A portion of the microwave digest was dry ashed to eliminate the HNO3 and
organic matrix. Dry ashing was performed in small beakers without problems,
because most organic compounds were destroyed during microwave digestion. Inexpensive,
reusable glass beakers performed satisfactorily and eliminated the need for
expensive quartz beakers. Magnesium from the ash aid had no e!ect on blank
absorbance and sensitivity when peak area was used for quantitation. Thus, matrix
matching with magnesium nitrate was not required for standards. However, magnesium
in great excess of levels recommended can interfere with HG-AAS (Reamer and
Veillon, 1981; Yban8 ez et al., 1992; Cervera et al., 1994).