Abstract
A safe, reliable, and efficient method is described for automated acid decomposition of biological samples, agricultural food products, and environmental material under high temperature and pressure. A high temperature/pressure asher that provides temperatures up to 320°C and pressures up to 100 bars (1450 psi) is used to heat 5 mL of ultrapure acid 4 h for complete sample decomposition. The unit is microprocessor-controlled with up to 5 programmable temperature levels and ramp time intervals. These levels and intervals are displayed on a CRT screen. Both temperature and pressure program set points and actual readings inside the autoclave can be monitored by an analyst as the decomposition program progresses. Biological samples and agricultural food products of 1.0 g each are weighed into 70 mL closed quartz vessels for acid digestion. The digested samples are analyzed by using an inductively coupled argon plasma (ICP) emission spectrometer for aluminum, boron, calcium, iron, lead, magnesium, manganese, phosphorus, potassium, sodium, strontium, sulfur, and zinc. Environmental material of 0.2 g each is weighed into 20 mL glassy carbon vessels for digestion and ICP analysis for calcium, iron, lead, magnesium, manganese, nickel, phosphorus, potassium, sodium, strontium, sulfur, titanium, and zinc. The average recovery for 31 elemental standards evaluated by digestion in the high temperature/ pressure asher provided an average recovery of 98.7%.
High‐temperature annealing characteristics of tungsten and tungsten nitride Schottky contacts to GaAs under different annealing conditions
