The method here reported is based on an in situ
dehydration process followed by dry ashing of the sample
in the presence of a retaining agent for volatile
porphyrinic compounds. The elements are determined by
flame atomic absorption spectroscopy (FAAS), using aqueous solutions for calibration of the instrument, with
addition of ionization suppressor for some of them. Good
recoveries were obtained for the five elements studied,
ranging from 95.8 to 104.3%. The relative standard
deviation for determination of any element was lower
than +4%.