Factorial design approach to microwave dissolution
A fractional factorial design has been used to explore the variables that affect microwave dissolution using perfluoroalkoxy (PFA)-Teflon digestion vessels. Optimum operating conditions for National Research Council of Canada, certified reference material TORT-1 Lobster Hepatopancreas and National Institute of Standards and Technology, Standard Reference Material (SRM) 1575 Pine Needles, were obtained using this procedure. The optimum conditions found for each variable are: 0.25 g sample mass, 6 ml of concentrated hydrochloric acid, 6 ml of concentrated nitric acid, 3 ml of concentrated hydrofluoric acid and 90% microwave power for a total dissolution time of 15 min. Results for Ca, Fe, Cu and Zn in TORT-1 and Ca and Fe in SRM 1575 were in agreement with the certified values.