title: Comparison of slurry sampling and microwave-assisted digestion for calcium, magnesium, iron, copper and zinc determination in fish tissue samples by flame atomic absorption spectrometry.
abstract: The development of a slurry sampling method for the determination of calcium, copper, iron, magnesium and zinc in fish tissue samples by flame atomic absorption spectrometry is described. In comparison with microwave-assisted digestion, the proposed method is simple, requires short time and eliminates total sample dissolution before analysis. Suspension medium was optimized for each analyte to obtain quantitative recoveries from fish tissue samples without matrix interferences. Nevertheless, iron recoveries higher than 46% were not found. Treatment of samples slurried in nitric acid by microwave irradiation for 15-30s at 75-285W permitted to achieve efficient recoveries for calcium, iron, magnesium and zinc. Further improvement in the matrix effects for iron determination was accomplished by the use of an additional step of short microwave-assisted suspension treatment. However, standard addition method was required for calcium and copper determination, being necessary hydrochloric acid as suspension medium for the last one. Although copper could not be determined in the certified reference material using microwave-assisted digestion, the accuracy of the slurry sampling method was verified for all the investigated analytes. Detection limits were 22.8+/-8.0, 0.884+/-0.092, 5.07+/-0.76, 35.5+/-0.7 and 1.17+/-0.04mugg(-1) for calcium, copper, iron, magnesium and zinc, respectively. The standard deviations obtained using slurry sampling method and microwave-assisted digestion were not significantly different, and the mean relative standard deviation of the over-all method (n=3) of the slurry sampling method for different concentration levels was below 12%.
authors.affiliation: Departamento de Química Analítica y Alimentaria, Area de Química Analítica, Universidad de Vigo, Facultad de Ciencias de Ourense, As Lagoas s/n, 32004 Ourense, Spain.
authors.forename: Raquel Alonso
authors.initials: RA
authors.lastname: Bugallo
authors.forename: Susana Río
authors.initials: SR
authors.lastname: Segade
authors.forename: Esperanza Fernández
authors.initials: EF
authors.lastname: Gómez