.99). The obtained LOQ was 19.3 AE 2.8 mg L À1 for Cu and 16.5 AE 0.2 mg L À1 for Fe. Aqueous and matrix matching calibration curves had average angular coefficients that were not statistically different, i.e. the matrix effect was absent for both analytes. The accuracy was checked by recovery tests with an average of 101 AE 4% (n ¼ 45) for Cu and 90 AE 3% for Fe (n ¼ 45). The certified reference material SeronormÔ Trace Elements Serum L-1 obtained was 1705 AE 20 mg L À1 for Cu (certified: 1691 AE 84 mg L À1 ) and 1.40 AE 1.22 mg L À1 for Fe (certified: 1.43 AE 0.08 mg L À1 ). Cu and Fe levels in 39 canine serum samples -9 uninfected, 19 symptomatic and 11 asymptomatic dogs naturally infected with Leishmania chagasiranged from 374 to 913 mg L À1 , and 1103 to 4260 mg L À1 , respectively. Cu was higher in symptomatic than in asymptomatic and control dogs, and Fe was significantly lower in symptomatic than in either asymptomatic or control dogs.