Orthogonal array design for the optimization of closed-vessel microwave digestion parameters for the determination of trace metals in sediments

Orthogonal array design was applied to the optimization of the closed-vessel microwave digestion of sediment samples. Five variables related to the digestion efficiency were studied: the addition of HF in digestion acid, the ratio between HCl and HNO3, the maximum pressure setting, the output power and the digestion time. In the experimental assignment, the digestion time at two levels and other variables at four levels were tested using an OA16(44 × 23) matrix. The interactions between the parameters were neglected. From the results, the optimum conditions for the closed vessel microwave digestion for sediment samples were established.