20
Method Information
Most water based samples should achieve constant weight settings in 1 - 3
minutes.
The microwave power and temperature settings should be appropriate to the
sample. The standard oven or vacuum oven temperature recommended in a
reference method for the sample should be followed. If no reference method is
available, a starting temperature of 100
°
C should be programmed. Because the
power level in the instrument is adjusted based on temperature feedback, most
samples can be dried using a 100% power level setting. If a sample contains a
strong microwave absorber such as carbohydrates, the power level will likely need
to be adjusted. In most instances, a 10% power change will be sufficient to prevent
overheating.
During the initial testing of a new sample, the weight display should be monitored
to ensure that the sample does not ignite and that a stable weight reading is
displayed. Sharp declines in weight indicate excessive sample heating. If ignition
occurs, the flame detection sensor will abort the analysis.
Samples that are strong absorbers of microwave energy should be diluted or tested
at reduced power levels. These products usually contain simple carbohydrates or
tightly held moisture that will not readily escape, causing overheating and/or
burning and non-reproducible results. These samples should be tested at a low
power. Examples of heat sensitive samples include powders, paper fibers, candy
and black liquor.